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STUDIES ON GERMINATION ECOLOGY, PHYTOTOXIC EFFECTS AND CONTROL

OF RHYNCHOSIA CAPITATA (ROTH) DC IN MUNGBEAN.

BY

Hafiz Haider Ali M.Sc. (Hons.) Agronomy

A thesis submitted in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSPHY

IN AGRONOMY

DEPARTMENT OF AGRONOMY FACULTY OF AGRICULTURE,

UNIVERSITY OF AGRICULTURE, FAISALABAD, PAKISTAN.

2013

The Controller of Examination,

University of Agriculture,

Faisalabad.

We, the supervisory committee, certify that the contents and the form of thesis

submitted by Mr. Hafiz Haider Ali, Regd. No. 2003-ag-1638 have been found

satisfactory and recommend that it be processed for evaluation by the External

Examiner (s) for award of Degree.

SUPERVISORY COMMITTEE: CHAIRMAN : ________________________ (Dr. Asif Tanveer) MEMBER : ___________________________ (Dr. Muhammad Ather Nadeem) MEMBER : _________________________ (Dr. Hafiz Naeem Asghar)

DEDDICATED

TO

MY BELOVED FATHER

i

ACKNOWLEDGEMENTS

Saying of Prophet Muhammad (PBUH) `A person who is not thankful to his benefactor is not

thankful to ALLAH'. All and every kind of praises is upon ALLAH ALMIGHTY, the strength of

universe, who ever helps in darkness & difficulties. All and every kind of respect to His Holy

Prophet Muhammad (PBUH) for unique comprehensive and everlasting source of guidance and

knowledge for humanity.

I would like to extend my heartiest gratitude to Dr. Asif Tanveer, Professor, Department of

Agronomy, University of Agriculture, Faisalabad, under whose supervision, scholastic guidance,

consulting behavior, this work was planned, executed and completed. I appreciate and thank to

members of my supervisory committee, Dr. Muhammad Ather Nadeem, Assistant Professor,

Department of Agronomy, University of Agriculture, Fasislabad for his helping attitude and Dr.

Hafiz Naeem Asghar, Assistant Professor, Institute of Soil and Environmental Sciences,

University of Agriculture, Faisalabad, for their valuable and continuous guidelines during the

preparation of this manuscript and kind hearted behavior throughout my doctoral studies. I am

also highly indebted to Higher Education Commission (HEC), Government of Pakistan for

granting me Indigenous fellowship throughout my doctoral study. I also thankful to HEC for the

award of International Research Support Initiative Programme (IRSIP) scholarship in Royal

Holloway, University of London, UK.

I shall be missing something if I don’t extend my admiration and appreciation to my sincere

friends M. Mansoor Javaid, M. Saleem Kashif, Asim Raza Chadhar and my family, especially

elder brothers M. Saeed Alvi, M. Raza Alvi, cousin Dr. Abid Mehmood, who supported me

morally with sentiment throughout my study. Last but not the least gratitude is to be expressed to

my affectionate father Salamat Ali Awan, my loving mother, my younger brothers and my

beloved sisters for their love, inspiration, good wishes and unceasing prayers for me to achieve

higher goals in life.

Hafiz Haider Ali

ii

DECLARATION

I hereby declare that contents of the thesis, “Studies on

germination ecology, phytotoxic effects and control of Rhynchosia

capitata (ROTH) DC in mungbean” are product of my own research

and no part has been copied from any published source (except the

references, standard mathematical or genetic

models/equations/formulate/protocols etc.). I further declare that this

work has not been submitted for award of any other diploma/degree.

The university may take action if the information provided is found

inaccurate at any stage. (In case of any default, the scholar will be

proceeded against as per HEC plagiarism policy).

Hafiz Haider Ali

2003-ag-1638

iii

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ……………………………………………...…… i

DECLARATION……………………………………………………. ii

TABLE OF CONTENTS ………………………………………………….…. iii

LIST OF TABLES ………….………………………………………….….. xii

LIST OF FIGURES ………………………………………………………… xviii

ABBREVIATIONS…………………………………………………………….. xix

ABSTRACT …………………………………………………………………. xxi

1. Introduction…….…………………………………………………………………. 1

2. Review of Literature…..………………………………………………………… 8

2.1. Dormancy ……………….……………………………………………………. 8

2.2 Germination Ecology …………………………………………….………….… 10

2.2.1 Temperature effect on seed germination ecology ……..……………………. 10

2.2.2 Light effect on seed germination ecology. ………………………………… 11

2.2.3 Salinity effect on seed germination ecology.………………………………. 11

2.2.4 Drought effect on seed germination ecology.…………………………. 12

2.2.5 Burial depth effect on seed germination ecology.………………………… 13

2.2.6 pH effect on seed germination ecology.……………………….…………… 14

2.3. Allelopathic effect of weeds…………………………….………………………..... 14

2.4 Weed crop competition ……………………………..……………………………16

2.5 Chemical weed control ………………………..……….……………………………. 18

3. Materials and Methods …………………………..………………………………..…… 20

3.1 Experimental soil analysis ………………………………………….……………….20

iv

3.2 Experimental site ……………………………………….……………...…………. 20

3.3 Meteorological data ……………………………………….………………..………… …20

3.4 LABORATORY EXPERIMENTS……………………………………………...24

3.4.1 Methods to break seed dormancy of Rhynchosia capitata………………………..24

3.4.2 Collection of seeds for experiments………………………………….…….. …24

3.4.3 Effect of dry heat seed treatment on dormancy release and germination of R.

capitata…………………………………………………………………….24

3.4.4 Effect of hot water seed treatment on dormancy release and germination of R.

capitata…………………………………………………………………….25

3.4.5 Effect of stratification on dormancy release and germination of R.

capitata…………………………………………………………………….25

3.4.6 Effect of seed treatment with KNO3 and thiourea on dormancy release and

germination of R. capitata………………………………………………..26

3.4.7 Effect of seed scarification with HCl and sand paper on dormancy release and

germination of R. capitata………………………….…………………….27

3.4.8 Effect of seed scarification with HNO3 on dormancy release and germination of

R. capitata………………………………………………………….……...27

3.4.9 Effect of seed scarification with H2SO4 on dormancy release and germination of

R. capitata…………………………………………………………………28

3.4.10 Effect of seed scarification with HCl + H2SO4 on dormancy release and


3.4.11 Effect of seed scarification with HNO3 + H2SO4 on dormancy release and


3.4.12 Germination test……………………………………………………………29

3.5 Seed germination ecology of R. capitata……………………………………..………30

3.5.1 Effect of temperature on the germination of R. capitata…………………..30

v

3.5.2 Effect of light and darkness on the germination of R. capitata.....…. …………30

3.5.3 Effect of different levels of salt stress on the germination of R. capitata.........31

3.5.4 Effect of different levels of osmotic potential on the germination of R.

capitata………………………………………………………………31

3.5.5 Effect of different levels of pH on the germination of R. capitata. …………32

3.5.6 Effect of different levels of sowing depth on the seedling emergence of R.

capitata………………………………………………………………32

3.5.7 Germination test. ……………………………………………………………..33

3.6 Allelopathic effects of Rhynchosia capitata (ROTH) DC on germination and seedling

growth of mungbean………………………………………………………………..34

3.6.1 Collection of plants……………………………………………………………..34

3.6.2 Preparation of water extracts of R. capitata…………………………………….34

3.6.3 Lab bioassay: Effect of water extracts of R. capitata plant parts on the

germination of mungbean …………………………………………34

3.6.4 Soil bioassay. Effect of different concentrations of R. capitata -infested soil on

the mungbean seedlings……………………………………………34

3.6.5 Determination of total soluble phenolics in R. capitata ………………….....35

3.6.6 Detection of Phytotoxins in aqueous R. capitata extracts ……………….….36

3.7 Collection of Data…………………………………………….…………………………37

3.7.1 Seed germination………………………………………………………………37

3.7.2 Seedling Emergence………….………………………………………………..37

3.7.3 Procedure for recording observations…………………….…………………..37

3.7.3.1Germination/emergence (%)…………………………………………………..37

3.7.3.2 Germination/emergence index (GI/EI)……………………………………… 38

vi

3.7.3.3 Time to 50% germination/emergence (days)……………………………..38

3.7.3.4 Mean germination/emergence time (MGT/MET)……….……………….38

3.7.3.5 Root and shoot dry weight (mg)…………………………………............39

3.7.3.6 Root length (cm)…………………………………………………………..39

3.7.3.7 Shoot length (cm)…………………..………………………………………...39

3.7.3.8 Seedling vigor index…………………………………………….…………39

3.8 Statistical Analysis…..…………………………………………………….…………..39

3.8 Field Experiment 1………………………..….……………………………………….41

3.8.1 Treatments……..………………….……..………….……………………….41

3.8.2 Seed bed preparation………………….……………………………………...41

3.8.3 Sowing……….…………………………………..……………………………41

3.8.4 Irrigation…………………….....................................................................41

3.8.5 Fertilizer application ………………………………………………………….41

3.8.6 Layout….…..………………………………………………………………….42

3.8.7 Maintenance of weed competition periods..…………….……………..……42

3.8.8 Harvesting ..……………………………………………………………..……42

3.9 Field Experiment 2.…………………………………………………………………….43

3.9.1 Treatments …………………………….……………………………………..43

3.10 Data collection ………….………………………………….………………..………..44

3.10.1 Rhynchosia capitata …………………..…………………………………….44

3.10.2 Procedure for recording data………………………………………………..44

3.10.2.1 Weed population….………………………………………………………44

vii

3.10.2.2 Fresh weight of weed per unit area (g m-2)……………………………….44

3.10.2.3 Dry weight of weed per unit area (g m-2)…………………………………45

3.10.2.4 Number of pods per plant of Rhynchosia capitata….…………….………44

3.10.2.5 Number of seeds per pod of Rhynchosia capitata ……………………......45

3.10.2.6 NPK contents of Rhynchosia capitata..……….……………………….....45

3.10.2.7 NPK uptake by Rhynchosia capitata………………………………………45

3.10.2.8 Micro nutrient contents of Rhynchosia capitata ..……………………….45

3.10.2.9 Micro nutrient uptake by Rhynchosia capitata…………………………..45

3.10.2.10 Weed control efficiency…………………..……………………….……..45

3.10.2.11 Relative competitive index……..………………………………………..46

3.10.3 Mungbean…………..…………………………...………………….…….....46

3.10.3.1 Plant population……………………..…………………………………….46

3.10.3.2 Plant height (cm)……………………………………..………….……….46

3.10.3.3 No. of pods per plant..…………………….…………………………......46

3.10.3.4 No. of grains per pod ….…………………………………......................47

3.10.3.5 1000- grain weight (g)........................................................................47

3.10.3.6 Biological yield (Kg ha-1) ……………….……………………………….47

3.10.3.7 Grain yield (Kg ha-1)……………………..……………………………….47

3.10.3.8 Percent yield increase over weedy check……….………………………..47

3.10.3.9 Harvest index (%)…………………………………………………………47

3.10.4 Economic analysis……………………………………………………………..…....48

3.10.4.1 Net benefits ………………………………………………………………48

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3.10.4.2 Dominance analysis ..………………………..…………………………..48

3.10.4.3 Marginal analysis .………………………………………………………..48

3.10.4.4 Marginal rate of return ..…………………………………………….48

3.10.5 Statistical analysis………………………………………………………………….49

4. Results and Discussion…………………………………………………………………………..50

4.1 Laboratory experiments:………………………..………..………………………………..50

4.1.1 Methods to break seed dormancy of Rhynchosia capitata (ROTH) DC.…….. ….50

4.1.2 Dry heat, hot water and stratification seed treatment...................................50

4.1.3 Seed treatment with thiourea and KNO3…………………….………………53

4.1.4 Scarification with HCl and sand paper………………………….……………..54

4.1.5 Scarification with HNO3…………………………………………………….....56

4.1.6 Scarification with H2SO4………………………………………….…………….56

4.1.7 Scarification with HCl + H2SO4………………..………………………………58

4.1.8 Scarification with HNO3 + H2SO4………………………………………………60

4.2 Seed Germination ecology of R. capitata……………………………….......................63

4.2.1 Temperature and Light.…………………………………….…………………...63

4.2.2 Salt Stress………..……………………………………..……………………..64

4.2.3 Osmotic Stress ..………………………………….…………………………....66

4.2.4 pH ……………………………………………………………………………….68

4.3.5 Burial Depth ……………………………………………………………….........70

4.3 Allelopathic effects of Rhynchosia capitata (ROTH) DC on germination and seedling

growth of mungbean.…………………………….…………………………………73

ix

4.3.1 Allelopathic effects of different plant parts of R. capitata on germination of

mungbean……………………………………………………………..73

4.3.2 Effect of different concentrations of leaf extracts of R. capitata on the

germination of mungbean ……………………………………………75

4.3.3 Effects of different concentrations of R. capitata soil incorporated residues on the

seedling emergence of mungbean……………………………………77

4.4 FIELD EXPERIMENT 1…..……………………………………………………………..81

4.4.1 Effect of weed competition periods on fresh weight of R. capitata (gm-2)……81

4.4.2 Effect of weed competition periods on dry weight of R. capitata (gm-2)……..81

4.4.3 Effect of weed competition periods on NPK contents (%) of R. capitata…….85

4.4.4 Effect of weed competition periods on NPK uptake (kg/ha) of R. capitata…..89

4.4.5 Effect of weed competition periods on Fe, Mn, Na and Zn contents (mg/Kg) of R.

capitata ………………………………………………………………………..93

4.4.6 Effect of weed competition periods on Ca content (%) of R. capitata ………..93

4.4.7 Effect of weed competition periods on Cu and Mg contents of R. capitata …..99

4.4.8 Effect of weed competition periods on Fe and Mn uptake by R. capitata …….102

4.4.9 Effect of weed competition periods on Na and Zn uptake by R. capitata ……102

4.4.10 Effect of weed competition periods on Ca, Cu and Mg uptake of R.

capitata……………………………………………………………………….107

4.4.11 Effect of weed competition periods on plant height of mungbean……………111

4.4.12 Effect of weed competition periods on number of pods per plant of

mungbean……………………………………………………………………..113

4.4.13 Effect of weed competition periods on number of grains per pod of

mungbean…………………………………………………………………......115

4.4.14 Effect of weed competition periods on 1000-grain weight (g) of

mungbean…………………………………………………………………….117

4.4.15 Effect of weed competition periods on biological yield (kg/ha) of

mungbean…………………………………………………………………….119

4.4.16 Effect of weed competition periods on grain yield (kg/ha) of

mungbean…………………………………………………………………….121

x

4.4.17 Effect of weed competition periods on relative competitive index (RCI) of R.

capitata……………………………………………………………………….124

4.4.18 Effect of weed competition periods on harvest index (%) of mungbean …….125

4.5 FIELD EXPERIMENT 2 ………………………………………………………………..127

4.5.1 Effect of herbicides on the number of weeds m-2 21 days after sowing in mungbean..127

4.5.2 Effect of herbicides on the number of pods per plant of R………………………..129

4.5.3 Effect of herbicides on the number of seeds per pod of R. capitata……………….129

4.5.4 Effect of herbicides on the fresh weight of weeds m-2 in mungbean at harvest……133

4.5.5 Effect of herbicides on the dry weight of weeds m-2 in mungbean at harvest……….135

4.5.6 Effect of herbicides on R. capitata control efficiency in mungbean…………...137

4.5.7 Effect of herbicides on N content (%) of R. capitata.…………………………….. 139

4.5.8 Effect of herbicides on P content (%) of R. capitata at harvest ……………………..139

4.5.9 Effect of herbicides on K content (%) of R. capitata at harvest…………………….140

4.5.10 Effect of herbicides on the N uptake (kg/ha) by R. capitata at harvest.………… 144

4.5.11 Effect of herbicides on P uptake (kg/ha) of R. capitata at harvest………………….144

4.5.12 Effect of herbicides on K uptake (kg/ha) of R. capitata at harvest.………………145

4.5.13 Effect of herbicides on Fe and Mn (mg/kg) content of R. capitata in mungbean at

harvest……………………………………………………………………………..149

4.5.14 Effect of herbicides on Na and Zn (mg/kg) content of R. capitata in mungbean at

harvest……………………………………………………………………………..152

4.5.15 Effect of herbicides on Ca (%) content of R. capitata in mungbean at harvest….…155

4.5.16 Effect of herbicides on Cu and Mg (mg/kg) content of R. capitata in mungbean at

harvest………………………………………………………………………………155

4.5.17 Effect of herbicides on Fe and Mn uptake (g/ha) of R. capitata at harvest……….159

xi

4.5.18 Effect of herbicides on Na and Zn uptake (g/ha) of R. capitata at harvest………162

4.5.19 Effect of herbicides on Ca, Cu and Mg uptake (kg/ha) of R. capitata at harvest….165

4.5.20 Effect of herbicides on plant height (cm) of mungbean………………………169

4.5.21 Effect of herbicides on number of pods per plant of mungbean…………….171

4.5.22 Effect of herbicides on number of grains per pod of mungbean……………..173

4.5.23 Effect of herbicides on 1000-grain weight (g) of mungbean…………………175

4.5.24 Effect of herbicides on biological yield (kg/ha) of mungbean…………….….177

4.5.25 Effect of herbicides on grain yield (kg/ha) of mungbean……………………..179

4.5.26 Effect of herbicides on harvest index of mungbean…………………………..182

4.5.27 Economic analysis…………………………………………………………….184

4.5.28 Dominance analyses…………………………………………………………..184

4.5.29 Marginal analyses …………………………………………………………….184

5. SUMMERY……………………………………………………………………………….188

Literature Cited……………………………………………………………………..194

xii

LIST OF TABLES

Table Page

3.1 Physico-chemical soil analysis of experimental area……………………… 22

3.2 Meteorological data during the crop growing season 2010, 2011 and 2012… 23

3.3 Determination of total water soluble phenolics in different plant parts of R.

capitata………………………………………………………………………. 36

4.1 Effect of dry heat seed treatment on breaking dormancy and germination of

Rhynchosia capitata…………………………………………………………. 51

4.1.2 Effect of hot water seed treatment on breaking dormancy and germination

of Rhynchosia capitata………………………………………………………. 51

4.1.3 Effect of cold stratification or prechilling seed treatment on breaking

dormancy and germination of Rhynchosia capitata…………………………. 52

4.1.4 Effect of potassium nitrate (KNO3) seed treatment on breaking dormancy

and germination of Rhynchosia capitata…………………………………….. 53

4.1. 5 Effect of thiourea [(NH2)2CS] seed treatment on breaking dormancy and

germination of Rhynchosia capitata………………………………………… 53

4.1.6 Effect of seed scarification with HCl and sand paper on breaking dormancy

and germination of Rhynchosia capitata……………………………………. 55

4.1.7 Effect of seed scarification with HNO3 on breaking dormancy and

germination of Rhynchosia capitata………………………………………… 57

4.1.8 Effect of seed scarification with HCl + H2SO4 on dormancy release and

germination of R. capitata…………………………………………………… 59

4.1.9 Effect of seed scarification with HNO3 + H2SO4 on dormancy release and

germination of R. capitata…………………………………………………… 60

4.2.1 Effect of different level of temperature on the germination of R. capitata…. 63

4.2.2 Effect of different levels of salt stress on the germination of R. capitata.. … 65

4.2.3 Effect of different levels of osmotic potential on the germination of R.

capitata……………………………………………………………………………….. 67

4.2.4 Effect of different levels of pH on the germination of R. capitata…………… 69

4.2.5 Effect of different levels of sowing depth on the seedling emergence of R. 71

xiii

capitata. ……………………………………………………………………………

4.3.1 Effect of R. capitata extract on the germination traits of mungbean……… 74

4.3.2 Effect of different concentrations of R. capitata leaf extract on the

germination traits of mungbean…………………………………………….. 76

4.3.3 Effect of R. capitata -infested soil on the germination indices and seedling

characteristics of mungbean………………………………………………… 79

4.4.1 Effect of different weed-crop competition periods on fresh weight of R.

capitata (gm-2) in mungbean………………………………………………… 83

4.4.2 Effect of different weed-crop competition periods on dry weight of R.

capitata (gm-2) in mungbean………………………………………………… 84

4.4.3 Effect of different weed-crop competition periods on N content (%) of R.

capitata………………………………………………………………………. 86

4.4.4 Effect of different weed-crop competition periods on P content (%) of R.

capitata………………………………………………………………………. 87

4.4.5 Effect of different weed-crop competition periods on K content (%) of R.

capitata………………………………………………………………………. 88

4.4.6 Effect of different weed-crop competition periods on N uptake (kg/ha) by R.

capitata………………………………………………………………………. 90

4.4.7 Effect of different weed-crop competition periods on P uptake (kg/ha) of R.

capitata………………………………………………………………………. 91

4.4.8 Effect of different weed-crop competition periods on K uptake (kg/ha) of R.

capitata………………………………………………………………………. 92

4.4.9 Effect of different weed-crop competition periods on Fe contents (mg/kg) of

R. capitata…………………………………………………………………… 94

4.4.10 Effect of different weed-crop competition periods on Mn content (mg/kg) of

R. capitata…………………………………………………………………… 95

4.4.11 Effect of different weed-crop competition periods on Zn content (mg/kg) of

R. capitata…………………………………………………………………… 96

4.4.12

Effect of different weed-crop competition periods on Na content (mg/kg) of

R. capitata……………………………………………………………………

xiv

97

4.4.13 Effect of different weed-crop competition periods on Ca content (%) of R.

capitata………………………………………………………………………. 98

4.4.14 Effect of different weed-crop competition periods on Cu content (mg/kg) of

R. capitata…………………………………………………………………… 100

4.4.15 Effect of different weed-crop competition periods on Mg content (mg/kg) of

R. capitata…………………………………………………………………… 101

4.4.16 Effect of different weed-crop competition periods on Fe uptake (g/ha) of R.

capitata……………………………………………………………………… 103

4.4.17 Effect of different weed-crop competition periods on Mn uptake (g/ha) of R.

capitata……………………………………………………………………… 104

4.4.18 Effect of different weed-crop competition periods on Na uptake (g/ha) of R.

capitata……………………………………………………………………… 105

4.4.19 Effect of different weed-crop competition periods on Zn uptake (g/ha) of R.

capitata………………………………………………………………………. 106

4.4.20 Effect of different weed-crop competition periods on Ca uptake (kg/ha) of

R. capitata…………………………………………………………………… 108

4.4.21 Effect of different weed-crop competition periods on Cu uptake (g/ha) of R.

capitata………………………………………………………………………. 109

4.4.22 Effect of different weed-crop competition periods on Mg uptake (kg/ha) of

R. capitata…………………………………………………………………… 110

4.4.23 Effect of different weed-crop competition periods on plant height of

mungbean……………………………………………………………………. 112

4.4.24 Effect of different weed-crop competition periods on number of pods per

plant of mungbean………………………………………………………….. 114

4.4.25 Effect of different weed-crop competition periods on the number of grains

per pod of mungbean………………………………………………………… 116

4.4.26 Effect of different weed-crop competition periods on 1000-grain weight (g)

of mungbean…………………………………………………………………. 118

4.4.27 Effect of different weed-crop competition periods on biological yield

(kg/ha) of mungbean……………………………………………………….. 120

xv

4.4.28 Effect of different weed-crop competition periods on seed yield (kg/ha) of

mungbean…………………………………………………………………… 123

4.4.29 Effect of weed competition periods on R. capitata relative competitive

index (RCI)………………………………………………………………….. 124

4.4.30 Effect of different weed-crop competition periods on harvest index of

mungbean……………………………………………………………………. 126

4.5.1 Effect of application of different herbicide treatments on the number of

weeds m-2 20 days after sowing in mungbean. ……………………………… 128

4.5.2 Effect of application of different herbicide treatments on the number of

pods per plant of R. capitata. ………………………………………………. 131

4.5.3 Effect of application of different herbicide treatments on number of seeds

per pod of R. capitata……………………………………………………… 132

4.5.4 Effect of application of different herbicide treatments on fresh weight of R.

capitata m-2 in mungbean at harvest. ……………………………………… 134

4.5.5 Effect of application of different herbicide treatments on dry weight of

weeds m-2 in mungbean at harvest…………………………………………. 136

4.5.6 Effect of application of different herbicide treatments on N content (%) of

R. capitata………………………………………………………………….. 141

4.5.7 Effect of application of different herbicide treatments on P content (%) of R.

capitata at harvest…………………………………………………………… 142

4.5.8 Effect of application of different herbicide treatments on K content (%) of

R. capitata at harvest………………………………………………………. 143

4.5.9 Effect of application of different herbicide treatments on N uptake (kg/ha)

by R. capitata at harvest……………………………………………………. 146

4.5.10 Effect of application of different herbicide treatments on P uptake (kg/ha) of

R. capitata at harvest………………………………………………………. 147

4.5.11 Effect of application of different herbicide treatments on K uptake (kg/ha)

of R. capitata at harvest……………………………………………………. 148

4.5.12 Effect of application of different herbicide treatments on Fe (mg/kg) content

of R. capitata in mungbean at harvest……………………………………… 150

4.5.13 Effect of application of different herbicide treatments on Mn (mg/kg) 151

xvi

content of R. capitata in mungbean at harvest………………………………

4.5.14 Effect of application of different herbicide treatments on Na (mg/kg)

content of R. capitata in mungbean at harvest………………………………. 153

4.5.15 Effect of application of different herbicide treatments on Zn (mg/kg)

content of R. capitata in mungbean at harvest……………………………… 154

4.5.16 Effect of application of different herbicide treatments on the Ca (%) content

of R. capitata in mungbean at harvest………………………………………. 156

4.5.17 Effect of application of different herbicide treatments on Cu (mg/kg)

content of R. capitata in mungbean at harvest………………………………. 157

4.5.18 Effect of application of different herbicide treatments on Mg (mg/kg)

content of R. capitata in mungbean at harvest……………………………… 158

4.5.19 Effect of application of different herbicide treatments on Fe uptake (g/ha) of

R. capitata at harvest……………………………………………………….. 160

4.5.20 Effect of application of different herbicide treatments on Mn uptake (g/ha)


4.5.21 Effect of application of different herbicide treatments on Na uptake (g/ha)

of R. capitata at harvest…………………………………………………….. 163

4.5.22 Effect of application of different herbicide treatments on Zn uptake (g/ha)


4.5.23 Effect of application of different herbicide treatments on Ca uptake (kg/ha)


4.5.24 Effect of application of different herbicide treatments on Cu uptake (g/ha)


4.5.25 Effect of application of different herbicide treatments on Mg uptake (g/ha)


4.5.26 Effect of application of different herbicide treatments on plant height (cm)

of mungbean………………………………………………………………… 170

4.5.27 Effect of application of different herbicide treatments on number of pods

per plant of mungbean……………………………………………………… 172

4.5.28 Effect of application of different herbicide treatments on number of grains

per pod of mungbean……………………………………………………….. 174

xvii

4.5.29 Effect of application of different herbicide treatments on 1000-grain weight

(g) of mungbean…………………………………………………………… 176

4.5.30 Effect of application of different herbicide treatments on biological yield

(kg/ha) of mungbean…………………………………………………........ 178

4.5.31 Effect of application of different herbicide treatments on grain yield (kg/ha)

of mungbean……………………………………………………………….. 181

4.5.32 Effect of application of different herbicide treatments on harvest index of

mungbean…………………………………………………………………… 183

4.5.33 Effect of application of different herbicide treatments on economic returns during 2010…………………………………………………………………. 185

4.5.34 Effect of application of different herbicide treatments on economic returns during 2011…………………………………………………………………. 185

4.5.35 Dominance analysis of different herbicide treatments during 2010………… 186

4.5.36 Dominance analysis of different herbicide treatments during 2011………… 186

4.5.37 Marginal rate of return of different herbicide treatments during 2010…….. 187

4.5.38 Marginal rate of return of different herbicide treatments during 2011……… 187

xviii

LIST OF FIGURES

Figure Page

1.1 Rhynchosia capitata plant characteristics…………………………………….. 5

1.2 A heavily infested field with R. capitata……………………………………… 5

4.1.1 Effect of seed scarification with H2SO4 on germination of Rhynchosia

capitata………………………………………………………………………… 57

4.1.2 Effect of seed scarification with H2SO4 on T50, MGT and GI of Rhynchosia

capitata……………………………………………………………………….. 58

4.2.1 Effect of sodium chloride (NaCl) concentration on germination of R. capitata.

……………………………………………………………………..... 65

4.2.2 Effect of osmotic potential on germination of R. capiata seeds……………… 67

4.2.3 Effect of planting depths on emergence of R. capitata seedlings……………. 71

4.3.1 Effect of R. capitata extract on the germination of mungbean……………… 74

4.3.2 Effect of different concentrations of R. capitata leaf extract on the

germination percentage of mungbean ……………………………………….. 76

4.3.3 Determination of total water soluble phenolics in different plant parts of R.

capitata………………………………………………………………………… 77

4.3.4 Effect of R. capitata -infested soil on the seedling emergence percentage of

mungbean……………………………………………………………………… 78

4.5.1 Effect of application of different herbicide treatments on weed control

efficiency in mungbean……………………………………………………….. 138

xix

ABBREVIATIONS

Abbreviation Full

% percent

a.i. active ingredient

cm centimeter (s)

d day (s)

E50 time to 50% emergence

EI emergence index

g gram (s)

g m-2 gram per square meter

GI germination index

h hour (s)

ha hectare

ha-1 per hectare

K Potassium

kg kilogram

kg ha-1 kilogram per hectare

L Litter

LSD Least Significant Difference

m meter

m-2 per square meter

MET mean emergence time

MGT mean germination time

ml millilitter

mm millimeter

mM milli Molar

MPa Mega Pascal

N Nitrogen

NS non-significant

P Phosphorus

xx

Rs. Rupees

T50 time to 50% germination

WCE Weed control efficiency

wk Week

xxi

ABSTRACT

Studies on dormancy, ecology, phytotoxic effects, competition and chemical control of Rhynchosia capitata (Roth) DC in mungbean (Vigna radiata (L.) Wilczek) were investigated in the laboratory experiments at Department of Agronomy, University of Agriculture, Faisalabad and under farmer’s field conditions. In laboratory experiments different treatments for breaking dormancy of R. capitata seeds were evaluated. Seeds were soaked in thiourea, KNO3, HCl, HNO3 and H2SO4 as well as scarified mechanically (sand paper). Results indicated that seeds of R. capitata show signs of physical dormancy that is mainly because of impermeability of their coat. Mechanical scarification, acid scarification (soaking of seeds in H2SO4 for 60 and 80 and in HCl for 12 and 15 h) were very effective in breaking dormancy and promoting germination. Seed soaking in HNO3 for 1 to 5 days showed little effect, while, various concentrations of thiourea and KNO3 were ineffective in breaking seed dormancy of R. capitata. Germination response of R. capitata to environmental factors such as temperature, salt stress, drought stress, pH, light and seeding depth were also studied. Germination increased as the temperature increased from 25oC and considerably reduced at 45oC. Germination of R. capitata seeds was not influenced by presence or absence of light. Increase in salt stress, moisture stress and seed burial depth significantly decreased the seed germination of R. capitata. Seeds of R. capitata had ability to germinate over a wide range of pH (5-10). In seed burial trial, maximum seedling emergence of 93 % was recorded at 2 cm depth, and seedlings failed to emerge from a depth of 12 cm. In third laboratory experiment, allelopathic influence of R. capitata on germination and seedling growth of mungbean along with detection of the phytotoxic materials liable for this action were studied. Aqueous extracts of root, shoot, leaf, fruit and whole plant (5%) adversely affected germination and seedling growth of mungbean, but higher inhibition was seen with R. capitata leaf water extract. A linear decrease in the germination characteristics of mungbean was observed with the decrease in the concentration of leaf extract from 5% to 1%. The soil incorporated residues (1-4% w/w) of R. capitata stimulated the development of root and hypocotyl at low concentrations and inhibited their development at elevated concentrations. Rhynchosia capitata soil incorporated residues (4% w/w) significantly reduced the seedling vigour index of mungbean in addition to its significant effect on total germination. A noteworthy amount of water soluble phenolic acids were found in extracts of different plant parts of R. capitata. Total phenolic acids were greater in leaf extract compared to that of stem, fruit or root extracts. Two phenolic acids, vanillic acid and 4-(hydroxymethyl) benzoic acid were found in R. capitata leaf extract. Effect of different weed crop competition periods i.e. full season competition, weed crop competition for 3, 4, 5, 6, 7 weeks and zero competition were studied under field conditions on mungbean. The results showed that full season weed competition produced highest weed fresh and dry weight, maximum NPK contents (%) and NPK uptake, highest Fe, Mn, Na, Zn, Ca, Cu and Mg contents and micronutrients uptake by R. capitata in both the years of study. The maximum plant height, number of pods per plant, grain number per pod and 1000-grain weight of mungbean was recorded in weed free plots. Increase in competition period decreased above parameters of mungbean significantly. Increase in R. capitata competition period decreased the mungbean grain yield significantly. In 2011, the weed-free plots gave the highest grain yield of 1688.6 kg ha-1 followed by competition 3 weeks after planting with 1582.0 kg ha-1 of seed

xxii

yield. The full season R. capitata competition decreased the grain yield to 869.3 kg ha-1. Similar trend was also observed during 2012. In second field experiment, the efficacy of herbicides namely pendimethalin + prometryn @ 875 g, 700 g and 525 g a.i ha-1, S-metolachlor @ 1440 g a.i ha-1 and pendimethalin @ 825 g a.i ha-1 in controlling R. capitata was evaluated. All doses of the herbicides suppressed the dry biomass of R. capitata from 60 to 78% in 2010 and 2011. Pendimethalin+prometryn @ 875g a.i. ha-1, recorded (74% in 2010 and 78% in 2011) maximum reduction in total weed dry weight. Among herbicide treatments, maximum grain yield was recorded with pendimethalin+prometryn @ 875 g a.i. ha-1 in both the years. Pendimethalin + prometryn @ 875 g a.i. ha-1 proved best treatments for effective control of R. capitata in mungbean and to get maximum economic benefits.

