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EFFECTS OF ORGANIC AND INORGANIC FERTILIZERS ON GROWTH,

YIELD AND NUTRITIONAL QUALITY OF WHITE CABBAGE

(Brassica oleracea L. var. capitata f. alba cv, Cape Horn)

GANJA SINGH RAI

A THESIS SUBMITTED IN PARTIAL FULFILLMENT

OF THE REQUIRMENTS FOR THE DEGREE OF

MASTER OF SCIENCE IN HORTICULTURE

GRADUATE SCHOOL

MAEJO UNIVERSITY

2010

Copyright of Maejo University

APPROVAL SHEET

GRADUATE SCHOOL, MAEJO UNIVERSITY

THE DEGREE OF MASTER OF SCIENCE IN HORTICULTURE

Title

EFFECTS OF ORGANIC AND INORGANIC FERTILIZERS ON GROWTH,

YIELD AND NUTRITIONAL QU ALITY OF WHITE CABBAGE

(Bras sica oleracea L. var. eapitata f. alba cv, Cape Horn)

By

GANJA SINGH RAI

APPROVED BY

Advisory Committee Chairperson .....~~~~g;,;') ..iCf o~ 10.... .. .................../ ./ ..

Advisory Committee Member

(Dr. Jiraporn lnthasan) ~ OS 0 /6........ ............. .. .J. ./ .

Advisory Committee Member ..............1~.~ F.~.~~~.I( . (Mr. Anan Pintarak)

;20 0 S- :ROIO ........ .............. ..J. / .

Advisory Committee Member

(Assistant Professor Dr. Thawalrat Ratanadachanakin)

...... .d .Q ./ ~?? .I...~.Q/. Q. .

Chairpe rson, Commi ttee on Master of ......................~. ;;~~~~ 11. . Science Program in Horticulture (Assistant Professor Dr. T eranuch Jaroenkit)

J;b J o \i'. J 01.16 . CERTIFIED BY ............ ..y . GRADUATE SCHOOL (Associate Professor Dr. Thep Pliongparnich)

........~~ .I. tl~j / ~~.~.~ .

III

Title Effects of Organic and Inorganic Fertilizers on Growth.

Yield and Nutritional Quality of White Cabbage iBrassica

oleracea L. val'. capitata f. alba cv . Cape Horn)

Author Mr. Ganja Singh Rai

Degree Master of Science in Horticulture

Advisory Committee Chairperson Associate Professor Nipon Jayamangkala

ABSTRACT

In this study, the field trial following the randomized complete block design

(RCBD) with three replications using white cabbage (Brassica olera cea L. var. capitata f. alba

cv, Cape Horn) as a test crop. was conducted at Maejo University, Thailand in 2008 to compare

between organic and conventional farming systems. The efficacy of composts alone as well as

their combination with poultry manure tea (PMT) in promoting growth. yield and nutritional

quality of white cabbage, was investigated in comparison to chemical fertilizers. The amount of

all added fertilizers was adjusted to total nitrogen (N) supply of 125 kg/ha in all treatments except

the control. Vitamin C and leaf nitrate contents were selected as indicators of nutritional quality

of cabbage.

In this study, the highest fresh weight yield of cabbage head (44 ton/ha) among

all the treatments was recorded in inorganic treatment. However, no significant difference was

observed between this inorganic yield and the highest yield among organic treatments (40 ton/ha)

produced by organic plot fertilized with poultry manure compost in combination with PMT in 1:3

proportion. Other organic treatments produced yields ranging from 31 to 37 ton/ha which were

significantly different from inorganic plot (P<O.OI). The lowest yield (J 2 ton/ha) was observed in

control. As for quality, vitamin C was higher in all the organically fertilized cabbages 006 to 139

mg/IOO g) than in inorganic cabbage (103 mg/IOOg) but leaf nitrate was lower in all organically

fertilized cabbages (163 to 309 mglkg) than chemically fertilized cabbage (589 rug/kg). These

integrated results showed the possibility for organic fanning to produce high quality cabbage with

yield similar to that of conventional fanning when compost is used in combination with PMT.

Keywords: cabbage, compost, nitrate. organic fanning, poultry manure tea, vitamin C.

IV

Acknowledgements

I wish to acknowledge to a number of person and the institutions for their

generous helps and great supports that have assisted me completing this project in time .

To begin with, I would like to express my sincere thanks and profound gratitude

to my principal advisor, Associate Professor Nipon Jayamnagkala, Maejo University for his

excellent guidance, impeccable instruction, continuous encouragement and prompt suggestions

rendered throughout my study period. I am also equally grateful to my advisory committee

members, Dr. Jiraporn Inthasan, Mr Anan Pintarak and Assistant Professor Dr. Thawalrat

Ratanadachanakin of Maejo University for their constructive comment, technical assistance and

useful suggestion that have immensely helped me to complete this thesis successfully.

My foremost note of gratitude goes to Thailand International Development

Cooperation Agency (Royal Thai Government) for awarding this prestigious scholarship to me. I

am deeply indebted to my Alma Mater, "Maejo University", Chiang Mai for imparting an

excellent education. Similarly, I am forever grateful to the Department of Agriculture, Royal

Government of Bhutan for nominating me to pursue this course of study.

My special thanks goes to Asst. Prof. Dr. Luckana Phetpradap, Head of erstwhile

Horticulture Department for her untiring support, motherly guardianship and for creating a

homely atmosphere during her tenure at Maejo University. Likewise, lowe special thanks to Dr.

Pornpan Pooprompan (Division of Ornamental Horticulture), Asst. Prof. Dr. Sirichai Unsrisong

(Agronomy Department) and Assoc. Prof. Prawit Puddhanon (Agronomy Department) who have

helped me in analyzing the data in analytical software program for thesis work.

Furthermore, I would like to express my gratitude to Asst. Prof. Dr. Sangvut,

Asst. Prof. Dr. Theeranuch Jaroenkit, Asst. Prof. Nopadol Jarasamrit, Dr. Sakesan Ussahatanonta

and Mr. Pricha Rattanang for their good guidance and imparting knowledge during my study

period. Similarly, I would like to acknowledge to all academic and administrative staffs of

erstwhile Horticulture Department, Vegetable Division and Pomology Division for their help

during my stay at Maejo University.

I would also like to extend my gratitude to the staff of Office of Vice President

for Foreign Affairs, Graduate School, Registrar Office, University Central Library and

v

Information Technology Center for their help. Thanks are due to Madam Diana Jantakad, Office

of the University President, Maejo University for arrangement of numerous study trips and

generous get-together dinner.

I will always remember the moments of joy, happiness and friendship that I

shared with my classmates, senior students as well as junior students of M.Sc. Horticulture from

Thailand, Nepal and Mynrnar during my stay at Maejo University. I cannot mention everyone

here but none is forgotten. I too owe them thanks for their never-ending help and company they

provided to me .

While back at home, my heartfelt thank goes to my beloved father , Buddhi M.

Rai and other family members Tika Rai and Rohan Rai for their unparalleled affection, moral

support, inspiration and encouragement given to me throughout my life as well as for their

unforgettable sacrifices and patience during my stay abroad.

Above all, I wish to offer my special gratitude to Almighty God for providing

light into my life and for being so gracious to protect me always.

GANJA SINGH RAI

May 2010

vi

Table of Contents

Page

ABSTRACT 1II

Acknowledgements IV

Table of Contents VI

List of Tables Vlll

List of Figures x

Abbreviations

Chapter 1 Introduction

XII

Objective of the Study 3

Chapter 2 Literature Review 4

The concept of organic agriculture 4

Cabbage production 8

Compost and composting 14

Use of manures as organic fertilizer 21

Manure tea 27

Vitamin C in vegetables and fruits 30

Nitrates accumulation in vegetables 34

Plant nutrients management in organic farming 38

Chapter 3 Materials and Methods 42

Compost preparation 42

Manure tea preparation 44

Raising of cabbage nursery 45

Soil sampling and analysis 47

Calculation of composts and poultry manure tea requirement 48

Field experiment 50

Measurement of plant height and leaf number per plant 53

Measurement of yield and yield components 54

Determination of quality 56

vii

Page

Data analysis 61

Matrix of Pearson's correlation coefficient between yield and yield

Appendix E: Abstract of paper presented in ie" National Graduate

Chapter 4 Results 62

Plant nutrient in composts and manure tea 62

Stock of plant NPK nutrients in the soil 63

Vegetative growth 65

Yield components 68

Yields 73

Quality aspects of cabbage 77

components 82

Chapter 5 Discussion 84

NPK nutrients in poultry manure tea 84

Stock ofNPK nutrients in the soil and mineralization of organic fertilizers 85

Vegetative growth 86

Yield of cabbage 88

Nutritional quality of cabbage 90

Chapter 6 Conclusions and Recommendations 93

Conclusions 93

Recommendations 94

Suggestions for future research 95

References 96

Appendices 109

Appendix A: Raw data of individual sample plants for head weight (gram) 110

Appendix B: The ANOVA Table and DMRT for cabbage head weight 112

Appendix C: Weather recorded during crop period 114

Appendix D: Report of result of the vitamin C content analysis in cabbage. 116

Research Conference on March 11, 2010 at Maejo University 118

Appendix F: Curriculum Vitae 120

Vlll

List of Tables

Table Page

Nutrient content of organic versus conventional crops 8

2 Guidelines for composting parameters 19

3 Manure production by selected animals and N content 25

4 Amount of total N (N03 and NH4) accumulated at weekly interval in

Chicken Manure Tea prepared with I: 1 dilution (35 lbs of chicken manure in 35

gallon of water) 28

5 Vitamin C content (mg/lOOg FW) of selected vegetables and fruit s 33

6 Maximum levels for nitrate as laid down in Commission Regulation

(EC) No 1881/2006 37

7 The average NPK nutrient concentrations and rates of ava ilability of various

organic materials 39

8 Estimated quantity of plant-avail able N from organic N applied in manure over 3

years 41

9 Added fert ilizers & nutrients in trial field (composts applied on fresh weight

basi s) 49

10 Amount of fertilizers applied 111 the experiment (composts applied on fresh

weight 52

11 NPK nutrients content and other physico-chemical properties of

Composts (dry weight basi s) and poultry manure tea 63

12 Stock of NPK nutrients in 0-25 em of field soil before and after harvest cropping 64

13 Effect of organic and inorganic fertilizers on the formation of cabbage leaves 65

14 Effects of organic and inorganic fertilizers on plant he ight before head formation 67

15 Effects of organic and inorganic fertili zers on plant height after head formation 67

16 Effects of organic and inorganic fertilizers on the yield components of cabbage 69

17 Effects of organic and inorganic fertilizers on different yields of cabbage 75

18 Effects of organic and inorganic fertilizers on the yield of cabbage 76

19 Effects of different treatments on head solidity, TSS and dry matter contents 79

IX

20

21

Effect of organic and inorganic fertilizers on vitamin C and nitrate contents of

cabbage

Matrix of Pearson's Correlation coefficient among different parameters of

cabbage as influenced by different types of fertilizers

Page

80

83

x

List of Figures

Figure Page

Growth stages of cabbage 11

2 Passive aerated compost windrow (A) and aerated static compost pile (B) 16

3 Passive aerated static pile composting 18

4 Compost temperature ranges 18

5 N mineralization of organic N in selected liquid animal manures applied

to a sandy soil 28

6 Structure of ascorbic acid (vitamin C) and L-dehydroascorbic acid (DHA) 31

7 Manure tea preparation. A = extraction of manure tea, B = filtration of manure

tea 43

8 Passive aerated static pile composting. A = composting in bag, B = matured

compost 43

9 Cabbage seed source and cabbage seedlings in nursery 46

10 Location of sample plants (denoted by letter S) in rows and plot 53

11 LCD Digital Hand Refractometer (Atago, PAL-I, Japan) used in the

determination ofTSS of cabbage 57

12 Hand Held Penetrometer (Wagner FDK Force Gage FT 10) used for the

determination of head solidity of cabbage 57

13 Spectrophotometer (NICOLET Evolution 300 LC, England) used for

determination of nitrate concentration of cabbage leaves 57

14 NPK nutrients contents in compost and poultry manure tea 62

15 Stock ofNPK nutrients in treatment soil after the harvest of cabbage 64

16 Weekly leaf number of cabbage as influenced by organic and

inorganic fertilizers 66

17 Effect of organic and inorganic fertilizers on fortnightly plant height of cabbage 68

18 Cabbage plants in the field at different stages of the growth 70

Stem diameter, frame leaf number and wrapper leaf number at the harvest

of cabbage

19

71

xi

Page

20 Effect of organic and inorganic fertilizers on plant height, head length and head

width of cabbage 72

21 Effect of organic and inorganic fertilizers on head weight of cabbage 74

22 Size and condition of cabbage heads as influenced by organic and


23 Total soluble solid (TSS) and dry matter content (% DM) of cabbage 80

24 Vitamin C and nitrate concentrations as affected by organic and


XII

Abbreviation/symbol

AA

ANOVA

Assist.

Assoc.

C

CF

cm

CMC

cv.

CV

DAT

DHA

DM

DMRT

EM

et al.

FAO

FW or f.w.

FYM

GMO

GAP

Ha or ha

IFOAM

K

Kg or kg

L or Lit.

Abbreviations and symbols used

Description

Ascorbic acid

Analysis of variance

Assi stant

Associate

Carbon

Con ventional farming

Centimeter

Cattle manure compost

Cultivar (variety)

Coefficient of variation

Day after transplanting

L-Dehydroascorbic acid

Dry matter

Duncan's Multiple Range Test

Effe ctive microorganisms

And other people

Food and Agriculture Organization

Fresh weight

Farmyard manure

Genetically Modified Organism (also Genetically Manipulated Organism)

Good Agriculture Practices

Hectare

International Federation of Organic Movements

Potassium

Kilogram

Litre

Lab Laboratory

XIII

LSD

mg

MJU

ml

mm

N

N02

N03

NS

OA

OM

P

PMC

PMT

ppm

Prof.

RCBD

SAS

TSS

UNCTAD

USDA

Vito C

WHO

).lg

Least significant difference

Milligram

Maejo University (Chiang Mai, Thailand)

Millilitre

Millimetre

Nitrogen

Nitrite

Nitrate

Not significant

Organic Agri culture

Organic matter

Phosphorus

Poultry manure compost

Poultry manure tea

Parts per million

Professor

Randomized Complete Block Design

Statistical Analysis System

Total soluble solid

United Nation Conference on Trade and Development

United States Department of Agriculture

Vitamin C

World Health Organization

Micro gram

Chapter 1

Introduction

Agriculture is one of humankind's most basic activities because all people need

to nourish themselves daily for survival. In fact, the civilization of humankind started only after

the introduction of agriculture in fertile valleys when hunter and food-gatherer turned into food

producer. History, culture and community values are all embedded in agriculture (IFOAM, 2009).

However, the chemical intensive technology so long promoted in agriculture by Green Revolution

has brought long-term damages to soil quality. It is increasingly being realized that the prolonged

and intensive use of chemical fertilizers and pesticides has resulted in continuous environmental

degradation, particularly of soil, vegetation and water resources (Singh, 2000; Gosh, 2004) .

Further, the continuous nutrient mining while using chemical fertilizers leads to an ever

increasing gap between nutrients depletion and replenishment, leaving the soil infertile and

unsustainable. The dependence of agriculture on exhaustible fossil fuels has not only caused the

pollution of soil at the production sites but also the pollution of both surface and ground water

resources through leaching of nitrogen leading to various health hazards to human and animals

(Mengel and Kirkby, 1982; Gosh, 2004; Havlin et al., 2005). Such concerns over environmental

pollution, health hazard and rapid climate changes have prompted scientists and policy-makers to

search alternatives to the conventional agricultural practices (Xu et aI., 2003). Organic farming is

the best option to ameliorate such devastations created by human action. However, most of the

farmers are reluctant in converting to large-scale organic farming often reasoning that the crop

yield is lower in organic farming compared to conventional farming (Xu et aI., 2003) . Despite the

various benefits to environment and health, organic farming has been criticized as low-yielding

and less efficient than conventional agriculture in its use of land (Trewavas, 2004).

Organic agriculture is often compared with conventional farming In terms of

yield and it is seen as a competitor of chemical farming. The main objective of organic farming or

any other sustainable agriculture is to produce safer, chemical free foods and protect environment

by refraining from the use of chemical fertilizers and pesticides in crop production. On the other

hand, the main aim of conventional farming is to boost crop yield through high external input of

chemical fertilizers and pesticides and in few cases by using GMOs. Therefore, it will be

2

extremely difficult for organic agriculture to fulfill the dual responsibilities of producing the safer

foods without using any external chemical input , and at the same time producing enough food for

all. Nonetheless, it is the inherent duty of any agriculture system to increase the crop productivity

in order to meet the food requirement by ever increasing human population in the world .

Therefore, an attempt, in addition to its present role of producing healthy foods and protecting

environment, has to be made in organic agriculture to increase crop yield to address food shortage

in the future.

One of the problems with organic fertilizers is that they work very slowly.

Lower yields in organic farming are often a result of lower availability of nitrogen, generally due

to inexperienced N management (Ramesh et al., 2005; Murphy et aI., 2007). Nitrogen in organic

fertilizers presents in two forms - organic N and inorganic N. Most of the N in organic fertilizers

present in organic form (Mengel and Kirkby, 1982 ; Havlin et al.. 2005; Antil et al., 2009). The

inorganic fraction of N (ammonia) in organic fertilizers is readily available for uptake by plants

and is as high in efficiency as mineral fertilizers . The problem is with the organic N (amino acids,

proteins, peptides, etc .) of organic fertilizers that persists in the soil for long period in unavailable

state and becomes available very slowly (Mengel and Kirkby, 1982 ; Havlin et al.. 2005; Murphy

et al., 2007). Unlike inorganic nitrogen, organic nitrogen becomes available to plants only when

soil microorganisms decompose organic compounds and then convert the released N to NH 4 by

the process of mineralization. Therefore, most of the solid organic fertilizers applied to the field

often mineralize outside the cropping period and the intended growing crop plants in the field do

not receive adequate N even though the sufficient N has been applied through these fertilizers.

This is the main reason for low crop yields in organic farming. However, the available data have

shown that liquid organic fertilizers provide nutrients instantly to the plants much like the

chemical fertilizers as they contain N mainly in inorganic form like ammonia (Mengel and

Kirkby, 1982; Price and Duddles, 1984; Gross et al., 2007). Further, Gross et al.(2007) have

reported that poultry manure extract in water can be economically used for supplementary

nitrogen side-dressing when available N from soils and solid composted manures is inadequate

for crop requirements. So far researches in organic crop production have been carried out mostly

using solid organic fertilizers and only a limited researches have been conducted on the use of

liquid organic fertilizers . In addition to their potential use in irrigation systems, liquid organic

3

fertilizers are easy to handle and transport, and can be applied uniformly and accurately in the

field (Mengel and Kirkby, 1982; Havlin et al., 2005). Therefore, there is a need for a field trial to

compare the crop yield between conventional farming and organic farming using both solid and

liquid organic fertilizers to address the question of yield reduction in organic farming.

There is an increasing demand for organic foods in the world, especially fruits

and vegetable crops that are consumed raw (Jakse and Mihelic, 1999; Nakano et al., 2003;

Tanrivermis, 2008). The consumers believe that organically produced foods not only have lower

risk of pesticide residues, but also are of superior nutritional values with higher amount of

antioxidants (vitamin C and E, and p-carotene), dietary fibres and protein content and less potent

toxic plant compound like nitrate. It is a known fact that the quality of crops is controlled by a

complex interaction of factors, including soil type and kind and quantity of fertilizers applied

(Warman and Harvard, 1998). Xu et al. (2003; Leu, 2004) reported that organically grown

Brassica vegetables and strawberry respectively had significantly higher level of cancer-fighting

antioxidants like vitamin C but lower nitrate content when compared with conventionally grown

counter parts. Nitrate causes methaemoglobinaemia and possibly some cancers in human when it

is converted to nitrite and N-nitroso compounds (Chen et al. , 2004).

Using white cabbage as a test crop species, this study was carried to find out

differences in yield , vitamin C concentration and leaf nitrate content between organic and

conventional farming systems.

Objectives of the study

The following are the specific objectives of this study:

1. To find out the yield differences between the cabbages grown under organic

farming and conventional fanning systems.

2. To find out the differences in vitamin C and nitrate contents between cabbages

grown with organic and inorganic fertilizers .

3. To evaluate the best organic fertilizer or a combination of organic fertilizers

that can produce high quality cabbage with yield equal to that of conventional farming.

Chapter 2

Literature Review

The concept of organic agriculture

Organic fanning is an approach to agriculture that emphasizes environmental

protection, animal welfare, food quality and health, sustainable resource use and social justice

objectives and it utilizes the market to help support these objectives and compensates for the

internalization of externalities (Stolze and Lampkin, 2009). Organic farming relies on crop

rotation, green manure, compost, biological pest control, and mechanical cultivation to maintain

soil productivity and control pests, excluding or strictly limiting the use of synthetic fertilizers

and synthetic pesticides, plant growth regulators, livestock feed additives, and genetically

modified organisms. IFOAM (2009) defines the overarching goal of organic farming as follows :

"Organic agriculture is a production system that sustains the health of soils, ecosystems and

people". Organic fanning is defined by the Codex Alimentarius Commission (FAO/WHO, 1999)

as "a holistic production management system that avoids use of synthetic fertilizers, pesticides

and genetically modified organisms, minimizes pollution of air, soil and water, and optimizes the

health and productivity of interdependent communities of plants, animals and people".

Organic agriculture is knowledge intensive. Fanners need to be aware of

underlying biological principles and ecological dynamics in order to make them work for their

own purposes. It relies on ecological processes, biodiversity and cycles adapted to local

conditions. Organic agriculture combines modern scientific research with traditional farming

techniques in a sustainable, efficient farming system (UNCTAD, 2002). Organic agriculture

builds up stocks of natural, social and economic resources over time, thus reducing many of the

factors that lead to food insecurity (UNCTAD, 2002). Organic agriculture restores the

environmental balance since agricultural contaminants such as inorganic fertilizers, herbicides

and insecticides used in conventional agriculture are not allowed in organic agriculture (Haring et

al., 200 I) . Organic agriculture has the potential to safeguard rural livelihoods and revitalize

smallholder agriculture. As a result, it can be an effective tool for protecting traditional

knowledge and reducing rural-urban migration. Agriculture is the main employer in rural areas

5

and wage labour provides an important source of income for the poor. Thus, by being labour

intensive, organic agriculture creates not only employment but improves returns on labour,

including also fair wages and non-exploitive working conditions (Ramesh et al., 2005 ; FAO,

2007).

International organic standards

Organic agricultural practices are internationally regulated and legally enforced

based on the standards set by the IFOAM (International Federation of Organic Agriculture

Movements), an international umbrella organization for organic organizations established in

1972. The Basic Standards for Organic Production and Processing of the IFOAM were first

published in 1980 and since then they have been subject to biennial review and republication. The

IFOAM's Basic Standards provide a framework for certifying bodies and standard-setting

organizations worldwide to develop their own certification standards taking into account specific

local conditions and it cannot be used for certifications on their own. To promote organic

agriculture and to ensure fair practices in international trade of organic food, the Codex

Alimentarius Commission, a joint body of FAOIWHO (I999) framed certain guidelines for the

production, processing, labeling and marketing of organically produced foods, with a view to

facilitate trade and prevent misleading claims. The word "Organic" in organic agriculture is a

labelling term that denotes the products have been produced in accordance with certain standards

during food production, handling, processing and marketing stages and certified by a duly

constituted certification body or authority (Ramesh et al., 2005). The organic label is therefore a

process claim rather than a product claim. Organic labels are obtained through third party

certification and grower group guarantee systems, both of which provide valid verification of

compliance with organic standards. Finally, "organic agriculture" is not just about production. It

includes the entire food supply chain, from production and handling, through quality control and

certification, to marketing and trade (FAO, 2007).

6

Organic agriculture and crop yield

Despite several benefits, critics raise concern that organic agriculture is not

capable of meeting the world's growing food needs due to low productivity per area (Borlaug,

2000; Trewavas, 2002) . Extensive research with regard to the productivity of the organic

agriculture system has been carried out in developed countries in order to address this criticism.

Productivity in organic production systems is management specific (FAO, 2007). Yields relative

to comparable conventional systems are directly related to the intensity of farming of the

prevailing conventional systems (Ramesh et al., 2005). This is not only the case for comparison

between regions, but also between crops within a region, and for individual crops over time. An

over-simplification of the impact of conversion to organic agriculture on yield indicates that:

1. In intensive farming systems, organic agriculture decreases yield, the

range depends on the intensity of external input use before conversion (Stanhill , 1990; Halberg

and Kristensen, 1997).

2. In the so-called green revolution areas (irrigated lands), conversion to

organic agriculture usually leads to almost identical yields (Kler et al., 2002).

3. In traditional rain-fed agriculture (with low external inputs), organic

agriculture has shown the potential to increase yields (Huang et al., 1993; Singh et al., 2001).

A number of studies have shown that under drought conditions, crops in organic

agriculture systems produce significantly higher yields than comparable conventional agricultural

crops (Stanhill, 1990; Dormaar et al., 1988), often out-yielding conventional crops (Lockeretz et

al., 1981; Ramesh et al., 2005) by 7-90%. The so-called organic transition effect, in which a yield

decline in the first 1-4 years of transition to organic agriculture, followed by a yield increase

when soils have developed adequate biological activity (Liebhardt et al., 1989; Neera et al.,

1999). It is estimated that yield reductions during the conversion period are 20 to 30 percent for

cereals, 10 to 20 percent for maize, 30 to 40 percent for potatoes, 10 to 40 percent for vegetables

and around 30 percent for fruits (Zundel and Kilcher, 2007) . In the medium and long term, when

soil fertility has recovered, yields will be slightly lower or comparable to the pre-conversion

yields. Both short- and long-term field trials with maize, wheat, beans, soya, safflower, potatoes

7

and tomatoes found no difference between organic and conventional crop yields (Poudel, et al.,

2002 ; Delate et al.; 2003, Denison et al.; 2004; Pimentel et al., 2005). However, other trials found

organic crop yields to be 5 to 35 percent lower than conventional crop yields (Mader et al., 2002;

Denison et al., 2004). Lower yields are often a result of lower availability of nitrogen, generally

due to inexperienced management such as introduction of green manuring. Hill and mountain

areas, often characterized by extreme weather conditions, inaccessibility, poor and steep soils

subject to erosion, low population density, poor infrastructure and training facilities, also have

favourable conditions such as pristine environments with low incidence of pests and diseases

(Zundel and Kilcher, 2007). Only small reductions in the first years after conversion have been

observed in converting this type of agriculture to organic agriculture (Avasthe, et al., 2005).