1

CHAPTER 1

Introduction

Pulses are the major source of high quality protein in Pakistan. Mungbean (Vigna

radiata (L.) Wilczek) is one of the major pulse crops in the irrigated and dry areas of

Pakistan. It is popular because of its short growth duration (70-90 days) and adaptation to

diverse agro-ecological conditions. The crop is potentially useful in improving

cropping pattern as it can be grown as a catch crop due to its rapid growth and

early maturing characteristics. It can also fix atmospheric nitrogen through the

symbiotic relationship between the host mungbean roots and soil bacteria and thus

improves soil fertility. It may play an important role to supplement protein in the

cereal-based low-protein diet of the people of Pakistan, but the acreage and

production of mungbean is steadily declining. In 2009, mungbean cultivated area was

231,100 ha and production was 157,400 t which is 11.3 % less than the previous year

(Government of Pakistan, 2012).

In Pakistan, the mungbean grain yield (760 kg ha-1) is much lower than the potential

(1800 to 2000 kg ha-1) yield (Arshad et al., 2008; Government of Pakistan, 2012). The

main factors which contribute towards low yield of crop include high cost of inputs,

conventional sowing methods, sowing on marginal land, low or no use of fertilizers and poor

weed management practices. Weed infestation is one of the most important factors

responsible for low yield of mungbean in Pakistan. Uncontrolled weeds can cause significant

reduction in mungbean grain yield which range from 27 to 100% (Malik et al., 2000; Pandey

and Mishra, 2003; Raman and Krishnamoorthy, 2005), depending upon type of weeds,

density of weeds, infestation duration of weeds, crop sowing time and method, growth stage,

fertilizer application method and other environmental factors (Mansoor et al., 2004; Arshad

et al., 2008).

An understanding of weed seed dormancy mechanisms is of ecological and economic

importance. Interactions of many environmental, edaphic, physiological and genetic factors

regulate weed seed dormancy in an agricultural system, (Radosevich et al., 1996). The

2

relationship between seed dormancy and success of a plant as an agricultural weed is

significant. Weed seeds vary extensively with respect to degree, duration, and basis of

dormancy. The existence of large population of weed seeds with varying degrees and states

of dormancy is the main reason for the annual weed problem. Seed germination is an

important factor in the determination of success of a weed in field conditions (Koger et al.,

2004). Numerous ecological characteristics, for example, temperature, light, pH and moisture

affect germination of weed seeds (Rizzardi et al., 2009). A few weeds grow throughout the

year, mainly due to their ability to germinate in a wide temperature range (Widderick et al.,

2004).

Temperature performs an imperative role in the determination of periodicity of the

germination of the seed and the distribution of the species (Gu et al., 2009). The germination

rate generally increases linearly with temperature, at least within a well-defined range and

significantly reduces at higher temperatures (Alvarado and Bradford, 2002). Seeds of some

weeds germinate well in dark and light and broad leaf weeds having small seeds are

photoblastic (Zhou et al., 2005). Some weed seeds can germinate in a wide pH range

(Chachalis and Reddy, 2000), while other weeds germinate well in acidic soils (Fried et al.,

2008). Other major factors that affect seed germination are water potential and salinity.

Studies have demonstrated that salinity may delay, reduce or prevent germination (Zhou et

al., 2005). Lack of moisture may also delay, reduce or prevent the germination and plant

growth (Norsworthy and Oliveira, 2005). In addition to these factors, the germination is also

affected by sowing depth (Norsworthy and Oliveira, 2006). Burial depth affects seed

germination and seedling emergence (Koger et al., 2004), and these depths vary in moisture

availability, diurnal temperature changes and exposure to light. All these attributes of the

microenvironment have the potential to influence the behaviour of the weed seeds.

Information on the factors that influence germination behaviour of weed seeds would be

useful in developing tillage and sowing systems that discourage establishment of weeds in

field crops.

Understanding the weed germination ecology is pre requisite for effective weed

management (Fenner and Thompson, 2005). Weeds are found in the environment they prefer

and weed control or weed management is to make the environment unfavorable for them

3

(Zimdahl, 1980). A comprehensive understanding of the factors influencing the germination

of weed seeds could facilitate the development of more effective weed management practices

through either suppressing germination or encouraging germination at times when seedlings

can be readily controlled (Chauhan and Johnson, 2010).

Weed species may interfere with plant growth through allelopathic mechanisms

(Putnam and Tang, 1986). Studies reported that several weed species hindered the growth

and development of crops (Dongre and Singh, 2007). The inhibitory action of weeds to the

crops is generally associated with the release of allelochemicals from their seeds, decaying

plant residues, leachates, exudates and volatiles from various plant parts (Narwal, 2004).

Allelopathy is also an important mechanism that facilitates a plant to ascertain itself in new

environments (Callaway and Aschehoug, 2000; Ridenour and Callaway, 2001). The

allelochemicals released from the weed plants are very important in determining the diversity

of these plants, their dominance in new ecosystems, succession after their dominance, climax

and eventually the productivity of these plants in agricultural systems (Chon and Nelson,

2010).

One of the most important aspects of all biological factors that reduce crop yield

considerably is competition of crops from weeds (Deen et al., 2003). This happens mainly

because weeds uses resources that otherwise would be available to the crops (McDonald et

al., 2004). Numerous studies have evaluated the duration and density of weed species in a

variety of crops and measured the significance of competition period and the timing of weed

control from the field (Norsworthy and Oliveira, 2004). Competition is the main aspect of

noxious weeds on crops. Because weeds and crops largely use the same resources for growth,

will compete when these resources are limited (Zimdahl, 1980). When weeds emerge in

newly establishing crop, the amount of resources already used by weeds or crops before the

competition starts is determined by the time of occurrence, relative growth rate and

population density (Knezevic et al., 2002). Weed management approaches that decrease

weed density or make best use of space or nutrient uptake by the crop, reduce the

competition consequences of weeds in crops (Bukun, 2004). Knowledge of competition of

weeds in crops and the factors affecting it, is necessary for taking right decisions for suitable

timings of weed management and also proficient use of herbicides (Evans et al., 2003).

4

There are different approaches to control weeds like manual or mechanical method,

cultural, biological and chemical methods. High yielding varieties of crops have little

tolerance from competition of weeds. Consequently, for the successful production of these

crops, it is prerequisite to use appropriate herbicides to control weeds. These herbicide must

be poisonous to the weeds, but not to the crop species. Herbicides (chemical control)

efficiently lessen density of weed plants in an agricultural system and also have a significant

and quick effect on the composition of weed species (Radosevich et al., 2007). As there is no

information on the use of appropriate herbicides for the control of newly emerging weed

species like Rhynchosia capitata, there is a dire need to evaluate herbicides for their

effectiveness in controlling R. capitata in mungbean. As mungbean is very tender and

sensitive crop to herbicides, study about effective control of R. capitata in mungbean is very

necessary to manage R. capitata problem and to increase mungbean yield.

The genus Rhynchosia of Fabaceae family is widely distributed in the mountainous

regions of the tropics. Rhynchosia capitata, an emerging annual summer season weed, is

indigenous to Pakistan (Jahan et al., 1994), India (Dogra et al., 2009), and Sri Lanka (ILDIS,

2010). It has invaded the cultivated areas of Southern Punjab of Pakistan and is increasingly

becoming a problematic weed in farming systems (Ali et al., 2011). In the field, this weed

emerges through the seed just after irrigation. It is twinning prostrate plant with many

branches spreading all around the rootstock and rooting at every node. An approximately one

month old plant starts flowering and the plant has oval-shaped pods with two seeds in each

pod (Sharma et al., 1978). The growing season is from May to October with minimum and

maximum average temperature of 29/21 ± 3 °C and 39/29 ± 3 °C, respectively, and average

rainfall of 650 mm (Ali et al., 2011).

5

Figure 1.1 Rhynchosia capitata plant characteristics

Figure 1.2 A heavily infested field with R. capitata.

6

Seed dormancy is major motive towards the success of this species, which permit the

seeds of this species to persist for long periods in the soil and thus escape the effects of post-

emergence weed control measures. The most successful weed management programs are

developed on the foundations of adequate ecological understandings. Knowledge of the

germination ecology of R. capitata would facilitate the development of an effective weed

control program. As there is no information about the dormancy, germination ecology,

allelopathic effects, competition and control of this species, its management is much difficult.

Keeping in view the importance of weed management in field crops and problem of R.

capitata in mungbean, the present study was planned with the following objectives;

1. To determine the dormancy behavior of R. capitata seeds in order to evolve effective

control strategy.

2. To determine the effect of temperature, light, salt stress, osmotic stress, seeding

depth, and pH on seed germination and seedling emergence of R. capitata.

3. To determine the effects of root, stem, leaf, fruit and whole plant water extracts and

soil infested with R. capitata on mungbean (Vigna radiate L.) germination and

seedling growth, and to determine water soluble and total phenolics responsible for

the allelopathic activity.

4. To study competitive effect of R. capitata on growth and yield of mungbean.

5. Optimize application of different herbicides in controlling R. capitata.

8

CHAPTER 2

REVIEW OF LITERATURE

2.1 Dormancy

Dormancy is a widespread feature of seeds of various weed species. It is a big

obstacle in the prediction of timing of weed seed germination and extent of emergence in

field situations (Roberto et al., 2000). Brasil (2009) examined that among 260 leguminoseae

seeds, about 85 % seeds had tegument impermeable to water. The existence of impermeable

layers of palisade cells in the seed coat is a most important factor for this seed tegument

impermeability to water (Baskin and Baskin, 1998). To overcome this type of dormancy,

deteriorating of the tegument is essential. The weakening of the tegument results into the

entry of water into the seed and start seed germination (Cavalheiro et al., 2007). This

phenomenon could also happen by the action of acids which usually takes place during the

process of digestion of seeds in the gut of dispersing animals (Russell et al., 2009).

Many species of Fabaceae family like seeds of Lupinus spp. exhibit dormancy that is

primarily due to seed coat water impermeability. Scarification of seeds of Texas bluebonnet

(Lupinus texensis Hook) with sulphuric acid for 30 to 60 min improved seedling emergence

(Davis et al., 1991). Acid scarification of big bend bluebonnet (Lupinus havardii S. Wats)

seeds for 120 min and perennial lupine (Lupinus perennis Wats.) seeds for 45 min,

respectively, resulted in 100% germination (Mackay et al., 1996). Sulphuric acid seed

treatment has been generally used to enhance germination of numerous hard seed coat

species (Tigabu and Oden, 2001).

Studies have been conducted to break licorice (Glycyrrhiza glabra L.) seed dormancy

by chemical and mechanical scarification treatments. Glycyrrhiza glabra L. seeds soaked in

sulfuric acid for 10 to 60 min germinated at 19 to 20°C (Shunkurullaev and Khamdamov,

1976). Maximum germination (98.3%) was obtained with seeds treated for 40 min. Only 7%

of control treatment seeds germinated. Khudahiber-genov and Mikhahilova (1972) showed

that untreated seeds of G. uralensis L. have 11% germination in the laboratory and 9% in the

field. Treatment in concentrated sulphuric acid increased germination from 60 to 94%. Seeds

germinated most vigorously at 40 to 50°C. Badalov and Pauzner (1979) demonstrated that

9

treatment of licorice seeds in 25 to 50 mg L-1 succinic acid combined with scarification in

sand increased laboratory and field germination. Soaking scarified seeds in 35 mg L-1

succinic acid for 24 hr increased laboratory germination to 98.7%.

The role of ecological features is very important in breaking the seed dormancy of

many legume species (Mucunguzi and Oryem-Origa, 1996; Teketay and Granstrom, 1997).

Generally, the buried viable weed seeds are present in the soil only due to the phenomenon of

dormancy. The presence of this dormancy in the weed species avoids the seed germination

even if the seeds get suitable environmental surroundings to germinate (Egley, 1989). The

impermeability of seed coat to water imbibitions also known as hardseededness, is the main

reason of seed dormancy of legume weeds. The presence of this phenomenon is an important

feature for the establishment of soil weed seed banks (Rice, 1989;Russi et al., 1992).

Presence of thin impermeable cuticle which prevents the seeds from imbibitions is also an

important feature of legume seeds (Baskin and Baskin, 1988).

Weed control is an integral part of efficient crop production that has assistance from

new methods of dormancy release (Gu et al., 2004). The intensity of dormancy differs

considerably between individual seeds within a given seed population (Baskin and Baskin,

1988). One of the most significant processes which decide the emergence of weed population

under field situations is most likely the changes in weed seed dormancy levels. It is very

essential to predict weed seed dormancy, timing and extent of weed emergence in field

condition to improve weed management approaches (Radosevich et al., 1996). Changes in

the intensities of weed seed dormancy may delay its germination in the soil profile over

many cropping seasons. Due to this reason, weed seedlings continue to emerge from soil in

field conditions constantly even after implementing comprehensive weed management

practices. It is very difficult to completely eliminate weeds from field due to the presence of

seed banks which are a major source of weed seeds with variable dormancy levels (Ali et al.,

2011).

10

2.2 Germination Ecology

One of the major objectives of seed germination ecology is how timing of

germination is organized in nature. Research on seed germination ecology helps to recognize

and explicate plant evolution and ecological adaptation (Baskin et al., 2004). Seed

germination is a susceptible stage in the plant life cycle and seedlings are frequently exposed

to variable environmental conditions. Consequently, for weed management, all chances for

mortality at seedling emergence stage of the weeds should be considered (Chauhan and

Johnson, 2009a). Germination plays an important role in crop/weed establishment and it is

affected by a number of factors (Bewley and Black, 1994). These factors include the state of

seeds itself i.e. dormancy, (Benech Arnold et al., 2000) temperature, light, salinity, pH,

sowing depth and water etc (Chachalis and Reddy, 2000; Koger et al., 2004; Chauhan and

Johnson, 2008, 2010). Only a thorough understanding of weed ecology can bring about

further improvements in current weed management practices. The extensive literature on

seed germination illustrates that germination is affected by numerous environmental factors

which include light, temperature, moisture and burial depth through tillage (Benech-Arnold

et al., 2000).

2.2.1 Temperature effect on seed germination ecology

As there is no information about R. capitata, some insights can be put on from the

related species of Fabaceae family. Temperature is the primary factor governing seed

germination. Many weed species have ability to germinate under wide range of temperature

levels. A range of alternating temperatures has little influence on germination of giant

sensitive plant (Mimosa invisa Mart.) seeds. Germination of seeds increased as exposure

temperature was increased from 25 °C to 120 °C but decreased progressively with additional

increases and there was no germination after exposure to 200 °C temperature (Chauhan and

Johnson, 2008). Owing to distribution of weed seeds at various soil depths, the germination

response of seeds may vary due to various soil temperatures and moisture levels. The weed

seed germination tend to increase as the temperatures was increased from 25 to160 °C, and

decrease gradually with further increases in temperature, and no germination was reported at

200°C temperature (Chauhan and Johnson, 2010). Similarly, Sicklepod (Senna obtusifolia

11

L.) germinated over a wide range of temperature of 15-50 oC and optimum temperature for

its germination was 15-30 oC. There was no germination of Sicklepod (S. obtusifolia L.) at 5,

10 and 12.5 oC (Norsworthy and Oliveira, 2006).

2.2.2 Light effect on seed germination ecology

Light is also considered as an imperative factor for the germination of weed seeds.

Many weed species respond to environment more readily with most favourable growth and

development according to the light stimulus (Maloof et al., 2000). Some seeds respond

uniformly in the presence and absence of light (Baskin and Baskin, 1988). However, some

species germinate easily even under complete light (Colbach et al., 2002) or darkness

surroundings (Thanos et al., 1989). Light enhanced the seed germination of sowthistle

(Sonchus oleraceus L.) but some seed germinated well in the dark (Chauhan et al., 2006a). In

another study, 100% seed germination of common sowthistle (Sonchus oleraceus L.) was

observed in light while the seed germination was 75% and 20% in darkness (Widderick et

al., 2004). Weed seed requirement for light could vary with temperature. It has been reported

that some species need a continuous temperature and light conditions to germinate. While,

some species has ability to germinate either under complete light or darkness under

alternating temperature conditions (Felippe, 1978). However, in many weed species like

Mimosa pudica L., the absence of light had no effect on the seed germination (Chauhan and

Johnson, 2009b). Similarly, in case of Mimosa invisa Mart., light is not a restrictive factor for

the germination of seeds (Chauhan and Johnson, 2008). Norsworthy and Oliveira (2006)

have also reported the similar results. They concluded that the sicklepod (Senna obtusifolia)

seed germination was not influenced by light. He observed 81% and 80% of seed

germination of sicklepod seed in natural light and in darkness, respectively.

2.2.3 Salinity effect on seed germination ecology

Salinity is considerable problem of most of the irrigated lands of Punjab, Pakistan

(Azhar and Tariq, 2003). Salts may also influence the seed germination by restricting the

12

availability of water or by causing injury through ions to the various metabolic systems of

seeds. Seeds of M. invisa have the ability to germinate when exposed to a broad range of

saline conditions. Seed germination of giant sensitive plant (Mimosa invisa L.) was tolerant

to NaCl concentration with greater than 90% germination up to a concentration of 100 mM

NaCl, and 55% germination occurred even at 250 mM NaCl. However, germination was

entirely hampered at 300 mM NaCl. The concentration for 50% inhibition of the maximum

germination, estimated was 255 ± 3.5 mM NaCl (Chauhan and Johnson, 2008). Germination

of Lotus creticus L. was significantly decreased when salt concentrations were increased to

levels higher than 300 mM (Rejili et al., 2009). The seed germination of the M. pudica

decreased with increased salt concentrations. Seed germination of M. pudica was observed

up to 40% even at 200 mmol L-1 of salt concentration, which showed that M. pudica was

tolerant to greater intensities of salt concentrations. However, the germination of this weed

was absolutely restrained at 300 mmol L-1 of salt concentration (Chauhan and Johnson,

2009b).

2.2.4 Drought effect on seed germination ecology

Other factors which may negatively affect the seed germination include mositure

stress (Wilson et al., 1985). Seeds exposed to unfavourable environmental conditions like

water stress have poor seedlings establishment (Albuquerque and Carvalho, 2003). Sicklepod

(S. obtusifolia) germination and radicle plus hypocotyl length decreased with decreasing

solution osmotic potential. Radicle plus hypocotyl elongation ceases when osmotic potentials

are below -0.5 MPa at 15 oC or less than -1 MPa at 30 oC during 7 day incubation

(Norsworthy and Oliveira, 2006). Similarly, Coffee senna (Cassia occidentalis L.)

germination was also affected by the interaction of solution osmotic potential and solution

pH with suboptimal and optimal temperatures (Norsworthy and Oliveira, 2005). The

germination of seeds of M. pudica reduced considerably with the decrease in the osmotic

potential from 0 to -1.0 MPa. No germination was reported at an osmotic potential of -1.0

MPa. However, 5% of the seeds still germinated at -0.8 MPa treatment which advocated that

M. pudica seeds had capacity to germinate under reasonable water stress situations (Chauhan

and Johnson, 2009b). Similarly, Germination of M. invisa decreased from 97 to 64% as

13

osmotic potential decreased from 0 to 20.8 MPa. No germination was reported at an osmotic

potential of 21.2 MPa. However, 13% germination occurred at 21.0 MPa treatment, which

suggests that seed of this species has ability to germinate under reasonable levels of water

stress conditions. The osmotic potential for 50% inhibition of the maximum germination was

-0.87 ± 0.03 MPa (Chauhan and Johnson, 2008).

2.2.5 Burial depth effect on seed germination ecology

Awareness about emergence patterns of weed seedlings from different soil depths is

important for successful implementation of many weed management strategies (Leon and

Owen, 2006). The location of weed seeds within the soil plays a significant role in seedling

emergence and seed survival (Reuss et al., 2001). Sicklepod (S. obtusifolia) emerged from a

10-cm depth in the sandy loam soil, but no emergence occurred in the sand soil at this depth.

Additionally, total germination increased by 6 and 43% for the sandy loam soil and the sand

soil compared with non covered seeds on the soil surface, respectively (Norsworthy and

Oliveira, 2006). The seed burial depth of M. pudica significantly affected its seedling

emergence; even then seedlings had ability to emerge from all burial depths (0–6 cm).

Seedling emergence rate from the seeds placed on the soil surface was 73%. However, the

emergence rate was 85 to 88% when the seeds were placed at the burial depths of 0.5 to 2

cm. Seedling emergence rate of M. pudica tend to decrease gradually as the seed burial depth

increased from 2 to 7 cm. Seedlings of M. pudica failed to emerge at the seed burial depth of

8 cm (Chauhan and Johnson, 2009b). Similarly, Chauhan and Johnson (2008) reported that

M. invisa seedlings emerged from all burial depths (0 to 8 cm). They observed that the

seedling emergence rate was 80 to 94% at depths of 0 to 2 cm. It tend to decrease

progressively as depth increased from 2 cm. Seedling emergence was completely inhibited at

the depth of 10 cm. Burial of weed seeds to variable depths may not only influence total

seedling recruitment from the soil, it could also affect the vigour of the seedlings that

establish (Cousens and Moss, 1990).Weed seed mortality in and on soil vary with weed

species, seed burial depth and soil disturbances (Mohler, 2001).

14

2.2.6 Effect of pH on seed germination ecology

For seed germination and subsequent growth of plants in the laboratory and under

field situations, plants required an optimal level of pH. Many weed seeds can germinate over

a broad array of pH (Chauhan and Johnson, 2008). Lefevre (1956) reviewed the pH tolerance

of 60 weeds and grouped them into Basophile (love basic soils), e.g., sow thistles (Sonchus

oleraceus), green sorrel (Rumex acetosa L.), quack grass (Elymus repens L.), and dandelion

(Taraxacum officinale); acidophile (love acid soil), e.g., red sorrel (Rumex cetosella), corn

marigold (Chrysanthemum segetum L.), and neutrophile. Generally, the seeds of Fabaceae

family are sensitive to acidity (Brkic et al., 2004). Norsworthy and Oliveira (2006) found that

Sicklepod (S. obtusifolia) germinated from pH 3 to pH 9, with predicted maximum

germination at a solution pH of 6.1. The range of pH in solution for optimum germination,

based on means separation, was from pH 5 to 7. Sicklepod seed germination was decreased

to 24% at pH 3 and to 13% at pH 9. Based on these results, Sicklepod germinates most

readily near neutral pH but can germinate under both acidic and basic conditions. Seed

germination of giant sensitive plant was more than 79% over pH levels of 4 to 10 (Chauhan

and Johnson, 2008). Similarly, a considerable seed germination rate of M. pudica was

observed over a wide range of pH. These results showed that the pH of the soil could not be a

preventive feature for the germination and emergence of this weed species under field

conditions (Chauhan and Johnson, 2009b).

2.3 Allelopathic effect of weeds

Weed species may interfere with plant growth through allelopathic mechanisms

(Putnam and Tang, 1986). Studies reported that several weed species hinder the growth and

development of crops (Dongre and Singh, 2007). However, some weed species also

demonstrated the encouraging effects on the seed germination, seedling emergence, growth,

development and yield of crop plants (Narwal, 2004). The inhibitory properties of weeds on

the growth and development of crops is associated with the release of allelochemicals from

different plant parts, decaying residues, leachates, exudates and volatiles (Narwal, 2004).

Allelopathy may also be one of numerous characteristics that enables a plant to set up itself

15

in a new environments (Callaway and Aschehoug, 2000; Ridenour and Callaway, 2001). The

successful development of a weed in an agricultural ecosystem is generally associated with a

number of factors. These include fast growth rate of weeds as compared to crop plants in

vicinity, adaptive nature of weeds in varying environmental condition, high reproductive rate

due to which the weeds complete their life cycle within a short period, and, in particular,

interference of weeds with crop plants by resource diminution (Chon and Nelson, 2010).

Several studies engaged in allelopathy research have been reported about the

interactions among weeds and crops (Todaria et al., 2005; Singh et al., 2007). The first

scientist who reported the toxic effects of weeds on crops was De Candolle (1932). He

described the detrimental effects of root exudates of Canada thistle (Cirsium arvense (L.)

Scop.) on the growth and development of oat (Avena sativa) plants in vicinity. It gained the

attention of other plant scientists, and presently, several studies have been reported to

describe the allelopathic potential of weeds on the crops (Steenhagen and Zimdahl, 1979;

Singh et al., 1989; Das and Das, 1996; Jabeen and Ahmed, 2009). Rice (1984) concluded that

numerous weed and crop plants have allelopathic prospective that influences the growth and

development of other plant species in vicinity. These inhibitory effects are generally

associated with the release of exudates and volatile compounds from living tissues or by

decaying plant residues in their neighbouring environment (Putnam, 1986; Basotra et al.,

2005; Singh et al., 2007).

Rashid et al. (2010) concluded that leaf and root leachates of kudzu (Pueraria lobata)

have strong allelopathic potential which could impair growth of lettuce (Lactuca sativa

var.asparagina L.) and radish (Raphanus sativus L.) seeds, root length, shoot length and their

seedling fresh weight. Kohli et al. (2006) conducted experiments on the allelopathic potential

of Acacia species. They reported that Acacia species had ability to affect growth and

development of crop plants by competing them for a wide range of environmental resources

as their litter interferes with the establishment and growth of the adjoining crop plants.

Seigler (2003) reported that Acacia species release various chemical substances into the

environment, including phenolic compounds in the litter. Perhaps, allelopathy is important in

the establishment and competitiveness of common legume weeds. Though many studies on

16

the allelopathic potential of other legume weeds have been published (Kamo et al., 2003;

Rashid et al., 2010), the allelopathy of R. capitata has not yet been examined.

2.4 Weed-crop competition

Weed species not only release toxic allelopathic compounds in the neighbouring

environment, but also compete with crop plants for light, water, nutrients and space.

Competition constitutes the major noxious aspect of weeds in crop cultivation. Since weeds

and crops largely use the same resources for their growth, they will compete when these

resources are limited (Zimdahl, 1980). The critical stage to control weeds is a key constituent

of an integrated weed management program. A period, time or phase in the life cycle of crop

plants during which they are very susceptible to the presence of weeds in their neighbouring

vicinity is regarded as critical period of competition (Evans et al., 2003). It is the most

vulnerable stage in the growth and development of crop plants during which weed

competition with crops cause considerable reduction in crop yield. This critical period of

weed competition differs from crop to crop and depends upon the time of weed emergence in

the field, type of weeds, weed density and crop management approaches (Knezevic et al.,

2002). To determine the start of critical period of weed-crop competition, it is important to

consider weed density in the field (Martin et al., 2001). The knowledge of critical period of

weed-crop competition is helpful for decision making in determining the exact timing and

requirements of weed control (Nieto et al., 1968; Raman and Krishnamoorthy, 2005).

Optimal timing of weed removal has been reported on the basis of weed height (Kalaher et

al., 2000), weeks after crop emergence (Sellers and Smeda, 1999), and crop growth stage

(Evans and Knezevic, 2000).

The timing of weed emergence in the field and weed competition duration had an

important effect on the yield of crops (Chikoye et al., 1995). Bosnic and Swanton (1997)

reported that if crop plants start their growth a few days earlier than weeds, it would transfer

the competitive equilibrium considerably in support of the crop plants. Naeem et al. (2000)

found that weed-crop competition duration had a considerable effect on final grain yield per

hectare in mungbean. The full season weed-crop competition duration significantly decreased

the grain yield of mungbean to 961 kg ha-1 compared with 1400 kg ha-1 in weed free

treatment. The results further led to the conclusion that weed competition with crop up to 20

17

DAE did not interfere in the growth and development of mungbean to a significant extent,

while extended competition duration had an adverse effect on yield potential of mungbean.

Utomo (1989) carried out experiments to find out the critical period of weed control in

mungbean crop. He found that the most critical time during which the mungbean plants were

most vulnerable to weed competition was from 3 to 6 weeks after planting of mungbean.

Similarly, Naeem and Ahmad (1999a) concluded that a period of 20 to 30 days after the

emergence of mungbean crop was very critical for its competition with weeds. Long-standing

weed-crop competition after 20 to 30 days of crop emergence resulted into considerable

decline in mungbean yield.

Naeem et al. (2000) conducted experiments to study the response of mungean yield to

different weed-crop competition durations. They observed a linear increase in weed dry

weight with the successive increase in weed-crop competition periods. Maximum reduction

in grain yield of mungbean occurred when weed competition persisted for 50 days after crop

emergence and weedy condition up to the harvest of crop. Malik et al. (2000) reported that

weed competition with mungbean decreased grain yield by 81%. According to Raman and

Krishnamoorthy (2005), if the weeds present in the mungbean crop during its full cropping

period, they may decrease the mungbean grain yield to 35%. Similarly, Punia et al. (2004)

conduted experiments to study the effect of various densities of Cyperus rotundus,

Echinochloa colona and Trianthema portulacastrum on mungbean growth and yield. They

concluded that the density of 160 plants m-2 of Trianthema portulacastrum, Echinochloa

colona and Cyperus rotundus decreased the grain yield of mungbean by 29.5%, 23.5% and

45.8%, respectively.

Senanayake and Pathirana (1987) investigated the threshold competition duration of

mungbean with respect to the natural weed flora. They allowed the weeds to compete with

the crop for different durations ranging from 5 to 42 days after sowing. They concluded that

threshold weed competition duration of mungbean to be 35 DAS without any seasonal

variation on threshold level. The gain on grain yield at threshold level was 101% and 102%

during both the years of study, respectively. For attaining an effective weed control,

knowledge of critical period of weed-crop competition and threshold density level is very

necessary, as they play a pivotal role in weed management (Deen et al., 2003).