Nutritional quality and safety of organically produced rood

There is a growing demand for organic foods driven primarily by the consumer's

perceptions of the quality and safety of these foods and to the positive environmental impact of

organic agriculture practices. It has been demonstrated that organically produced foods have

lower levels of undesirable and harmful substances like pesticides, veterinary drug residues and

nitrate contents (Ramesh et al., 2005) that help in reducing cancers. The nutritional quality of

organic foods as compared to conventionally (with high external inputs) produced includes

generally higher vitamin C, higher zinc/phytate ratio, higher plant secondary metabolites and

conjugated fatty acids in milk. However, there have been many claims that eating organic foods

increases exposure to microbiological contaminants (Avery, 1998). But studies investigating these

claims have found no evidence to support them (Pell, 1997; Jones, 1999). Analysis of pesticide

residues in produce in the US and Europe has shown organic products have significantly lower

pesticide residues than conventional products (Woese et al., 1997; FAO, 2000b). Nitrates are

significant contaminants of foods, generally associated with intensive use of nitrogen fertilizers.

Studies that compared nitrate contents of organic and conventional products found significantly

higher nitrates in conventional products (FAO, 2000b; Muramoto, 2000). There are also claims

that food produced by organic methods tastes better and contains a better balance of vitamins and

minerals than conventionally grown food . However, there is no clear scientific evidence, with

8

some studies showing increase in vitamin C, minerals and proteins, more sweeter and less tart

apples (Reganold et al., 2001) and others not (Woese et al., 1997). Quality after storage has been

reported to be better in organic products relative to conventional products after comparative tests

(Benge et al., 2000; Reganold et al., 200 I).

It is a known fact that the quality of crops is controlled by a complex interaction

of factors, including soil type and the ratio of minerals in added compost, manure and fertilizer.

So it is difficult to separate the influence of the environment and farming system (Warman and

Harvard, 1998). There is scope to generate information on the quality of produce generated on

organic farms in future studies.

Table 1 Nutrient content of organic versus conventional crops.

Number of comparisons** Mean % Level of

Nutrient Organic Organic No No. ofdifference* significance p higher lower difference studies

done Vitamin C +27.0% <0.0001 83 38 11 20 Nitrates -15.1% <0.0001 43 127 6 18 Iron +21.1% <0.001 51 30 2 16 Magnesium +29.3% <0 .001 59 31 12 17 Phosphorus +13.6% <0.01 55 37 10 18

Note. * Plus and minus signs refer to conventional crops as the baseline for comparison. For example, vitamin C is 27.0% more abundant in the organic crop (conventional J00%, organic 127%).

** A comparison consists of a single nutrient in a single organic crop grown in one season compared to the same conventionally grown crop from the same season, for example, 0.30 mg of zinc in organic cabbage compared to 0.25 mg of zinc in conventional cabbage, both grown in 1986.

Source: Worthington (200 I)

Cabbage production

Cabbage is one of the world's leading vegetables in terms of total production

and is grown in numerous regions across the world (Bewick, 1994; Yanga et al., 2008). Because

of its adaptability to the wide range of climate and soil, and its general use as food crop, cabbage

is widely cultivated in the world. Cabbage is a versatile crop and can be consumed in varied

9

forms (Nonnecke, 1989; Tindall, 1993). It is widely used as salad (e.g. coleslaw) as well as

cooked vegetable that is consumed alone or mixed with other vegetables. Cabbages are consumed

in preserved and fermented form like sauerkraut and Kimchi. In terms of storability (shelf life),

cabbage takes the first place among all the leafy vegetables. Nonnecke (1989) has reported that

well-trimmed cabbage heads can be stored up to six months at 0° C in near moisture-saturated air

condition without any major losses in color and quality, while Hounsome et al. (2009) stated that

white cabbage can be stored under refrigerated conditions for up to 10 months. There are three

types of heading cabbage under capitata group: (1) white cabbage or Dutch cabbage, Brassica

oleracea var. capitata L. alba subgroup, (2) red cabbage, Brassica oleracea var. capitata L. rubra

subgroup and (3) savoy cabbage, Brassica oleracea var. capiuua L. sabauda subgroup.

Origin of cabbage

It is believed that modem hard-head cabbage cultivars were descended from

wild non-heading Brassicas originating in the eastern Mediterranean (Nonnecke, 1989; Tindall,

1993; Bewick, 1994; Guerena, 2006) The Latin name Brassica is derived from the Celtic word

"bresic", meaning cabbage (Guerena, 2006).

Botany of cabbage

Cabbage, Brassica oleracrea L. var. capitata (Zn = 18), belongs to the

Brassicaceae (previously Cruciferae) or mustard family (Guerena, 2006). Cabbage is from a

group of plants known as the cole crops. This group of plants includes broccoli , cauliflower,

Brussels sprouts, collards, kale and kohlrabi, and they readily intercross each other. Cabbage is a

dicotyledonous, herbaceous, biennial plant (Bewick, 1994). The first year of growth produces the

head and in the second year it flowers and produces seed if the head is vernalized properly

(Nonnecke, 1989). During the early growth and development of the cabbage plant, the first leaves

expand and unfold to form the frame (Dickson and Wallace, 1986). As the cabbage plant

develops, it initially rosettes until a basic number of leaves are formed. The terminal bud at this

10

point then begins to grow, forming an ever increasing overlaps of leaves that eventually become

the head. Finally, the head is filled with a number of sessile fleshy leaves.

The weight of 1000 seeds of cabbage is 4 grams (Tindall, 1993).

Climate and temperature requirement

Cabbages are well adapted to cool temperatures. A temperature range of 15-200

C is considered as optimum for growth and head formation of the crop (Tindall, 1993; Bewick,

1994). Some cultivars are able to withstand temperatures excess of 30° C (Dickson and Wallace,

1986; Tindall, 1993). Temperature in excess of 30° C generally suppresses growth. The minimum

temperature is 0° C but cold hardened plants can tolerate temperature as low as -10° C (Bewick,

1994). A temperature range of 5° C variation between day and night temperatures is necessary for

adequate head development. The temperatures below 10° C for 5-6 weeks induce flowering once

the head is mature. The optimum soil temperature range for seed germination is 8 to 35° C and

germination occurs in 4 - 8 days (Poincelot, 2004).

Soil requirement

Many soil types are satisfactory for cabbage production, although fertile sandy

or silty loams are better suited for early cabbage and heavy soils for late and over-wintering

cabbage. On heavy soils, plants grow more slowly and the keeping quality is improved. A pH

range of 6.0-7.5 is considered as optimum for growing cabbage and application of lime is

required to improve pH if it is below 6 (Nonnecke, 1989; Tindall, 1993). Slightly alkaline soils

are less likely to be affected by acid-loving club-root organisms (Guerena, 2006). Cabbage plants

are moderately tolerant to saline conditions (Daugovish et al., 2008).

Fertility and nutrients management

The cabbage is a heavy feeder crop , especially for nitrogen and potassium

(Guerena, 2006). On the other hand, the excess of nitrogen can lead to the excessive vegetative

11

Stage 1 : Cotyledons (seed leaves) No true leaves present.

Stage 4: 9 to 12 true leaves The base of stem is still visible from the above.

Stage 2 : Seedling Up to 5 true leaves.

Stage 5: Precupping Approximately 13 to 19 leaves. By the end of this stage, the base of the stem and the bases of all leaves are concealed when the plant is viewed from above.

Stage 3: 6 to 8 true leaves Ready for transplanting

Stage 6: Cupping Approximately 20 to 26 leaves. The innermost heart leaves, which are still growing in an upright fashion, are concealed by the larger, older leaves surrounding them.

Stage 7: Early head formation Head diameter will be approximately 10 em. The inner heart leaves, now quickly developing as a ball-like structure of overlapping leaves, are concealed by the surrounding larger leaves.

Stage 8: Head fill. Head diameter will be approximately 10 - 20 em. A firm round head is visible within the wrapper leaves (4 outer loose leaves that touch the mature head). The head has not yet fully developed and

thus, is not of harvestable size.

Stage 9: Mature. Head diameter will be approximately 15 - 30 em. No new visible leaf production will occur after the head has attained maximum hardness and size. The head is ready for harvest and may split if not harvested in time.

Figure 1 Growth stages of cabbage.

Source: FAO (2000a)

12

growth, which delays head formation in cabbage (Guerena, 2006). Cabbage is vel)' sensitive to

micronutrient deficiencies. Nonnecke (1989) has reported that the cabbage is most sensitive to

three micronutrients - boron, copper and zinc. The commonest occurrence is boron deficiency

(Nonnecke, 1989). Severely affected plants develop rosetting and destruction of the terminal

shoot. The copper deficiency in cabbage is marked by the formation of a faint inter-veinal

chlorosis of expanding leaves. Zinc deficiency causes pitcher-like cupping with out-curved

margins of expanded leaves.

It is most important to analyze the soil first to determine its nutrients content. A

soil test is the most accurate guide to fertilizer requirement. Oregon State University (2004) has

recommended the following guideline for N, P and K fertilization in cabbage:

1. Nitrogen: Total application of 90-110 kg N per hectare should be appl ied

depending on the N status of the soil. Broadcast half the quantity of N to the field before

transplanting and apply remaining halfN just before the last cultivation or 2 weeks before the first

harvesting.

2. Phosphorus: Phosphorus fertilizer should be banded at the time of seeding or

transplanting. Bands should be located 2-3 inches to the side of the seeds or plants and 3-4 inches

deep.

If the soil test for P shows (ppm) 0-30 30 -50 Over 25

Add this amount ofPps (kg/ha) 170 - 220 110- 170 90 - 110

3. Potassium: Band applications of K should limit to 100 kg ~O/ha , and

broadcast remaining K and work into the soil prior to planting. Apply the following quantity of K:

If the soil test for K shows (ppm) 0-150 150 - 200 200 - 250 Ove r 250

Add this amount of ~O (kg/ha) 170 - 220 100 - 170 65 - 100 None

Spacing and depth

Cabbage is generally transplanted though the direct seeding is also practised

elsewhere. The seed requirement is 500-700 g/ha for transplanted seedlings, to give a plant

13

population of 30,000 plants/ha. The seedlings are ready for transplanting when they have 6-8 true

leaves (FAO , 2000a). The in-row spacing must be approximately 30 ern and between-row spacing

must be 60 cm. The wider spacing is required for late maturing cultivars. The cabbage head size

can be regulated by adjustment of the planting density (Tindall, 1993), closer the spacing, smaller

the head.

Irrigation and drainage

Cabbage and other cole crops are generally shallow-rooted, with roots ranging

from 18-24 inches long (Guerena, 2006). Cabbages are heavy user of water. When the soil water

(field capacity) contents drop below 60%, supplemental watering is essential. The average soil

moisture requirement for cabbage is 60-100% (Nonnecke, 1989). A rule of thumb is that

vegetables need about 1 inch of water per week from rain or supplemental irrigation to grow

vigorously (Guerena, 2006). However, over-watering can cause heads to burst immaturely due to

high turgor pressure (Nonnecke, 1989). Cabbage also performs poorly if the soil is not well

drained.

Harvesting and yield

Cabbages are harvested when the heads are finn and solids. Head size may vary

according to the cultivars but firmness is the determining factor. The hard heads usually crack or

split if they are left too long in the field to size up, thereby reducing their marketability (Guerena,

2006).

Cabbage head yields are generally 12-40 ton/ha, depending on environmental

conditions, soil fertility level, availability of irrigation and period to maturity required by different

cultivars (Tindall, 1993; Kahn et al., 2009). Early maturing cultivars may produce heads of 1-2 kg

in 60-90 days, while heads weighing 2-5 kg may be produced by late cultivars in 90-120 days.

14

Compost and composting

In organic farming, where the use of chemical fertilizers is prohibited, composts

and manures are the main sources of fertilizer (Hadas and Rosenberg, 1992; Gross et al.. 2007) .

Compost is the organic product resulting from the controlled biological decomposition of organic

material that has been sanitized through the generation of heat and stabilized to the point that it is

beneficial to plant growth (USCC, 2008). Compost is a dark, soil-like, partially decomposed

organic matter produced under controlled conditions through the action of microorganisms on

organic matters (Starbuck, 2010). It is easily crumbled, has an earthy aroma and bears little

physical resemblance to the raw material from which it is originated. It contains living organisms

that require water and oxygen to survive. The starting raw materials for composting are

commonly referred to as feedstuffs. The feedstuffs may be of plant origin like crop straws,

grasses and wood chips or animal origin like manures and animal carcasses. In fact , any waste

containing organic compounds serve as raw materials for composting (Neklyudov, et al., 2006).

When decomposition is complete, compost turns to a dark brown, powdery material called humus

(Starbuck, 2010) .

Composting

Composting is the aerobic (oxygen requiring) decomposition of organic

materials by microorganisms under controlled conditions (Pace et al., 1995). Composting is a

method of speeding natural decomposition of organic materials under controlled conditions

(Starbuck, 2010). Composting is a biological process in which microorganisms convert organic

materials such as manure, sludge, and leaves into a soil-like material called compost under

aerobic conditions (Zhao et al., 2008). During composting, the microorganisms consume oxygen

(02) while feeding on organic matter generating heat and large quantities of carbon dioxide (C02)

and water vapour is released into the atmosphere (Pace et al., 1995) . The CO2 and water losses

can amount to half the weight of the initial materials, thereby reducing the volume and mass of

the final product (Pace et al., 1995). The processes occurring in a compost pile are similar to

those that break down organic matter in soil but decomposition in compost pile occurs more

15

rapidly because the environmental conditions are made ideal for the microbes to do their work

(Starbuck, 2010). The final product of composting is humus-like compost, which can be used as

an agent for soil amelioration or as an organic fertilizer (Neklyudov et al., 2006) .

Types of Composting

1. Active composting versus passive composting

The composting process can be either active or passive depending on how much

attention/interference is given to run the composting process. The active composting is also called

"hot" composting and requires more maintenance than a passive composting. It is the fast

composting process that can be completed in as little as 4 weeks and the temperature during

composting rises far beyond ambient temperature, often up to 70° C. The heat produced, which is

associated with compost formation, facilitates the destruction of most weed seeds and pathogens.

Active composting requires more frequent turning but it produces compost much faster than

passive composting.

Passive composting is also called "cold" composting and it will produce the

same product as active composting but it will take a longer time for composting. It is a slow

process and the composting completes in a few months instead of a few weeks. The term passive

refers to the minimal human intervention. Passive composting involve simply stacking the

material in piles or pits to decompose over a long period with little agitation and management

(Misra et al., 2003). Passive composting is easier, requires less labor and takes 8-12 months to

complete.

2. Aerobic composting versus anaerobic composting

Aerobic composting takes place in the presence of ample oxygen, usually

oxygen levels greater than 5% (air is about 21% oxygen) (Hirrel and Riley, 2004). In this process,

aerobic microorganisms break down organic matter and produce carbon dioxide (C02) , ammonia,

water, heat and humus. Although aerobic composting may produce intermediate compounds such

as organic acids, aerobic microorganisms decompose them further. The resultant compost, with

its relatively stable form of organic matter, has little risk of a phytotoxicity. The heat generated

16

Compost or peat moss cover

Perforated pipe

B A

Figure 2 Passive aerated compost windrow (A) and aerated static compost pile (B) .

Source: USDA (2000)

accelerates the breakdown of proteins, fats and complex carbohydrates such as cellulose and

hemi-cellulose. Hence, the processing time is shorter. Moreover, this process destroys many

microorganisms that are human or plant pathogens, as well as weed seeds, provided it undergoes

sufficiently high temperature.

In anaerobic composting, decomposition occurs where oxygen is absent

or In lim ited supply. Anaerobic composting is the slow decay of organic matter through

fermentation. Unlike aerobic composting, the compost pile will not heat up. Microorganisms that

thrive in a low-oxygen environment (mostly bacteria) reduce nitrogen containing or sulphur-

containing compounds into intermediate compounds including methane, organic acids, hydrogen

sulphide and other substances. Many of these compounds have strong odours and some present

phytotoxicity. As anaerobic composting is a low-temperature process, it leaves weed seeds and

pathogens intact.

Aerobic composting process

The aerobic composting process begins as soon as the raw materials are mixed in

the compost pile. In many cases, the temperature rises rapidly to 70-80° C within the first week of

composting. The composting process is carried out by the different types of microorganisms at

different ranges of temperature. During the initial stage of the process oxygen and the easily

degradable components of the raw materials are rapidly consumed by the microorganisms (Pace

17

et al., 1995). Initially, the psychrophilic organisms (optimum temperature less than J00 C) work

on the feedstuff for a brief period. Since the heat produced during decomposition often goes

higher than 10° C within the first couple of days, most of these organisms cannot survive at

temperature higher than 10° C. This rise in temperature favours mesophilic organisms (optimum

growth temperature range is 20-45° C) that multiply rapidly on the readily available sugars and

amino acid s. They generate heat by their own body metabolism and raise the temperature to a

point where their own activities become suppressed. Then a few thermophilic fungi and several

thermophilic bacteria (optimum growth temperature range is 50-70° C or more) continue the

process, raising the temperature of the materials to 65° C or higher. These organisms bring about

a major phase of decomposition of plant cell-wall materials such as cellulose and hemi-cellulose

and at this time the pile will begin "settling". The center of a properly made heap should reach a

temperature of 45-65° C in 4 to 6 days (Starbuck , 20 I0) . The temperature of the compost pile is

directly related to the microorganism activity in the pile and is a good indicator of decomposition.

This peak heating phase is important for the quality of the compost as the heat kills most weed

seeds and pathogens. At high temperature (above 60° C) many pathogenic microorganisms fail to

sustain competition with their counterparts accumulated during composting (Neklyudov et al.,

2006).

The pH of the pile will be very acidic at first, at a level from 4.0 to 4.5. By the

time the process is complete, the pH should rise to approximately 7.0 to 7.2 (Starbuck, 20 I0). The

active composting stage is followed by a curing stage and the pile temperature decreases

gradually. The start of this phase is identified when turning no longer reheats the pile. During the

curing period the materials will continue to slowly decompose and the materials continue to

breakdown until the last easily decomposable raw materials are consumed by the remaining

microorganisms (Pace et al., 1995). The curing process helps bring compost to full maturity and

can last several months. The curing phase is important in the composting process because it helps

to further decompose and stabilize potentially toxic organic acids and resistant compounds. It is

important that compost is mature before applying it to the field because immature compost can

consume all of the 02 from the root zone and greatly inhibits root growth. The curing of the

compost provides a safety measure against the risks of using immature compost such as nitrogen

hunger, 02 deficiency and toxic effects of organic acids on plants. Eventually, the temperature

18

Figure 3 Passive aerated static pile composting.

Source : Washington State University (2009)

Heating Temperature Substrate plateau depletion)

Thermophilic ~ (conversion)o '- 105

-~ = Mesophilic I(degradat lcn ,i': ~

Q 50 I -1-----'- ~

~ , Psychrophilic I (maturation)

Time

Figure 4 Compost temperature ranges.

Source: USDA (2000)

8

19

Table 2 Guidelines for composting parameters.

Condition Reasonable range Preferred range

Carbon to nitrogen (C:N)ratio 20:1- 40: 1 25:1-30 :1

Moisture content 40-65 % 50-60%

Oxygen concentrations Greater than 5% Much greater than 5%

Particle size (diameter in inches) 1/8-1/2 Varies

pH 5.5-9.0 6.5-8 .0

Temperature (F) 110-150 (44-65 ° C) 130-140 (55-60° C)

Source: Pace et at. (1995 )

declines to ambient temperature. By the time composting is completed the pile becomes more

uniform and less active biologically although mesophilic organisms recolonize the compost. The

compost becomes dark brown to black in colour, relatively stable and easy to handle (Pace et al. ,

1995). The particles reduce in size and become consistent and soil-like in texture. In the process,

the amount of humus increases, the ratio of carbon to nitrogen (C:N) decreases, pH neutralizes

and the exchange capacity of the material increases.

Microorganisms in composting

As a rule , aerobic composting consists in the natural biological decomposition of

organic wastes components and involves diverse species of organisms (Neklyudov et al., 2006) .

The speed at which organic materials decompose depends on the decomposers , type of organic

materials and composting method used (Hirrel and Riley, 2004). Microorganisms account for

most of the decomposition, as well as the rise in temperature that occurs in the composting

process. During the first stage of composting, bacteria increase rapidly. Later actinomycetes

(filamentous bacteria), fungi and protozoa go to work. After much of the carbon in the compost

has been utilized and the temperature has fallen, centipedes, millipedes, sowbugs, earthworms and

other organisms continue the decomposition.

20

Factors affecting aerobic composting process

Aeration and oxygen, moisture content in feedstuff, carbon to nitrogen (C:N)

ratio, temperature, particle size of feedstuffs and pH of mixture are the important factors that

affect aerobic composting process.

1. Aeration and oxygen: Aeration is the source of oxygen, and thus,

indispensable for aerobic composting. Where the supply of oxygen is not sufficient, the growth of

aerobic microorganisms is inhibited, composting process may tum anaerobic resulting in slower

decomposition and formation of bad odour (Pace et at., 1995). A minimum oxygen concentration

of 5% within the pore spaces is necessary.

2. Moisture content of feedstuff: Composting materials should maintain

moisture content of 40-65% moisture. Where the pile is too dry, composting occurs more slowly,

while moisture content in excess of 65% develops anaerobic condition that causes nutrients to

leach out and bad odour is produced (Hirrel and Riley, 2004 ; Pace et al., 1995). Moisture content

generally decreases as composting proceeds, therefore, it is necessary to add water to the compost

pile.

3. C:N ratio of raw materials: Microbes use carbon for energy and growth,

while nitrogen is essential for protein production. The optimal C:N ratio of raw materials is

between 25: I and 30: I although ratios between 20: I and 40: I are also acceptable. Where the ratio

is higher than 40: I, the growth of microorganisms is limited, resulting in a longer composting

time. The C:N ratio of less than 20: I leads to underutilization of N and the excess N may be lost

to the atmosphere as ammonia or nitrous oxide and odour can be a problem.

4. Temperature: Composting takes place within two temperature ranges known

as mesophilic and thermophilic (Pace et al., 1995). Heat generated by the decomposing

microorganisms increases the compost temperature (Hirrel and Riley , 2004). While the ideal

temperature for the initial composting stage is 20-45° C, at subsequent stages with the

thermophilic organisms taking over, a temperature range of 50-70° C may be ideal. Pathogens are

normally destroyed at 55° C and above, while the critical point for elimination of weed seeds is

62° C.

21

5. Particle size: The rate of aerobic decomposition increases with decrease in

particle size (Hirrel and Riley, 2004). Breaking particles into smaller pieces allows the

microorganisms to digest more material, multiply faster and generate more heat. Chopping,

shredding or chipping materials accelerates the composting process.

6. pH: Although the natural buffering effect of the composting process lends

itself to accepting material with a wide range of pH, the pH level should not exceed eight. At

higher pH levels, more ammonia gas is generated and may be lost to the atmosphere.

Use of manures as organic fertilizer

Livestock manure is traditionally a key fertilizer in organic farming and for

sustainable soil management (Groot et al. 2003; Kuepper, 2003; Janssen and Oenema 2008, Antil

et al., 2009). Manure is organic matter used as organic fertilizer in agriculture that contributes to

the fertility of the soil by adding organic matter and nutrients. Use of nitrogen (N) from animal

sources decreases the need for inorganic fertilizers in conventional farming (Antil et al., 2009).

Animal manure supplies all major nutrients (N, P, K, Ca, Mg and S) necessary for plant growth,

as well as micronutrients, hence it acts as a mixed fertilizer (Purser and Jahns, 2005). The

quantities of secondary and micronutrients supplied by manure are generally sufficient to prevent

deficiency. Besides providing valuable macro and micronutrients to the soil, manure supplies

organic matter to improve the soil's physical and chemical properties. It also increases infiltration

of water and enhances retention of nutrients, reduces wind and water erosion, and promotes

growth of beneficial organisms. Main contribution of manure is through the transfer of plant

nutrients from grazing areas to crop areas. Hence, its proper management may result in a

substantial contribution to the crop nutrient supply.

Animal manures are the digestive by-products of the feed ingested by animals

and any associated bedding materials used in the animal production operation (Rasnake, 2002).

Therefore, the nutrient content of manure is closely related to the chemical content of feeds

consumed by the animals. During digestion some of the nutrients, vitamins and minerals in the

feed are retained by the animals in their body but most of the nutrients pass through the animal in

urine or faeces. Nutrients content of animal manure and their availability to crops vary widely,

22

which depend on the following factors (Rasnake et al., 2000; Kuepper, 2003 ; Purser and Jahns,

2005; Havlin et al., 2005; Whiting et al., 2006):

1. Species, class and age of animal.

2. Kind of feed consumed.

3. Type of animal housing and kind of bedding used.

4. Method of handling, collection and storage of manure.

5. Rate and method of application of manure.

6. Kind of soil and crops on which it is used.

Because of this variability in nutrient content, a chemical analysis on each

sample of manure should be obtained before applying manure to the field. However, average

nutrient contents are useful in determining overall waste management plans but should not be

used to determine actual land application rates. Application rates of manure are usually based on

nitrogen (N), phosphorus (expressed as Pps) and potassium (expressed as ~O) contents.