18

2.5 Chemical weed control

Physical, mechanical, habitat management, biological, cultural and chemical weed

controls are different methods reported for control of weeds in agricultural crops. Amongst

these methods, chemical weed control is most trustworthy, easy, effective, economical, time

saving and less affected by unfavorable environmental conditions like wind, humidity,

temperature and rainfall etc. and most practicable during critical period of weed-crop

competition (Marwat et al., 2008; Bibi et al., 2008). The major challenge for farmers is

effective weed management (Singh et al., 2003). If weeds are managed properly, crop plants

can make the best use of soil and other environmental resources leading to enhanced crop

productivity (Marwat et al., 2008).

For successful crop production, use of appropriate herbicide is prerequisite. Windley

et al. (1999) tested the efficacy of 6 herbicides against T. portulacastrum and Macroptilium

lathyroides and found that all herbicides reduced the populations of these weed species. All

herbicides increased mungbean yield from the control value of 1563 kg ha-1 to 1882 kg ha-1.

Kurtz (1981) concluded that pendimethalin at 1.12 kg + metribuzin 0.56 kg ha-1 was the most

efficient, giving 96 per cent control of barnyard grass (Echinochloa crusgalli) and

significantly improved the soybean yield. Wilhm and Meggitt (1981) revealed that when 1kg

pendimethalin ha-1 was combined with metribuzin, control of jimson weed (Datura

stramonium) and velvet leaf (Abutilon theophrasti) was 90 % at 10 weeks after herbicide

treatment. Application of 0.75 kg pendimethalin ha-1 gave best control of weeds in a stand

of soybean (cv. Bragg) and significantly increased seed yield but control of Ipomea spp.,

Amaranthus spp. and Sida spinosa was most complex (Rogers et al., 1981). Godec and

Opacic (1988) found that pre-sowing application of pendimethalin resulted in outstanding

control of weeds like Amaranthus retroflexus, Chenopodium album, Polygonum

lapathifolium and E. crusgalli.

Aslam et al. (1991) reported that pendimethalin was the only herbicide treatment

which resulted in effective grass weed control as well as effective broad leaved weed control.

Joshi et al. (1997) concluded that pre plant herbicide incorporation of pendimethalin 50EC @

1 kg a.i ha-1 did not vary significantly with weedy check in soybean. Sharma and

Raghuwanshi (1999) found that pendimethalin @ 1 kg ha-1 as pre-emergence herbicide

treatment resulted in effective control of grasses except Rottboellia exaltata, which emerged

19

in late season and caused severe competition at productive stage of soyabean. Pendimethalin

1 kg ha-1 had no effect on scurvy weed (Commelina cyanea), and due to removal of

competition of grasses by this herbicide, these weeds achieved maximum vigor than

untreated control. Similar findings have also been observed earlier by Kuruchania et al.

(1999). Singh and Singh (1992) reported significant reduction in the weed biomass with

pendimethalin.

Panneerselvam and Lourduraj (2000) concluded that application of alachlor @ 1 kg

a.i ha-1 was most efficient in controlling weeds. It was followed by pendimethalin @ 0.75 kg

a.i ha-1 in soybean. Rohitshav et al. (2003) concluded that application of pendimethalin @

1.5 kg a.i ha-1 as pre-emergence herbicide produced soybean grain yields that were

comparable to weed free treatment. Rajput and Kushwah (2004) conducted experiments to

study integrated management of weeds in soybean crop. They revealed that application of

pendimethalin @ 1.0 kg ha-1 as pre-emergence herbicide was most economical and efficient

in controlling weeds in soybean crop.

To sum up, Mungbean (Vigna radiata L. Wilczek) is one of the major pulse crops in

the irrigated and dry areas of Pakistan. Rhynchosia capitata has become a major problem in

these areas. In order to maximize the success of weed management approaches, an

understanding of weed seed dormancy mechanisms is of ecological and economic

importance. From an ecological perspective, germination can be viewed as being dependent

on seed dormancy (Baskin and Baskin, 2004). Understanding weed germination ecology is

pre requisite for effective weed management (Fenner & Thompson, 2005). Most weeds have

characteristics of tolerance to wide range of environmental conditions (Chauhan and

Johnson, 2010). Weed management is to make the environment unfavorable for them

(Zimdahl, 1999). Comprehensive understanding of the factors influencing the germination of

weed seeds could facilitate the development of more effective weed management practices

(Chauhan and Johnson, 2008). Allelopathy is one of numerous characteristics which enable a

plant to ascertain itself in new environmental conditions (Ridenour and Callaway, 2001).

Allelopathy is a mechanism for the impressive success of invasive plants and may contribute

to the ability of particular species to become dominant in invaded plant communities (Hierro

and Callaway, 2003). The timing of weed emergence in the field and weed competition

20

duration had an important effect on the yield of crops (Chikoye et al., 1995). Bosnic and

Swanton (1997) reported that if the crop plants start their growth a few days of earlier then

weeds, it would transfer the competitive equilibrium considerably in support of the crop

plants. The major challenge for farmers is effective weed management (Singh et al., 2003).

Amongst a wide range of weed control methods, chemical weed control is most trustworthy,

easy, effective, economical, time saving and less affected by unfavorable environmental

conditions like wind, humidity, temperature and rainfall. For successful crop production, use

of appropriate herbicide is prerequisite.

21

CHAPTER 3

MATERIALS AND METHODS

3.1 Experimental soil analysis

The soil where the field experiments were carried out was analysed each year

before the sowing of mungbean crop. The soil was sandy to sandy loam in nature with

main properties and nutrient concentrations given in the table 3.1.

3.2 Experimental site

Seed germination ecology and allelopathic effects of R. capitata was studied

under laboratory conditions, Department of Agronomy, University of Agriculture,

Faisalabad (31º N, latitude and 73º E, longitude), Pakistan. Field experiments were laid

out under farmer’s field conditions in District Layyah (30o 57ʹ N, 70o 56ʹ E), Punjab,

Pakistan.

3.3 Meteorological data

During the growing season of mungbean, meteorological data regarding

temperature and rainfall (means on monthly basis) were obtained for the years 2010 and

2011 from Agronomic Research Station, Karor, district Layyah, Punjab, Pakistan (table

3.2).

22

Table 3.1 Physico-chemical soil analysis of experimental area

Characteristic

Soil sample depth

2010 2011 2012

0-15

cm

15-30

cm

30-45

cm

Mean 0-15

cm

15-30

cm

30-45

cm

Mean 0-15 cm 15-30

cm

30-45

cm

Mean

Soil pH 7.8 7.8 7.7 7.7 8.00 8.4 8.5 8.3 7.8 8 8.1 8.03

EC (dSm-1

) 0.95 0.92 0.98 0.95 1.1 1.18 1.05 1.11 0.95 1 1.04 1.04

Organic Matter (%) 0.83 0.67 0.52 0.67 0.58 0.63 0.41 0.55 0.73 0.78 0.62 0.71

Total Nitrogen (%) 0.043 0.047 0.039 0.043 0.029 0.033 0.031 0.029 0.039 0.041 0.039 0.039

Available P (mg kg-1

) 9.1 9.3 7.6 8.66 5.5 5.7 5.42 5.54 8.1 8.3 7.7 8.03

Available K (mg kg-1

) 210 140 70 140 240 260 222 240 210 170 140 173.3

Texture Sandy loam Sandy loam Sandy loam

23

Table 3.2 Meteorological data during the crop growing season 2010, 2011 and 2012

Mean minimum

Temperature (°C)

Mean maximum Temperature

(°C)

Rain Fall (mm)

Month

2010 2011 2012 2010 2011 2012 2010 2011 2012

JUNE 28.6

29.6

29.1 41.46

43.1

42.1

10

36 41

JULY 29.03

29.83

29.02 38.54

39.19

39.01

175

37 57

AUGUST 29.4 29.45

29.38 35.53

38

37.1

310

88 177

SEPTEM

BER

27.2 27.16

27.21 33.96

36.23

35.23

155 9 59

24

3.4. LABORATORY EXPERIMENTS

3.4.1 EXPERIMENT 1: METHODS TO BREAK SEED DORMANCY OF

RHYNCHOSIA CAPITATA.

3.4.2 Collection of seeds for experiments:

Mature pods of R. capitata were collected from more than 500 plants from Vigna

radiata (L.) R. Wilczek fields around Layyah, Southern Punjab, Pakistan (30o 57ʹ N, 70o

56ʹ E) in October 2010. Immediately after collection, seeds were isolated from the pods,

separated from the undesired materials and unripe seeds and stored (4 to 5 months) at

room temperature (25±1.4 oC) until used in the experiments. Only mature and uniform-

sized seeds were used for various seed germination experiments.

3.4.3 Experiment I: Effect of dry heat seed treatment on dormancy release and

germination of R. capitata

Treatments Time

T1 Oven (70 oC) 1 hour



T4 Oven (70 oC) 1 day

T5 Oven (70 oC) 2 days



T8 Oven (200 oC) 5 min





For this seed experiment, the seeds were placed in shallow containers in a

preheated oven according to prescribed temperature and duration. After the treatment,

the seeds were cooled immediately and sown.

25

3.4.4 Experiment II: Effect of hot water seed treatment on dormancy release and

germination of R. capitata

Treatments Time

T1 5 min

T2 15 min

T3 30 min

T4 60 min

T5 90 min

T6 120 min

T7 150 min

Seeds were placed in boiling water for a specific length of time depending, then

immediately removed from the boiling water and kept at room temperature to cool before

sowing.

3.4.5 Experiment III: Effect of stratification on dormancy release and germination

of R. capitata

Treatments Time

T1 5 min

T2 10 min

T3 30 min

T4 60 min

T5 3 hour

T6 6 hour

T7 12 hour

T8 1 day

T9 2 days

T11 4 days

T11 8 days

T12 15 days

T13 30 days

The seeds were placed in a tightly glass jar, and stored in the refrigerator at a

temperature of 35º- 41º F (2-5 ºC).

26

3.4.6 Experiment IV: Effect of seed treatment with KNO3 and thiourea on

dormancy release and germination of R. capitata

Seeds were soaked in different concentrations of:

1. Potassium nitrate (KNO3)

Treatments Concentrations (mg L-1)

T1 0

T2 10 000

T3 20 000

T4 30 000

T5 40 000

T6 50 000

T7 60 000

2. Thiourea [(NH2)2CS]

Treatments Concentrations (mg L-1)

T1 0

T2 2500

T3 5 000

T4 7 500

T5 10 000

The seeds were soaked in these concentrations for 24 h at 30 °C. The ranges of

these concentrations were selected after preliminary trials in which seeds were immersed

in KNO3 at the concentrations of 0, 500, 1 000, 2 500, 5 000 and 7 500 mg L-1 and

thiourea with the concentrations of 100, 200, 300, 400, 500, 600 and 1000 mg L-1 which

had no effect on breaking of seed dormancy.

27

3.4.7 Experiment V: Effect of seed scarification with HCl and sand paper on

dormancy release and germination of R. capitata

Treatments Soaking time (Hours)

T1 0 (Control)

T2 3

T3 6

T4 9

T5 12

T6 15

T7 18

T8 Sand paper scarification

The seeds were rubbed against the rough surface of the sand paper (the seed coat

was sanded with a # 80 wood sandpaper at an area opposite from the embryo until the

cotyledon was exposed). Immediately after prescribed soaking period in HCl (36%),

seeds were removed, rinsed several times in clean distilled water. Untreated seeds were

used as a control.

3.4.8 Experiment VI: Effect of seed scarification with HNO3 on dormancy release

and germination of R. capitata

Treatments Soaking time (days)

T1 0 (Control)

T2 1

T3 2

T4 3

T5 4

T6 5

Seeds were then rinsed several times in clean distilled water after treatment with

HNO3 (65%). Untreated seeds were used as a control.

28

3.4.9 Experiment VII: Effect of seed scarification with H2SO4 on dormancy release

and germination of R. capitata

Treatments Soaking time (Min)

T1 20

T2 40

T3 60

T4 80

T5 100

T6 120

These treatments were selected after conducting preliminary trials of soaking

seeds in sulphuric acid (98%) for 2, 4, 6, 8, 10 min, which had no effect on breaking

dormancy. Thereafter, the seeds were rinsed several times in clean distilled water.

Untreated seeds were used as a control.

3.4.10 Experiment VIII: Effect of seed scarification with HCl + H2SO4 on dormancy

release and germination of R. capitata.


T1 Control

T2 20 min HCl + H2SO4 30 min






The seeds were treated with HCl for 20, 40, 60, 80, 100 and 120 min separately

and then with H2SO4 for 30 minutes at 30 °C. The seeds were then rinsed several times

in clean distilled water after treating with acids. Untreated seeds were used as a control.

29

3.4.11 Experiment IX: Effect of seed scarification with HNO3 + H2SO4 on dormancy

release and germination of R. capitata.


T7 Control

T7 20 min HNO3 + H2SO4 30 min






The seeds were treated with HNO3 for 20, 40, 60, 80, 100 and 120 min separately

and then with H2SO4 for 30 minutes at 30 °C. The seeds were then rinsed several times

in clean distilled water after treating with acids. Untreated seeds were used as a control.

3.4.12 Germination test

After rinsing, seeds were allowed to dry out on the blotter paper at laboratory

temperature (30 °C) before placing in Petri dishes. The seeds were surface sterilized by

soaking in 5% sodium hypochlorite (NaOCl) solution for 5 min and subsequently rinsed

five times with sterilized water. Twenty five seeds per Patri dish were placed on double

layered Whatman N° 10 filter paper moistened with 10 mL of distilled water in sterilized

Petri dishes with 15 cm diameter. All dishes were sealed with a strip of parafilm to

reduce water loss and were placed at 30 °C in germinator.

30

3.5 EXPERIMENT 2: SEED GERMINATION ECOLOGY OF R. CAPITATA.

3.5.1 Experiment 1: Effect of temperature on the germination of R. capitata.

To know whether seeds of R. capitata have capacity to germinate under various

temperatures, as seed might experience a wide range of temperature conditions in

southern Punjab of Pakistan, seeds (4 to 5 months old) were placed in germinators at

various temperatures:

Treatments Temperature

T1 20 °C

T2 25 °C

T3 30 °C

T4 35 °C

T5 40 °C

T6 45 °C

3.5.2 Experiment 2: Effect of light and darkness on the germination of R. capitata.

The influence of light on germination of R. capitata seeds was tested. Seeds

scarified with sand paper were placed evenly at Whatman No. 10 filter paper in 9 cm

diameter Petri dish wrapped in two layers of aluminium foil to ensure no light

penetration (dark), or left uncovered to allow light exposure (light/dark) and placed in a

germinator at 30oC.

Treatments

L1 0 hour light (complete darkness)

L2 10 hours light

31

3.5.3 Experiment 3: Effect of different levels of salt stress on the germination of R.

capitata.

In this experiment, seeds (4 to 5 months old) were placed in Patri dishes to evaluate the

response under different levels of salinity stress.

Treatments NaCl concentration (mM)

T1 0 (Control)

T2 50

T3 100

T4 150

T5 200

T6 250

These concentrations were given to each Petri dish separately.

3.5.4 Experiment 4: Effect of different levels of osmotic potential on the

germination of R. capitata.

The germination response of R. capitata seeds (4 to 5 months old) under

different levels of moisture stress was evaluated under laboratory conditions.

Polyethylene glycol with a molecular weight of 8000 (PEG-8000) was used as a drought

stimulator and water stress levels of:

Treatments Osmotic potential (MPa)

T1 0 (control)

T2 -0.2

T3 -0.4

T4 -0.6

T5 -0.8

T6 -1.0

These concentrations were developed according to the equation proposed by

Michel (1983). The selected ranges of osmotic potentials imitate water stress levels

occurring in most farming systems of Punjab, Pakistan in summer season.

32

3.5.5 Experiment 5: Effect of different levels of pH on the germination of R.

capitata.

The effect of pH on germination of R. capitata seeds (4 to 5 months old) was

studied using buffer solutions of pH 5 to 10 prepared as described by Reddy and Singh

(1992) to simulate the pH ranges of Pakistani soils. A 2-mM solution of MES [2-(N-

morpholino) ethanesulfonic acid] was adjusted to pH 5 or 6 with 1 N NaOH. A 2-mM

solution of HEPES [N-(2-hydroxymethyl) piperazine-N-(2-ethanesulfonic acid)] was

adjusted to pH 7 or 8 with 1 N NaOH. A pH 9 or 10 buffer was prepared with 2-mM

tricine [N-tris(hydroxymethyl) methylglycine] and adjusted with 1 N NaOH. Unbuffered,

deionized water (pH 6.3) was used as a control.

Treatments pH

pH1 6.0

pH2 6.2 (Control)

pH3 6.5

pH4 7.0

pH5 7.5

pH6 8.0

3.5.6 Experiment 6: Effect of different levels of sowing depth on the seedling

emergence of R. capitata.

To study the effect of different levels of sowing depth on the seedling emergence

of R. capitata, 50 scarified seeds of R. capitata were placed on the soil surface in 14-cm-

diam plastic pots and then covered with soil to achieve burial depths of:

Treatments Seeding depth (cm)

T1 0

T2 2

T3 4

T4 6

T5 8

T6 10

T7 12

33

The sandy loam soil was used for this experiment with 0.7 % organic carbon and

a pH of 7.5. Soil was sieved after passing through a 3 mm sieve. Pots were watered as

needed to maintain adequate soil moisture. Emergence was counted daily and the

experiment was run until 40 d after burial. The temperature of the glasshouse was

fluctuated between 32.6 ± 3.7°C during day and 23.8 ± 3.2 during night.

3.5.7 Germination test.

The seeds were surface sterilized by soaking in 5% sodium hypochlorite

(NaOCl), solution for 5 min and subsequently rinsed thoroughly with sterilized water.

After rinsing, the seeds were allowed to dry out on the blotter paper at laboratory

temperature (25±1.4 °C). Seed germination was estimated by placing 25 seeds evenly in

a 9 cm-diameter Petri dish containing two layers of Whatman No. 1 filter paper,

moistened with 5 ml distilled water or a treatment solution. Seeds of R. capitata had high

levels of innate dormancy and were scarified by sand paper (the seed coat was sanded

with a # 80 wood sandpaper at an area opposite from the embryo until the cotyledon was

exposed) before applying any treatment (Ali et al., 2011). Scarified seeds were used in

all experiments. All the dishes were sealed with a strip of parafilm to reduce water loss

and placed in a germinator at 30 oC except experiment 1.

34

3.6 EXPERIMENT 3: ALLELOPATHIC EFFECTS OF RHYNCHOSIA

CAPITATA (ROTH) DC ON GERMINATION AND SEEDLING GROWTH OF

MUNGBEAN.

3.6.1 Collection of plants

Rhynchosia capitata plants were collected from a natural population around

Layyah, Southern Punjab, Pakistan (30o 57ʹ N, 70o 56ʹ E) in October 2010. The plants

were dried at room temperature (30°C±4) for seven days. Plant material was further

dried in an oven at 70°C for 48 h.

3.6.2 Preparation of water extracts of R. capitata.

The dried pieces of the R. capitata plant (roots, stems, leaves, fruits) were

separated and weighed. These plant parts and whole plant were immersed separately in

tap water at a ratio of 1:20 (w/v) at room temperature for 24 h (Hussain and Gadoon,

1981). The water extracts of the different parts of R. capitata were obtained by filtering

through 10- and 60-mesh sieves. Our preliminary trials suggested that R. capitata leaf

exhibited strong allelopathic affect. Therefore, Owing to greater inhibitory activity of

leaves, different concentrations (1- 4%) were made by further diluting leaf extract (5%)

with distilled water. After 24 hour, the solutions were filtrated and centrifuged at 12000

rpm, after which extracts were collected. These extracts were individually bottled and

tagged. Mungbean seeds were used to test the effect of R. capitata on its germination and

early seedling growth. The study was carried out in the Laboratory, Department of

Agronomy, University of Agriculture, Faisalabad, Pakistan, during 2010 and 2011.

3.6.3 Lab bioassay

Effect of water extracts of R. capitata plant parts on the germination of mungbean.

In this experiment, mungbean seeds were treated with root, stem, leaf, fruit and

whole plant extracts and distilled water as a control. Twenty five seeds of mungbean

were placed on filter paper in 9 cm diameter petri dishes. Before sowing, mungbean

seeds were surface-sterilized with 1.5% (v/v) sodium hypochlorite solution for 1 min and

washed (three times; 3 min/wash) in distilled water. In each petri dish, 10 mL of extract

35

or distilled water was added according to the treatment. To avoid the drying out of seeds

throughout the incubation period, the petri dishes were sealed with parafilm. The

temperature of the laboratory was fluctuated between 32.6 ± 3.7°C during day and 23.8 ±

3.2 during night.

3.6.4 Soil bioassay

Effect of different concentrations of R. capitata residues infested soil on the

mungbean seedlings.

The decomposition of plants could release phenolic compounds in soil, which, in

turn, might interfere with the results; sites with no R. capitata plants were chosen to

collect soil for this experiment. Field soil was dried, crushed, mixed, and placed into 14-

cm-diam plastic pots. The soil was sandy loam with 0.7 % organic carbon and a pH of

7.1. The dried R. capitata plants were crushed and mixed with soil of these pots at the

rate of 1, 2, 3 and 4% (w/w) per pot. After watering, these pots were kept in a

greenhouse for 10 days. Then, 10 seeds of mungbean were sown in each pot. Before

sowing, mungbean seeds were surface-sterilized with 1.5% (v/v) sodium hypochlorite

solution for 1 min and washed (three times; 3 min/wash) in sterile distilled water. The

temperature was fluctuated between 31.6 ± 3.7°C during day and 23.8 ± 3.2 during night.

After sowing, an adequate water was supplied was to ensure field capacity. After 21

days, the seedlings were uprooted and washed with water. Seedling fresh weight, length

of roots and shoots was measured. Roots and shoots were oven dried at 65 °C for 72 h

until a constant weight was obtained to measure dry weight of root, shoot and seedlings.

3.6.5 Determination of total soluble phenolics in R. capitata

Total soluble phenolics were determined as described by Randhir and Shetty

(2005) and were expressed as gallic acid equivalents.

36

3.6.6 Detection of Phytotoxins in aqueous R. capitata extracts.

Due to their greater suppression potential, aqueous R. capitata leaf extracts were

chemically analyzed on Shimadzu HPLC system (Model SCL-10A, Tokyo, Japan) for

identification and quantification of their suspected phytotoxins. The conditions of

separation are listed in table 3.3.

The peaks were detected by UV detector. Standards of suspected phytotoxins

(Aldrich, St Louis, USA) were run similarly for identification and quantification.

Standards of phenolics were prepared in different concentrations. Vanillic acid and 4-

(hydroxymethyl) benzoic acid were identified by their retention time with authentic

standards. Concentration of each isolated compound was determined by the following

equation:

factor Dilution standardthe of ionConcentrat standardthe of Area

samplethe of Area(ppm) ionConcentrat

Table 3.3 HPLC conditions for determination of phytotoxins in aqueous R. capitata

leaf extract.

Parameter Characteristic

Column dimensions 25 cm length ×4.6 mm diameter, particle size

of 5 µm

Diatomite Supleco wax 10

Attenuation 0.01ppm

Rate of recorder 10 mm min-1

Detector SPD-10A vp-detector

Detection UV,280 nm

Flow rate 0.25 ml min-1

Volume injection sample 50 µl

Type of Column Shim-pack CLC-Octadecyl Silicate (ODS) (C-

18)

Mobile phase Isocrartic;100% methanol

Temperature 25 ◦C

37

3.7 Collection of Data

Data on following observations were recorded during course of study

3.7.1 Seed germination

Germination (%)

Time to 50% germination (days)

Mean germination time (days)

Germination index

3.7.2 Seedling Emergence

Emergence %

Time to 50% emergence (days)

Mean emergence time (days)

Emergence index

Root length (cm)

Shoot length (cm)

Root dry weight (mg)

Shoot dry weight (mg)

Seedling vigor index (SVI)

3.7.3 Procedure for recording observations

Data on various parameters of germination/emergence of R. capitata were

recorded by the following procedures.

3.7.3.1 Germination/emergence (%)

A seed was considered germinated when the tip of the radicle (2 mm) had grown

free of the seed. Germination counts were made every day for 3 weeks. However, in seed

burial depth experiment, when a cotyledon becomes visible on surface, R. capitata

38

seedling emergence was recorded. Seedling emergence data was recorded up to 30 days.

Total germinated/emerged seeds were counted and their germination/emergence

percentage was calculated by using the following formula.

Germination or emergence percentage = Germinated or emerged seeds

----------------------------- X 100

Total seeds

3.7.3.2 Germination/emergence index (GI/EI)

The germination index (GI) was calculated as described by the Association of

Official Seed Analysts (1990) by using the following formula:

countfinalofDays

seedsgerminatedofNo.

countfirstofDays

seedsgerminatedofNo.GI

3.7.3.3 Time to 50% germination/emergence (days)

Time taken to 50% germination of seedlings (T50) was calculated according to the

following formula of Coolbear et al. (1984),

(N/2-ni)(tj-ti)

T50 = ti + ------------------

nj- ni

Where N is the final number of germinated seeds, and ni and nj are the cumulative

number of seeds germinated by adjacent counts at times ti and tj, respectively, when ni <

N/2 < nj.

3.7.3.4 Mean germination/emergence time (MGT/MET)

Mean germination time was calculated according to the equation of Ellis and

Roberts (1981).

MGT= ∑ (Dn) / ∑ n

Where n is the number of germinated seeds or emerged seedlings on day D and D

is the total number of days counted from the beginning of germination.

39

3.7.3.5 Root and shoot dry weight (mg per plant)

Fresh biomass of root and shoot from each pot was oven dried at 70 °C for 48

hours and weighed for root and shoot dry weight (mg per plant).

3.7.3.6 Root length (cm)

The survived plants (if any) were uprooted from each pot under wet condition.

Root and shoot of all the seedlings were separated and root length was measured in cm

from the point where root and shoot joins to the end of the root. Then the average root

length was calculated.

3.7.3.7 Shoot length (cm)

Separated shoots were taken and their length was measured in cm from the point

where root and shoot joins to the end of the shoot. Then the average shoot length was

worked out.

3.7.3.8 Seedling vigour index

Seedling vigour index (SVI) was calculated according to the following formula of

Abdul-baki and Anderson (1973):

SVI = Germination /Emergence % × Radical length (cm)

3.8 Statistical Analysis:

Each experiment had a completely randomized design (CRD) with four

replicates. All experiments were repeated. The data from the repeated experiments were

combined because there was no time-by-treatment interaction.

Germination (%) values at different concentrations of NaCl, osmotic potential as

well as emergence (%) of the seeds buried at different depths were fitted to a functional

40

three-parameter logistic model (Chauhan et al., 2006b) using Sigma Plot 2008 (version

11.0). The model fitted was

{G (%) = G max / [1 + (x/x50)Grate]} ---------- (1)

Where,

G = Total germination at x concentration

Gmax = Maximum germination

x50 = NaCl concentration or osmotic potential for 50% inhibition of the maximum

germination

Grate = Slope of graph

Similarly, in case of seedling emergence, the model fitted was

{E (%) = E max / [1 + (x/x50) Erate]}

E = Total emergence at x sowing depth

Gmax = Maximum emergence

x50 = Sowing depth of 50% inhibition of R. capitata maximum emergence

Erate = Slope of graph

In all other experiments, means were separated using LSD at P = 0.05.

Statistical analysis of the measured/observed data was done by using Fisher's

Analysis of Variance techniques (Steel et al., 1997). Least significant difference (LSD)

test was applied at 5% probability level to test the significance of treatment means.

41

3.8 FIELD EXPERIMENT 1: EFFECT OF DIFFERENT WEED-CROP

COMPETITION PERIODS ON THE GROWTH AND YIELD OF MUNGBEAN.

3.8.1 Treatments

T1 Zero competition

T2 Weed crop competition for 3 weeks after planting





T7 Full season competition

3.8.2 Seed bed preparation

The seed bed was prepared by cultivating the soil 2-3 times with the tractor

mounted cultivator each followed by planking.

3.8.3 Sowing

The seed of mungbean approved variety AZRI-2006 was purchased from Ayub

Agricultural Research Institute, Faisalabad, Pakistan. Recommended seed rate (25 kg ha-

1) was used to plant this crop using single row hand drill in 30 cm apart rows. Plant to

plant distance of 15 cm was maintained by thinning out the surplus plants 10 days after

emergence.

3.8.4 Irrigation

A pre-soaking irrigation was applied before the seed bed preparation. When soil

reached at proper moisture level (filed capacity), the seed bed was prepared and sowing

was done. Irrigations were applied as and when needed at different plant development

42

stage to avoid any moisture stress to plants, until the crop achieved the physiological

maturity.

3.8.5 Fertilizer application

Nitrogen and phosphorus were applied @ 25 and 50 kg ha-1 in the form of

diammonium phosphate (DAP) and urea, respectively at the time of sowing of

mungbean.

3.8.6 Layout

The field experiment was conducted under irrigated conditions for two crop years

(2011 and 2012) at farmer field in District Layyah, Southern Punjab, Pakistan (30o 57ʹ N,

70o 56ʹ E). The experiments were laid out in randomized complete block design (RCBD)

with 4 replications.

3.8.7 Maintenance of weed competition periods

The experiment was conducted on a field heavily infested with R. capitata. Soils

of the area were sandy loam in nature, slightly alkaline with pH 8.2 and low in organic

matter (0.5%). Weeds were removed manually with a hand hoe from respective

plots after prescribed duration and kept weed free till harvest. All other agronomic

operations except those under study were kept normal and uniform for all the treatments.

3.8.8 Harvesting

Each year, mungbean was harvested manually in the 2nd week of September.

After harvesting the crop was left in the field for two days for sun drying. Thereafter

mungbean was threshed manually.

43

3.9 FIELD EXPERIMENT 2: CONTROL OF RHYNCHOSIA CAPITATA (ROTH)

DC IN MUNGBEAN WITH DIFFERENT HERBICIDES.


(2010 & 2011) at farmer field in District Layyah, Southern Punjab, Pakistan (30o 57ʹ N,

70o 56ʹ E). This area was selected because heavy infestation of R. capitata has been

reported in previous years. Soils of the area are sandy loam in nature, slightly alkaline

with pH 8.2 and low in organic matter (0.5%).

The experiment was laid out in randomized complete block design (RCBD) with

4 replications. Seven weed control methods were included in the study. These were:

3.9.1 Treatments

T1 Weedy check

T2 Pendimethalin+ prometryn @ 875 g a.i ha-1 (Penthalene Plus-35 EC@ 2500 ml ha-1)

T3 Pendimethalin+ prometryn @ 700 g a.i ha-1 (Penthalene Plus-35 EC @ 2000 ml ha-1)

T4 Pendimethalin+ prometryn @ 525 g a.i ha-1 (Penthalene Plus-35 EC @ 1500 ml ha-1)

T5 S-metolachlor @ 1440 g a.i ha-1 (Dualgold-960 EC @ 1500 ml ha-1)

T6 Pendimethalin @ 825 g a.i ha-1 (Stomp-330 EC @ 2500 ml ha-1)

T7 Control (weed free)

Pendimethalin and prometryn was available in pre-mixed formulation. All herbicides

were purchased from local market and were applied one day after sowing of crop.

Volume of spray (300 L ha-1) was determined by calibration as described by Rao et al.

(1992). Spraying was done with Knapsack hand sprayer fitted with T-Jet nozzle

maintaining a pressure of 207 kp. The seed of mungbean approved variety AZRI-2006

was purchased from Ayub Agricultural Research Institute, Faisalabad, Pakistan. It was

planted in 29th June 2010 and 7th July, 2011. Recommended seed rate (25 kg ha-1) was

used to plant this crop using single row hand drill in 30 cm apart rows. Each plot size

was 4.5 m × 1.8 m. Nitrogen and phosphorus were applied @ 25 and 50 kg ha-1 in the

form of diammonium phosphate (DAP) and urea, respectively at the time of sowing of

mungbean. Plant to plant distance of 15 cm was maintained by thinning out the surplus

plants 10 days after emergence. All other agronomic operations except those under study

were kept normal and uniform for all the treatments.