Nutrients in manure may be lost or converted to other forms during storage and

handling, affecting their availability for use by growing plants. Bedding and water have a diluting

effect on the final nutrient concentration of waste and result in less nutrient value per volume but

using bedding with sufficient absorption capacity to capture urine helps to reduce N losses (Purser

and Jahns, 2005). The type of housing and handling system can affect the final nutrient

composition of manures. When manure is exposed to the weather, ammonia gas is released and is

lost through volatilization, and nitrates is leached out with the rain , phosphorous is washed or

drained away with the liquid portion and potassium is either washed away or carried off in the

urine (Purser and Jahns, 2005). In contrast, there is considerably less N loss from a completely

covered feedlot with manure pack or a liquid lagoon. If urine is not collected and bedding is

sparsely used, losses of Nand K in particular will be high as most urine is lost. Urine collection

will minimize K losses but N losses will often remain high as volatilization will increase

depending on climatic conditions, storage time and storage method. Mixing of manure with the

soil, especially during warm weather, increases nitrogen availability to crops. As little as 0.5 inch

of rainfall after manure is applied also helps move nitrogen into the soil and prevent its loss

(Rasnake et al., 2000).

23

NPK nutrients availability from manure

Not all the nutrients In manure are available to crops during the year of

application because some are in their organic form, while others can be lost after application.

How well an animal manure performs as a plant nutrient source, is determined by the chemical

form in which nutrients occur, how the manure is applied, when it is applied and how much is

used (Rasnake, 2002).

1. Nitrogen: Availability of N to crop is dependent on release of N from the

manure and loss of N from the soil. Nitrogen in manure is in three forms - organic, ammonia, and

nitrate. Often organic-N is the predominant form of N in animal manure and 50 to 75% may be

present as organic N (Havlin et al., 2005; Antil et al., 2009). Organic N occurs as proteins, amino

acids, amines, amino sugars and complex N-compounds. Organic N in manure is composed of

stable (20 - 30%) and unstable (35-70%) forms (Havlin et al., 2005). Urea and uric acid are the

main components of unstable organic N and they are readily mineralized to plant available NH4 +

(Table 3). The stable organic N will mineralize in the first and subsequent years after application.

The soluble N (mostly ammonium) in animal manures ranges from about 1/3 of the total N in

poultry manure to about 2/3 or more in lagoon liquids. This soluble portion has the same

availability to plant as N contained in commercial fertilizers. Very little nitrate-N is detected in

manures (Leikam and Lamond, 2003). The remaining N in manure is contained in insoluble

organic compounds. Organic nitrogen becomes available to plants when soil microorganisms

decompose organic compounds, such as proteins, and then convert the released N to NH4 • This

process is known as mineralization, which occurs very slowly over a period of years. Organic-N

is not available to crops until it has been converted to ammonium form. The amount mineralized

in the first year depends upon the manure source, soil temperature, moisture , and handling. In

general, all inorganic N and a portion of the organic N of manure are available in the first year

following application (Curless et al., 2004). A general estimate is that 50% of the organic

nitrogen becomes available the first year, 25% the second year, 12.5% the third year, and so forth

(Whiting et al., 2006). The time of manure application also affects the amount of nutrient

available to a crop. The greatest response from animal manure application can be obtained by

promptly incorporating it into the soil. Timing of manure applications should be as close as

24

possible to periods of maximum plant uptake of N. Generally, manures and composts have their

strongest effect on a crop or cover crop if applied just in advance of planting (Kuepper, 2003).

Higher availability is expected when manure application matches the crop nutrient uptake.

Therefore, the application of manure should be synchronized as closely as possible with the

period of nutrient demand by the crop. Covering manure storage areas and protecting them from

rain reduces leaching losses considerably. Nitrogen tends to be more readily available from

poultry manures or liquid manures than other manures, primarily because these manures have a

higher nitrogen-to-carbon (C:N) ratio, which increases microbial activity (Rasnake et al., 2000;

Antil et al., 2009). Theses manures also have higher percentages of N as inorganic N, which

increases N availability during the year of application (Rasnake, 2002). Other manures have more

organic N that is released slowly and can carry over to the next year.

2. Phosphorus (P): The rate of manure applied is usually based on the plant

available N content of the manure and the recommended N rate for the crop to be grown. But

managing manures for their Pps and ~O contents can also be important. Both organic and

inorganic phosphorus forms are present in manure. Whether P exists in manure as predominantly

organic P or inorganic P depends on the species and animal production intensity. The animal and

poultry under intense production are likely to have higher amount of dicalcium phosphate added

to the ration, which passes through as inorganic P (50% to 60% of total P) and this inorganic P,

which acts similar to chemical fertilizer form of P is readily available during the first year of

application when soil pH is favourable (Rasnake, 2002). On the other hand, beef cattle and broiler

manures will have more than 50% of their total P as organic P, which is released more slowly as

the manure is decomposed. Most organic P compounds are esters of orthophosphate (Hl04

' )

including inositol phosphates, phospholipids and nucleic acids (RNA and DNA) (Havlin et al.,

2005). Organic P is degraded by microorganisms to produce other organic compounds and

inorganic P is released. Phosphatase enzymes catalyze the mineralization reaction of organic P. In

general, 60%-70% of total P is considered to be available during the first year of application for

all manure types.

25

Table 3 Manure production by selected animals and N content.

Manure Waste Component ------------------- N Form -------------------------Animal

Amino UricProduction* Faeces Urine Urea NH

4+ Other

Acid AcidSpecies --------------------- ---- ----- % of Total ---- ---- ---- ------ ----- ----- ----(TonlYear)

Poultry 4.5 25 75 27 04 08 61 01

Sheep 6.0 50 50 21 34 < 1.5 43

Horse 8.0 60 40 24 25 < 1.0 49

Beef 8.5 50 50 20 35 < 0.5 44

Dairy 12.0 60 40 23 28 < 0.5 49

Swine 16.0 33 67 27 51 < 0.5 22

Note: * Based on 1000 Ib (450 kg) animal weight.

Source: Havlin et al. (2005 )

3. Potassium (K): Potassium is not present in organic forms in manure. All K in

manure and other organic wastes is present in soluble, plant-available form as inorganic K+

(Leikam and Lamond , 2003; Havlin et al., 2005). Consequently, potassium availability from

manure is not related to mineralization rates or soil microbial activity. The total Kp present in

manure should theoretically be potentially available for crop uptake in the year of application.

However, research frequently supports crediting only about 80% to 90% of the total ~O from

manure in the year of application due to difficulty in uniformly applying manure.

Manure contains salts like dissolved potas sium chloride (KCl) and sodium

chloride (NaCI ). Repeated application of large amounts of manure leads to salinization of the soil ,

making it unsuitable for many crops (Kuepper, 2003 ; Whiting et al., 2006). Heavy metals can be

a problem, especially where industrial scale production systems are used (Kuepper, 2003).

Manure from laying hens can raise soil pH due to the calcium supplements in their diet. Some

manure may contain contaminants such as residual hormones, antibiotics, pesticides, disease

26

organisms, and other undesirable substances. To avoid salt problems associated with the use of

manure or compost made with manure, limiting the application rate to one inch per year when

cultivated six to eight inches deep and thoroughly cultivate the manure or compost into the soil is

recommended (Whiting et al., 2006). Continual manure use tends to acidify soil. As manure

breaks down it releases various organic acids that assist in making soil minerals available

(Kuepper, 2003). Horse manure is legendary in its potential to introduce a major weed seed

problem into a garden (Whiting et al., 2006). A growing trend in the use of manure is to compost

it before application. Composted manure has fewer odors . The nitrogen in composted manure will

be primarily in stable organic forms and first year relea se rates will be significantly less than with

fresh manure. For example, in composted dairy manure, only 5-20% of the nitrogen will be

available the first year (Whiting et al., 2006). Composting the manure before application kills

most weed seeds and pathogen if the pile is heated to above 65° C and the pile is turned to heat

process the entire product (Kuepper, 2003; Whiting et al., 2006). Due to the potential of

transmitting human pathogens, such as E. coli, fresh manure should not be used on fruits and

vegetables (Kuepper, 2003; Whiting et al., 2006) . The basic regulations on the use of manures for

organic crop production are that (I) raw manure may not be applied to food crops within 120 days

of harvest where edible portions have soil contact (i.e. , root vegetables, strawberries, etc.) which

are consumed without cooking, (2) raw manure may not be applied to food crops within 90 days

of harvest where edible portions do not have soil contact (i.e., most tree fruits) and (3) the

application of cat and dog manures and night soil on soil used for human food is not rec

ommended as these animals have diseases and parasites that can be transmitted to humans

through their manure (Kuepper, 2003; Purser and Jahns , 2005). But such restrictions do not

apply to feed and fiber crops that are not used as human food. As raw manure breaks down in the

soil, manure releases chemical compounds such as skatole, indole, and other phenol s. When

absorbed by the growing plants , these compounds can impart off-flavors and odors to the

vegetables (Kinsey , 1994 ; Kuepper, 2003). For this reason, raw manure should not be applied

directly to vegetable crops; it should instead be spread on cover crops planted the previous

season. Guano is the dried excrement of various species of bats and seabirds and is mostly used in

organic farming as a source of N. However, guano is connected with serious human illness,

Histoplasmosis caused by fungus Histoplasm capsulatum producing symptoms similar to

27

influenza or pneumonia (Kuepper, 2003; Gross et al., 2007). Use of respirators and masks are

recommended when handling guano in order to avoid inhaling fungus spores from air.

Manure tea

Another excellent use of manure is to make manure tea that can be used as a

liquid fertilizer. Manure enriched brews of various composition have been used by growers

around the world for many years for fertility management and disease control (Suslow, 1999).

Supplementary nitrogen side-dressing in the form of organic liquid fertilizers is often needed in

organic cropping systems because the available N from soils and solid composted manures is not

adequate for crop requirements (Gross et al., 2007). The most common method of making manure

tea is "bucket-fermentation" method and is called passive manure tea or non-aerated manure tea

forming an ammonia-rich solution (Gross et al., 2007; Hargeaves et al., 2008). Manure teas are

made by putting a small quantity of manure in a perforated bag into a tube of water for 7-14 days

when the color of water is turned to the dark tea (Suslow, 1999; Diver, 2002). The quantity of

manure and water used in making manure tea is usually in the ratio of I: I to I:10 weight/volume

(wir) (Price and Duddles, 1984; Suslow, 1999; Hargeaves et al., 2008; Kim et aI., 2009). In

essence, manure tea is a solution of water in which livestock manure has been soaked for an

appropriate period of time. Water for manure tea should be free of salts, heavy metals, pesticides

I and chlorine, since chlorine kills beneficial microorganisms (Martens, 200 I ; Ingham, 2003). The

various products like molasses, kelp powder and fish hydroysates are mixed in the manure tea

drub during extraction as food sources for beneficial bacteria and fungi. While rock dust, humic I

acids and yucca extract are added as microbial catalysts (Diver, 2002; Ingham, 2003). The

nutrients from the manure dissolve into the water making a concentrated liquid garden fertilizer.

Marl ure tea is made using either fresh (raw) manure or composted (aged) manure (Sus low, 1999).

Th . resulting tea is rich in a diverse population of beneficial bacteria, fungi and protozoa

(Mirtens, 2001). The manme 'ea after extraction is very strong and cannot be applied to plants in

its resent form as it injuries the plant by burning. Therefore, it has to be diluted with water at

least in 4: I ratio (four buckets of water for each bucket of manure solution) before applying to the

plants. The solution is then growing flowers and vegetables. The manure tea solution can also be

1

---

28

Poultry ~ 900- SO"'t:l Ql 70 .~

60ctl... Swine:'0Ql

C -10 E _\0

Z 20

.~ Beef cattle C 10 ctl C'l 0 ... 0 0 8 11 16 20

Week

Figure 5 N mineralization of organic N in selected liquid animal manures applied to sandy soil.

Source: Havlin et al. (2005)

Table 4 Amount of total N (NO, and NH 4 ) accumulated at weekly interval in Chicken Manure

Tea prepared with 1; I dilution (35 Ibs of chicken manure in 35 gallon water).

Particular 1 Week 2 Week 3 Week 4 Week

---------------------- ppm (parts per million) --------------------

10 10 10

725 1142 1456 1514

735 1152 1466 1514

Source: Price and Duddles (1984)

applied to the crop as a foliar diluted to the color of ice tea and is used as a starter solution for

transplants or as side-dress to source of nutrients. Like other organic matters, manure tea is

beneficial to soil. They build up the organic content of the soil, which improves its drainage and

structure. Manure tea provides nutrients to both present and future crop plants. As a liquid

fertilizer, manure tea can quickly provide with nutrients to the plants presently growing in the

field. It also enriches the soil as it continues to decompose, making the field fertile for the next

29

crop to be planted. Manure tea provides macro and micro-nutrients as well as some useful

enzymes. However, a laboratory analysis by Price and Duddles (J 984) showed that raw poultry

manure tea is not a complete fertilizer solution but that nitrogen, phosphorous, potassium and zinc

are at adequate levels in the solution for the production of tomato. Manure tea is primarily a

potent source of nitrogen. Nitrogen in manure tea is present mostly in ammonium (NH4+) form

and very little is present in nitrate form (Price and Duddles, 1984 ; Gross et al., 2007). Nitrate

accumulation in leafy vegetables through application of fertilizers containing nitrate is a serious

human health problem as consumption of nitrate causes methaemoglobenaemia and possible

cancers. Since the nitrate is present in low concentration in manure tea, the application of manure

tea reduces the chances of nitrate accumulation in leafy vegetables. For this reason, it is most

commonly used on vegetables but can also be used for other grain crops. Beside nutrients, manure

tea also provides water to the growing crops, especially in dry weather conditions. Manure tea as

foliar spray have also been suggested as organic treatments against certain plant diseases (Suslow,

1999; Gross et al., 2007). However, one possible danger concerning manure tea, is the potential

presence of some harmful bacteria, such as Escherichia coli, Listeria monocytogenes and

Salmonella spp. when raw manure is used for manure tea (Suslow, 1999; Kim et al., 2009).

Studies thus far, have determined a period of at least 10 days to 70 days for the destruction of E.

coli 0 l57:H7 and S. typhimurium in liquid manure slurries held at temperatures between 4° C and

20° C (Suslow, 1999). Other potential pathogens and parasites may survive the incubation period

for manure tea . Research by others strongly suggests that mixing other organic components

(generally plant origin) into the steeping drum water will increase the survival potential of E. coli

0157:H7. Therefore, the manure tea is best used for crops that will be adequately cooked prior to

consumption, for crops that produce fruits well above the area of application of the fertilizer and

non-edible plants, such as nursery seedlings. After field application of manure tea , the appropriate

waiting periods before harvest of food crops have to be observed to minimize the risk from

pathogens. Establishing good agricultural practices (GAP) while using manure tea on crops can

reduce the risk of contamination with pathogens (Suslow, 1999).

30

Vitamin C in vegetables and fruits

Vitamin C, also known as ascorbic acid (C6HP6)' is a white crystalline solid

with molecular weight of 176.12 which is very soluble in water (Halliwell, 2001), the first

discovered by Szent-Gyorgyi at the University of Szeged in Hungary in 1932 (Lawson et al.,

2004; Wolucka and Montagu, 2007). Among the vitamins, vitamin C is an essential

micronutrients required for normal metabolic function of the human body (Khan et al., 2006).

Ascorbic acid is synthesized by plants and by most animals, but not by primates (including

humans), guinea pigs and some fish, and the missing enzyme in these animals is gulonolactone

oxidase which catalyses the last reaction in ascorbate biosynthesis (Halliwell, 2001; Khan et al.,

2006). Thus, vitamin C must be obtained externally through the diet including fruits and

vegetables as well as food supplements and pharmaceutical preparations. It cannot be stored in

the body or kept for later use. The body uses only what it needs and the rest is passed in the urine.

Thus, it should be taken every day to obtain adequate quantity of this vitamin. The recommended

dietary allowance (RDA) for ascorbic acid in the USA is 90 mg/day, in the UK it is 40 mg/day

and in Singapore 30 mg/day (Halliwell, 200 I). A lack of vitamin C in the diet causes the

deficiency disease, scurvy (profuse bleeding through gums) in human due to improper formation

of collagen (Halliwell, 2001; Khan et al., 2006). This potentially fatal disease can be prevented

with as little as 10 mg vitamin C (Khan et al., 2006), an amount easily obtained through

consumption of fresh fruit and vegetables. It helps the body in forming connective tissues, bones,

teeth, blood vessels and plays a major role as an antioxidant that forms part of the body defense

system against reactive oxygen species and free radicals, thereby preventing tissues from

oxidative damage (Xu et al., 1996; Romay et al., 1998, Okiei et al., 2009). It is widely used in the

treatment of certain diseases such as scurvy, common cold, anemia, hemorrhagic disorders,

wound healing as well as infertility (Okiei et al., 2009). Vitamin C inhibits intra-gastric

nitrosamine formation in human body and enhances the immune system (Lee and Kader, 2000;

Halliwell, 2001). It lowers blood pressure and cholesterol levels (Khan et al., 2006)). Not only

does a vitamin C intake markedly reduce the severity of a cold , it also prevents secondary viral or

bacterial complications. Vitamin C as an antioxidant, reportedly reduces the risk of developing

cancers of the breast, cervix, colon, rectum, lung , mouth, prostate and stomach (Lee and Kader,

31

HO 0 0 --CH2 ~ ;/

\ C-C

CH I \/'""c C

HO / "u/ ~ H

Figure 6 Structure of ascorbic acid (vitamin C) and L-dehydroascorbic acid (DHA).

2000; Khan et al., 2006; Singh et al, 2007). The most important vitamin in fruits and vegetables

for human nutrition is vitamin C. More than 90% of the vitamin C in human diets is supplied by

fruits and vegetables (Lee and Kader, 2000; Podsedek, 2007). Ascorbic acid (AA) is the principal

biologically active form but L-dehydroascorbic acid (DHA), an oxidation product, also exhibits

biological activity. Since DHA can be easily converted into AA in the human body it is important

to measure both AA and DHA in fruits and vegetables for vitamin C activity (Lee and Kader,

2000).

The reason plants produce vitamin C is for their own use , as vitamin C is

essential for all living plant tissues. Apart from well known functions in oxidative stress defense,

associated with its antioxidant properties and its abilities to detoxify reactive oxygen species, it

also has important roles in the regulation of plant cell growth and expansion, photosynthesis, as

well as hormone functions (Smirnoff, 2000; Davey et al., 2006 ; Podsedek, 2007). Under stress,

such as pathogen or chemical exposure, ascorbate oxidase levels are increased (Conklin and

Barth, 2004; Davey et al. , 2006). AA is present in plant tissues undergoing active growth and

development. The amount of AA in plants varies among species as well as among cultivars (Lee

and Kader, 2000).

Many preharvest and postharvest factor s influence the vitamin C content of

horticultural crops. Large genotypic variation in vitamin content has been reviewed by Lee and

Kader (2000). Other preharvest factors include climatic conditions and cultural practices (Lee,

1974; Weston and Barth, 1997). All these factors are responsible for the wide variation in vitamin

C content of fruits and vegetables at harvest. In general , cruciferous vegetables contain higher

content of AA and sulfur compounds than non-cruciferous vegetables. Total sulfur content

32

correlates well with the AA content of vegetables (Albrecht et al., 1991) . Vitamin C contents of

fruits and vegetables are also variable among cultivars and tissues. Nelson et al. (1972) found AA

ranging from 19.3 to 71.5 mg/l00g in six strawberry cultivars from four locations. Usually skin

tissues have more AA content to protect the fruit from outside stress caused by light and

oxidation.

Climatic conditions including light and temperature have a strong influence on

the chemical composition of horticultural crops (Lee and Kader, 2000). Outside fruit exposed to

maximum sunlight contain higher amount of vitamin C than inside and shaded fruit on the same

plant. In general, the lower light intensity during growth reduces the AA content of plant tissues.

Lisiewska and Kmiecik (1996) reported that increasing the amount of nitrogen fertilizer from 80

to 120 kg ha'J

decreased the vitamin C content by 7% in cauliflower. Reduced levels of vitamin C

in juices of oranges, lemons, grapefruits, and mandarins resulted from the application of high

levels of nitrogen fertilizer to those crops, while increased potassium fertili zation increased AA

content (Nagy, 1980; Mengel and Kirkby, 1982; Lee and Kader, 2000). Based on these reports,

nitrogen fertilizers, especially at high rates, seem to decrease the concentration of vitamin C in

many fruits and vegetables. Plant growth is generally enhanced by the nitrogen fertilization so

that a relative dilution effect may occur in the plant tissues. Nitrogen fertilizers are also known to

increase plant foliage and thus may reduce the light intensity and accumulation of AA in shaded

parts (Lee and Kader, 2000). Since excess use of nitrogen fertilizers increases the concentration of

NO) and simultaneously decreases that of AA, it may have a double negative effect on the quality

of plant foods (Mozafar, 1993). The vitamin C concentration is inversely correlated to the

nitrogen supply in white cabbage (Freyman et al., 1991). Masamba and Nguyen (2008) found

significantly higher vitamin C content in organic Valencia oranges (51.8 mg/IOO g) as compared

to conventional ones (43.4 mg/l00 g fresh weight). Leeks grown with less frequent irrigation

showed increased concentrations of vitamin C and protein (Sorensen et al., 1995). High vitamin C

content may serve as a protective strategy against drought injury. Therefore, from a nutritional

point of view, horticultural crops grown under low nitrogen supply, and irrigated less frequently,

may be preferred due to the high concentrations of vitamin C and low concentrations of nitrate.

The use of agricultural chemicals, such as pesticides and growth regulators may indirectly affect

the nutritional quality of fruits and vegetables (Lee and Kader, 2000). Mechanical injuries such as

33

Table 5 Vitamin C content (mg/100g FW) of selected vegetables and fruits.

Commodity Ascorbic Acid L-dehydroascorbic Acid Total

Vegetables

Broccoli (fresh) 89.0 7.7 96.7

Broccoli (boiled) 37.0 2.6 39.6

Cabbage (fresh) 42.3 42 .3

Cabbage (boiled) 24.4 24.4

Cauliflower (fresh) 54 .0 8.7 62.7

Peppers (red) 151.0 4 .0 155.0

Peppers (green) 129.0 5.0 134.0

Spinach (fre sh) 62.0 13.0 75.0

Tomatoes (fresh) 10.6 3.0 13.6

Fruits

Banana (fresh) 15.3 3.3 18.6

Kiwifruit (fresh) 59.6 5.3 64.9

Lemon (fresh) 50.4 23.9 74 .3

Mandarins (fresh) 34.0 3.7 37.7

Persimmon (fre sh) 110.0 100.0 210.0

Persimmon (5 days at 5°C) 122.0 87.0 209.0

Source: Lee and Kader (2000)

bruising, surface abrasions and cuts can result in accelerated loss of vitamin C. Excessive

trimming of outer leaves of Chinese cabbage had a greater effect on reduction of vitamin C

content stored at 4° C for 11 day s (Klieber and Franklin, 2000). Losses in vitamin C occur when

vegetables are severely cut or shredded as in the case of cabbage , lettuce, carrots, and other

vegetables sold as salad mixes (Lee and Kader, 2000). Processing methods and cooking

procedures can result in significant losses of vitam in C in fruits and vegetables (Fennema, 1977;

Lee and Kader, 2000; Khan et al., 2006).

34

Nitrates accumulation in vegetables

Nitrogen fertilizers playa significant role in agriculture in securing higher yield

and quality of crops. However, excessive use of nitrate fertilizers not only contaminates

envirorunent due to leaching and surface run-off, but it also leads to accumulation of nitrate in

leafy vegetables beyond safe limits (Anjana et al., 2007). Nitrate contamination in vegetables

occurs when crops absorb more than they require for their sustainable growth (Prasad and Chetty,

2008). Consumption of nitrate and nitrite is known to cause adverse effects on human and other

animals. About 80% of the total nitrate concentration in a normal human diet is believed to be a

direct result of vegetables intake (Luo et al., 2006; Prasad and Chetty, 2008; EFSA, 2008), and

the rest from drinking nitrate-contaminated water and additives/preservatives used in meat and

certain foods (Coss et al., 2004; Prasad and Chetty, 2008). Thus, reducing nitrate content in

vegetables can decrease a risk of human illness. Leafy vegetables like lettuce, spinach, cabbage

and collard greens contain amounts of nitrate than other vegetables. Compared to nitrate, nitrite

content in vegetables is very low and is mainly formed through endogenous nitrate conversion

(Luo et al., 2006; Shokrzadeh et al., 2007; EFSA , 2008). Nitrate per se is relatively non-toxic, but

its metabolites and reaction products e.g., nitrite, nitric oxide and N-nitroso compounds that are

formed endogenously in the stomach have raised concern because of implications for adverse

health effects such as methaemoglobinaemia and some cancers (EFSA, 2008). When nitrate is

ingested, it is absorbed from the small intestine (gut) into the blood. Nitrates then enter the large

intestine from the blood. Under the normal condition with low pH in the intestine, the nitrate is

simply processed and removed as waste without any harmful effects. However, other conditions

such as a high gastric pH (p'H > 5.5) in the intestine, leads to bacterial growth followed by rapid

conversion of nitrate to nitrite (Prasad and Chetty, 2008). This nitrite is then reabsorbed into the

blood where it will oxidize blood's hemoglobin iron (Fell) to methaemoglobin (Fe'\ Unlike

hemoglobin that carries oxygen throughout our body, methaemoglobin is unable to transport

oxygen (Mengel and Kirkby, 1982). One of the signs of methaemoglobinaemia is cyanosis

(turning a blue color). Nitrite is also a precursor of nitrosamines, as nitrite reacts with secondary

amines to form toxic and carcinogenic nitrosomine compounds (Shokrzadeh et al., 2007). There

have been studies in farming communities that have found increased rates of gastric, colon and

35

bladder cancers (Zhong et al., 2002; Chen et al., 2004; Prasad and Chetty, 2008) and

nasopharyngeal and esophageal cancers (Eichholzer and Gutzwiller, 1998; Luo et al., 2006).