44

3.10 Data collection for field experiments

The data for field experiments were recorded on following parameters

3.10.1 Rhynchosia capitata

Weed population (m-2)

Fresh weight of weed (g) at harvest

Dry weight of weed (g) at harvest

Number of pods per plant

Number of seeds per pod

NPK contents of Rhynchosia capitata (%)

Micro nutrient contents of R. capitata (%)

NPK uptake by R. capitata (kg/ha)

Micro nutrient uptake by R. capitata (g/ha, kg/ha)

Weed control efficiency

Relative competitive index (RCI)

3.10.2 Procedure for recording data

Standard procedures were adopted for recording the data on various growth and

yield parameters of R. capitata.

3.10.2.1 Weed population (Field experiment 2)

Number of R. capitata plants per unit area (m-2) was recorded in each growing

season (i.e. 21 days after emergence) by counting all the weed plants randomly at two

different places (m-2) in each plot and then average was calculated.

3.10.2.2 Fresh weight of weed per unit area (g m-2)

Rhynchosia capitata plants per unit area (m-2) were uprooted randomly at two

different places in each plot after prescribed competition durations (field experiment 1)

or at maturity (field experiment 2) and these samples were weighted by using an

electrical balance, then average fresh weight of weed per unit area was calculated.

45

3.10.2.3 Dry weight of weed per unit area (g m-2)

The dry weight of R. capitata was determined after oven-drying at 70oC until

constant weight was achieved.

3.10.2.2 Number of pods per plant of R. capitata

Number of pods per plant was counted by selecting 5 plants at random from each

plot and then average was taken (in field experiment 2 only).

3.10.2.5 Number of seeds per pod

Number of seeds per pod of R. capitata plant was counted by selecting 10 pods

from each plant at random from each plot and then average was taken (in field

experiment 2 only).

3.10.2.6 NPK contents of Rhynchosia capitata

Oven dried samples of Rhynchosia capitata were ground with grinder and NPK

contents (%) were determined as suggested by AOAC (1984).

3.10.2.7 NPK uptake by Rhynchosia capitata

NPK concentrations in R. capitata were multiplied with its dry weight to calculate N,

P and K uptake by R. capitata.

3.10.2.8 Micro nutrient contents of R. capitata

Oven dried samples of Rhynchosia capitata were ground with grinder and micro

nutrient contents were determined as suggested by Jan et al. (2011).

3.10.2.9. Micro nutrient uptake by Rhynchosia capitata

Micro nutrient concentrations in R. capitata were multiplied with its dry weight to

calculate micro nutrient uptake by R. capitata.

3.10.2.10 Weed control efficiency

Based on the weed dry matter produced, weed control efficiency was calculated

using the formula

W1 - W2

Weed control efficiency = ------------------------- X 100

W1

46

Where,

W1 = Dry matter of weeds in control plots

W2 = Dry matter of weeds in treated plots

3.10.2.11. Relative competitive index (RCI)

Jolliffe et al. (1984) formula was used to describe relative competitive index

(RCI) of R. capitata.

Where Yweed free was yield of weed free plot and Yweed was yield in the presence of weed.

3.10.3 Mungbean

Plant population per plot (4.5 m × 1.8 m)

Plant height (cm)

No. of Pods per plant

No. of seeds per pod

1000- grain weight (g)

Biological yield (Kg ha-1)

Seed yield (Kg ha-1)

Percent yield increase over weedy check

Harvest index (%)

3.10.3.1 Plant population

After 30 days of seedling emergence number of mungbean plants per plots were

counted and population of all the plots was maintained equal after thinning.

3.10.3.2 Plant height (cm)

Height of ten mungbean plants selected at random from each plot was taken from

ground to the top of plant with the help of a meter rod. Then average height was

calculated.

47

3.10.3.3 No. of pods per plant

Number of pods per plant was counted by selecting 5 mungbean plants at random

from each plot and then average was taken.

3.10.3.4 No. of grains per pod

Number of grain per pod of mungbean plant was counted by selecting 10 pods

from each plant at random from each plot and then average was taken.

3.10.3.5 1000- grain weight (g)

Five samples per plot of 1000 grains of mungbean were weighed on an electrical

balance and then average was taken to calculate 1000-grain weight in grams.

3.10.3.6 Biological yield (Kg ha-1)

All the mungbean plants of each net plot was harvested with a sickle at maturity

and tied into a bundle. After five days sun drying, it was weighed with an electrical

balance and biological yield kg ha-1 was calculated.

3.10.3.7 Grain yield (Kg ha-1)

Dried samples of each plot were threshed manually. Grain yield of each plot was

recorded and converted into kilograms per hectare.

3.10.3.8 Percent yield increase over weedy check

It was calculated with the formula given by Frans et al. (1986).

% Yield increase over weedy check = Yweedy check – Ytreatment / Yweedy check × 100

Where yield of weedy check plot is denoted by Yweedy check and yield of respective plot is

denoted by Ytreatment.

48

3.10.3.9 Harvest index (%)

Harvest index of mungbean was calculated by using the following formula

3.10.4 Economic analyses

Economic analyses were carried out to look into comparative benefits of different

agronomic practices and weed management methods used in these studies. Marginal

analysis was carried out according to procedures devised by Byerlee (1988).

3.10.4.1 Net benefits

It was calculated by deducting cost that varies from gross benefit (CIMMYT,

1988).

3.10.4.2 Dominance analysis

For dominance analysis, treatments were arranged in order of increasing variable

costs. A treatment was considered dominated (D) if the variable costs were higher than

the preceding treatment, but its net benefits were equal or lower (CIMMYT, 1988).

3.10.4.3 Marginal analysis

In economic analyses, the costs that vary are not compared with net benefits. For

such a comparison, marginal analysis is required. The marginal analysis involves the

dominance analysis and marginal rate of return that are detailed below.

3.10.4.4 Marginal rate of return

Marginal rate of return is the marginal net benefit i.e., the change in net benefit

divided by the marginal cost i.e., change in costs expressed as a percentage. MRR was

determined by using the formula given by (CIMMYT, 1988).

Marginal benefit

MRR (%) = -------------------- x 100

Marginal cost

49

3.10.5 Statistical analysis

Statistical analysis of the measured/observed data was done by using Fisher's

Analysis of Variance techniques (Steel et al., 1997). Least significant difference (LSD)

test was applied at 5% probability level to test the significance of treatment means.

50

CHAPTER 4

Results and Discussion

4.1 Laboratory experiments

4.1.1 EXPERIMENT 1: METHODS TO BREAK SEED DORMANCY OF

RHYNCHOSIA CAPITATA (ROTH) DC.

In this experiment, effects of following methods were used to break the seed

dormancy of R. capitata

4.1.2 Dry heat, hot water and stratification seed treatment

Various seed treatments (dry heat, hot water and stratification) of R. capitata

showed no response in breaking dormancy (table 4.1.1, 4.1.2, 4.1.3). The ungerminated

seeds were still hard and viable (except oven 200 oC treatment) and germinated

successfully when scarified with sand paper.

In leguminous weed species, dry heat breaks physical seed dormancy by

modification of the seed coat mechanically. After this, the fractured seed coat allows

further imbibitions and hence germination takes place (Bradstock and Auld, 1995).

Rigorous heat applied to seeds may rupture their hard seed coats or may soften waxy

coverings present over the seeds (Tarrega et al. 1992). However, in our study (table

4.1.1), a range of dry heat treatment had no effect on breaking seed dormancy of R.

capitata. Seed treatments with hot water had been described to improve germination of

hard seed coat species by uplifting water and O2 permeability of the testa of seed coat

(Teketay, 1998; Aydın and Uzun, 2001). However, in this study, various hot water seed

treatments failed to encourage R. capitata seed germination (table 4.1.2). The response

of R. capitata seeds to a range of stratification treatments (table 4.1.3) is similar to that

repoted by Susko et al. (2001) in kudzu (Pueraria lobata). He reported that keeping

kuzdu seeds at 5°C for 0-6 weeks did not influence seed germination.

51

Table-4.1.1 Effect of dry heat seed treatment on breaking dormancy and

germination of Rhynchosia capitata.

Treatment Time Result

Oven (70 oC) 1 hour No germination



Oven (70 oC) 1 day No germination

Oven (70 oC) 2 days No germination



Oven (200 oC) 5 min No germination





Table-4.1.2 Effect of hot water seed treatment on breaking dormancy and



Boiling water 5 min No germination







52

Table-4.1.3 Effect of stratification seed treatment on breaking dormancy and



Refrigerator (35º- 41º F) 5 min No germination




Refrigerator (35º- 41º F) 3 hour No germination



Refrigerator (35º- 41º F) 2 days No germination





53

4.1.3 Seed treatment with thiourea and KNO3

Seeds of R. capitata showed no response to various concentrations of thiourea

(10000 to 60000 mg L-1) and KNO3 (2500 to 10000 mg/L) as thiourea and KNO3

botched to crack the seed coat and hence imbibitions (table 4.1.4, 4.1.5). The seeds after

the prescribed soaking treatments were still hard and viable, germinated successfully

when scarified with sand paper.

Thiourea has been known to stimulate germination by reducing the preventive

effect of seed coat, in sweet cherry (Prunus avium L.) seeds (Çetinbaş and Koyuncu,

2006). Similarly, KNO3 was very effective in breaking dormancy of many species

(Previero et al., 1996) and had been stated as being a growth-regulating substance in

Salvia species (Yücel, 2000). Both these chemicals were unable to break dormancy in R.

capitata seeds in present investigation. It could be due to its too hard seed coat.

Table-4.1.4 Effect of potassium nitrate (KNO3) seed treatment on breaking

dormancy and germination of Rhynchosia capitata.

KNO3 Concentrations (mg L-1) Result

0 No germination

10 000 No germination






150 min No germination

Table-4.1. 5 Effect of thiourea [(NH2)2CS] seed treatment on breaking dormancy

and germination of Rhynchosia capitata.

Thiourea concentrations (mg L-1) Result

0 No germination

2500 No germination

5000 No germination

7500 No germination


54

4.1.4 Scarification with HCl and sand paper

Treatment with sand paper was very effective in breaking the seed dormancy and

the result is shown in table 4.1.6. Results indicated that germination of seeds

mechanically scratched with sand paper significantly increased of 100% as compared to

HCl treatments. In addition, the seeds mechanically scarified with sandpaper had the

minimum time to 50% germination (0.66 d) and mean germination time (2.16 d) as

compared to all other treatments. When seed were scarified with HCl (36%) for 3, 6, 9,

12, 15 and 18 hours, seeds germination significantly (p < 0.05) increased over control

(table 4.1.6).

Seeds treated with HCl for 12, 15 and 18 hours had the minimum response time,

with 50% of seeds germinating in all replicates within 1.75, 1.13 and 1.20 days

respectively. Minimum MGT (2.94 and 2.95) was detected in seeds treated with HCl for

18 and 15 h, respectively. Both were statistically alike. Seeds treated with HCl for 3, 6

and 9 h took significantly more mean time to germinate than other treatments, but

remained at par with one another. Maximum GI (7.75) was observed in sand paper

scarification followed by 6 days when the seeds were treated with HCl for 15 h.

However, there was no germination in control treatment.

55

Table-4.1.6 Effect of seed scarification with HCl and sand paper on breaking

dormancy and germination of Rhynchosia capitata.

Treatments Germination

%

T50 (d) MGT (d) GI

Control

HCl (3 h)

HCl (6 h)

HCl (9 h)

HCl (12 h)

HCl (15 h)

HCl (18 h)

Sand paper

LSD (P < 0.05)

0.00 f

17.50 e

25.00 e

35.00 d

65.00 c

90.00 b

35.00 d

100.0 a

8.8119

0.00 g

3.62 a

3.25 b

2.25 c

1.75 d

1.13 e

1.20 e

0.66 f

0.3669

0.00 e

4.08 ab

4.37 a

4.15 ab

3.88 b

2.95 c

2.94 c

2.16 d

0.4497

0.00 g

0.47 f

0.69 f

1.35 e

3.11 c

6.00 b

2.19 d

7.75 a

0.4668

Means followed by the same letter in a column did not differ significantly according to

LSD test (P < 0.05).

T50 = Time taken to 50% germination, MGT = Mean Germination time, GI =

Germination Index, LSD = Least Significance Difference.

56

4.1.5 Scarification with HNO3

Soaking of R. capitata seeds in HNO3 for 1 to 5 days had little effect on seed

germination (table 4.1.7). Total germination did not reach over 17.50 % and was slow

and irregular. Germination percentages of seeds in all HNO3 treatments were statistically

at par with one another. Minimum T50 and MGT were recorded in seeds treated with

HNO3 for 3, 4 and 5 d, respectively. The control treatment (untreated) had no effect on

germination. The remaining seeds were still hard and viable, germinated successfully

when scarified with sand paper.

4.1.6 Scarification with H2SO4

The scarification of R. capitata seed with H2SO4 induced seed germination in all

treatments (figure 4.1.1). Seed germination percentage increased with increasing soaking

time (up to 80 min) and began to decrease with the further increase in soaking time.

Seeds soaked in H2SO4 for 60 and 80 min had the most rapid time to 50% germination,

with 50% of the seeds germinating in all replicates within 0.66 and 0.80 d, respectively

(figure 4.1.2). Minimum MGT (2.09 and 2.15 d) was detected 60 and 80 min of soaking

in H2SO4. Maximum GI was recorded when seeds were soaked in H2SO4 for 60 min.

There was no germination in control treatment.

The decline in germination rate at 100 and 120 min soaking in H2SO4 and 18 h

soaking in HCl was the result of the damaging effect to seed embryo due to prolonged

soaking time. The similar response was observed by Sadeghi et al. (2009) who found

that complete removal of the seed coat caused rapid imbibitions, which caused the

fracture and burst of the endosperm. Similarly, Aliero (2004) reported that prolonged

emersion of seeds in H2SO4 injure the seeds as the acid may rapture vital parts of the

embryo.

57

Table-4.1.7 Effect of seed scarification with HNO3 on breaking dormancy and



%

T50 (d) MGT (d) GI

Control

HNO3 (1 d)

HNO3 (2 d)

HNO3 (3 d)

HNO3 (4 d)

HNO3 (5 d)

LSD (P < 0.05)

0.00 b

12.50 a

17.50 a

17.50 a

15.00 a

17.50 a

7.0031

0.00 d

4.31 a

3.25 b

2.50 c

2.50 c

2.50 c

0.7363

0.00 c

4.41 a

3.91 ab

3.33 b

3.58 ab

3.33 b

1.0325

0.00 c

0.28 b

0.47 a

0.59 a

0.43 ab

0.59 a

0.1698





Figure 4.1.1 Effect of seed scarification with H2SO4 on germination of Rhynchosia

capitata (LSD (P < 0.05) = 4.8134).

Axis X: Sulphuric acid soaking time (min)

Axis Y: Germination (%)

58

Figure 4.1.2 Effect of seed scarification with H2SO4 on T50, MGT and GI of

Rhynchosia capitata (LSD (P < 0.05) for T50 = 0.4397, MGT = 0.0576

and GI = 0.4386).


Germination Index

LSD = Least Significance Difference.

4.1.7 Scarification with HCl + H2SO4

When ungerminated seeds of HCl treatments (20, 40, 60, 80, 100 and 120 min)

were retreated with H2SO4 for 30 minutes, the seeds germination significantly (p < 0.05)

increased over control (table 4.1.8), but did not differ statistically in HCl treatments for

different times. Seeds treated with HCl for 80, 100 and 120 min. + H2SO4 for 30 min.

had the minimum response time, with 50 percent of the seeds germinating in all

replicates within 0.94, 0.78, and 0.90 days, respectively. Minimum MGT (2.15) was

detected in seeds treated with HCl for 100 min + H2SO4 for 30 min, followed by HCl for

120 min + H2SO4 for 30 min (2.17). Both were statistically at par with each other. Seeds

treated with HCl for 20, 40 and 60 min. + H2SO4 for 30 min. took significantly more

mean time to germinate than other treatments, but remained at par with one another.

59

Maximum GI (5.70) was detected in seeds treated with HCl for 100 and 120 min. +

H2SO4 for 30 min. However, there was no germination in control treatment.

Table-4.1.8 Effect of seed scarification with HCl + H2SO4 on dormancy release and



(%)

T50 (days) MGT(days) GI

Control

20 min HCl + H2SO4 30 min






LSD (P<0.05)

0.00 b

75.00 a

72.50 a

70.00 a

72.50 a

72.50 a

75.00 a

6.6153

0.00 c

1.33 a

1.28 a

1.24 a

0.94 b

0.78 b

0.90 b

0.1836

0.00 d

2.28 a

2.29 a

2.27 a

2.20 b

2.15 c

2.17 bc

0.0414

0.00 d

4.87 bc

4.66 c

4.62 c

5.20 ab

5.70 a

5.70 a

0.5342

Means sharing the same letter in a column did not differ significantly at 5 % probability

level.



60

4.1.8 Scarification with HNO3 + H2SO4

Soaking of R. capitata seeds in HNO3 for 20, 40, 60, 80, 100 and 120 min. +

H2SO4 for 30 min resulted in significant increase in germination of the seeds (table

4.1.9). Maximum germination percentage (77.50 %) was recorded when seeds were

treated with HNO3 (120 min) + H2SO4 for 30 min, but did not differ significantly from

seeds treated with HNO3 for 60, 80 and 100 min. + H2SO4 for 30 min. Minimum (T50)

germination and MGT was recorded in seeds treated with HNO3 for 120 min + H2SO4

for 30 min, while maximum values were recorded in seeds treated with HNO3 for 20 min

+ H2SO4 for 30 min. Germination index was increased with increasing the soaking time

of seeds in HNO3+ H2SO4 for 30 min. The control treatment (untreated) had no effect on

germination.

Table-4.1.9 Effect of seed scarification with HNO3 + H2SO4 on dormancy release

and germination of R. capitata.


(%)


Control

20 min HNO3 + H2SO4 30 min






LSD (P<0.05)

0.00 d

65.00 c

70.00 bc

72.50 ab

72.50 ab

75.00 ab

77.50 a

6.6153

0.00 e

2.56 a

1.60 b

1.18 c

0.90 cd

1.00 cd

0.70 d

0.3919

0.00 e

3.16 a

2.61 b

2.25 cd

2.03 d

2.48 bc

2.14 d

0.2940

0.00 f

2.83 e

4.25 d

4.95 c

5.37 b

5.33 bc

6.20 a

0.4099

Means sharing the same letter in a column did not differ significantly at 5 % probability

level



61

Mechanical restrictions which include avoidance of water and oxygen uptake,

and synthesis of chemical inhibitors are some of the possible mechanisms that cause

sturdy inhibitory effect of the seed coat on germination of seeds (Taiz and Zeiger, 2002).

The results of various treatments in our study confirm that seeds of R. capitata exhibit

dormancy due to hard seed coat. Various seed scarification methods break down R.

capitata seed coat impermeability that resulted in considerable increase in germination

percentage (12-100%). The different chemicals (thiourea, KNO3) and acids (HCl, HNO3

and H2SO4) had been widely used for breaking dormancy of many hard seed coat species

like European milkvetch (Astragalus hamosus L.), blackdisk medick [Medicago

orbicularis (L.) Bartal.] (Patane and Gresta, 2006) and Albizia spp. (Tigabu and Oden,

2001).

In present investigation, the best treatment for removing hard seed dormancy,

which caused the highest germination percentage, was seed scarification with H2SO4 and

sand paper. Similar results were obtained in experiments with African locust bean

(Parkia biglobosa) seeds (Aliero, 2004), European milkvetch (Astragalus hamosus L.)

and blackdisk medick [Medicago orbicularis (L.) Bartal.] seeds, (Patane and Gresta,

2006) and Enterolobium contortisiliquum (Vell.) Morong seed (Malavasi and Malavasi,

2004) in which seed dormancy was broken by soaking seeds in H2SO4 and with sand

paper scarification. The significantly maximum and rapid imbibitions and germination

percentages were abserved in mechanical scarification treatment in this study as

compared to untreated (control) seeds and also completely overcome the seed coat

impermeability.

Hydrochloric acid was used to most closely imitate the stomach environment of

animals. Total germination of the HCl treated seeds increased as compared to control

over an extended period (up to 18 h) indicating a slow release from seed dormancy.

These results were similar with those of Russel et al. (2009) who found that Benghal

dayflower seeds exposed to HCl soaking treatments germinate successfully with a little

loss in viability after each treatment. Seeds from 18 h treatment were extremely soft and

mouldy at the end of the germination test, so less germination was recorded in this

treatment. The mechanism of possible seed germination influenced by H2SO4 is due to

its capability to rupture seed coat, hence leading to water absorption and thus imbibition

of seeds. Gradual increase in germination percentage and GI; and decrease in MGT and

T50 with increase in soaking time of seeds in HCl from 3 to 15 h and treatment with

62

H2SO4 for 20, 40, 60 and 80 min revealed that HCl and H2SO4 were adequate to rupture

the hard seed coat of R. capitata seeds to induce germination.

These studies indicated that the success of this species is largely attributed to the

occurrence of seed dormancy, which allows the seed to persist for long periods in soil

and thus escape the effects of post germination weed control measure.

63

4.2 Experiment 2: Seed Germination ecology of R. capitata.

In this experiment, effects of following ecological factors were studied on


4.2.1 Temperature and Light.

Rhynchosia capitata seed germination was significantly highest (97.5%) at 30 oC

followed by 82.5% at 35 oC (table 4.2.1). The significantly minimum germination

(17.5%) was recorded at 45 oC. Rhynchosia capitata seeds took minimum time (0.83

days) to complete 50% germination at 25 oC, which was statistically at par with 30 oC

and 20 oC in which the seeds took 0.89 days and 0.91 days to complete 50% germination,

respectively. Minimum mean germination time (2.16 days) was observed at 25 oC while

the seeds took significantly maximum MGT (2.87 days) at 45 oC.

Table 4.2.1 Effect of different level of temperature on the germination of R. capitata


(%)


Temperature

45 0C

40 0C

35 0C

30 0C

25 0C

20 0C

LSD (0.05)

17.5 e

65.0 c

82.5 b

97.5 a

75.0 b

55.0 d

8.0230

2.76 a

1.35 b

1.46 b

0.89 c

0.83 c

0.91 c

0.1150

2.87 a

2.32 b

2.24 bc

2.19 bc

2.16 c

2.19 bc

0.1557

0.66 d

4.04 c

5.71 b

7.12 a

5.70 b

4.04 c

0.7082


LSD test (p < 0.05).

T50: Time needed for 50% germination; MGT: Mean germination time; GI: Germination

index; LSD: Least significance difference.

64

Since R. capitata seed germination was observed in both light and dark

environments equally, therefore data for this experiment is not presented. The response

of R. capitata over a range of temperatures is similar to that reported for other weed

species such as giant sensitive plant (Mimosa invisa L.) (Chauhan and Johnson, 2008).

Rhynchosia capitata germinates over a broad range of temperatures and in the presense

or absence of light. It may allow R. capitata seeds to germinate in impenetrable and

shaded neighbourhoods for instance beneath a crop canopy. The optimum temperatures

for R. capitata seed germination were comparable to those of summer temperatures in

the cultivated areas of southern Punjab, Pakistan. Temperature below a constant

temperature of 25 oC was not favourable for germination; as a result, spread of this weed

may be limited to warmer temperatures of summer season of these regions. Similar

results may be attained in soil under field situations at these temperature conditions as

this weed start to germinate just after the irrigation or rainfall.

The response of R. capitata to light and dark was similar to that observed by

Chauhan and Johnson (2008) in giant sensitive plant (Mimosa invisa L.) in which seed

germinated equally in light as well as in dark. As seeds of R. capitata germinated in

complete darkness, this could explain why germination occurs from deep depths in soils,

under plant canopy and litter shade.

4.2.2 Salt Stress.

A three-parameter logistic model {G (%) = 94.6/ [1 + (x/137.6)6.2], r 2 = 0.96}

was fitted to the germination data obtained at different concentrations of NaCl (figure

4.2.1). The data suggest that R. capitata seed germinated even at high salinity level.

Germination was greater than 90% at 0 mM NaCl and some germination (10 %)

occurred even at 200 mM NaCl. Germination was completely inhibited at 250 mM

NaCl. The concentration for 50% inhibition of the maximum germination, estimated

from the fitted model (Equation 1), was 137.6 mM NaCl.

The data presented in the table 4.2.2 show that with the increase in NaCl

concentration from 0 to 250 mM, R. capitata seeds took considerably more time to reach

the T50 and complete germination compared with those in the distilled water treatment.

The seeds soaked in 50 and 100 mM salt concentration took less time to reach the T50

and for mean germination than those soaked in the 150, 200 and 250 mM of NaCl

concentration. The increasing levels of NaCl concentration (50 to 250 mM) significantly

65

decreased the germination index of R. capitata compared with the distilled water with

the maximum reduction noted in the 250 mM NaCl concentration.

NaCl concentration (mM)

0 50 100 150 200 250

Ger

min

atio

n %

0

20

40

60

80

100 G(%) = 94.6/[1+(x/137.6)5.2 R2 = 0.96

137.6

FIGURE 4.2.1 Effect of sodium chloride (NaCl) concentration on germination of R.

capitata.

Line represents the functional three-parameter logistic model {G (%) = G max / [1 +

(x/x50)Grate]} fitted to the data.

Table 4.2.2 Effect of different levels of salt stress on the germination of R. capitata.

Treatments T50 (days) MGT(days) GI

NaCl (mM)

0

50

100

150

200

250

LSD (0.05)

0.58 d

1.50 c

1.56 c

2.12 b

2.37 ab

2.56 a

0.3456

2.09 d

2.86 c

2.89 c

2.97 b

3.00 b

3.39 a

0.0679

8.50 a

5.66 b

5.25 b

4.04 c

3.02 d

1.66 e

0.5426





66

The results reveal that seeds of R. capitata have ability to germinate even at high

soil salinity and such soil types are common in many parts of Punjab, Pakistan (Azhar

and Tariq, 2003). Similar results were obtained by Chauhan et al. (2006a) in annual

sowthistle (Sonchus oleraceus) in which more than 90% of seeds germinated at a low

level of salinity (40 mM NaCl) and some seeds (7.5%) germinated even at 160 mM

NaCl.

It is a recognized statement that presences of considerable amounts of salts

adversely affect the seed germination owing to the interruption in physiological and

metabolic processes taking place in various parts of plant (Afzal et al., 2006). Response

of R. capitata to salinity may be due to its effect on seed germination by generating an

outer osmotic potential that avoids uptake of water by seeds or owing to the lethal effects

of Na+ and Cl- ions on the seed germination that was also reported by Khajeh-Hosseini et

al. (2003). In other words, R. capitata was found reasonably more tolerant to salt stress

as it gave 7.5% seed germination at 200 mM of NaCl concentration with respect to its

control treatment against higher salinity level.

4.2.3 Osmotic Stress.

A three-parameter logistic model {G (%) = 94.8 / [1 + (x/-0.8)], r 2 = 0.98} was

fitted to the germination values (%) obtained at different osmotic potential (figure 4.2.2).

Germination decreased from 100 to 15% with the increase in osmotic potential from 0 to

-0.6 MPa. However, seed germination of R. capitata was entirely inhibited at osmotic

potential of -1.0 MPa or greater. However, more than 10% germination at an osmotic

potential of -0.6 MPa showed that some seeds of R. capitata can germinate under

marginal drought conditions. The osmotic potential for 50% inhibition of the maximum

germination, estimated from the fitted model (Equation 1), was -0.48 MPa.

The data presented in the table 4.2.3 reveal that increasing levels of osmotic

potential (MPa) has significant effects on T50 (days), MGT (days) and GI of R. capitata.

The seeds took minimum time (0.66 days) to complete 50% germination at 0 Mpa of

osmotic potential. There was a gradual increase in the time to complete 50% germination

by R. capitata seeds with the increase in osmotic potential from -0.2 to -1.0 MPa.

Minimum mean germination time (2.16 days) was observed at 0 Mpa while the seeds

took significantly maximum MGT (4.10 days) at -1.0 MPa. Minimum germination index

(0.32) was observed at -1.0 MPa, which was statistically at par with -0.8 MPa of osmotic

potential in which 0.41 GI was recorded.

67

0.0

Ger

min

atio

n %

0

20

40

60

80

100

Osmotic potential (MPa)

-0.2 -0.4 -0.6 -0.8 -1.0

G(%) = 94.8/[1+(x/-0.48)R2 = 0.98

-0.48

FIGURE 4.2.2 Effect of osmotic potential on germination of R. capiata seeds. Line

represents the functional three-parameter logistic model {G (%) = G max / [1 + (x/x50)Grate]} fitted

to the data.

Table 4.2.3 Effect of different levels of osmotic potential on the germination of R.

capitata.

Treatments T50 (days) MGT(days) GI

Osmotic potential (MPa)

0

-0.2

-0.4

-0.6

-0.8

-1.0

LSD (0.05)

0.66 e

1.28 d

2.45 c

2.50 c

3.25 b

3.62 a

0.3581

2.16 c

2.27 c

3.12 b

3.25 b

3.83 a

4.10 a

0.3336

7.83 a

5.79 b

3.12 c

0.89 d

0.41 de

0.32 e

0.4848





68

The results suggest that R. capitata is a weed favoured by a moist environment

which may occur in the field conditions just after rainfall or irrigation. Lowest

germination (15 %) at an osmotic potential of -0.8 MPa point outs that R. capitata can

germinate under reasonable water stress environments, which is a common characteristic

of the summer season in the dry region of Punjab, Pakistan. Likewise, germination of

annual sowthistle (Sonchus oleraceus) also decreased from 95% to 11% as osmotic

potential increased from 0 to -0.6 MPa and was completely inhibited at osmotic potential

greater than -0.6 MPa (Chauhan et al., 2006a). In contrast to R. capitata, some weed

species such as trumpet creeper (Chachalis and Reddy, 2000) were exceedingly

susceptible to low osmotic potential. Germination of R. capitata over this variety of

osmotic potentials indicates that this weed could create a serious threat under the

conditions of low and high soil moisture levels.

4.2.4 pH.

Seeds of R. capitata had ability to germinate over a broad array of pH (5-10).

Seed germination was less affected with increasing rate of pH from 6 to 8 and then

diminished at higher pH levels (table 4.2.4). Maximum germination (97.5%) was

recorded at pH 7, followed by 95% and 92.5 % at pH level of 8 and 6, respectively but

these were statistically at par with one another. Seed germination was 85% and 75% at

pH 5 and 10, respectively. However, at pH level of 10, time to 50% germination (1.66

days) and MGT (2.97 days) was maximum as compared to other pH levels.

In Pakistan, the soils are mostly developed from calcareous, alluvial and loessial

deposits, so most of the soils have alkaline pH and low organic matter contents under

canal and tube well irrigated areas of Punjab (Niaz et al., 2007). Therefore, germination

and survival of R. capitata over a broad array of pH specifys that pH may not be a

preventive factor for seed germination in most soil conditions of Pakistan. These results

were in line with those reported for seeds of giant sensitive plant (Mimosa invisa) which

germinated best between pH 4 and 10 (Chauhan and Johnson, 2008.). Our data suggest

that this species will be problematic in summer crops and pastures throughout Punjab,

Pakistan, where soil pH can vary widely.

69

Table 4.2.4 Effect of different levels of pH on the germination of R. capitata.


(%)


pH

5.0

6.0

7.0

8.0

9.0

10.0

LSD (0.05)

85.0 c

92.50 abc

97.50 a

95.00 ab

87.50 bc

75.00 d

8.0230

0.95 b

0.73 c

0.84 bc

0.93 bc

1.58 a

1.66 a

0.2078

2.19 c

2.11 d

2.17 c

2.19 c

2.29 b

2.97 a

0.0375

6.29 bc

7.66 a

7.41 a

7.00 ab

5.62 c

4.02 d

0.7116





70

4.2.5 Burial Depth.

The seedling emergence data of R. capitata were also fitted to three-parameter

logistic model {E (%) = 88.08 / [1 + (x/7.74) 8.4]}, r 2 _ 0.99; where E represents seedling

emergence (%) and x represents depth (cm) of seed burial]. Seedling emergence of R.

capitata decreased with increased planting depth (figure 4.2.3). Seedling emergence was

greater than 80% when R. capitata seeds were placed on the soil surface and no

seedlings emergence was recorded from seeds placed at a depth of 12 cm. The

emergence of seedlings at deeper soil layers (10 cm) showed that light is not a preventive

feature for the seed germination of R. capitata.

When the seed buried at 10 and 12 cm depths were examined, it was found that

most of the seed at 10 cm depth and all seeds from 12cm depth were dead. Little or no

seedling emergence from these depths may be linked to seed energy reserves (Mennan

and Ngouajio, 2006). We used scarified seeds in experiment to study seedling emergence

at different depths. Seedling emergence might be expected to emerge over an extended

period as the scarification processes require time in field conditions (Chauhan and

Johnson, 2008).

Seedlings of R. capitata had ability to emerge from soil over varying depths

(table 4.2.5). Rhynchosia capitata seedlings took maximum time to 50% emergence from

10 cm depth. The seeds placed at soil surface took statistically minimum time (6.5 days)

to complete 50% emergence. Minimum MET (9.63 days) was detected when seeds were

placed at soil surface. Seeds placed at 10 cm depth took significantly more mean time to

emerge from soil than all other treatments. Maximum GI (0.74) was detected when seeds

were placed at 2 cm depth. However, seedling failed to emerge from 12 cm of soil depth.

Sharp decrease in seedling emergence due to increased planting depth has been

observed in annual sow thistle (Sonchus oleraceus) by Chauhan et al. (2006a). The

seedling emergence of R. capitata from the seeds that were positioned on the soil surface

advocates that no till crop husbandry practices in which a large proportion of the R.

capitata seed bank remains on the soil surface after crop planting will favour seedling

establishment of R. capitata. Similarly, conventional tillage practices which buried the

seeds up to 6 cm depths would also enhance seedling emergence under field conditions.

Whereas, deep tillage operations which bury seeds deep in the soil (10 to 12 cm or even

more), can restrict the emergence of this weed. Adequate understanding of germination

and emergence behaviour of R. capitata would help to develop strategies that will not

71

only suppress germination of this weed but also will facilitate forecast ecological array

and prospective for spreading into new agricultural systems.

Burial depth (cm)

0 2 4 6 8 10 12

Em

ergen

ce %

0

20

40

60

80

100

E(%) = 88.08/[1+(x/7.74)8.4

R2 = 0.99

FIGURE 4.2.3 Effect of planting depths on emergence of R. capitata seedlings. Line

represents the functional three-parameter logistic model {E (%) = E max / [1 + (x/x50)

Erate]} fitted to the data.

Table 4.2.5 Effect of different levels of sowing depth on the seedling emergence of R.

capitata.

Treatments T50 (days) MET(days) EI

Seeding depth (cm)

0

2

4

6

8

10

12

LSD (0.05)

6.50 e

8.00 cd

7.62 d

8.68 c

10.0 b

11.1 a

0.00 f

1.0359

9.63 e

10.51 d

10.64 d

10.98 c

11.66 b

12.10 a

0.00 f

0.2348

0.74 d

1.08 a

0.93 b

0.81 c

0.34 e

0.27 f

0.00 g

0.0716


LSD test (p < 0.05). T50 = Time taken to 50% germination, MGT = Mean Germination

time, GI = Germination Index, LSD = Least Significance Difference.

72

The results of this experiment suggest that R. capitata was able to germinate over

a broad range of temperatures (20 to 40 oC); however, germination was greatest at

temperatures of 30 and 35 oC. Furthermore, R.capitata germinated under reasonable

levels of water stress (-0.8 MPa), salinity (200 mM) and shows rapid germination under

varying pH levels (5-10). Seedling emergence appears to be optimum from the soil

surface and the species may therefore be well suited to establishment under no-till given

moist warm conditions generally found in summer in southern Punjab of Pakistan. As

increased seed burial depth decreased seedling emergence, therefore, high soil-

disturbance tillage systems will reduce seedling establishment of R. capitata. The

elevated capability of R. capitata seeds to germinate over a broad range of ecological

factors proposes that this weed species will be bery challenging for the farmers in near

future if not managed properly.

73

4.3 Experiment 3. Allelopathic effects of Rhynchosia capitata (Roth) DC on

germination and seedling growth of mungbean.

In this experiment, effects of following factors were studied on the germination

and seedling growth of R. capitata.

4.3.1 Allelopathic effects of different plant parts of R. capitata on germination of

mungbean

Allelopathic effects of different plant parts of R. capitata on germination

percentage of mungbean are presented in the figure 4.3.1. The results showed that water

extracts of various R. capitata plant parts reduced the germination percentage of the

mungbean seed compared with the distilled water (control). The minimum germination

(62%) was observed in leaf extract of R. capitata, while, the maximum was found in

control treatment (97%).

Moreover, water extracts of the root, stem, leaf whole plant and fruit of R.

capitata significantly affected the time taken to 50% germination (T50), mean

germination time (MGT) and germination Index (GI) of mungbean as compared to

control treatment (table 4.3.1). The mungbean seeds took significantly more time to

reach the T50 and complete germination with root, stem, leaves, whole plant and fruit

extracts of R. capitata compared with those in the distilled water. The seeds soaked in

the root and fruit extract took less time to reach the T50 and for mean germination than

those soaked in the stem, leaves and whole plant extracts of R. capitata. Maximum mean

germination time (5.31 days) was recorded with leaf extract followed by whole plant

extract (4.65 days). The root, stem, leaves, whole plant and fruit extracts significantly

decreased the germination index of mungbean with the maximum reduction in the leaf

extract compared with that of distilled water. .

These results suggest that the phytotoxicity of R. capitata leaf, stem, fruit, whole

plant and root extracts may be due to restriction of water uptake and, hence, inhibition of

seed germination. Rice (1984) reported that seed protease activities decrease

considerably due to the interruption in water uptake. This phenomenon had an important

role in the hydrolysis of protein during seed germination and to a significant level was

also associated with the water imbibition and uptake by seeds. These results are similar

to the results of Babar et al. (2009) who stated that chickpea seeds soaked in root extract

of Asphodelus tenuifolius Cav. took more time for germination. Similarly, Tawaha and

74

Turk (2003) also observed an inhibitory effect of allelochemicals on water imbibition by

wild barley (Hordeum leporinum) in a study on the allelopathic effects of black mustard

(Brassica nigra).

Figure 4.3.1 Effect of R. capitata extract on the germination of mungbean

Table 4.3.1 Effect of R. capitata extract on the germination traits of mungbean

Treatments T50 (d) MGT (d) GI

Control

Root Extract

Stem Extract

Fruit Extract

Leaves Extract

Whole Plant Extract

LSD (0.05)

0.69 e

3.48 d

4.32 c

3.36 d

6.61 a

5.28 b

0.45

2.17 e

3.91 d

4.55 c

3.88 d

5.31 a

4.65 b

0.089

18.41 a

11.08 b

9.85 c

11.25 b

6.99 e

8.08 d

1.004





75

4.3.2 Effect of different concentrations of leaf extracts of R. capitata on the

germination of mungbean

Figure 4.3.2 represents the effect of different concentrations of leaf extracts on

the germination of mungbean seeds. The results showed that there was a gradual

decrease in germination percentage of mungbean seeds with the increasing concentration

of leaf extract of R. capitata. The 5% leaf extract of R. capitata caused the maximum

reduction in the germination percentage compared to other concentrations as well as

distilled water treatment.

The data presented in the table 4.3.2 demonstrate the effect of the application of

different concentrations of R. capitata leaf extracts on the different germination traits of

mungbean. The data revealed that the all the concentrations of leaf extract increased the

time taken to reach the 50% germination compared with the distilled water, but the

significant increase was recorded with 5% leaf extract. The 1% extract of R. capitata leaf

increased the mean germination time but the marked increase in mean germination time

of mungbean seeds was recorded at higher concentrations (2% - 5%) of R. capitata,

compared with the control. The germination index of mungbean seeds significantly

decreased with the increasing concentrations of leaf extract, but it was statistically

similar at 2% and 3% leaf extracts.

The results of our studies showed that leaves of R. capitata enjoyed significantly

greater allelopathic effect as compared to other parts of the plant. Maximum total

phenolics were detected in leaf extract as compared to all other extracts (figure 4.3.3)

which showed that inhibition of germination is due to the presence of more phenolics in

leaf extract. The greater number of growth inhibitors were detected in the leaves of R.

capitata elucidates its stronger inhibitory activity. These results were supported by the

findings of Kadioglue et al. (2005). They stated that different plant part extracts of some

broad and narrow leaf weeds inhibited the seed germination rate and final seed

germination of lentil (Lens culinaris), chickpea (Cicer arietinum), and wheat (Triticum

aestivum). Our findings were also in line with that of Tanveer et al. (2010), who

concluded that leaf extract had a better inhibitory result than extracts of other plant parts

while investigating the allelopathic effect of root, stem, leaf, and fruit water extracts and

soil infested of Euphorbia helioscopia L. on the seed germination and subsequent

seedling growth of wheat, chickpea, and lentil crops. Similarly, Dongre and Singh

76

(2007) also concluded that the leaves extracts of different weeds like Amaranthus viridis,

Parthenium hysteroporus and Polygonum plebeium drastically inhibited the growth of

wheat (Triticum aestivum).

Figure 4.3.2 Effect of different concentrations of R. capitata leaf extract on the

germination percentage of mungbean

Table 4.3.2 Effect of different concentrations of R. capitata leaf extract on the

germination traits of mungbean

Treatments T50 (d) MGT (d) GI

Control

1% Extract

2% Extract

3 % Extract

4% Extract

5% Extract

LSD (0.05)

0.68 e

3.14 d

4.12 c

4.43 c

5.10 b

6.61 a

0.4487

2.17 d

4.56 bc

4.54 c

4.57 bc

4.67 b

5.31 a

0.1016

18.16 a

11.87 b

10.22 c

9.57 c

8.16 d

6.99 e

0.9005





77

Figure 4.3.3 Determination of total water soluble phenolics in different plant parts

of R. capitata.

4.3.3 Effects of different concentrations of R. capitata soil incorporated residues on

the seedling emergence of mungbean

The effects of different concentrations of R. capitata soil incorporated residues

on the emergence percentage of mungbean seedlings are presented in the figure

4.3.4.The results showed that mungbean seedling emergence percentage was

significantly highest (95 %) in R. capitata free soil followed by that (55%) in 1% soil

residues of R. capitata. The significantly minimum emergence percentage (10 %) of

mungbean was recorded in 4 % soil residues of R. capitata.

The data presented in table 4.3.3 showed the impact of different concentrations of

soil residues of R. capitata on the emergence charactristics of mungbean. Mungbean

seedlings took minimum time (0.48 days) to complete 50 % emergence in control

treatment, whereas significantly maximum time to complete 50 % emergence was

recorded in 4 % soil residues of R. capitata in which the seeds took 12.75 days.

Emergence index was significantly maximum (3.85) in control treatment followed by

0.88 and 0.49 in 1% and 3% soil residues of R. capitata, respectively. The significantly

minimum mean emergence time (MET) (3.51 days) was observed in control treatment

while the seeds took maximum MET (10.91 days) in 4% soil residues of R. capitata.

Rhynchosia capitata infested soil significantly inhibited the root length, shoot

length, shoot dry weight, seedling dry weight and seedling vigour index of mungbean

(table 4.3.3). In all cases, the largest seedlings in terms of root and shoot length were

78

found in the control treatment that had no R. capitata residues. The results of this

experiment indicate that the 4% soil incorporated residues of R. capitata caused

maximum reduction in root and shoot length as well as seedling vigour index of

mungbean seedlings. Similarly, minimum dry weights of root, shoots and seedlings were

also observed in 4% soil residues as compared to other concentrations of R. capitata soil

residues as well as control treatment.

These findings are supported by the results of Rashid et al. (2010), who reported

impaired growth of lettuce (Lactuca sativa) and radish (Raphanus sativus) seeds (root

length, shoot length and fresh weight of roots and shoots) by allelopathic potential of leaf

and root leachates of kudzu (Pueraria lobata). Tanveer et al. (2008) also reported that

minimum GI and germination percentage of rice seeds was observed when treated with

leaf leachates of common cocklebur (Xanthium strumarium). Similarly, Stavrianakou et

al. (2004) also documented the inhibition of germination, germination index and increase

in germination time of chickpea and lentil with the extract of different weeds.

Figure 4.3.4 Effect of R. capitata -infested soil on the seedling emergence percentage

of mungbean.

79

Table 4.3.3 Effect of R. capitata -infested soil on the germination indices and

seedling characteristics of mungbean.

Treatments T50

(d)

EI MET

(d)

Root

Length (mm)

Shoot

length (mm)

Root dry

weight (mg)

Shoot dry

weight (mg)

Seedling dry

weight (mg)

SVI

Control

1% Residue

2% Residue

3% Residue

4% Residue

5% Residue

LSD (0.05)

0.48 d

5.20 c

6.50 c

8.50 b

12.75 a

NG

1.6033

3.85 a

0.88 b

0.49 c

0.34 cd

0.11 d

NG

0.2991

3.51 d

8.37 c

9.48 b

10.75 a

10.91 a

NG

1.0085

64.00 a

49.50 b

43.75 b

28.25 c

20.25 c

NG

9.2027

45.25 a

26.50 b

18.50 c

14.00 cd

9.25 d

NG

6.2929

45.25 a

26.50 b

18.50 c

14.00 cd

9.25 d

NG

6.2929

122.50 a

94.00 b

83.25 c

64.25 d

32.50 e

NG

8.5745

278.25 a

235.00 b

211.00 c

167.25 d

89.25 e

NG

13.060

609.00 a

272.50 b

186.50 c

92.00 d

21.75 d

NG

72.845



SVI: Seedling vigor index, T50: Time needed for 50% germination; MGT: Mean

germination time; GI: Germination index; NG: Non germinated; LSD: Least significance

difference.

Two phenolic acids (vanillic acid and 4-(hydroxymethyl) benzoic acid) were

found in the R. capitata extract and vanillic acid was the most important. A wide range

of phenolic acids have been reported in numerous crop plants and weeds and soils of

agricultural systems (Inderjirt, 1996). These phenolic acids are frequently revealed as

recognized allelochemicals (Inderjit et al., 1999). Inderjit (1996) concluded that of

variety of these various phenolic acids found in crops and weeds collectively affect the

nearby plants and a single phenolic acid is not responsible for the strong inhibitory

activity. Similer observations have been reported by Einhellig (1999) concluded that

combination of various phenolic acids have additive inhibitory and/or synergistic

inhibitory effect on the neighbouring plants.

80

The results obtained in these experiments demonstrate that the water extracts of

R. capitata possess allelochemicals that restrained the germination and seedling growth

of mungbean. The presence of considerable amount of phenolic acids suggests that it is

essential to keep this weed under check particularly at the seedling emergence stage so

that its inhibitory effects on the crop may be avoided.

81

4.4 FIELD EXPERIMENT 1

EFFECT OF DIFFERENT WEED-CROP COMPETITION PERIODS ON THE

GROWTH AND YIELD OF MUNGBEAN.

4.4.1 Effect of weed competition periods on fresh weight of R. capitata (gm-2)

Effect of weed-crop competition periods on the fresh weight of R. capitata (gm-2)

in mungbean is presented in table 4.4.1. The data showed that with the increase in weed

competition, R. capitata fresh weight also increased. Full season weed competition

produced highest R. capitata fresh weight which was statistically different from all other

R. capitata competition periods during both the years of study. Competition periods of 3

weeks gave minimum weed fresh weight during both the years. In trend comparison of

different weed-crop competition periods (3 to 7 weeks), linear trend was significant,

whereas, quadratic and cubic trends were non-significant during both the years of study.

Increase in fresh weight of R. capitata was due to prolonged weed growth and

development resulting from increase in competition period. The effect of varying weed

competition durations appeared to be more pronounced particularly where weed-crop

competition was for longer duration. Akhtar et al. (2000) also found that with the

increase in weed-crop competition duration, weed biomass also increased.

4.4.2 Effect of weed competition periods on dry weight of R. capitata (gm-2)

The data related to dry weight of R. capitata presented in table 4.4.2 reveal that

dry weight of R. capitata was considerably affected by varying R. capitata competition

periods. The results showed that significantly maximum dry weight of R. capitata (58.25

g) was observed in plots where R. capitata plants were allowed to compete with the

mungbean crop all over the cropping season. The significantly minimum R. capitata dry

weight was recorded in plots with 3 week R. capitata competition in 2011. Similar trend

was observed in 2012. Rhynchosia capitata dry weight demonstrated an increasing

tendency as the R. capitata competition period was extended. The competition periods of

3 and 4 weeks were statistically similar in 2011. However, R. capitata dry weight

increased as the competition period was increased. Trend comparison of different weed-

crop competition periods (3 to 7 weeks) showed that linear trend was significant whereas

quadratic and cubic trends were non-significant during both the years of study.

The linear trend of different weed-crop competition periods (3 to 7 weeks) which

showed that there was a linear increase in the R. capitata dry weight with the increase in

82

weed-crop competition periods. Increase in R. capitata dry weight with long-standing R.

capitata competition period may possibly be owing to the additional time benefited by R.

capitata to germinate and carry on its subsequent growth and development resulting into

further buildup of photosynthates and better biomass. These results are in line with those

of Naeem et al. (2000) who also reported linear increase in weed dry weight with

increase in weed-crop competition period in mungbean.

83

Table 4.4.1 Effect of different weed-crop competition periods on fresh weight of R.

capitata (gm-2) in mungbean.

Weed-crop competition duration for 2011 2012

Zero week ----- -----

3 weeks after planting 82.00 f 96.25 f

4 weeks after planting 114.50 e 136.25 e

5 weeks after planting 146.50 d 173.75 d

6 weeks after planting 175.25 c 217.25 c

7 weeks after planting 201.75 b 257.75 b

Full season 232.25 a 286.75 a

LSD 7.660 15.975

Trend comparison of different weed-crop competition periods (3 to 7 weeks)

Linear Trend ** **

Quadratic Trend NS NS

Cubic Trend NS NS



NS and ** indicate non-significant and significant at P ≤ 0.01 level of probability, respectively.

84

Table 4.4.2 Effect of different weed-crop competition periods on dry weight of R.

capitata (gm-2) in mungbean.


Zero week ----- -----

3 weeks after planting 21.00 e 24.75 f

4 weeks after planting 27.25 de 30.25 e





LSD 6.392 4.760


Linear Trend ** **


Cubic Trend NS NS




85

4.4.3 Effect of weed competition periods on NPK contents (%) of R. capitata

The data presented in the tables 4.4.3, 4.4.4 and 4.4.5 indicate the effect of

different weed-crop competition periods on the NPK contents of R. capitata. The data

showed that significant differences in NPK contents of R. capitata were observed

between both the study years, being higher in second year of study. The significantly

maximum NPK contents (%) of R. capitata were recorded in the plots where R. capitata

plants were allowed to compete with the crop all over the cropping season during both

the years of study. There was a linear increase in the NPK contents (%) of R. capitata

with increase in R. capitata competition period from 3 to 7 weeks. The significantly

minimum NPK contents of R. capitata were recorded in competition period of 3 weeks

during both the years of study. In trend comparisons of different weed-crop competition

periods (3 to 7 weeks), the linear trend was significant, whereas quadratic and cubic

trends were found non-significant during both the years of study.

Weeds are generally luxury feeders for NPK. In competition periods of 3, 4 and 5

weeks, R. capitata plants were not grown completely, hence resulted into fewer

competitions. Due to this reason, R. capitata plants had minimum NPK contents as

compared to other treatments. The linear increase in the NPK contents with the

enhancement of R. capitata competition periods may possibly owing to more use of

nutrients and environmental resources by R. capitata hence more NPK contents.

86

Table 4.4.3 Effect of different weed-crop competition periods on N content (%) of

R. capitata.


Zero week ----- -----

3 weeks after planting 1.37 f 1.49 f






LSD 0.272 0.217


Linear Trend ** **


Cubic Trend NS NS




87

Table 4.4.4 Effect of different weed-crop competition periods on P content (%) of R.

capitata.


Zero week ----- -----

3 weeks after planting 1.39 d 1.40 e


5 weeks after planting 1.65 c 1.75 d

6 weeks after planting 1.80 b 1.94 c

7 weeks after planting 1.98 a 2.19 b


LSD 0.138 0.166


Linear Trend ** **


Cubic Trend NS NS




88

Table 4.4.5 Effect of different weed-crop competition periods on K content (%) of

R. capitata.


Zero week ----- -----







LSD 0.134 0.085


Linear Trend ** **


Cubic Trend NS NS




89

4.4.4 Effect of weed competition periods on NPK uptake (kg ha-1) of R. capitata

Effect of weed-crop competition periods on the N uptake (kg/ha) by R. capitata

was significant (table 4.4.6). The significantly maximum N uptake by R. capitata (22.66

kg ha-1) was observed in the plots where R. capitata plants were allowed to compete with

mungbean all through the cropping season. The minimum N uptake by R. capitata (3.12

kg ha-1) was recorded in plots with 3 weeks competition period in 2011. Similar trend

was observed in 2012. Higher N uptake by R. capitata in weedy check can be attributed

to greater biomass achieved all through the cropping season. These results are supported

by the research findings of Anjum et al. (2007) and Ikram et al. (2012) who reported that

N uptake by weeds increased in weedy check. Similarly, Gaikwad and Pawar (2003) also

reported that weeds removed 33.53 Kg ha-1 of N in weedy plots.

Effect of different weed-crop competition periods on the P uptake (kg/ha) by R.

capitata was also significant during both the years of study (table 4.4.7). The

significantly maximum P uptake (12.29 kg ha-1) by R. capitata was recorded in plots

having full season R. capitata competition during both the study years. The minimum P

uptake (2.92 kg ha-1 in 2011) was noted in plots having 3 weeks weed competition. The

treatments where R. capitata plants were allowed to compete for 4 and 5 weeks had P

contents, which were statistically at par with each other in 2011. However, in 2012, the

minimum P uptake was recorded in plots having 3 weeks R. capitata competition, but it

was statistically at par with P uptake at 4 weeks of R. capitata competition. These results

are in line with those of Gaikwad and Pawar (2003), who observed that weeds removed

15.78 Kg ha-1 of P in weedy plots. More uptake of P by R. capitata in 2012 than in 2011

was due to more weed growth favored by more rainfall received during 2012. Similar

observations were also recorded by Kelayniamam and Halikatti (2002) and Anjum et al.

(2007) in weedy check treatments.

The data presented in the table 4.4.8 reveal the effects of weed-crop competition

periods on the K uptake of R. capitata during 2011 and 2012. The significantly

maximum K uptake (18.36 kg ha-1 in 2011 and 21.98 kg ha-1 in 2012) was observed in

plots having full season R. capitata competition. The minimum K uptake (4.54 kg ha-1 in

2011 and 5.52 kg ha-1 in 2012) by R. capitata was recorded in plots having 3 weeks

competition. The K uptake increased with increase in weed-crop competition periods.

These results are in accordance with the research findings of Anjum et al. (2007) who

reported that K uptake by T. portulacastrum was 41.57 kg ha-1 in the treatments where

weeds were allowed to grow all through the cropping season. The faster growth of weeds

90

causes quick depletion of nutrients from soil. Weeds removed 72.19 Kg ha-1 of K2O in

weedy plots (Gaikwad and Pawar, 2003).

In trend comparisons of different weed-crop competition periods (3 to 7 weeks),

the linear trend was significant, whereas quadratic and cubic trends were found non-

significant during both the years of study.

Table 4.4.6 Effect of weed-crop competition periods on N uptake (kg/ha) by R.

capitata.


Zero week ----- -----







LSD 2.397 1.895


Linear Trend ** **

Quadratic Trend ** **

Cubic Trend NS NS




91

Table 4.4.7 Effect of different weed-crop competition periods on P uptake (kg/ha) of

R. capitata.


Zero week ----- -----







LSD 1.119 1.477


Linear Trend ** **

Quadratic Trend NS **

Cubic Trend NS NS




92

Table 4.4.8 Effect of different weed-crop competition periods on K uptake (kg/ha)

of R. capitata.


Zero week ----- -----







LSD 1.824 1.516


Linear Trend ** **


Cubic Trend NS NS




93

4.4.5 Effect of weed competition periods on Fe, Mn, Na and Zn contents (mg/Kg) of

R. capitata

The data (table 4.4.9) reveal that the highest Fe contents were observed in the

plots where R. capitata plants were allowed to compete with mungbean all through the

cropping season. These were statistically at par with those of 7 weeks of weed

competition during both the years of study. The significantly minimum Fe contents were

found in 3 weeks R. capitata competition, which were statistically at par with those of 4

weeks of R. capitata competition. The data (table 4.5.13) regarding Mn contents of R.

capitata showed a similar trend with the highest Mn contents in the plots where R.

capitata was permitted to compete with the crop all through the cropping season. The

significantly minimum Mn contents were found in 3 weeks weed competition during

both the years of study.

The data presented in the table 4.4.10 and table 4.4.11 indicate the effect of

weed-crop competition periods on Na and Zn content of R. capitata. Results revealed

that Na and Zn contents of R. capitata were considerably influenced by weed-crop

competition periods during both the years of study. The significantly minimum Na and

Zn contents were found in 3 weeks of R. capitata competition. The plots where R.

capitata were allowed to compete with mungbean crop all through the cropping season

remained higher to the rest of the treatments in both years of study. In trend comparisons

of different weed-crop competition periods (3 to 7 weeks), the linear trend was

significant, whereas, quadratic and cubic trends were recorded non-significant during

both the years of study. These results are similar to the findings of Khattak et al. (2006),

who found that Fe, Mn, and Zn contents of amarnath (Amaranthus retroflexus L.) were

28.7, 3.8, and 4.3 per 100 g dry weights, respectively. The contents of these minerals in

wild onion (Allium stellatum L.) were 0.46, 0.56, and 2.98, mg per 100 g dry weight,

respectively.

4.4.6 Effect of weed competition periods on Ca content (%) of R. capitata

It is evident from table 4.3.13 that significant differences in Ca contents of R.

capitata in different weed competition periods were observed between the years, being

higher in 2012. The significantly minimum Ca content was found in 3 weeks R. capitata

competition. The plots where R. capitata plants were allowed to compete with the

mungbean crop all through the cropping season remained higher to the rest of the

treatments during both years of study. In trend comparisons of different weed-crop

94

competition periods (3 to 7 weeks), the linear trend was significant, whereas, quadratic

and cubic trends were non-significant during both the study years. These results are in

accordance with those of Khattak et al. (2006), who observed that Ca contents of

amaranth (Amaranthus retroflexus L.) and wild onion (Allium stellatum L.) were 721.2

and 45.5 mg per 100 g dry weight, respectively.

Table 4.4.9 Effect of weed-crop competition periods on Fe contents (mg/kg) of R.

capitata.


Zero week ----- -----


4 weeks after planting 47.59 d 58.97 cd



7 weeks after planting 90.99 a 100.29 ab


LSD 8.864 14.77


Linear Trend ** **


Cubic Trend NS NS




95

Table 4.4.10 Effect of different weed-crop competition periods on Mn content

(mg/kg) of R. capitata.


Zero week ----- -----

3 weeks after planting 31.02 f 38.77 e

4 weeks after planting 35.42 e 48.06 d

5 weeks after planting 40.25 d 60.49 c

6 weeks after planting 47.80 c 72.63 b

7 weeks after planting 57.05 b 79.75 ab


LSD 3.707 7.725


Linear Trend ** **


Cubic Trend NS NS




96

Table 4.4.11 Effect of different weed-crop competition periods on Zn content



Zero week ----- -----




6 weeks after planting 23.50 bc 33.72 b



LSD 2.602 3.310


Linear Trend ** **


Cubic Trend NS NS




97

Table 4.4.12 Effect of different weed-crop competition periods on Na content



Zero week ----- -----


4 weeks after planting 16.76 cd 20.18 de

5 weeks after planting 19.50 c 24.74 cd

6 weeks after planting 23.50 b 28.50 bc



LSD 3.400 5.799


Linear Trend ** **


Cubic Trend NS NS




98

Table 4.4.13 Effect of different weed-crop competition periods on Ca content (%) of

R. capitata.


Zero week ----- -----


4 weeks after planting 0.66 cd 0.89 c


6 weeks after planting 0.89 b 1.24 a

7 weeks after planting 1.02 ab 1.30 a


LSD 0.137 0.104


Linear Trend ** **


Cubic Trend NS NS




99

4.4.7 Effect of weed competition periods on Cu and Mg contents of R. capitata

The data presented in the table 4.4.13 and 4.4.14 reveal the effects of weed-crop

competition periods on the Cu and Mg contents of R. capitata during 2011 and 2012.

The significantly maximum Cu and Mg contents were observed in the plots where R.

capitata plants were allowed to compete with the mungbean crop all through the

cropping season. The minimum Cu and Mg contents of R. capitata were recorded in

plots with 3 weeks of R. capitata competition. These were statistically at par with those

of 4 weeks of R. capitata competition during 2012, and different in 2011. The Cu and

Mg contents increased with increase in duration of R. capitata competition. In trend

comparisons of different weed-crop competition periods (3 to 7 weeks), the linear trend

was significant, whereas, quadratic and cubic trends were found non-significant during

both the years of study. These results are in line with those of Khattak et al. (2006), who

reported that amaranth (Amaranthus retroflexus L.) had 1.1 and 654.8 mg per 100 g dry

weight of Cu and Mg contents and wild onion (Allium stellatum L.) had 2.98 and 154.7

mg per 100 g dry weight of Cu and Mg contents, respectively.

100

Table 4.4.14 Effect of different weed-crop competition periods on Cu content



Zero week ----- -----

3 weeks after planting 5.94 f 6.41 d






LSD 0.139 0.858


Linear Trend ** **


Cubic Trend NS NS




101

Table 4.4.15 Effect of different weed-crop competition periods on Mg content



Zero week ----- -----

3 weeks after planting 23.53 f 26.82 d

4 weeks after planting 26.25 e 30.48 cd





LSD 2.702 4.585


Linear Trend ** **


Cubic Trend NS NS




102

4.4.8 Effect of weed competition periods on Fe and Mn uptake by R. capitata

Data pertaining to Fe uptake by R. capitata reveal that considerable effect of

weed-crop competition periods was observed during both the study years (table 4.4.16).

The results depicted that the significantly maximum Fe uptake by R. capitata was

recorded in the plots where R. capitata was allowed to compete with the mungbean crop

all through the cropping season. The minimum Fe uptake by R. capitata was recorded in

plots with 3 weeks R. capitata competition, which was statistically at par with 4 weeks of

R. capitata competition during both the years of study.

The data presented in the table 4.4.17 show the effect of weed-crop competition

periods on the Mn uptake (g/ha) of R. capitata. It is evident from the results that the Mn

uptake by R. capitata differed significantly during both the years of research. The

significantly maximum Mn uptake by R. capitata was recorded in the plots where R.

capitata plants were allowed to compete with the mungbean crop all through the

cropping season. The minimum Mn uptake of R. capitata was recorded in the plot with 3

weeks weed competition. It was statistically at par with those of 4 weeks of R. capitata

competition during 2011 and statistically different in 2012. In trend comparisons of

different weed-crop competition periods (3 to 7 weeks), the linear trend was significant,

whereas quadratic and cubic trends were found non-significant during both the years of

study.