Meanwhile, numerous studies have reported that consumption of vegetables

helps to reduce the incidence of cancer (Block and Langseth 1994 ; Eichholzer and Gutzwiller

1998; Chung et al., 2003) since antioxidants such as ascorbate and tocopherol (vitamin E) present

in vegetables suppressed the formation of carcinogenic agents like nitrosamine or cyanosis as a

result of the formation of methaemoglobin of nitrites (Bartsh et al. 1988 ; Chung et al., 2003) .

Therefore, it has been argued that naturally occurring nitrates in foods are not toxic (Walker 1990 ;

Chung et al., 2003), which is one of the reasons why many countries and health organizations

including the USA and the CODEX do not have regulations controlling nitrates in vegetables. On

the other hand, the European Union established guidelines first in February 1997 for each season

on some vegetables such as lettuce and spinach and has it been amended several times (Chung et

al., 2003; Shokrzadeh et al., 2007; EFSA, 2008). The current maximum levels are laid down in

the Commission Regulation (EC) No 1881/2006 of 19 December 2006 setting maximum level

for certain contaminants in foodstuffs (Table 6) .

Though plants readily take up both ammonium (NH4+) and nitrate (NO)') forms

of soil nitrogen, most of the nitrogen is taken up as nitrate. The fate of most of this nitrate is to be

incorporated into proteins and nucleotides by reducing NO) to NH 2• Nitrate is first reduced to

nitrite by nitrate reductase enzyme (NR) in the cytosol. This nitrite formed is subsequently

reduced to ammonia by nitrite reductase enzyme (NiR) in the chloroplasts or plastids. Ammonia

is then incorporated into the amino acids glutamine using the C-skeletons produced via other

metabolic pathways such as respiration and photosynthesis. Nitrate reduction occurs in both aerial

portions and root of plants. The relative importance of these two sites of nitrate conversion is

considered most important. Unfavourable growing conditions can interfere with normal nitrate

use and lead to nitrate accumulation in the plant. Nitrate accumulation in a tissue or organ of a

plant occurs when the rate of nitrate uptake from soil and translocation to other plant parts

exceeds the rate of assimilation into proteins (Maynard and Barker, 1979). It is generally known

that when plants are provided with excess nitrate, only a small amount of the nitrate taken up by

the roots is immediately assimilated in roots and shoots, while the majority is stored in vacuoles

of both roots and shoots (Luo et al., 2006). Nitrate is portioned between an active metabolic pool

36

in the cytosol (reduction) and a storage pool (accumulation) in the vacuole (Lillo et al., 2004; Luo

et al., 2006). Nitrate accumulation is genetically controlled and is modified by environment,

fertilizer management and crop production practices (Maynard and Barker, 1979). Applying

nitrate fertilizer in amounts beyond the ability of the crop to use them results in an accumulation

of nitrate when some other essential nutrient is lacking (Maynard and Barker, 1979; Luo et al.,

2006).

Phosphorus, potassium and sulfur have major roles in, photosynthesis and

production of proteins and tissues, thereby decreasing nitrate within the plant (Beegle and Durst,

200 I). Nitrate is the usual form of soil N available to plants (Maynard and Barker, 1979). Forms

and rates of N fertilizers have been reported to affect vitamin C and nitrate concentration in

plants. Organic N has to be mineralized first and then it is converted to nitrate form from

ammonium N by nitrification before plant can take up and accumulate as nitrate in plant tissues

(Pascale et al., 2006). Besides, there are various other factors responsible for nitrate accumulation

in vegetables and fodders . The amount of nitrate in plant tissues will also depend on plant species,

stage of maturity, part of the plant and nitrogen fertilization. Plant organs differ in the ability to

accumulate nitrate, highest nitrate concentrations are generally found in petioles while lower

concentrations in root, seed, fruit and flower parts. The nitrate contents are often found in the

following order: petiole > leaf blade > root (Olday et al. , 1976; Chen et al., 2005 ; Luo et al.,

2006), which is possibly caused by their difference in water content (Wang and Li , 1996). This

means that leafy crops have fairly large nitrate concentrations while root and fruit crops have

relatively small concentrations. Another consequence of the transport system is that young leaves

have lower nitrate concentration than older leaves. Such a relation was also shown for cabbage

with greatest nitrate concentrations in the outer leaves and much smaller nitrate concentration in

the innermost leaves (Greenwood and Hunt, 1986). Cabbage is classified as a vegetable

containing very high nitrate levels ranging from 1500 to 4000 mg N kg-I (Luo et al., 2006).

Nitrate accumulation differs among species and among cultivars within a

species. Genetic differences in nitrate accumulation of different cultivars have been found among

leafy vegetables (Chen et al., 2004; Luo et al., 2006). A greater activity of nitrate reductase may

account for the lower nitrate content of some cultivars (Luo et al., 2006; Olday et al., 1976). Light

intensity is the key factor in determining nitrate concentrations in leaf crops. Winter-sown crops

37

Table 6 Maximum level for nitrate as laid down in Commission Regulation (EC) No

1881/2006.

Foodstuff Maximum level (mg nitrate/kg)�

Harvested I October to 3 I March 3,000�Fresh spinach (Spinacia oleracea)

Harvested I April to 30 September 2,500

Preserved, deep-frozen or frozen 2,000

spinach

Harvested 1 Octob er to 31 March :

Fresh lettuce (Lactuca sativa L.) I. Lettuce grown under cover 4,500

(protected and open-grown lettuce) 2. Lettuce grown in the open air 4,000 ---:-,--------.,..=---:----:-:-~------=---------

excluding lettuce listed below Harvest ed 1 April to 30 September:

I . Lettuce grown under cover 3,500

2. Lettuce grown in the open air 2, 500

Lettuce grown under cover 2,500Iceberg-type lettuce

Lettuce grown in the open air 2,000�

Processed cereal-based foods and�

baby foods for infants and young 200�

children�

Source: EFSA (2008)

have generally higher nitrate concentration than summer crops in the same environment. The

accumulation of nitrates is enhanced under conditions of water stress due to lower nitrate

reductase activity and/or reduced avail ability of photosynthates and C-skeletons, which in tum,

lowers nitrate assimilation rate into protein (Maynard and Barker, 1979). Another strategy for

lowering nitrate concentration might be to harvest crops on the afternoon of a sunny day, when

the maximum amount of nitrate assimilation has just occurred. Greens harvested in the afternoon

on a sunn y day will contain low nitrate than those picked on a cloudy day, or early in the

morning. Vitamin C (ascorbic acid) is very efficient at preventing the conversion of nitrate to

nitrite in plant tissue and within the human body (Bartsh et al. 1988; Chung et at., 2003 ;

Nantachit and Winijkul, 2007).

38

Plant nutrients management in organic farming

The management of nutrients in organic farming systems presents a formidable

challenge, as the use of inorganic fertilizers is not permitted. A major difference between

conventional cropping systems and organic systems is the role of biological processes in organic

systems (Guerena, 2006). Most synthetic fertilizers are immediately available to plants and do not

require biological processes to make them available. Nutrient management in organic systems is

more complex. The wider aim of soil management in organics is to create a healthy, biologically

active soil flora and fauna by maintaining good levels of so il organic matter and minimizing soil

disturbance caused by tillage. Changing hom a synthetic fertilizer regime to one based on

legumes for N fixation, manures and mineral fertili zers can considerably increase soil biology,

which results in many positive benefits. However, there is significant scientific evidence and

farmer experience that this change takes several years and can result in an initial drop in crop

yields in the first two to three years of conversion until the soil biological processes have

increased sufficiently to support good yields again. Organic inputs cannot easily be added to the

soil to provide the exact balance of nutrients needed by the plant for at least three reasons (Barry

and Merfield, 2008). First, many organic inputs (such as cover crops, crop residues , weeds, and

compost) are added to the soil for reasons other than fertility management, yet they contribute to

the pool of nutrients in the soil. Second, most organic materials, including compost and manure

have only a small component of soluble nutrients, and most of their nutrients must be transformed

through biological processes before they become available to plants. Thirdly, most manures and

composts do not have a consistent nutrient content unlike synthetic fertilizers. They also contain

a ratio of nutrients (i.e . N:P:K) different from that needed for optimal plant growth.

Therefore, the success of organic farming depends upon the adequate

management of soil properties achieved through the enhancement of soil organic matter and soil

biological activity (Nelson and Mikkelsen, 2008). Practices and inputs used by organic farming

promote biologically healthy soils that sustain fertility in ways different from the conventional

systems. Organic agriculture aims to 'feed the soil to feed the plant' by maintaining soil biology

and nutrients at optimum levels throughout the rotation rather than the non-organic approach of

applying nutrients to feed the current crop to maximize the yield. One view is the 'law of return'

39

Table 7 The average NPK nutrient concentrations and rates of availability of various organic

materials.

Organic material

0/0 Nitrogen

0/0 Phosphate (P2OS)

% Potash (K2O)

Nutrient availability

Remarks

Composts 1-3 1-2 1-2 Moderate Alkaline Sewage sludge 2-6 1-4 0-1 Moderate Zinc, iron Kelp 1-1.5 0.5-1 5-10 Moderate Zinc, iron Rock phosphate 0 20 0 Moderate Available P 2-3%

Plant products Sawdust 0-1 0-0.5 0-1 Very slow Cottonseed meal 6 3 I Slow Acidic Wood ashes 0 1-2 3-7 Rapid Seaweed extract 1 2 5 Rapid Zinc, iron Alfalfa meal 2 I 2 Rapid Weed seeds Soybean meal 7 2 I Rapid

Cotton gluten 9 0 0 Rapid Reduces germination

Animal products Bone meal 1-6 11-30 0 Moderate Alkaline Blood meal 12 1-2 0-1 Rapid Acidic Feather meal 12 0 0 Moderate Hoof/horn meal 12-14 1.5-2 0 Moderate Alkaline Fish meal 6-12 3-7 2-5 Rapid Acidic Fish emulsion 5 2 2 Rapid Micronutrients Guano (high N) 10 3 I Moderate Bioremidation Guano (high P) 3 10 1 Moderate Bioremidation Cattle manure 2-3 0.5-1 1-2 Moderate Weed seeds Horse manure 1-2 0.5-1 1-2 Slow Weed seeds Swine manure 2-3 0.5-1 1-2 Rapid Poultry manure 3-4 1-2 1-2 Rapid Sheep manure 3-4 0.5-1 2-3 Moderate Weed seeds

Source: Koenig and Johnson (1999; Card et al., 2006)

where it is considered essential that any nutrients removed in crops or livestock must be returned

to maintain fertility i.e., a balanced nutrient budget (Barry and Merfield, 2008). A healthy has a

40

diverse population of soil organisms that enhance plant growth in various ways, such as through

symbiotic relationships with the plant and exuding enzymes into the soil. Organics, therefore ,

takes a long term, whole farm systems approach to nutrient management (Guerena, 2006).

Nutrient inputs for organic production are typically focused on carbon- based nutrient sources

(Guerena, 2006; Nelson and Mikkelsen, 2008). This is achieved through crop rotation, cover

cropping, composting and by using organically accepted fertilizer products that feed the soil.

Organic systems use legumes and algae to fix atmospheric nitrogen in the soil to

make nitrogen available to plants (Barry and Merfield, 2008). Usually the nitrogen available from

green manure or compost is enough for most crops (Guerena, 2006). Organic sources of

supplemental nitrogen include guano, pelleted compost, fish emulsion, blood meal , feather meal ,

cottonseed meal, alfalfa meal, and kelp. The mineralization of nitrogen and its availability to

plants varies greatly, depending on the nitrogen source, the temperature, humidity , texture of the

material, and microbial activity. The on-farm produced manures , compost, slurry and cover crop

residues usually provide enough phosphorus and potassium for plants (Guerena, 2006; Nelson

and Mikkelsen, 2008). If additional phosphorus is needed, rock phosphate may be an option.

While, granite dust, material derived from langbeinite (potassium magnesium sulphate), kelp

meal, and wood ash (if not contaminated with synthetic substances) are acceptable sources of

potash. The on-farm inputs like manures and compost also provide adequate micronutrients to the

crops. Seaweed products are sources of supplemental micronutrients (Guerena, 2006).

With soil health being a key focus of organic systems, a significant portion of

organic standards relate to soil management, particularly what materials can and cannot be used

as fertilizers . Certification system has three 'categories' that it puts farm inputs into (J) permitted,

(2) restricted and (3) prohibited (Barry and Merfield, 2008). Permitted arc allowed to be used

without any restriction. Restricted are allowed to be used but normally only after the permission

has been given by the certification agent, and the prohibited are completely banned. The aim for

organically approved fertilizers is to allow biological soil processes through microbial activity to

progressively release the nutrients contained in the fertilizer so plants get a more balanced and

continuous supply of nutrients. Many of these biological processes are temperature dependent. So

more plant available nutrients are released during the growing season when the soil is warmer and

when the plants need them, while less nutrients are released in the cold of winter when there is a

41

Table 8 Estimated quantity of plant-available N from organic N applied in manure over 3 years.

Manure Source Year-l Year-2 Year-3

----------------------- '10 N Mineralized ----------------Liquid manure 30 12 6

Solid manure 25 12 6

Compost 20 6 3

Source : Havlin et at. (2005)

greater risk of nutrient leaching and many plants are barely growing (Barry and Merfield, 2008;

Nelson and Mikkelsen, 2008). This also means that it is not normally possible to gct a 'quick

response' from organic fertilizers. so if a deficit occurs it will take some time to correct.