4.4.9 Effect of weed competition periods on Na and Zn uptake by R. capitata

Effect of weed-crop competition periods on Na and Zn uptake by R. capitata was

also significant during both the years of study (table 4.4.18 and 4.4.19). The significantly

maximum Na and Zn uptake by R. capitata was recorded in weedy check where R.

capitata plants were allowed to grow all through the cropping season. The minimum Na

and Zn uptake by R. capitata was recorded in plots with 3 weeks R. capitata

competition. There was a linear increase in the Na and Zn uptake by R. capitata with the

increase in the duration of R. capitata competition periods.

In trend comparisons of different weed-crop competition periods (3 to 7 weeks),

the linear trend was significant, whereas, quadratic and cubic trends were found non-

significant during both the years of study. Weeds are usually luxury feeders for available

nutrients. The minimum Fe, Mn, Na and Zn uptake by R. capitata in competition period

of 3 weeks was due to less growth of R. capitata plants as compared to other competition

periods which reduced its dry weight and ultimately less Fe, Mn, Na and Zn uptake by R.

103

capitata plants was observed during both the years of study. However, linear increase in

the Fe, Mn, Na and Zn uptake by R. capitata with increase of R. capitata competition

periods (4 weeks to full season competition) may possibly owing to more use of nutrients

and environmental resources by R. capitata hence more Fe, Mn, Na and Zn uptake by R.

capitata was recorded.

Table 4.4.16 Effect of weed-crop competition periods on Fe uptake (g/ha) of R.

capitata.


Zero week ----- -----







LSD 8.925 6.542


Linear Trend ** **


Cubic Trend NS NS




104

Table 4.4.17 Effect of different weed-crop competition periods on Mn uptake (g/ha)

of R. capitata.


Zero week ----- -----







LSD 3.232 3.293


Linear Trend ** **


Cubic Trend NS NS




105

Table 4.4.18 Effect of different weed-crop competition periods on Na uptake (g/ha)

of R. capitata.


Zero week ----- -----


4 weeks after planting 4.53 cd 6.03 e

5 weeks after planting 5.95 c 9.17 d

6 weeks after planting 9.47 b 13.81 c

7 weeks after planting 15.62 a 19.20 b


LSD 1.689 2.070


Linear Trend ** **


Cubic Trend NS NS




106

Table 4.4.19 Effect of different weed-crop competition periods on Zn uptake (g/ha)

of R. capitata.


Zero week ----- -----







LSD 1.480 2.574


Linear Trend ** **


Cubic Trend NS NS




107

4.4.10 Effect of weed competition periods on Ca, Cu and Mg uptake of R. capitata

The data presented in the table (4.4.20, 4.4.21, 4.4.22) indicate the effect of

weed-crop competition periods on the Ca, Cu and Mg uptake of R. capitata. The uptake

of Ca, Cu and Mg by R. capitata was variable and also significantly affected by various

weed-crop competition periods during both the years of study. The significantly

maximum Ca, Cu and Mg uptake was found in the plants where R. capitata plants were

allowed to grow all through the cropping season in 2011 and 2012. The statistically

minimum Ca, Cu and Mg uptake by R. capitata was recorded in plots with 3 weeks R.

capitata competition. As found in the uptake of other micronutrient uptake by R.

capitata, there was a linear increase in the Ca, Cu and Mg uptake by R. capitata with the

increase in the duration of R. capitata competition periods. In trend comparisons of

different weed-crop competition periods (3 to 7 weeks), the linear trend was significant,

whereas, quadratic and cubic trends were found non-significant, during both the years of

study.

The results obtained in micronutrient uptake by R. capitata under different

competition periods reveal that R. capitata was able to utilize a considerable amount of

micronutrients during both the years of study. As the R. capitata competition period was

prolonged, the uptake of these micronutrients tends to increase. Hence the mungbean

plants had fewer micronutrients available for its better growth and development with the

increase in R. capitata competition durations. The micronutrients are very important in

terms of quality of mungbean grains and various other metabolic processes of plant.

Therefore, if the crop has to be grown with superior quality and better growth, the

competition of crop with R. capitata should be lessened. The weed control strategies

should be adopted particularly within 3 to 4 weeks after planting crop to reduce the

resource utilization by this weed.

108

Table 4.4.20 Effect of different weed-crop competition periods on Ca uptake (kg/ha)

of R. capitata.


Zero week ----- -----







LSD 0.945 0.785


Linear Trend ** **

Quadratic Trend NS **

Cubic Trend NS NS




109

Table 4.4.21 Effect of different weed-crop competition periods on Cu uptake (g/ha)

of R. capitata.


Zero week ----- -----







LSD 0.527 0.782


Linear Trend ** **

Quadratic Trend ** NS

Cubic Trend NS NS




110

Table 4.4.22 Effect of different weed-crop competition periods on Mg uptake

(kg/ha) of R. capitata.


Zero week ----- -----


4 weeks after planting 7.16 de 2.50 de





LSD 2.941 1.679


Linear Trend ** **


Cubic Trend NS NS




111

4.4.11 Effect of weed competition periods on plant height of mungbean

Plant height is a good indicator of intensity of competition amongst plants. The

data presented in the table 4.4.23 indicate that the mungbean plant height was drastically

affected by various R. capitata competition periods. The significantly maximum plant

height of mungbean (67.75 cm and 57.25 cm) was recorded in weed free treatment

during 2011 and 2012, respectively. This was statistically at par with the results of 3 and

4 weeks of competition period during both the years of study. However, these R. capitata

competition periods were statistically at par with the weed free treatment during both the

years of study. In trend comparisons of different weed-crop competition periods (3 to 7

weeks), the linear trend was significant, whereas quadratic and cubic trends were found

non-significant during both the years of study.

The significantly minimum mungbean plant height was observed in the plots

where R. capitata plants were allowed to compete with the crop all through the cropping

season. The plant height of mungbean tends to decrease linearly with the increase of R.

capitata competition periods. It might have been owing to greater utilization of nutrients

and environmental reserves by R. capitata plants, hence, more exhaustion of

environmental reserves. These results are in line with those of Naeem et al. (2000) who

found that weed competition duration had a significant effect on plant height of

mungbean. They further concluded that weed competition with crop up to 20 DAE did

not interfere in the growth and development of mungbean to a significant extent, while

extended competition duration had an adverse effect on plant height and yield potential

of mungbean.

112

Table 4.4.23 Effect of different weed-crop competition periods on plant height of

mungbean.


Zero week 67.75 a 57.25 a

3 weeks after planting 64.25 ab 55.25 ab

4 weeks after planting 60.50 b 51.25 bc


6 weeks after planting 51.25 cd 44.75 de


Full season 43.75 e 41.25 e

LSD 4.579 4.205


Linear Trend ** **


Cubic Trend NS NS




113

4.4.12 Effect of weed competition periods on number of pods per plant of

mungbean.

Number of pods per plant is an important variable contributing considerably to

the final crop yield in mungbean. Table 4.4.24 shows the effect of various weed

competition periods on the number of pods per plant of mungbean. Number of pods per

plant was considerably affected by different R. capitata competition periods during both

the years of study. The highest number of pods per plant of mungbean was observed in

plots where R. capitata was not present to compete with the crop during both the study

years. These were statistically at par with plots having weed-crop competition up to 3

weeks after planting of mungbean in 2011. There was a gradual decrease in number of

pods per plant with increase in duration of R. capitata competition from 3 to 7 weeks.

Minimum pods per plant were produced where R. capitata was allowed to compete all

through growth period of mungbean, during both the years. Trend comparison of

different weed-crop competition periods (3 to 7 weeks) showed that linear trend was

significant whereas quadratic and cubic trends were non-significant during both the years

of study.

Lack of R. capitata plants in weed free treatment or their little time existence in

crop competition for 3 and 4 weeks might have facilitated the mungbean crop to take full

advantage of growth and development, hence generated greater number of pods. While

the R. capitata plants competing with mungbean for 7 weeks or entire season obtained

highest opportunity to make use of environmental reserves to the detriment of mungbean

crop. It eventually resulted into a fewer number of mungbean pods per plant.

Furthermore, fewer accessibility of space to mungbean plants owing to higher R.

capitata density may possibly have become the explanation of lesser number of pods.

These results are supported by the findings of Naeem et al. (2000), who reported that

number of pods per plant of mungbean was severely affected by the prolonged

competition of weeds.

114

Table 4.4.24 Effect of different weed-crop competition periods on number of pods

per plant of mungbean.









LSD 2.2225 2.395


Linear Trend ** **


Cubic Trend NS NS




115

4.4.13 Effect of weed competition periods on number of grains per pod of

mungbean.

Number of grains per pod of mungbean had direct relation with grains yield. The

data presented in table 4.4.25 indicate that duration of weed competition had significant

effect on the number of grains per pod. Although, there was progressive decrease in

grain number per pod with successive increase in duration of weed-crop competition, but

all the treatments had little numeric difference during both the years of study. In 2011,

the highest grains per pod were recorded in plots where R. capitata plants were allowed

to compete with mungbean crop all through the season. Similar trend was observed in

2012. In trend comparison of different weed-crop competition periods (3 to 7 weeks), the

linear trend was significant, whereas, quadratic and cubic trends were non-significant

during both the years of study.

The highest number of grains per pod in R. capitata free treatment may possibly

be owing to the fact that R. capitata was not allowed to struggle with the mungbean crop

for nutrients and other environmental reserves. Moreover, greater photosynthetic

effectiveness of mungbean plants supported by the adequate accessibility of water,

nutrients and radiation in the lack of R. capitata plants may also be the reason of more

number of grains per pod in zero competition plots. The minimum number of grains per

pod was recorded in weedy check most probably due to greater R. capitata density,

which cause additional exhaustion of nutrients, hence resulted into fewer photosynthesis

eventually number of grains per pod were influenced. These findings are in great analogy

with those of Pascua (1988). He concluded that the number of grains per pod were

greater in the plots that had lower weed fresh weight in mungbean.

116

Table 4.4.25 Effect of different weed-crop competition periods on the number of

grains per pod of mungbean.



3 weeks after planting 10.25 ab 9.25 ab

4 weeks after planting 9.75 ab 8.75 bc

5 weeks after planting 9.50 bc 8.12 c

6 weeks after planting 8.75 cd 8.00 c


Full season 8.000 d 8.12 c

LSD 0.999 0.830


Linear Trend ** **


Cubic Trend NS NS




117

4.4.14 Effect of weed competition periods on 1000 grain weight (g) of mungbean.

Statistical means recorded for 1000-grain weight given in table 4.4.26 reveal that

the effect of different durations of weed competition was significant. There was a linear

decrease in 1000-grain weight of mungbean with successive increase in duration of weed

competition from zero up to full season R. capitata competition. Weed free conditions

and R. capitata competition up to 3 and 4 weeks after planting gave the highest 1000-

grain weight compared with that of full season R. capitata competition in 2011. The data

for 2012 indicated almost similar trend. In trend comparison, the linear and cubic trends

were significant whereas quadratic trend was non-significant during both years of study.

The maximum 1000-grain weight in zero competition treatment may possibly be

owing to the fact that weed free plots were maintained all through the cropping season. It

eventually produced better plant growth of mungbean grain and higher quantities of

photosynthates were formed, thus, there was higher 1000-grain weight. The minimum

1000-grain weight in full season R. capitata competition treatment may possibly be

owing to greater R. capitata densities and more competition which caused additional

exhaustion of nutrients and moisture that otherwise were available to mungbean plants. It

comes out to be reasonably rational that the mungbean crop completely utilized the

environmental reserves in the plots with zero competition of R. capitata with mungbean.

The removel of R. capitata plants near the beginning of mungbean growth stages assisted

mungbean plants to completely utilize the growth resources exclusive of facing any R.

capitata competition effects. Results of this study confirmed the findings of Musa et al.

(1996).

118

Table 4.4.26 Effect of different weed-crop competition periods on 1000-grain weight

(g) of mungbean.









LSD 2.977 2.538


Linear Trend ** **


Cubic Trend * **



NS, * and ** indicate non-significant, significant at P ≤ 0.05 and at P ≤ 0.01 level of probability, respectively.

119

4.4.15 Effect of weed competition periods on biological yield (kg/ha) of mungbean.

The data presented in the table 4.4.27 show that total biological yield of

mungbean was considerably affected by various weed competition periods. The

maximum biological yield of 4495.7 kg ha-1 in 2011 and 4202.9 kg ha-1 in 2012 was

recorded in R. capitata free plots. It was statistically different from all other R. capitata

competition periods. A significant reduction in the biological yield of mungbean was

observed with the increase in R. capitata competition period. The significantly minimum

biological yield of mungbean was recorded in the treatment where R. capitata plants

were allowed to grow all through the cropping season. In trend comparison, the linear

and cubic trends were significant whereas quadratic trend was non-significant during

both years of study.

The maximum biological yield attained in the plots that were kept weed free.

Owing to these weed free conditions, the mungbean plants resulted into better growth

and biomass production. Similarly, greater biological yield of mungbean in R. capitata

free plots was possibly be due to higher number of grains per pod, heavier grains and

efficient vegetative growth of mungbean. The minimum biological yield of mungbean in

competition of R. capitata all through the season might be due to greater R. capitata

density that resulted into stressed and suppressed mungbean growth and development,

lesser plant height and fragile plants. These results are in close conformity with those of

Bayan and Saharia (1998) who reported decreased biomass with increased weed

competition period in mungbean. These results are also in great analogy by the findings

of Muhammad and Ahmad (1999). They reported that minimum biological yield of

mungbean was found in the plots where weed competition was extended up to 50 days

after their emergence.

120

Table 4.4.27 Effect of different weed-crop competition periods on biological yield

(kg/ha) of mungbean.


Zero week 4495.7 a 4202.9 a



5 weeks after planting 3707.0 cd 3651.3 d



Full season 3224.5 f 3120.5 g

LSD 153.24 155.41


Linear Trend ** **


Cubic Trend * NS




121

4.4.16 Effect of weed competition periods on grain yield (kg/ha) of mungbean.

Weed competition duration had a significant effect on mungbean grain yield per

hectare in both the study years. Increase in R. capitata competition period considerably

decreased the grain yield (table 4.4.28). In 2011, the weed-free plots gave the highest

grain yield of 1688.6 kg ha-1 which was 94.24 % greater than plots in which R. capitata

was allowed to grow all through the growing season. It was followed by R. capitata

competition for 3 weeks after planting of mungbean with 1582.0 kg ha-1 of grain yield

which was 81.98% higher than weedy check. The treatments where R. capitata was

allowed to grow all through the growing season decreased the mungbean grain yield to

869.3 kg ha-1. Similar trend was also observed during 2012. The treatments where R.

capitata plants were allowed to grow all through the cropping season decreased the grain

yield to 961 kg ha-1 compared with 1400 kg ha-1 in weed free treatment. Trend

comparison of different weed-crop competition periods (3 to 7 weeks) showed that the

linear and cubic trends were significant during 2011. Quadratic and cubic trends were

non-significant and linear trend was significant during 2012.

The decrease in grain yield with increase in competition period was due to

decrease in the major components of grain yield like number of pods per plant, number

of grains per pod and 1000-grain weight. The results further led to the revelation that R.

capitata competition with crop up to 3 weeks after planting of mungbean crop had little

interference in the growth and development of mungbean, while, extended R. capitata

competition duration had an adverse effect on yield potential of mungbean. These results

are in great analogy with those of Naeem et al. (2000), who found that weed competition

duration had a significant effect on final grain yield per hectare in mungbean.

Similar results have also been obtained by Utomo (1989). He reported that the

mungbean crop was most sensitive to competition from weeds during 3 to 6 weeks after

planting. Similarly, Naeem and Ahmad (1999a) concluded that the most critical period

for weed competition in mungbean was from 20 to 30 days after crop emergence.

Extended weed competition after this period resulted into considerable mungbean yield

reduction. Malik et al. (2000) also reported that weed competition with mungbean

decreased grain yield by 81% and according to Raman and Krishnamoorthy (2005),

weed-crop competition for the whole mungbean crop season decreased the mungbean

grain yield by 35%. It was also observed in these experiments that the R. capitata

completes its growth stages with the mungbean crop and a great quantity of R. capitata

seed was dispersed into the soil before the crop is harvested. If R. capitata can be

122

eliminated or disturbed earlier than its seed set, the mungbean yield losses can be

lessened in the long run. So it can be concluded that the weeds should be removed at an

early stage of crop growth. Any delay in weed control may result into the utilization of

nutrients and other resources available to crop by weeds, hence depriving the crop from

its share.

123

Table 4.4.28 Effect of different weed-crop competition periods on grain yield


Weed-crop competition

duration for

2011

2012

Yield increase (%) over

full season competition

2011 2012

Zero week 1688.6 a 1495.5 a 94.24 86.05

3 weeks after planting 1582.0 b 1404.0 b 81.98 74.67

4 weeks after planting 1477.8 c 1300.3 c 69.99 61.76

5 weeks after planting 1308.3 d 1187.3 d 50.50 47.71

6 weeks after planting 1155.6 e 1036.3 e 32.93 28.92

7 weeks after planting 975.8 f 878.8 f 12.25 9.330

Full season 869.3 g 803.8 g ------ -------

LSD 46.899 52.739 ------ -------

Trend comparison of different weed-crop competition periods

(3 to 7 weeks)

Linear Trend ** **


Cubic Trend * NS




124

4.4.17 Effect of weed competition periods on relative competitive index (RCI) of R.

capitata

Table 4.4.29 showed relative competitive index of varying R. capitata

competition durations with mungbean. Relative competitive index was increased with

increase in R. capitata competition. The plots where R. capitata was allowed to grow all

through the season resulted in maximum relative competitive index (94.24% grain yield

loss). However, minimum relative competitive index/yield loss (12.26%) was observed

with lowest R. capitata competition duration (3 weeks) during 2011 (table 4.4.29).

During 2012, trend regarding relative competitive index of R. capitata and mungbean

yield reduction was similar (table 4.4.29). Our findings are comparable with the results

obtained by those of Cowan et al. (1998). They revealed soybean yield losses of 32 to 99

% with varying density levels of pigweed (Amaranthus retroflexus L.) and barnyard

grass (Echinochloa crus-galli). Similarly, Zubair et al. (2011) found a significant crop

yield reduction with weeds presence.

Table 4.4.29 Effect of weed competition periods on R. capitata relative competitive

index (RCI)

Weed-crop competition duration for RCI (%)

2011 2012

Zero week ------ -------

3 weeks after planting 12.262 11.38





Full season 94.248 86.05

125

4.4.18 Effect of weed competition periods on harvest index (%) of mungbean

The production efficiency of a crop is also calculated in terms of harvest index.

Harvest index given in table 4.4.30 show that various R. capitata competition periods

considerably affected the harvest index of mungbean crop. The maximum harvest index

(37.60 % in 2011) was recorded in zero competition which was statistically at par with

the R. capitata competition period of 3 and 4 weeks. Similar results were obtained during

2012. The statistically minimum harvest index was recorded in plots kept weed free all

through the season during both the years of study. The linear decrease in harvest index of

mungbean with the increase in R. capitata competition periods may possibly owing to

decrease in ratios of economic yield to the biological yield of mungbean. Harvest index

of zero competition treatment and R. capitata competition period of 3 and 4 weeks were

statistically the same, however there was minute statistical difference in the harvest index

of both these treatments.

In trend comparison of different weed-crop competition periods (3 to 7 weeks),

the linear and cubic trends were significant, whereas, quadratic trend was non-significant

during 2011. However, both quadratic and cubic trends were non-significant and linear

trend was significant during 2012.

126

Table 4.4.30 Effect of different weed-crop competition periods on harvest index of

mungbean.



3 weeks after planting 38.39 a 35.05 a

4 weeks after planting 38.43 a 33.81 ab




Full season 26.97 e 25.80 d

LSD 1.678 2.037


Linear Trend ** **


Cubic Trend * NS




127

4.5 FIELD EXPERIMENT 2

CONTROL OF RHYNCHOSIA CAPITATA (ROTH) DC IN MUNGBEAN WITH

DIFFERENT HERBICIDES.

4.5.1 Effect of herbicides on the number of R. capitata (m-2) 21 DAS.

The data presented in the table 4.5.1 illustrate the effect of the application of

different herbicides on the R. capitata density (m-2). It is obvious from the table 4.5.1

that R. capitata density m-2 was significantly affected by various herbicides. Weed

density was higher in 2010 in all treatments as compared to 2011. The lowest R. capitata

density was shown by pendimethalin+prometryn @ 875 g a.i. ha-1 treatment (12.25). It

was statistically at par with all other herbicide treatments in year 2010. Control had the

highest weed population of 26.25 m-2. Similarly, in 2011, highest R. capitata population

(18.22 m-2) was found in control treatment. In herbicide treatments,

pendimethalin+prometryn @ 875 g a.i. ha-1 showed significant effect in reducing number

of R. capitata m-2 21 DAS. It was statistically at par with pendimethalin+prometryn @

700 g a.i. ha-1, S-metolachlor @ 1440 g a.i ha-1 and pendimethalin @ 825 g a.i ha-1.

All contrast comparisons were found to be non-significant except the contrast

between weedy check vs all during both the years. In trend comparisons, quadratic

responses were non-significant during both the years. However, linear response was non-

significant during 2010 and significant during 2011 (4.5.1). Different doses of

pendimethalin+prometryn demonstrated a significant effect on number of weeds, and the

difference was more pronounced during 2nd year of study. This might be due to less

rainfall received during 2011. Effectiveness of herbicides in 2010 was unsteady due to

severe rainfall conditions. This higher amount of rainfall in 2010 favoured weed to grow

more vigorously. The minimum number of R. capitata in treatments where herbicides

were applied is the result of phytotoxic consequences of herbicides on R. capitata. These

findings are in a great accordance with the previous work of Windley et al. (1999) who

tested the efficacy of 6 herbicides against T. portulacastrum and Macroptilium

lathyroides and found that all herbicides significantly reduced the populations of these

weed species. Similarly, Godec and Opacic (1988) also concluded that pre-sowing

application of pendimethalin resulted in outstanding control of weeds like Amaranthus

retroflexus, Chenopodium album, Polygonum lapathifolium and Echinochloa crusgalli in

soybean.

128

Table 4.5.1 Effect of application of different herbicide treatments on number of

R. capitata (m-2) 21 days after sowing in mungbean.

Treatments 2010 2011

Weedy check 26.25 a 18.22 a

Pendimethalin+prometryn at 875 g a.i. ha-1 12.25 b 8.55 d

Pendimethalin+prometryn at 700 g a.i. ha-1 15.25 b 11.70 cd

Pendimethalin+prometryn at 525 g a.i. ha-1 15.75 b 15.07 ab

S-metolachlor @ 1440 g a.i ha-1 16.25 b 14.17 bc

Pendimethalin @ 825 g a.i ha-1 14.50 b 11.92 bc

LSD 5.316 3.269

Contrast

Weedy check vs all 26.25 vs 14.8 * * 18.22 vs 12.82 * *

Pendimethalin+prometryn vs S-metolachlor 14.41 vs 16.25 NS 11.77 vs 14.17 NS

Pendimethalin+prometryn vs pendimethalin 14.41 vs 14.50 NS 11.77 vs 11.92 NS

S-metolachlor vs pendimethalin 16.25 vs 14.50 NS 14.17 vs 11.92 NS

Trend comparison of different levels of pendimethalin+prometryn

Linear Trend NS **





129

4.5.2 Effect of herbicides on the number of pods per plant of R. capitata.

The data presented in the table 4.5.2 indicate the effect of different herbicides on

the number of pods per plant of R. capitata. Number of pods per plant of R. capitata

were variable in first and second years of study being less in the second year. All

herbicides reduced the number of weeds but the effect of pendimethalin+prometryn @

875 g a.i. ha-1 was more pronounced that reduced the number of pods per plant to 23.5 in

2010 and 18.50 in 2011. Weedy check treatment, which had 37.5 and 32.5 pods per plant

of R. capitata in 2010 and 2011, respectively remained superior to the rest of the

treatments in both the years.

Contrast comparisons for number of pods per plant of R. capitata in mungbean at

harvest showed that weedy check vs all other treatments was significant during both the

years of study (table 4.5.2). The contrasts between pendimethalin+prometryn vs S-

metolachlor, pendimethalin+prometryn vs pendimethalin and S-metolachlor vs

pendimethalin were found to be non-significant during both the years of study. Trend

comparisons regarding different levels of pendimethalin+prometryn on the number of

pods per plant of R. capitata were significant for linear response; however it was non-

significant for quadratic response during 2010 and 2011 (table 4.5.2). Although all

herbicides reduced the number of R. capitata as compared to weedy check treatment but

complete control of R. capitata in herbicide treatments was not achieved. This might be

due to the presence of a large weed seed bank in the soil and its emergence even after the

herbicide sprays. Therefore, complete control of weeds is not possible in field conditions.

Similarly Sharma et al. (1999) also reported that significant reduction in broad leaf weed

density was observed in herbicides treated plots as compared to weedy check in soybean.

4.5.3 Effect of herbicides on the number of seeds per pod of R. capitata.

The data presented in the table 4.5.3 show the effect of different herbicides on the

number of seeds per pod of R. capitata. All the herbicide treatments had nominal effect

on seeds per pod. However, the control treatment exhibited slightly more number of pods

per plant as compared to all other treatments. All the contrasts for application of different

herbicide treatments on the number of seeds per plant of R. capitata in mungbean at

harvest showed non-significant trend during 2010 and 2011. Similarly, trend comparison

130

of different levels of pendimethalin+prometryn also showed non-significant linear and

quadratic responses during both the years of study (table 4.5.3).

Weed species are best adapted to high fertility and high disturbance environments

(Baker, 1974). Diverse selection pressures have led to discrete physiological traits

pertaining to nutrient acquirement and growth of weeds, which in turn, influences the

competitive balance between crops and weeds (DiTomaso, 1995). These traits comprise

seed size, relative growth rate and rate of nutrient uptake by weeds (Bonifas et al., 2005).

In our experiment, pod number of R. capitata is also a unique characteristic of this

species that is associated with the success of this weed in highly disturbing

environments. As the application of different herbicides significantly affected the pod

number of R. capitata, the weed still produced notable number of pods. These pods could

be the source of future weed seed bank of soil if weed plants are not disposed off from

the field.

131


pods per plant of R. capitata.



Pendimethalin+prometryn at 875 g a.i. ha-1 23.50 c 18.50 c

Pendimethalin+prometryn at 700 g a.i. ha-1 30.25 abc 25.25 abc

Pendimethalin+prometryn at 525 g a.i. ha-1 34.25 ab 29.25 ab

S-metolachlor @ 1440 g a.i ha-1 27.00 bc 22.00 bc

Pendimethalin @ 825 g a.i ha-1 29.25 abc 24.25 abc

LSD 8.751 8.751

Contrast

Weedy check vs all 37.50 vs 28.85 * 32.50 vs 23.85 *





Linear Trend ⃰⃰ ⃰⃰




NS and * indicate non-significant and significant at P ≤ 0.05 level of probability, respectively.

132


seeds per pod of R. capitata.



Pendimethalin+prometryn at 875 g a.i. ha-1 1.50 a 1.50 b

Pendimethalin+prometryn at 700 g a.i. ha-1 1.50 a 1.50 b

Pendimethalin+prometryn at 525 g a.i. ha-1 1.75 a 1.75 ab

S-metolachlor @ 1440 g a.i ha-1 2.00 a 2.00 ab

Pendimethalin @ 825 g a.i ha-1 2.25 a 2.25 ab

LSD 0.909 0.926

Contrast

Weedy check vs all 2.25 vs 1.8 NS 2.50 vs 1.8 NS





Linear Trend NS NS




NS indicates non-significant at P ≤ 0.05 level of probability.

133

4.5.4 Effect of herbicides on the fresh weight of R. capitata (gm-2) in mungbean at

harvest.

The table 4.5.4 indicates the effect of different herbicide treatments on fresh

weight of R. capitata. Analysis of the data showed that all the weed control treatments

had significant effect on fresh weight of R. capitata in both years of study. The results

showed that a significant difference between years regarding the fresh weight of R.

capitata was recorded being minimum during the second year. The lowest fresh weight

of R. capitata (160.63 and 162.81 g m-2) were recorded in plots sprayed with

pendimethalin+prometryn @ 875 g a.i. ha-1 and pendimethalin @ 825 g a.i ha-1 ,

respectively in 2010. Where as in 2011, lowest fresh weight of R. capitata (115.31 and

130.94 g m-2) was recorded in the plots sprayed with pendimethalin+prometryn @ 875g

a.i. ha-1 and pendimethalin +prometryn @ 700 g a.i. ha-1, respectively. The highest fresh

weight of R. capitata (274.06 and 226.06 g m-2) was noted in weedy check treatment in


Contrast comparisons for fresh weight of R. capitata (m-2) in mungbean at

harvest showed that contrast of weedy check vs all and S-metolachlor vs pendimethalin

were significant during 2010. A similar trend was recorded for these contrasts during

2011 (table 4.5.4). Trend comparison of different levels of pendimethalin + prometryn

showed that linear response was significant during both the years of study. However,

quadratic response was non-significant during both the years (table 4.5.4).

The fresh weight of weed is a signal of the growth potential of weeds and is a

better standard for the judgment of weed crop competition than weed density. The data

revealed that the application of all herbicide treatments significantly reduced R. capitata

fresh weight. Maximum fresh weight of R. capitata in weedy check was due to presence

of R. capitata throughout the growth period of crop. These results are in great analogy

with those of Tanveer et al. (2003) who reported that herbicide application reduced fresh

weight of weeds and variation in fresh weight of weeds in herbicide treated plots was due

to their different effectiveness in controlling them. Similarly, Singh and Singh (1992)

also reported significant reduction in the weed biomass with pendimethalin.

134

Table 4.5.4 Effect of application of different herbicide treatments on fresh weight

of R. capitata (gm-2) in mungbean at harvest.



Pendimethalin+prometryn at 875 g a.i. ha-1 160.63 e 115.31 d

Pendimethalin+prometryn at 700 g a.i. ha-1 181.25 cd 130.94 cd

Pendimethalin+prometryn at 525 g a.i. ha-1 192.81 bc 163.13 b

S-metolachlor @ 1440 g a.i ha-1 202.50 b 172.19 b

Pendimethalin @ 825 g a.i ha-1 162.81 de 137.81 c

LSD 19.929 17.173

Contrast

Weedy check vs all 274.06 vs 180 * * 229.06 vs 143.87 * *

Pendimethalin+prometryn vs S-metolachlor 178.23 vs 202.50 * * 136.46 vs 172.19 * *


S-metolachlor vs pendimethalin 202.50 vs 162.81 * * 172.19 vs 131.81 * *


Linear Trend * * * *





135

4.5.5 Effect of herbicides on dry weight of R. capitata (gm-2) in mungbean at

harvest.

The data given in the table 4.5.5 describe the effect of the application of different

herbicides on dry weight of R. capitata. The analyzed data of dry weight of R. capitata

showed that the variations between dry weight of R. capitata in herbicide treatments and

check treatment were considerable in both the years of study. It indicates that all weed

control treatments significantly decreased the dry weight of R. capitata. The minimum

dry weight of 16.25 and 12.37 g m-2 was observed in plots that were sprayed with

pendimethalin+prometryn @ 875 g a.i. ha-1 in 2010 and 2011, respectively. It was

statistically at par with pendimethalin+prometryn @ 700 g a.i. ha-1, where 17.12 and 14 g

m-2 dry weight of R. capitata was recorded in both years of study, respectively.

However, the highest weed dry weight was found in weedy check treatment.

Contrast of weedy check vs all and pendimethalin+prometryn vs S-metolachlor

showed that there was a significant difference in dry weight of R. capitata m-2 in

mungbean at harvest during both the years. However, contrast of

pendimethalin+prometryn vs pendimethalin was non-significant. Contrast for S-

metolachlor vs pendimethalin was significant during 2010 while non-significant during

2011. Trend comparison of different levels of pendimethalin+prometryn showed that the

linear response was significant during 2011 but non-significant during 2010. The

quadratic response was found to be non-significant during both the years of study. These

results are in accordance with those of Chattha et al. (2007) who found maximum

reduction in dry biomass of Trianthema monogyna, Sorghum halepense, Digera

arvensis, Echinochloa colona and Cynodon dactylon occurred with different herbicides.

Highest R. capitata dry weight was recorded in weedy check where no herbicide was

applied all through the crop growing period. These results are almost in agreement with

those of Giri et al. (2006) and Oad et al. (2007). They recorded maximum dry weight of

weeds in the weedy control treatment.

136

Table 4.5.5 Effect of application of different herbicide treatments on the dry

weight of weeds R. capitata (gm-2) in mungbean at harvest.



Pendimethalin+prometryn at 875 g a.i. ha-1 16.25 d 12.37 d

Pendimethalin+prometryn at 700 g a.i. ha-1 17.12 d 14.00 cd

Pendimethalin+prometryn at 525 g a.i. ha-1 22.25 bc 17.50 bc


Pendimethalin @ 825 g a.i ha-1 19.87 cd 16.62 bc

LSD 4.9840 3.861

Contrast

Weedy check vs all 65.87 vs 20.19 * * 56.62 vs 15.69* *

Pendimethalin+prometryn vs S-metolachlor 18.54 vs 25.50 * * 14.62 vs 18.00 *


S-metolachlor vs pendimethalin 25.50 vs 19.87 * 18.00 vs 16.62 NS


Linear Trend NS ⃰⃰





137

4.5.6 Effect of herbicides on R. capitata control efficiency in mungbean.

All doses of the herbicides suppressed the dry weight of R. capitata from 60 to

78% in 2010 (figure 4.5.1). Similar trend of R. capitata control efficiency was observed

during 2011. Pendimethalin+prometryn @ 875g a.i. ha-1, recorded reduction 74% in

2010 and 78% in 2011 in total dry weight of R. capitata. These results are in line with

those of Panneerselvam and Lourduraj (2000), who concluded that weed control

efficiency was better with alachlor at 1 kg a.i ha-1 which was followed by pendimethalin

at 0.75 kg a.i ha-1 in soybean. Similar results have also been discussed by Naeem and

Ahmad (1999b) in mungbean.

The minimum R. capitata dry weight in herbicide treated plots was possibly be

owing to the action of herbicides that decreased R. capitata density. The results were in

line with those of Ali et al. (2003). They revealed that the dry weight of weeds from

herbicide treated plots was considerably less than weedy check plots. The difference in

dry weight of R. capitata by the application of different herbicides might have been due

to variation in their suppressive effect on R. capitata. Similar trend was also observed in

T. portulacastrum dry weight by the application of herbicides in cotton (Richardson et

al., 2007 and Everman et al., 2007). Rhynchosia capitata utilized the environmental

resources for a longer period in the weedy check plot and ultimately produced more dry

weight than plots where weeds were controlled by different herbicide treatments. These

results are in consonance with those of Rajput and Kushwah (2004), who reported that

pre-emergence application of pendimethalin at 1.0 kg ha-1 was the most cost-effective for

controlling the weeds in soybean.

138

Figure 4.5.1 Effect of application of different herbicide treatments on weed

control efficiency in mungbean.

139

4.5.7 Effect of herbicides on N content (%) of R. capitata.

The data presented in the table 4.5.6 indicate the effect of different herbicide

treatments on the nitrogen content of R. capitata at harvest. Nitrogen content of R.

capitata was variable and also significantly affected by the application of different

herbicide treatments in both the years of study. The significantly minimum nitrogen

content was found in the plants where pendimethalin+prometryn @ 875 g a.i. ha-1 was

applied. Weedy check treatment, which had 3.93 and 3.51 % nitrogen contents in 2010

and 2011, remained higher to the rest of the treatments in both years.

Contrast comparison for weedy check vs all was significant during both the years.

However, contrasts for pendimethalin+prometryn vs S-metolachlor, pendimethalin +

prometryn vs pendimethalin and S-metolachlor vs pendimethalin were non-significant

during 2010 and 2011. Trend comparison showed that the linear trend was significant

where as quadratic response was non-significant during both the years of study.

4.5.8 Effect of herbicides on P content (%) of R. capitata at harvest.

It is evident from table 4.5.7 that a significant difference in P content of R.

capitata was observed between the study years, being maximum in first year. Although,

the maximum P contents were recorded in weedy check treatment in both years but there

is a notable difference between both these treatments. Among herbicide treatments,

maximum P contents were recorded with pendimethalin in both the years. It was

followed by S-metolachlor. The statistically minimum P contents were recorded from

pendimethalin+prometryn at 875 g a.i. ha-1 in 2010 and 2011.

All the contrast comparisons were found significant during both the years of

study. Among trend comparisons of different levels of pendimethalin+prometryn, linear

response was significant during both the years of study. Quadratic response was non-

significant during 2010 and 2011.

4.5.9 Effect of herbicides on K content (%) of R. capitata at harvest.

The effects of different herbicides on the K content of R. capitata are presented in

the table 4.5.8. All the herbicides significantly affected K concentration of R. capitata

plants in 2010 and 2011. The data showed that maximum K content was found in weedy

check treatment during both the years. Minimum P contents (2.22% and 2.32% in 2010

140

and 2011, respectively) were found in plants where pendimethalin+prometryn at 875 g

a.i. ha-1 was applied. The statistically maximum P contents (3.31% and 3.09% in 2010

and 2011, respectively) were recorded in weedy check treatment. All the contrast

comparisons presented in the table are significant except the contrast between S-

metolachlor vs pendimethalin during both the years of study. As regard the trend

comparison, the linear trend was significant whereas the quadratic trend was non-

significant during both the years of study.

Weeds are generally luxury feeders for NPK. The considerably higher NPK

contents of R. capitata in weedy check treatment was due to the fact that the R. capitata

plants were allowed to grow freely all through the season with no interruption. The R.

capitata plants absorbed more NPK form soil throughout the season due to no

interference of herbicides during both the years of study. The minimum NPK contents of

R. capitata in pendimethalin+prometryn at 875 g a.i. ha-1 was due to the toxic effects of

this herbicide on R. capitata plants which hinder their growth and ultimately less NPK

contents were recorded in this treatment.

141

Table 4.5.6 Effect of application of different herbicide treatments on N content

(%) of R. capitata.





Pendimethalin+prometryn at 525 g a.i. ha-1 2.09 b 2.38 b

S-metolachlor @ 1440 g a.i ha-1 2.08 b 1.86 c

Pendimethalin @ 825 g a.i ha-1 2.20 b 1.79 c

LSD 0.226 0.220

Contrast

Weedy check vs all 3.93 vs 1.90** 3.51 vs 1.82**

Pendimethalin+prometryn vs S-metolachlor 1.75 vs 2.08** 1.92 vs 1.86 NS

Pendimethalin+prometryn vs pendimethalin 1.75 vs 2.20** 1.92 vs 1.79 NS



Linear Trend ** **





142

Table 4.5.7 Effect of application of different herbicide treatments on P content (%)

of R. capitata at harvest.



Pendimethalin+prometryn at 875 g a.i. ha-1 1.40 e 0.71 e




Pendimethalin @ 825 g a.i ha-1 2.27 a 1.66 b

LSD 0.182 0.149

Contrast


Pendimethalin+prometryn vs S-metolachlor 1.62 vs 2.08** 0.94 vs 1.51**

Pendimethalin+prometryn vs pendimethalin 1.62 vs 2.27** 0.94 vs 1.66**

S-metolachlor vs pendimethalin 2.08 vs 2.27 ⃰⃰ 1.51 vs 1.66 ⃰⃰


Linear Trend ** **





143

Table 4.5.8 Effect of application of different herbicide treatments on K content (%)

of R. capitata at harvest.




Pendimethalin+prometryn at 700 g a.i. ha-1 2.50 d 2.59 c

Pendimethalin+prometryn at 525 g a.i. ha-1 2.80 c 2.90 b


Pendimethalin @ 825 g a.i ha-1 3.15 b 2.92 b

LSD 0.150 0.102

Contrast

Weedy check vs all 3.31 vs 2.74* * 3.09 vs 2.74* *

Pendimethalin+prometryn vs S-metolachlor 2.50 vs 3.04* * 2.60 vs 2.98* *

Pendimethalin+prometryn vs pendimethalin 2.50 vs 3.15* * 2.60 vs 2.92* *



Linear Trend ** **





144

4.5.10 Effect of herbicides on N uptake (kg/ha) by R. capitata at harvest.

Effect of application of herbicides on N uptake by R. capitata was significant

during both the years of study (table 4.5.9). The significantly maximum N uptake by R.

capitata (25.96 kg ha-1 in 2010 and 19.96 kg ha-1 in 2011) was recorded in weedy check

where R. capitata were allowed to grow throughout the season. The minimum N uptake

by R. capitata (2.16 kg ha-1) was recorded in plots where pendimethalin+prometryn @

875 g a.i. ha-1 was applied which was statistically at par with those of

pendimethalin+prometryn @ 700 g a.i. ha-1 during both the years of study.

In contrast comparison, weedy check vs all contrast was significant during both

the years. The contrast of pendimethalin+prometryn vs S-metolachlor was significant

during 2010 but was non-significant during 2011. However, contrasts for

pendimethalin+prometryn vs pendimethalin and S-metolachlor vs pendimethalin were

non-significant during 2010 and 2011. Trend comparison showed that the linear trend

was significant where as quadratic response was non-significant during both the years of

study.

Weeds usually absorb nutrients faster and relatively in larger amounts than the

crops and therefore, receive greater benefits. Higher N uptake by R. capitata at harvest in

plots kept weedy all through the season can be attributed to higher R. capitata dry

weight. These results are supported by the research findings of Anjum et al. (2007) and

Ikram et al. (2012) who reported that N uptake by weeds increased in weedy check and

reduced under the influence of herbicides. Similarly, Gaikwad and Pawar (2003) also

reported that weeds removed 33.53 Kg ha-1 of N in weedy plots.

4.5.11 Effect of herbicides on P uptake (kg/ha) of R. capitata at harvest.

Effect of herbicides on P uptake by R. capitata was significant. The significant

variation in uptake of P by R. capitata in different treatments was observed which may

be due to variation in its dry weight (table 4.5.10). The significantly maximum P uptake

(15.75 kg ha-1 in 2010 and 11.78 kg ha-1 in 2011) was recorded in weedy check. The

minimum P uptake (2.25 kg ha-1 in 2010 and 0.89 kg ha-1 in 2011) was noted in plots

where pendimethalin+prometryn at 875 g a.i. ha-1 was applied against R. capitata.

Among the contrast comparisons, all the contrasts were found significant except

the contrast between S-metolachlor vs pendimethalin during both the years of study.

145

Among trend comparisons of different levels of pendimethalin+prometryn, linear


significant during 2010 and 2011. More P uptake by R. capitata in plots sprayed with S-

metolachlor than other weed control treatments indicates its poor control which caused

more escape of weed. These results are in line with those of Gaikwad and Pawar (2003),

who observed that weeds removed 15.78 Kg ha-1 of P in weedy plots. More uptake of P

by R. capitata in 2010 than in 2011 can be attributed to higher R. capitata dry weight

owing to more weed growth favored by heavy rainfall received during 2010. Similar

observations were noted by Kelayniamam and Halikatti (2002) and Anjum et al. (2007)

with application of herbicides.

4.5.12 Effect of herbicides on K uptake (kg/ha) of R. capitata at harvest.

The data presented in the table 4.5.11 reveal the effects of different herbicides on

the K uptake of R. capitata during 2010 and 2011. The significantly maximum K uptake

(21.84 kg ha-1 in 2010 and 17.53 kg ha-1 in 2011) was observed in weedy check (table

4.5.11). The minimum K uptake (3.64 kg ha-1 in 2010 and 2.83 kg ha-1 in 2011) by R.

capitata was recorded in plots where pendimethalin+prometryn at 875 g a.i. ha-1 was

applied, which was statistically at par with that of pendimethalin+prometryn at 700 g a.i.

ha-1. The K uptake decreased with increase in dose of pendimethalin+prometryn from

525 to 875 g a.i. ha-1. Among other herbicide treatments, S-metolachlor showed the

maximum K uptake by R. capitata during both the years of study.

All the contrast comparisons were found significant during both the years except

S-metolachlor vs pendimethalin which was significant in 2010 and non-significant in

2011. Trend comparison showed that the linear trend was significant where as quadratic

response was non-significant during both the years of study. More uptake of K by R.

capitata in 2010 than in 2011 can also be attributed to higher R. capitata dry weight.

These results are in accordance with the research findings of Anjum et al. (2007) who

reported that K uptake by T. portulacastrum was 41.57 kg ha-1. The faster growth of

weeds causes quick depletion of nutrients from soil. Weeds removed 72.19 Kg ha-1 of

K2O in weedy plots in soybean field (Gaikwad and Pawar, 2003).

146

Table 4.5.9 Effect of application of different herbicide treatments on N uptake

(kg/ha) by R. capitata at harvest.



Pendimethalin+prometryn at 875 g a.i. aha-1 2.16 d 1.82 c

Pendimethalin+prometryn at 700 g a.i. ha-1 3.10 cd 2.72 bc



Pendimethalin @ 825 g a.i ha-1 4.40 bc 2.99 bc

LSD 1.705 1.793

Contrast


Pendimethalin+prometryn vs S-metolachlor 3.31 vs 5.35 ** 2.90 vs 3.37 NS




Linear Trend ** **





147

Table 4.5.10 Effect of application of different herbicide treatments on P uptake






Pendimethalin+prometryn at 525 g a.i. ha-1 4.08 c 2.05 bc


Pendimethalin @ 825 g a.i ha-1 4.52 bc 2.77 b

LSD 1.112 1.127

Contrast


Pendimethalin+prometryn vs S-metolachlor 3.03 vs 5.31 ** 1.41 vs 2.73 **

Pendimethalin+prometryn vs pendimethalin 3.03 vs 4.52 ⃰⃰ 1.41 vs 2.77 **


Trend comparison of different levels of Pendimethalin+prometryn

Linear Trend ** **





148

Table 4.5.11 Effect of application of different herbicide treatments on K uptake








Pendimethalin @ 825 g a.i ha-1 6.26 c 4.85 b

LSD 1.457 1.146

Contrast



Pendimethalin+prometryn vs pendimethalin 4.71 vs 6.26 ⃰⃰ 3.85 vs 4.85 ⃰⃰

S-metolachlor vs pendimethalin 7.74 vs 6.26 ⃰⃰ 5.37 vs 4.85 NS


Linear Trend ** **





149

4.5.13 Effect of herbicides on the Fe and Mn (mg/Kg) content of R. capitata in

mungbean at harvest.

The data (table 4.5.12) reveal that the highest Fe contents were found in weedy

check in both the years. While all other treatments had varying Fe contents in a way that

weedy check was followed by pendimethalin @ 825 g a.i ha-1 that was statistically at par

with pendimethalin+prometryn at 700 g a.i. ha-1 in 2010 and different in 2011. The

treatment pendimethalin+prometryn at 875 g a.i. ha-1 proved to be minimum in Fe

contents that may be due to efficient R. captitata control which resulted in less weed

interference with the crop for the nutrients. This fact is also obvious from the contrast

comparison as the contrast comparison of weedy check vs all is highly significant. In

case of comparison between different herbicides the combination of

pendimethalin+prometryn was found to be significant over all other herbicides or their

combinations. However, trend comparison was not significant neither linear nor

quadratic.

The data (table 4.5.13) regarding Mn contents of R. captitat shows a similar trend

as like Fe content with the highest Mn contents in weedy check followed by

pendimethalin @ 825 g a.i ha-1. It was statistically at par with pendimethalin+prometryn

at 525 g a.i. ha-1. The contrasts show a more vivid effect as weedy check vs all was

highly significant and similarly the combination of pendimethalin+prometryn was more

effective than using any herbicide alone according to treatment pattern. The considerably

higher Fe and Mn contents of R. capitata in weedy check treatment was due to the fact

that the R. capitata plants were allowed to grow freely all through the season with no

interference. The minimum Fe and Mn contents of R. capitata in

pendimethalin+prometryn at 875 g a.i. ha-1 was due to the toxic effects of herbicide on

the growth of R. capitata plants which hinder their growth and ultimately less Fe and Mn

contents were recorded in this treatment.

150

Table 4.5.12 Effect of application of different herbicide treatments on Fe content

(mg/kg) of R. capitata in mungbean at harvest.



Pendimethalin+prometryn at 875 g a.i. ha-1 41.10 c 34.57 d



S-metolachlor @ 1440 g a.i ha-1 101.72 ab 64.14 c


LSD 18.607 13.155

Contrast


Pendimethalin+prometryn vs S-metolachlor 63.09 vs 101.72* * 55.25 vs 64.14 NS









151

Table 4.5.13 Effect of application of different herbicide treatments on Mn content







S-metolachlor @ 1440 g a.i ha-1 77.46 a 53.78 b


LSD 12.419 6.841

Contrast





Trend comparison of different levels of Pendimethalin+prometryn






152

4.5.14 Effect of herbicides on Na and Zn content (mg/kg) of R. capitata in mungbean

at harvest.


different herbicide treatments on the Na and Zn content of R. capitata at harvest. Results

indicate that Na and Zn content of R. capitata were significantly affected by the

application of different herbicide treatments in both the years of study. The significantly

minimum Na and Zn content were found in the plants where pendimethalin+prometryn

@ 875 g a.i. ha-1 was applied. These were statistically at par with those of

pendimethalin+prometryn at 700 g a.i. ha-1 during both the years of study except Na

content in 2011. Weedy check treatment remained higher to the rest of the treatments in

both years of study.

All the contrast comparison except S-metolachlor vs pendimethalin, were

significant during both the years. Trend comparison showed that the linear trend was

significant where as quadratic response was non-significant during both the years of

study. The significantly maximum Na and Zn contents of R. capitata in weedy check

treatment was due to the uninterrupted growth and development of R. capitata plants all

through the growing season. The minimum Na and Zn contents of R. capitata in

pendimethalin+prometryn at 875 g a.i. ha-1 was due to the harmful effects of herbicide on

the growth of R. capitata plants which hamper their growth and ultimately minimum Na

and Zn contents were observed in this herbicide treatment.

153

Table 4.5.14 Effect of application of different herbicide treatments on Na content



Weedy check 34.95 ab 24.55 a



Pendimethalin+prometryn at 525 g a.i. ha-1 29.23 b 23.31 a

S-metolachlor @ 1440 g a.i ha-1 36.40 a 24.74 a

Pendimethalin @ 825 g a.i ha-1 29.45 b 22.35 a

LSD 5.775 3.086

Contrast











154

Table 4.5.15 Effect of application of different herbicide treatments on Zn content






Pendimethalin+prometryn at 525 g a.i. ha-1 28.58 b 14.36 c



LSD 5.389 3.261

Contrast











155

4.5.15 Effect of herbicides on Ca content (%) of R. capitata in mungbean at harvest.

It is evident from Table 4.5.16 that significant differences in Ca contents of R.

capitata in different herbicide treatments were observed between the study years, being

maximum in 2010. Among herbicide treatments, minimum Ca contents were recorded

with pendimethalin+prometryn at 875 g a.i. ha-1 in both the years. The contrast of weedy

check vs all was found significant during both the years of study. The contrasts of

pendimethalin+prometryn vs S-metolachlor and pendimethalin+prometryn vs

pendimethalin were significant during 2010 but these were non-significant during 2011.

Among trend comparisons of different levels of pendimethalin+prometryn, linear


significant during 2010 and 2011. These results are in line with those of Głowacka

(2011) who found that mean calcium content in the weeds was over 8 times higher than

in the crop.

4.5.16 Effect of herbicides on Cu and Mg (mg/kg) content of R. capitata in

mungbean at harvest.

The data presented in the table 4.5.17 and table 4.5.18 reveal the effects of

different herbicides on the Cu and Mg contents of R. capitata during 2010 and 2011. The

significantly maximum Cu and Mg contents were observed in weedy check. The

minimum Cu and Mg contents of R. capitata were recorded in plots where

pendimethalin+prometryn at 875 g a.i. ha-1 was applied. The Cu and Mg contents

decreased with increase in dose of pendimethalin+prometryn from 500 to 875 g a.i. ha-1.

Among other herbicide treatments, S-metolachlor showed the maximum Cu and Mg

contents of R. capitata during both the years of study.

All the contrast comparisons were found significant during both the years except

S-metolachlor vs pendimethalin which was non-significant during 2010 and 2011. Trend

comparison showed that the linear trend was significant where as quadratic response was

non-significant during both the years of study. The significantly maximum Ca, Cu and

Mg contents of R. capitata in weedy check treatment was due to the more favorable

growth and development of R. capitata plants throughout the cropping season. The

minimum Ca, Cu and Mg contents of R. capitata in pendimethalin+prometryn at 875 g

a.i. ha-1 treatment was due to the harmful effects of herbicide on the growth of R.

capitata plants which hamper their growth and ultimately Ca, Cu and Mg contents.

156

Table 4.5.16 Effect of application of different herbicide treatments on Ca content

(%) of R. capitata in mungbean at harvest.






S-metolachlor @ 1440 g a.i ha-1 1.14 b 0.72 c


LSD 0.119 0.081

Contrast



Pendimethalin+prometryn vs pendimethalin 0.96 vs 1.21* * 0.74 vs 0.69 NS








157

Table 4.5.17 Effect of application of different herbicide treatments on Cu content




Pendimethalin+prometryn at 875 g a.i. ha-1 6.33 e 3.21 e




Pendimethalin @ 825 g a.i ha-1 10.22 a 7.48 b

LSD 0.800 0.667

Contrast











158

Table 4.5.18 Effect of application of different herbicide treatments on Mg content









LSD 7.451 4.105

Contrast











159

4.5.17 Effect of herbicides on Fe and Mn uptake (g/ha) of R. capitata at harvest.


different herbicides on the Fe and Mn uptake of R. capitata at the harvest of mungbean.

The data indicated that all the herbicide treatments significantly affected the Fe and Mn

uptake of R. capitata. The application of pendimethalin @ 825 g a.i ha-1 resulted in

minimum Fe and Mn uptake in 2010 and 2011. However, highest Fe and Mn uptake

were found in treatment where R. capitata was allowed to grow throughout the season

during both of the study years.

Contrast comparison of pendimethalin+prometryn vs S-metolachlor and

pendimethalin + prometryn vs pendimethalin was significant during 2010 and non-

significant during 2011. A non-significant contrast of S-metolachlor vs pendimethalin for

Fe and Mn uptake of R. capitata was observed during 2010 and 2011 (table 4.5.19 and

table 4.5.20). Trend comparisons of different levels of pendimethalin+prometryn showed

that linear trend was significant where as quadratic response was non-significant during

both the years. Weeds usually absorb nutrients faster and relatively in larger amounts

than the crops and therefore, receive greater benefits. Higher Fe and Mn uptake of R.

capitata at harvest in plots kept weedy all through the season can be attributed to higher

R. capitata dry weight during both the years of study. Similar trend was observed in

other treatments. Minimum Fe and Mn uptake of R. capitata was observed in

pendimethalin+prometryn at 875 g a.i. ha-1, which was due to the toxic effects of this

herbicide treatment on R. capitata.

160

Table 4.5.19 Effect of application of different herbicide treatments on Fe uptake

(g/ha) of R. capitata at harvest.



Pendimethalin+prometryn at 875 g a.i. ha-1 6.81 e 4.40 c

Pendimethalin+prometryn at 700 g a.i. ha-1 10.67 de 7.70 bc




LSD 7.720 8.522

Contrast






Linear Trend ** **





161

Table 4.5.20 Effect of application of different herbicide treatments on Mn uptake





Pendimethalin+prometryn at 700 g a.i. ha-1 7.70 de 5.27 cd




LSD 6.088 4.355

Contrast


Pendimethalin+prometryn vs S-metolachlor 9.30 vs 19.99 * * 5.95 vs 9.77 NS




Linear Trend ** **





162

4.5.18 Effect of herbicides on Na and Zn uptake (g/ha) of R. capitata at harvest.

Effect of application of herbicides on Na and Zn uptake by R. capitata was also

significant during both the years of study (Table 4.5.21 and 4.5.22). The significantly

maximum Na and Zn uptake by R. capitata was recorded in weedy check where R.

capitata was allowed to grow throughout the season in 2010 and 2011. The minimum Na

and Zn uptake by R. capitata was recorded in plots where pendimethalin+prometryn @

875 g a.i.ha-1 was applied. It was statistically at par with those of

pendimethalin+prometryn @ 700 g a.i. ha-1.

In contrast comparison, weedy check vs all contrast was significant during both

the years. The contrast of pendimethalin+prometryn vs S-metolachlor was significant

during 2010 but was non-significant during 2011. However, contrasts for

pendimethalin+prometryn vs pendimethalin and S-metolachlor vs pendimethalin were

non-significant during 2010 and 2011. Trend comparison showed that the linear trend

was significant where as quadratic response was non-significant during both the years of

study. The significantly maximum Na and Zn uptake by R. capitata in weedy check

treatment was due to the more favorable growth and development of R. capitata plants

throughout the cropping season. Due to this reason, more dry weight of R. capitata was

recorded and hence more Na and Zn uptakes. The minimum Na and Zn uptakes by R.

capitata in pendimethalin+prometryn at 875 g a.i. ha-1 was due to the harmful effects of

this herbicide treatment on the growth of R. capitata plants which reduced its dry weight

and ultimately less Na and Zn uptakes were recorded during both the years of study.

163

Table 4.5.21 Effect of application of different herbicide treatments on Na uptake









LSD 2.694 1.765

Contrast






Linear Trend ** **





164

Table 4.5.22 Effect of application of different herbicide treatments on Zn uptake





Pendimethalin+prometryn at 700 g a.i. ha-1 3.50 d 1.34 bc




LSD 2.539 2.228

Contrast






Linear Trend ** **





165

4.5.19 Effect of herbicides on Ca (kg/ha), Cu and Mg uptake (g/ha) of R. capitata at

harvest.

The data presented in the table (4.5.23, 4.5.24, 4.5.25) indicate the application of

different herbicide treatments on the Ca, Cu and Mg uptake by R. capitata at harvest of

mungbean. The uptake of Ca, Cu and Mg by R. capitata was variable and also

significantly affected by the application of different herbicide treatments during both the

years of study. The significantly minimum Ca, Cu and Mg uptake by was R. capitata

found in the plots where pendimethalin+prometryn @ 875 g a.i. ha-1 was applied. It was

statistically at par with pendimethalin+prometryn @ 700 g a.i. ha-1 treatment. Weedy

check treatment remained higher to the rest of the treatments in both years

Contrast comparison for weedy check vs all was significant during both the years.

However, contrasts for pendimethalin+prometryn vs pendimethalin and S-metolachlor vs

pendimethalin were non-significant in case of Ca and Mg uptake during 2010 and 2011.

Trend comparison showed that the linear trend was significant where as quadratic

response was non-significant during both the years of study. Higher Ca, Cu and Mg

uptake by R. capitata in plots kept weedy all through the season can be attributed to

higher R. capitata dry weight during both the years of study. Similar trend was observed

in other treatments. The minimum Ca, Cu and Mg uptake by R. capitata in

pendimethalin+prometryn at 875 g a.i. ha-1 and pendimethalin+prometryn at 700 g a.i.

ha-1 treatments was due to the harmful effects of these herbicide treatments on the growth

of R. capitata plants which reduced its dry weight and ultimately less Ca, Cu and Mg

uptake by R. capitata during both the years of study.

166

Table 4.5.23 Effect of application of different herbicide treatments on Ca uptake

(kg/ha) of R. capitata at harvest.




Pendimethalin+prometryn at 700 g a.i. ha-1 3.41 c 2.11 cd



Pendimethalin @ 825 g a.i ha-1 4.84 b 2.32 bcd

LSD 1.379 1.121

Contrast






Linear Trend ** **





167

Table 4.5.24 Effect of application of different herbicide treatments on Cu uptake









LSD 0.454 0.346

Contrast


Pendimethalin+prometryn vs S-metolachlor 1.36 vs 2.39 * * 0.63 vs 1.23* *

Pendimethalin+prometryn vs pendimethalin 1.36 vs 2.03 * 0.63 vs 1.24* *

S-metolachlor vs pendimethalin 2.39 vs 2.03 NS 1.23 vs 1.24NS


Linear Trend ** **





168

Table 4.5.25 Effect of application of different herbicide treatments on Mg uptake









LSD 3.653 2.613

Contrast






Linear Trend ** **





169

4.5.20 Effect of herbicides on plant height (cm) of mungbean.

Data presented in table 4.5.26 show that promising plant height was obtained in second

year, which was a good indicator of better crop stand, because of effective weed control.

All the weed control treatments considerably affected the plant height of mungbean.

Maximum plant height was recorded in weed free treatment in both the years. It was

followed by pendimethalin+prometryn @ 875 g a.i. ha-1 during both the years of study.

Minimum plant height was recorded in S-metolachlor @ 1440 g a.i ha-1 in both the years.

Contrasts of control vs all and weedy check vs all showed that difference between

mungbean plant height was significant during both the years of study. However contrasts

of all herbicide treatments were non-significant during 2010. Similar trend in contrasts of

mungbean plant heights was recorded during 2011 (table 4.5.26). Trend comparison of

different levels of pendimethalin+prometryn showed that the linear trend was significant

during 2011 whereas it was non-significant during 2010. The quadratic trend during both

the years was non-significant.

Plant height is a function of the genetic as well as the environmental conditions (Sarwar,

1994), which contributes to biomass production of a crop. These results contradicts the

findings of Naeem and Ahmad (1999b), who found that plant height of mungbean was

not significantly affected by different weed control methods. In this study, application of

different herbicides as well as weed free treatment showed significantly better plant

height of mungbean as compared to weedy check treatment. It may possibly be owing to

the reason that R. capitata plants were controlled effectively in plots where herbicides

were applied in comparison with weedy check plots all through the cropping season. In

herbicide treated plots, the mungbean plants got maximum benefit from nutrients

resources, water and light and thus developed taller and vigorous. Mungbean plants seem

to be larger in 2011 as compared to 2010 in all treatments. It might be due to severe

rainfall in received in 2010 which reduced the effect of applied herbicides and favoured

vigorous weed growth in crop. Due to more competition from weeds in 2010, the crop

development was affected and eventually, plant height was reduced. These results are in

accordance with those of Chattha et al (2007) who found an increasing trend in

mungbean plant height with herbicide application as compared to weedy check

treatment.

170

Table 4.5.26 Effect of application of different herbicide treatments on plant height

(cm) of mungbean.


Weedy check 38.50 d 47.50 c

Pendimethalin+prometryn at 875 g a.i. ha-1 53.75 ab 59.00 b


Pendimethalin+prometryn at 525 g a.i. ha-1 43.50 cd 52.00 bc

S-metolachlor @ 1440 g a.i ha-1 39.00 d 52.50 bc

Pendimethalin @ 825 g a.i ha-1 47.00 bcd 55.00 bc

Control (Weed free) 58.75 a 68.50 a

LSD 8.894 7.581

Contrast

Control vs all 58.75 vs 45.25* * 68.50 vs 53.95 * *

Weedy check vs all 38.50 vs 48.62* 47.50 vs 57.45 * *

Pendimethalin+prometryn vs S-metolachlor 49 vs 39.00 NS 56.25 vs 52.50 NS

Pendimethalin+prometryn vs pendimethalin 49 vs 47.00 NS 56.25 vs 55.00 NS



Linear Trend NS ⃰⃰





171

4.5.21 Effect of herbicides on number of pods per plant of mungbean.

The data presented in the table 4.5.27 show the effect of different herbicide

treatments on the number of pods per plant of mungbean. Number of pods per plant of

mungbean was considerably affected by different weed control methods in both the years

of study. These were also variable in first and second years of study being maximum in

the second year (table 4.5.27). Among herbicide treatments, maximum pods per plant

were observed when pendimethalin+prometryn was applied @ 875 g a.i. ha-1 in both the

years and remained superior to the rest of treatments in both years.

More number of seeds pod-1 in second year might be due to better crop stand in

this year. The high rainfall in 2010 not only reduced the effect of herbicides but also

favoured vigorous weed growth in mungbean crop. Eventually, crop development was

reduced due to severe competition from weeds as compared to 2011. The weeds took less

nutrients from soil in 2011 as compared to 2010 and therefore crop performed better in

respect of growth and yield in 2011. Contrast comparison of control vs all and weedy

check vs all were found significant in 2010 and 2011. All the contrast comparisons for

herbicide treatments were found non-significant during both the years of study. The

linear trend was significant in case of trend comparison of different herbicide treatments

in 2010, whereas it was non-significant during 2011. The quadratic trend during both the

years was non-significant.

In both the years of study, number of pods increased from 13.75 to 25.75 (2010) and

17.25 to 28.75 (2011) which might be due to less weed competition which positively

affected the pods per plant. Comparatively less effect of other control treatments except

pendimethalin+prometryn at 875 g a.i. ha-1 seems due to incomplete weed control that

resulted ultimately poor crop stand and less number of pods plant-1 in both years of

study.

172


pods per plant of mungbean.






S-metolachlor @ 1440 g a.i ha-1 20.75 c 26.50 b



LSD 4.008 5.892

Contrast

Control vs all 31.00 vs 20.29* * 40.00 vs 24.75 * *

Weedy check vs all 13.75 vs 23.16* * 17.25 vs 28.54 * *

Pendimethalin+prometryn vs S-metolachlor 22 vs 20.75 NS 26.41 vs 26.50 NS

Pendimethalin+prometryn vs pendimethalin 22 vs 21.25 NS 26.41 vs 25.50 NS



Linear Trend ⃰⃰ NS





173

4.5.22 Effect of herbicides on number of grains per pod of mungbean.

The data presented in the table 4.5.28 depict the effect of the application of

different herbicides on the number of grains per pod of mungbean. The results reveal that

weed free (control) treatment has statistically maximum number of grains per pod as

compared to all other treatments in 2010 and 2011. It was followed by

pendimethalin+prometryn @ 875 g a.i. ha-1 in both the years. The treatment in which the

R. capitata was allowed to grow freely has the minimum grains per pod in both years. In

case of herbicides, minimum grains per pod were recorded when pendimethalin was

applied @ 825 g a.i ha-1 in 2010. Similar trends have been observed in 2011.

Contrast comparisons for number of grains per pod of mungbean showed that

contrasts of control vs all, weedy check vs all and pendimethalin+prometryn vs S-

metolachlor were significant. A similar trend was recorded for these contrasts during

2011 (table 4.5.28). Contrasts for pendimethalin+prometryn vs pendimethalin and S-

metolachlor vs pendimethalin were found non-significant during 2010 and 2011. In trend

comparison of different levels of pendimethalin+prometryn, the linear trend was

significant during for both of the years; whereas quadratic trend was found non-

significant.

The improvement in number of grains per pod of mungbean under different weed

control treatments may be attributed to comparative reduction in weed growth which was

maximum during second year of study. These results are quite in collaboration with

those of Khan et al. (2011).

174

Table 4.5.28 Effect of application of different herbicide treatments on the number

of grains per pod of mungbean.



Pendimethalin+prometryn at 875 g a.i. ha-1 9.50 ab 9.50 a

Pendimethalin+prometryn at 700 g a.i. ha-1 8.75 bc 8.75 ab

Pendimethalin+prometryn at 525 g a.i. ha-1 7.75 d 7.75 bc

S-metolachlor @ 1440 g a.i ha-1 7.25 d 7.25 c



LSD 0.981 1.091

Contrast

Control vs all 10.0 vs 8.12 * * 9.50 vs 8.12 * *

Weedy check vs all 7.50 vs 8.54** 7.50 vs 8.45*

Pendimethalin+prometryn vs S-metolachlor 8.66 vs 7.25* 8.66 vs 7.25*

Pendimethalin+prometryn vs pendimethalin 8.66 vs 8 NS 8.66 vs 8 NS

S-metolachlor vs pendimethalin 7.25 vs 8 NS 7.25 vs 8 NS







175

4.5.23 Effect of herbicides on 1000-grain weight (g) of mungbean.

Examination of data presented in the table 4.5.29 reveal significantly higher

1000-grain weight in second year. The reason might be same as discussed in the last

section. Data regarding 1000-grain weight of mungbean demonstrated that all weed

control treatments caused a significant effect on 1000-grain weight of mungbean in both

years. Among different weed control treatments, weed free treatment exhibited 45.25 g

in 2010 and 55 g 1000-grain weight in 2011. Although, the rest of the treatments

performed less efficiently than control, however were statistically better than that of

weedy check in both of the years.

Significant difference in 1000-grain weight of mungbean was noted among

contrasts of control vs all and weedy check vs all during both years of study. Contrast

between pendimethalin+prometryn vs S-metolachlor was significant during 2010 but it

was non-significant during 2011 (table 4.5.29). The contrasts between

pendimethalin+prometryn vs pendimethalin and S-metolachlor vs pendimethalin showed

non-significant trend in both of the years. Trend comparisons of different levels of

pendimethalin+prometryn for 1000-grain weight of mungbean are also presented in the

table 4.5.29. Linear response was significant during both of the years. However,

quadratic response was non-significant during 2010 and 2011.

The herbicide treatments showed significantly better 1000-grain weight as

compared to weedy check treatment during both the years of study. This might be due to

adequate weed control during the cropping period, which provided maximum moisture

and nutrients for healthy plant growth and hence pod formation which ultimately leads

towards better grain weight. Similar results have also been discussed by Khaliq et al.

(2002).

176

Table 4.5.29 Effect of application of different herbicide treatments on 1000-grain

weight (g) of mungbean.


Weedy check 26.00 c 29.25 d

Pendimethalin+prometryn at 875 g a.i. ha-1 42.00 a 49.50 ab

Pendimethalin+prometryn at 700 g a.i. ha-1 34.00 b 45.25 bc

Pendimethalin+prometryn at 525 g a.i. ha-1 30.50 bc 40.50 c

S-metolachlor @ 1440 g a.i ha-1 29.50 bc 42.00 c



LSD 6.759 6.014

Contrast



Pendimethalin+prometryn vs S-metolachlor 35.5 vs 29.50* 45.08 vs 42.00 NS









177

4.5.24 Effect of herbicides on biological yield (kg/ha) of mungbean.

The perusal of table 4.5.30 indicate a significant difference in biological yield of

mungbean between study years being maximum during the second year. The maximum

biological yield of mungbean was observed in weed free treatment (control) in both the

years. Among different doses of pendimethalin+prometryn, maximum biological yield

of mungbean was recorded when the pendimethalin+prometryn was applied @ 875 g a.i.

ha-1 in 2010 which was statistically at par with that of pendimethalin alone. Similarly,

application of pendimethalin+prometryn @ 875 g a.i. ha-1 resulted in the maximum

biological yield of mungbean which was statistically at par with other doses of

pendimethalin+prometryn.

Contrast comparisons for biological yield of mungbean showed that contrast of

weedy check vs all and control vs all were significant in both the years. In herbicide

treatments, contrast of all herbicide doses in 2010 were non-significant. A similar trend

was recorded for pendimethalin+prometryn vs pendimethalin contrasts during 2011

(table 4.5.30). Contrast for pendimethalin+prometryn vs S-metolachlor and S-

metolachlor vs pendimethalin was also found significant during 2011. Linear trend of

different levels of pendimethalin+prometryn in 2010 is significant where as it was non-

significant during 2011. The quadratic trend of different levels of

pendimethalin+prometryn was non-significant during both years.

Greater biological yield was recorded in weed free and herbicide treated plots. It

might be due to effective weed control in these plots which minimize the competition of

mungbean with R. capitata. The mungbean plant characteristics like height and number

of pods were more in herbicide treated as compared to weedy check plots. These

characteristics contributed in increasing biological yield of mungbean. These results are

in agreement with those of Chattha et al (2007) who found an increasing trend in

mungbean biomass with herbicide application as compared to weedy check treatment.

178

Table 4.5.30 Effect of application of different herbicide treatments on biological

yield (kg/ha) of mungbean.


Weedy check 3087.7 e 3279.2 d

Pendimethalin+prometryn at 875 g a.i. ha-1 4008.1 ab 3963.9 bc

Pendimethalin+prometryn at 700 g a.i. ha-1 3691.7 cd 4108.4 b

Pendimethalin+prometryn at 525 g a.i. ha-1 3388.0 de 3991.0 b

S-metolachlor @ 1440 g a.i ha-1 3806.9 bc 3791.7 c



LSD 309.08 196.84

Contrast

Control vs all 4189.5 vs 3630* * 4464.6 vs 3854.81* *

Weedy check vs all 3087.7 vs 3813.63*

*

3279.2 vs 4052.38 *

*

Pendimethalin+prometryn vs S-metolachlor 3695.93 vs 3806.9NS 4021.1 vs 3791.7 * *

Pendimethalin+prometryn vs pendimethalin 3695.93 vs 3797.6NS 4021.1 vs 3994.7 NS

S-metolachlor vs pendimethalin 3806.9 vs 3797.6 NS 3791.7 vs 3994.7 *


Linear Trend ** NS





179

4.5.25 Effect of herbicides on grain yield (kg/ha) of mungbean.

It is evident from table 4.5.31 that a significant difference in grain yield of

mungbean was observed between the two years, being maximum in second year. This

might be due to less R. capitata plants due to efficient control providing healthy

environment for crop plants during this year. High amount of rainfall in 2010 favoured

prompt and vigorous weed growth even in the intervals (7 days) between the weeding

practices in weed free plots. The favourable atmospheric conditions during 2011 also

resulted into better crop stand as compared to 2010. Therefore, the minor difference in

the yield of weed free plots in both the years was observed. Examination of data also

indicates that all herbicide treatments caused statistically different effect on grain yield

of mungbean in both the years of study. Among herbicide treatments, maximum grain

yield was recorded with pendimethalin+prometryn @ 875 g a.i. ha-1 in both the years. It

was followed by pendimethalin+prometryn @ 700 g a.i. ha-1 in 2010 but was statistically

at par in 2011.

Contrast of control vs all, weedy check vs all and pendimethalin+prometryn vs S-

metolachlor were significant during both the years of study. Contrast of

pendimethalin+prometryn vs pendimethalin was non-significant during 2010 (table

4.5.31) but it was significant during 2011. Contrary to it, contrast of S-metolachlor vs

pendimethalin was significant during 2010 and it showed non-significant trend during

2011. Among trend comparisons of different levels of pendimethalin+prometryn, linear

response was significant during both the years of study. Quadratic response was

significant during 2010 and non-significant during 2011 for mungbean grain yield.

Data also reveal that all weed control methods caused statistically significant

effect on grain yield of mungbean in both the years. Increase in grain yield of mungbean

may be attributed to more number of pods per plant and number of grains per pod. These

results are in accordance with those of Cheema et al. (2000) and Chattha et al. (2007).

Number of pods per plant is an important yield component of mungbean and greatly

affects the economic yield. Comparatively more number of pods of mungbean in

herbicide treated plots resulted in increased grain yield of crop in this experiment.

Similar observations were reported by Khan et al. (2011) who concluded that grain yield

of mungbean decreased due to lesser number of pods per plant.

More grain yield in weed control treatments than weedy check was due to

improved growth and development of mungbean plants, which resulted in more seed

assimilates. These results are in line with Naeem and Ahmad (1999a), who concluded

180

that the enhancement in grain yield under different weed control methods has direct

relation with weed growth reduction. In these experiments, application of different

herbicide treatments significantly increased the grain yield of mungbean. These results

are supported by the previous findings of Rana and Pal (1997) and Mathew and

Sreenivasan (1998) who found that crops grown with proper weeding could produce

higher yields. Similarly, Windley et al. (1999) tested the efficacy of 6 herbicides against

T. portulacastrum and Macroptilium lathyroides and found that all herbicides not only

reduced the populations of these weed species, but also increased mungbean yield from

the control value of 1563 kg ha-1 to 1882 kg ha-1.

181

Table 4.5.31 Effect of application of different herbicide treatments on grain yield



Weedy check 642.4 e 796.3 e



Pendimethalin+prometryn at 525 g a.i. ha-1 1097.7 c 1188.1 cd

S-metolachlor @ 1440 g a.i ha-1 960.8 d 1115.7 d

Pendimethalin @ 825 g a.i ha-1 1072.9 c 1183.3 cd


LSD 31.537 35.841

Contrast

Control vs all 1485.9 vs 1015.03* * 1661.5 vs 1138.8**

Weedy check vs all 642.4 vs 1115.61* * 796.3 vs 1283.06*

*


Pendimethalin+prometryn vs pendimethalin 1138.03 vs 1072.9

NS

1245.96 vs1183.3 NS

S-metolachlor vs pendimethalin 960.8 vs 1072.9* 1468.2 vs 1183.3

NS


Linear Trend ** *

Quadratic Trend * NS




182

4.5.26 Effect of herbicides on harvest index of mungbean.

The data presented in the table 4.5.32 show the effect of different herbicide

treatments on the harvest index of mungbean. It reveals that harvest index (%) was

considerably more in the second year. This was probably, because of better grain yields

obtained during this year. It was observed that maximum harvest index was achieved in

control treatment in both years. In 2010, harvest index of 41.75 was obtained while in

2011, it was 49.00 in control treatment. Herbicide treatment, pendimethalin+prometryn

@ 875 g a.i. ha-1 resulted in the statistically significant harvest index (29.86% in 2010

and 32.68 % in 2011) as compared to all other herbicides applied. It was statistically at

par with pendimethalin+prometryn @ 700 g a.i. ha-1 in both the years. Minimum harvest

index was observed in weedy check treatment in which the R. capitata were allowed to

grow freely.

Contrasts comparisons showed that contrast of weedy check vs all and control vs

all showed a significant difference for harvest index (table 4.5.32). In herbicide

treatments, contrast of pendimethalin+prometryn vs S-metolachlor and S-metolachlor vs

pendimethalin were significant during 2010. However, contrasts of different herbicide

treatments were non-significant during 2011 (table 4.5.32). Contrast of

pendimethalin+prometryn vs pendimethalin in 2010 was also non-significant. A similar

trend in contrasts for mungbean harvest index (%) was achieved during 2011. Trend

comparison of different levels of pendimethalin+prometryn showed that the linear trend

was significant in 2010 and it was non-significant in 2011. The quadratic trend in both

the years was non-significant.

As found in this study, Cousin et al. (1985) reported that harvest index was the

most important factor influencing the grain yield in legumes. Shrivastava et al. (2001)

also concluded that biological yield and harvest index were important traits affecting the

grain yield. Highest percentage of harvest index in control (weed free) plots might be due

to more economic yield (kg ha-1). Harvest index percentage was considerably more in the

2011. This was probably, because of better yields obtained during this year. These results

are in line with those of Chattha et al. (2007) who found a significant difference between

years regarding harvest index of mungbean being maximum during the second year.

183

Table 4.5.32 Effect of application of different herbicide treatments on harvest index

of mungbean.


Weedy check 20.82 e 24.32 d



Pendimethalin+prometryn at 525 g a.i. ha-1 32.76 ab 29.83 c

S-metolachlor @ 1440 g a.i ha-1 25.28 d 29.45 c

Pendimethalin @ 825 g a.i ha-1 28.26 c 29.64 c


LSD 1.382 1.315

Contrast





S-metolachlor vs pendimethalin 25.28 vs 28.26* 29.45 vs 29.64 NS


Linear Trend ** NS





184

4.5.27 Economic analysis

The economic analysis of weed control practices is essential to look at the results

from farmer’s point of view as the farmers are more interested in costs and benefits. The

table indicates that all weed control practices gave higher net benefits than weedy check

treatment. The maximum net benefits (62745) were obtained in the plots kept weed free.

It was followed by plots where pendimethalin + prometryn @ 875g a.i ha-1 were applied.

During 2010, maximum benefit cost ratio (2.40) was observed in mungbean plots

sprayed with pendimethalin + prometryn @ 875g a.i ha-1 followed by pendimethalin +

prometryn @ 700 g a.i ha-1 (table 4.5.33). A similar trend in net benefits and benefit cost

ratio was recorded during 2011 (table 4.5.34).

4.5.28 Dominance analyses

A treatment was considered dominated if its variable cost was greater than the

previous treatment however its net benefits were lower. Such treatment was considered

dominated (D). The dominated treatment was not included in the calculation of marginal

rate of return (MRR). Thee dominance analysis of different treatments are presented in

the table 4.5.35 and 4.5.36. The treatments where pendimethalin @ 825g a.i ha-1 and S-

metolachlor @ 1440g a.i ha-1 were applied, were dominated as their net benefits did not

increase with the increase in variable cost during both the years of study.

4.5.29 Marginal analyses

A net benefit is not a final criterion for recommendation to a common farmer;

hence, marginal analysis was performed to determine the most profitable weed control

treatment. It is calculated by comparing the total variable cost with net benefits. The

table 4.5.37 and table 4.5.38 show the marginal analysis during 2010 and 2011. The

results showed that marginal rate of return was higher (1249.03% and 936.51%) in

mungbean plots where pendimethalin + prometryn @ 525g a.i ha-1 was applied during

2010 and 2011.

185

Table 4.5.33 Effect of application of different herbicide treatments on economic

returns during 2010.

Treatments Gross income (Rs.

ha-1)

Cost that vary (Rs.

ha-1)

Net benefits (Rs. ha-1)

Benefit cost ratio

T1 51392 36127 15265 1.42

T2 95704 39827 55877 2.40

T3 89608 39327 50281 2.27

T4 87816 38827 48989 2.26

T5 76864 40127 36737 1.91

T6 85832 39627 46205 2.16

T7 118872 56127 62745 2.11

Table 4.5.34 Effect of application of different herbicide treatments on economic returns during 2011.

Treatments Gross

income (Rs. ha-1)

Cost that vary (Rs.

ha-1)

Net benefits (Rs. ha-1)

Benefit cost ratio

T1 63704 40462 23241.7 1.57

T2 103528 44606 58921.6 2.32

T3 100456 44046 56409 2.28

T4 95048 43486 51561 2.18

T5 89256 44942 44313 1.98

T6 94664 44382 50281.6 2.13

T7 132920 62862 70057 2.11

T1 Weedy check T2 Pendimethalin + Prometryn @ 875g a.i ha-1 (Penthilin Plus-35 EC@ 2500 ml ha-1) T3 Pendimethalin + Prometryn @ 700g a.i ha-1 (Penthilin Plus-35 EC @ 2000 ml ha-1) T4 Pendimethalin + Prometryn @ 525g a.i ha-1 (Penthilin Plus-35 EC @ 1500 ml ha-1) T5 S-metolachlor @ 1440g a.i ha-1 (Dualgold-960 EC @ 1500 ml ha-1) T6 Pendimethalin @ 825g a.i ha-1 (Stomp-330 EC @ 2500 ml ha-1) T7 Control (weed free)

186

Table 4.5.35 Dominance analysis of different herbicide treatments during 2010

Treatments Cost that vary (Rs. ha-1) Net benefits (Rs. ha-1)

T1 36127 15265

T4 38827 48989

T3 39327 50281

T6 39627 46205 D

T2 39827 55877

T5 40127 36737 D

T7 56127 62745

Table 4.5.36 Dominance analysis of different herbicide treatments during 2011

Treatments Cost that vary (Rs. ha-1) Net benefits (Rs. ha-1)

T1 40462 23241.7

T4 43486 51561

T3 44046 56409

T6 44382 50281.6 D

T2 44606 58921.6

T5 44942 44313 D

T7 62862 70057


187

Table 4.5.37 Marginal rate of return of different herbicide treatments during 2010

Treatments Cost that vary (Rs.ha-1)

Marginal cost (Rs.ha-

1)

Net benefit (Rs.ha-1)

Marginal

benefit (Rs.ha-

1)

MRR

(%)

T1 36127 15265

T4 38827 2700 48989 33724 1249.03

T3 39327 500 50281 1292 258.4

T2 39827 500 55877 5596 1119.2

T7 56127 16300 62745 6868 237.33

Table 4.5.38 Marginal rate of return of different herbicide treatments during 2011

Treatments Cost that vary (Rs.ha-1)

Marginal cost (Rs.ha-

1)

Net benefit (Rs.ha-1)

Marginal

benefit (Rs.ha-

1)

MRR

(%)

T1 40462 23241.7

T4 43486 3024 51561 28320 936.51

T3 44046 560 56409 4848 865.71

T2 44606 560 58921.6 2512 449.11

T7 62862 18256 70057 11136 60.99


188

CHAPTER 5

SUMMARY

Mungbean (Vigna radiata (L.) Wilczek) is one of the major pulse crops in the

irrigated and dry areas of Pakistan. The mungbean grain yield (760 kg ha-1) is much lower

than the potential (2000 kg ha-1) yield in Pakistan. Weed infestation is one of the most

important factors responsible for low yield of mungbean. Rhynchosia capitata, an emerging

annual summer season weed, poses a major threat to mungbean’s successful production in

the cultivated areas of Southern Punjab of Pakistan and is increasingly becoming a

problematic weed in farming systems. Keeping in view the importance of weed management

in field crops, the present study has been planned to be realized about dormancy,

germination, phytotoxicity, competition and control of R. capitata in mungbean.

Results of our study are summarized as under.

Laboratory experiment 1

Experiment was conducted with the hypothesis that whether R. capitata seeds could be

released from dormancy with different seed treatment methods. The objective of this research

was to determine the effect of different methods and identify the best method to break seed

dormancy and promote germination of R. capitata seeds.

Seeds of R. capitata showed no response to various concentrations of thiourea and

KNO3 since thiourea and KNO3 failed to crack the seed coat and its imbibition.

Results indicated that germination of seeds mechanically scratched with sand paper

significantly increased of 100% as compared to HCl treatments. When seed were scarified

with HCl (36%) for 3, 6, 9, 12, 15 and 18 hours, seeds germination significantly increased

over control.

Soaking of R. capitata seeds in HNO3 for 1 to 5 days had little effect on seed germination.

Total germination did not reach over 18 % and was slow and irregular.

The scarification of R. capitata seed with H2SO4 induced seed germination. Seed germination

percentage increased with increasing soaking time (up to 80 min) and began to decrease with

the further increase in soaking time.

189


Effect of varying levels of environmental factors e.g. temperature, light, water

availability, pH, salt stress and seeding depth on R. capitata germination and emergence was

tested in laboratory, department of Agronomy, University of Agriculture, Faisalabad,

Pakistan.

Germination increased as the temperature increased from 25oC and significantly

reduced at 45oC.

Germination of R. capitata seeds was not influenced by presence or absence of light.

Increase in salt stress, moisture stress and seed burial depth significantly affected the

seed germination of R. capitata.

Seeds of R. capitata had ability to germinate over a wide range of pH (5-10)

In seed burial trial, maximum seedling emergence of 93 % was at 2 cm depth, and

seedling did not emerge from a depth of 12 cm.


The main objectives of this research were to study the effects of root, stem, leaf, fruit and

whole plant water extracts and soil infested with R. capitata on mungbean (Vigna radiate L.)

germination and seedling growth, and to determine water soluble and total phenolics

responsible for the allelopathic activity.

Aqueous extracts of root, shoot, leaf, fruit and whole plant adversely affected

germination and seedling growth of mungbean, but higher inhibition was seen with R.

capitata leaf water extract.

A linear decrease in the germination characteristics of mungbean was observed with

the decrease in the concentration of leaf extract from 5% to 1%.

The soil incorporated residues of R. capitata stimulated the growth of root and

hypocotyl at low concentrations (1% w/w), while it inhibited their growth at higher

concentration (4% w/w).

Rhynchosia capitata soil incorporated residues (4% w/w) significantly reduced the

total germination and seedling vigour index of mungbean.

190

Two phenolic acids including vanillic acid and 4-(hydroxymethyl) benzoic acid were

found in R. capitata leaf extract.

Field experiment 1


(2011 & 2012) at farmer field in District Layyah, Southern Punjab, Pakistan (30o 57ʹ N, 70o

56ʹ E). This area was selected because heavy infestation of R. capitata has been reported in

previous years. Soils of the area are sandy loam in nature, slightly alkaline with pH 8.2 and

low in organic matter (0.5%). The experiments were laid out in randomized complete block

design (RCBD) with 4 replications. Seven weed crop competition durations were included in

the study. These were weed crop competition throughout the season, weed crop competition

for 0, 3, 4, 5, 6, 7 weeks after planting of mungbean. Recommended seed rate (25 kg ha-1)

was used to plant this crop using single row hand drill in 30 cm apart rows. Each plot size

was 4.5 m × 1.8 m. Nitrogen and phosphorus were applied @ 25 and 50 kg ha-1 in the form

of diammonium phosphate (DAP) and urea, respectively. Plant to plant distance of 15 cm

was maintained by thinning out the surplus plants 10 days after emergence. Weeds were

removed manually with a hand hoe from respective plots after prescribed duration and

kept weed free till harvest. All other agronomic operations except those under study were

kept normal and uniform for all the treatments.

Weeds fresh and dry weight showed an increasing trend as the competition period

was prolonged. Full season weed competition produced highest weed fresh and dry

weight which was statistically different from all other competition periods during


The significantly maximum NPK uptake by R. capitata was recorded in plots where

weeds were allowed to grow throughout the season. The minimum NPK uptake by R.

capitata was recorded in plots with 3 weeks competition period in 2011. Similar trend

was observed in 2012.

Highest Fe, Mn, Na, Zn, Ca, Cu and Mg contents and their uptake was recorded in the

plots where R. capitata plants were tolerated to compete with the mungbean all

191

through the cropping season. These were statistically at par with 7 weeks of R.

capitata competition in both the years of study.

The maximum plant height of mungbean was recorded in weed free treatment in 2011

and 2012. This was statistically at par with 3 and 4 weeks of competition period

during both the years of study.

The highest number of pods per plant, grains per pod and 1000-grain weight was

recorded in plots where R. capitata plants were tolerated to compete with the

mungbean all through the cropping season during both the study years. These were

followed by plots having R. capitata competition up to 3 weeks after planting of

mungbean.

The maximum biological yield of 4495.7 kg ha-1 in 2011 and 4202.9 kg ha-1 in 2012

was recorded in weed free plots as significantly different from all other treatments.

Increase in competition period decreased the biological yield of mungbean

significantly.

Increase in competition period decreased the mungbean grain yield significantly. In

2011, the weed-free plots gave the highest grain yield of 1688.6 kg ha-1 followed by

competition of 3 weeks after planting with 1582.0 kg ha-1 of grain yield. Similar trend

was also observed during 2012.

The maximum harvest index was recorded in weed free treatment which was

statistically at par with the competition period of 3 and 4 weeks. Similar results were

obtained during 2012.

Field experiment 2 The field experiment was conducted under irrigated conditions for two crop years

(2010 & 2011) at farmer field in District Layyah, Southern Punjab, Pakistan (30o 57ʹ N, 70o

56ʹ E). The experiments were laid out in randomized complete block design (RCBD) with 4

replications. Seven weed control methods were included in the study. These were weedy

check, pendimethalin + prometryn @ 875 g a.i ha-1, 700 g a.i ha-1 and 525 g a.i ha-1, S-

metolachlor @ 1440 g a.i ha-1 and control (weed free). All other agronomic operations except

those under study were kept normal and uniform for all the treatments.

192

All weed control treatments significantly reduced the dry weight of R. capitata. The

lowest dry weight of 16.25 and 12.37 g m-2 was recorded in plots sprayed with

pendimethalin+prometryn @ 875 g a.i. ha-1 in 2010 and 2011, respectively. However,

the highest weed dry weight was found in weedy check treatment. All doses of the

herbicides suppressed the dry biomass of R. capitata from 60 to 78% in 2010 and

2011. Pendimethalin+prometryn @ 875g a.i. ha-1, recorded (74% in 2010 and 78% in

2011) reduction in total weed dry weight.

The significantly maximum NPK uptake by R. capitata was recorded in weedy check

where weeds were allowed to grow all through the cropping season. The minimum

NPK uptake by R. capitata was recorded in plots where pendimethalin+prometryn @

875 g a.i. ha-1 was applied.

All the weed control methods significantly affected plant height, number of pods per

plant and 1000-grain weight of mungbean. Maximum plant height, number of pods

per plant and 1000-grain weight was recorded in weed free treatment in both the

years. Among different herbicide treatments, pendimethalin+prometryn @ 875 g a.i.

ha-1 caused a pronounced affect on plant height, number of pods per plant and 1000-

grain weight of mungbean during both the years of study.

Although, the maximum seed yield was recorded in weed free treatment in both years

but there is a considerable difference between both years. All herbicide treatments

caused statistically different effect on grain yield of mungbean in both the years of

study. Among herbicide treatments, maximum grain yield (1196.3 kg/ha in 2010

1294.1 kg/ha in 2011) was recorded with pendimethalin+prometryn @ 875 g a.i. ha-1.

Conclusion

Seed coat was the major barrier to Rhynchosia capitata seed germination and softening the

seed coat of Rhynchosia capitata by means of soaking in concentrated H2SO4, HCl and HNO3

significantly increased seed germination.

Mechanical scarification has also been shown to be the best method to overcome this coat-

imposed dormancy.

Optimum temperature for R. capitata germination was 25 ºC.

193

Presence or absence of light did not influence germination.

Germination of R. capitata was adversely affected by salt stress above 150 mM and

osmotic potential above –0.8 MPa.

Rhynchosia capitata had ability to germinate over a wide range of pH (5-7).

Rhynchosia capitata can emerge better on soil surface and at 0 to 6 cm seeding depth.

Leaves of R. capitata had high phytotoxic ability to inhibit mungbean seedling

emergence as compared to other plant parts.

The soil residues of R. capitata are toxic to mungbean seedlings at concentrations

greater than 1%.

Total phenolic acids’ content was higher in leaf extract compared to that of stem, fruit

or root extracts.

Full season weed competition produced highest weed fresh and dry weight, NPK and

micronutrients uptake by R. capitata. While the minimum were recorded in 3 weeks

competition period during both the years of study.

The highest number of pods per plant, grains per cob and 1000-seed weight was

recorded in plots where weeds were allowed to compete with the crop during both the

study years.

Increase in competition period decreased the seed yield significantly. Weed-free plots

gave the highest grain yield followed by competition 3 weeks after planting.

Pendimethalin+prometryn @ 875g a.i. ha-1 resulted in most effective weed control

treatment and resulted in highest suppression of the dry biomass of R. capitata (74%

in 2010 and 78% in 2011).

Maximum seed yield of mungbean was recorded with pendimethalin+prometryn @ 875 g

a.i. ha-1 in both the years.

Recommendation

Inputs to the seed bank of R. capitata should be reduced by controlling it before

flowering stage. Therefore a deep tillage practice is suggested to bury its seeds at greater

depths. No residues of this weed should be present in the field to avoid its allelopathic

interference. Rhynchosia capitata should be controlled within 3 weeks after sowing of

194

mungbean. Pendimethalin + prometryn @ 875 g a.i. ha-1 proved best treatments for

effective control of R. capitata in mungbean and to get maximum economic and net

benefits.

Future Thrusts

• The models should be developed that describe the forecasting of timing and degree of

weed emergence for setting up more efficient weed control approaches.

• The assessment of the allelochemicals and their isolation, identification, release, and

movement under field conditions are important future research guidelines.

• Effectiveness of other herbicides which can execute better then

pendimethalin+prometryn should be evaluated against R. capitata.

• It is essential to study phytotoxicity and residual toxicity of herbicides on

crop and weeds.

195

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