Therefore, it is essential to have a long -term nutrient strategy, which is also a requirement under

organic certification standards.

Phophorus (P) and potassium (K) content in commercial organic fertilizers are

expressed as 'Yo P20S and % K20 respectively. In addition, the recommended fertilizer dose of

crops is usually given in % P20 ~ and % K20 by most fertilizer recommending institutes. On the

other hand, most so il test laboratories usc % P and % K in so il analysis result to show the

concentration of phosphorus and potassium respectively in the soil. The conversions between % P

and % Pps and also between % K and % Kp are accomplished as follow (Havlin et al., 2005):

Phosphorus Potassium

% P = % Pps x 0.43 % K = % k,o x 0.83

% Pps = % P x 2.29 % Kp = % K x 1.2

Chapter 3�

Materials and Methods�

Compost preparation

1000 kg of compost prepared with clipped tropical grasses, pruned plant twigs

and leaves without containing any manure was purchased from the Maejo Market, Chiang Mai, to

further develop it into nutrient-rich composts by adding animal manures. This quantity of

compost was equally divided into two parts (i.e. 500 kg each) to prepare two types of composts,

viz. cattle manure compost and poultry manure compost by applying Passive Aerated Static Pile

Composting method as described by Misra et at. (2003). Fresh manures from layer hens and dairy

cattle were collected from the Maejo University Dairy Farm when animals were not fed hormones

or special feed additives. To first 500 kg of market compost, 20 kg of cattle manure, 5 kg

dolomite powder and 5 kg rice-bran were added to make cattle manure compost (CMC). These

feedstuffs for compost were placed on concrete floor and they were thoroughly mixed with spade

and shovel. Sufficient fresh water was sprinkled to the compost mixture to raise the moisture

content of compost to about 50%. The compost mixture was then placed in a heavy-duty

polyethylene bag that had the dimension of 2.25 m height and 1.00 m diameter. The four

perforated plastic pipes, each having four rows of 1.27 em diameter holes drilled in it, were

sufficiently inserted into the compost bag at the four comers for aeration. The mouth of the bag

was closed and the upper ends of four inserted pipes were exposed to the open air to facilitate the

aeration in the interior of the compost pile. Similarly, the poultry manure compost (PM C) was

prepared from remaining 500 kg of market compost by adding to it 20 kg of poultry manure, 5 kg

dolomite powder and 5 kg rice-bran and applying the same procedure that was used for cattle

manure compost.

The composting period allowed was one month and followed by another one

month cunng period. After 2 months when the composting and curing were completed, the

samples from compost were analyzed for nutrient (NPK) content and other physico-chemical

properties at the Department of Soil Science Laboratory, Maejo University. Before 4 days of

compost application to the field, 165 grams each of effective microorganism (EM) No. 12

43

prepared by the Department of Land Development Office, Maerim, Chiang Mai, Thailand was

thoroughly mixed in both cattle manure compost and poultry manure compost. The composts,

thus prepared, were used in experiment to constitute the treatments as organic fertilizer, solely or

in reciprocal quantity with chicken manure tea.

Figure 7 Manure tea preparation. A = extraction of manure tea, B = filtration of manure tea.

Figure 8 Passive aerated static pile composting. A = composting in bag, B = matured compost.

44

Manure tea preparation

The poultry manure tea (PMT) was prepared in I: I weight/volume (w/v) ratio by

steeping burlap sack containing 20 kg of fresh poultry manure in 20 litre of fresh water in 40 litre

plastic bucket for 15 days. The chicken manure tea was prepared with "Bucket Fermentation

Method" as described by Suslow (1999; Ingham, 2003). The continuous extraction of water

soluble plant nutrients (NPK) from chicken manure was carried out for 2 weeks in chlorine-free

water supplied with microbial food (i.e . molasses). Since chlorine in water can kill beneficial

microorganisms , the water was treated with ascorbic acid (vitamin C) to remove chlorine gas by

applying the procedure described by Land (2005). The vitamin C tablet (l00 mg) was procured

from Maejo University Infirmary. The main steps involved in manure tea preparation were as

below:

I. 60 kg fresh poultry manure was collected from the Maejo University

Dairy Farm from beneath the cage containing laying hens when they were not fed hormones or

special feed additives.

2. Poultry manure was placed in a burlap sack and the open end of the sack

was tied with string.

3. Water free from pesticides and other contaminants was collected in 20

litre capacity plastic jerry can from filtered drinking water tap at Patinya House, Maejo, Thailand.

4. 5 g of vitamin C was finely ground and then it was added to the 40 litre

capacity bucket containing 20 litre of filtered water.

5. The water in the bucket was left overnight in the shade to allow chlorine

gas to escape and neutralize the water.

6. I litre of molasses was added to the 20 litre de-chlorinated water in the

bucket as a food source for beneficial microorganisms during fermentation period.

7. The water in the bucket was thoroughly stirred with stick to dissolve

molasses.

8. The burlap sack containing 20 kg poultry manure was suspended in the

bucket containing 20 litre of de-chlorinated water. This was achieved by hanging the burlap sack

on a horizontally placed stick on the bucket so that the bag was fully dipped into the water but its

45

lower portion did not rest at the bottom of the bucket. This apparatus was set up under the roof in

the shaded area.

9. The bucket was partially closed with lid in order to avoid flies getting

into the bucket but at the same time assure good aeration in the bucket.

10. The manure solution was stirred 2 times every day (morning and

evening) till the completion of extraction period .

11. The manure in the sack was steeped for 15 days. Then the sack was

removed from the bucket and the manure solution was filtered through muslin cloth into another

container.

12. The stained manure tea was preserved in airtight bucket for later use in

the experiment.

In total three buckets of poultry manure tea were prepared simultaneously each

containing 20 litre. 50 ml of filtered manure tea, thus prepared, was collected in a plastic vial for

analysis of NPK nutrient contents and pH at the Department of Soil Resources and Environment

Laboratory, Maejo University. The manure tea was diluted 4 times (llitre manure tea in 4 litre of

fresh water) during side-drenching the cabbage plants in the field to avoid burning of plants by

concentrated manure tea. In the previous work done by Adhikari (2009), it was shown that the

total NPK contents in chicken manure bio-ferment (poultry manure tea) continuously increased

from third day of extraction to fifteenth day of extraction. To see whether the NPK content would

increase or decrease in poultry manure tea after 15 day, we extended extraction period beyond 15

days and analyzed NPK content in poultry manure tea both at 15 day of extraction and 21 day of

extraction in the preliminary experiment.

Raising of cabbage nursery

The white cabbage, Brassica oleracrea L. var. capitata f. alba (2n = 18) of

family Brassicaceae was used in the experiment. Since the organic seed of cabbage was not

available in Thailand at the time of experiment, 20 g seed (I sachet) of the best variety in the

conventional farming, a heart-shaped F1 hybrid variety "Cape Hom" produced by Sakata Seed,

46

(A) Certified F, seed of "Cape Hom" cabbage (B) Seed sown in nursery trays filled with media

(C) Cabbage seedlings raised in nursery trays (D) Seedlings in poly bags before transplanting

Figure 9 Cabbage seed source and cabbage seedlings in nursery

Japan, was purchased from the market in Maejo for use in the experiment (Figure 9 A). This

Cape Hom variety producing pointed head of green colour, is the early variety of cabbage that

can be harvested 60 day after transplanting. The seeds were washed 5 times with clean water

before sowing to remove the chemical (Thiram) used in treating the seeds. The nursery was raised

on October 21,2008 in the glasshouse of Vegetable Division, Department of Horticulture, Maejo

University. Six plastic nursery trays each having 105 cells were filled with 7 kg of peat moss

nursery media purchased from the market. 2- 3 seeds were sown per cell to a depth of about 1.5

em in the trays and adequate watering was immediately done with watering cane. The trays were

47

then placed in iron shelves in the glasshouse where ample sunshine was available throughout the

day. The SO% germination was observed S days after sowing the seed. When the true leaves were

formed in the seedling (height Scm) thinning was done to keep only I strong seedling per hole to

get healthy seedlings. Irrigation was given to the nursery every day with watering can in the

evening. Later at the stage of 4-S true leaves, 4S0 bigger and healthy seedlings were transferred to

black poly bags filled with a mixture of field soil and nursery media in equal proportion (SO%

each). The irrigation was done immediately after planting and the pots were placed in the partial

shade for 3 days. After third day , the potted plants were kept in the open space in full sunshine.

The 2S-day old seedlings were transplanted on IS/l1I2008 when they had 6-8 true leaves.

Soil sampling and analysis

The soil samples from 0-2S em depth of the field were collected 2 weeks before

transplanting the seedlings as well as 1 week after harvesting of plants for analysis of NPK

nutrient contents, organic matter content and other physico-chemical properties at the Department

of Soil Resources and Environment Laboratory, Maejo University. The result of the soil analysis

of trial field is presented in Table (12). The % carbon was obtained by dividing % OM content by

2, as practised by Jakse and Mihelic (1999). While % N was calculated by multiplying % OM

with O.OS.

Determination of total N in soil by Kjeldahl Method

The total N was determined by the Kjeldahl method (AOAC, 1984). In the

presence of H2S04, potassium sulfate (~S04) and catalyst cupric sulfate (CuS04), amino nitrogen

of many organic materials was converted to ammonium. Free ammonia also converted to

ammonium. After addition of base, the ammonia was distilled from an alkaline medium and

absorbed in boric acid. The ammonia was determined colorimetrically by titration with a standard

mineral acid.

n HCL x f HCI x (rnl HCI - ml Blank) x 0.014 x 100 %N = Ws

48

Where: n = Normality of Hel, f= Standarization factor, Ws = Weight of sample.

Determination of available phosphorus in soil

The available P in the soil was determined by extracting P using Bray 2 solution

as extractant (Matt, 1970). The extracted phosphorus was measured by colorimetric method,

based on the reaction with ammonium molybdate and development of the 'Molybdenum Blue'

colour. The absorbance of the compound was measured at 882 nm in a spectrophotometer and

was directly proportional to the amount of phosphorus extracted from the soil.

25 20 Available P in soil in ppm = (ppm in solution - ppm blank) x - x

5 Ws

Where: Ws = weight of soil sample.

Determination of exchangeable potassium in soil

The exchangeable K in the soil was determined by the method described by van

Reeuwijk (1987). 2.5 g soil was shaken for I hour with 50 mL of 0.05M hydrochloric acid. After

settling overnight to clear solution, an aliquot was diluted for potassium determination by atomic

absorption.

100 ppm Kin soil = (ppm solution - ppm blank) X - X df

Ws

Where: Ws = Weight of soil ample; df = dilution factor

Calculation of composts and poultry manure tea requirement

The amount of inorganic fertilizers, composts and manure tea added to the soil,

were based on the nutrient requirement of cabbage crop and the nutrient content in organic

fertilizers (Table 11), as well as based on stock of nutrients present in the soil (Table 12). The N,

49

Table 9 Added fertilizers & nutrients in trial field (composts appli ed on fresh weight basis).

lAdded Added nutrients (g/m )

Treatment Fertilizers T ype zfertilizer/m N PlO ~ KzO

T I Ca ttle Manure Com pos t (100%) 1835 g 12.5 43.8 9.6

T2 Poult ry Manure Compost ( 100%) 171 1 g 12.5 41.5 8.5

T3 Cattle Manure Co mpos t (50%) 917 g 6.3 2 1.9 4.7

Poultry Manure Tea (50%) 1.89 L 6.3 3.2 15.3

Total 12.5 11.0 16.8

T4 Poultry Manu re Compost (50%) 855 g 6.3 20 .7 4.2

Poult ry Manure Tea (50%) 1.89 L 6.3 3.2 15.3

Total 12.5 10.5 16.6

T5 Poultry Manure Compost (25%) 428 g 3.1 10.3 2.1

Poultry Manure Tea (75%) 2.84 L 9.4 4.8 23 .0

Total 12.5 6.6 21.0

T6 Control Total 0.0 0.0 0.0

T7 Urea (46% N) 27. 17 g 12.5 0.0 0.0

GTSP (46% Pps) 19.02 g 0.0 8.8 0.0

MoP (50% KP ) 3 1.26 g 0.0 0.0 15.6

Total 12.5 8.8 15.6

Pp s and ~O were appl ied at the rate of 125 kg, 87.5 kg and 156 kg respec tively for one hectare

based on the result of soi l analysis before plantin g and the recommendation pro vided by Oregon

State University (2004) for cabbage. The treatments were so adjusted that in all the treatment s,

except control , the amount of added N was the same, while P, K and other nut rient s differed

among treatments. The amo unt of added fert ilizers (both organic and inorganic) was adjusted to a

total N supply of 125 kg ha· ' . It was ass umed that all organ ic fer tilizers (catt le manure compos t,

poultry manure compost and poultry manure tea) would mineralize totall y (100% minerali zat ion )

within the cropping period of 70 days so that the total N content would avail able to the plants

durin g the cropping sea son. No fertili zers were applied in control plot.

50

The NPK nutrients content in poultry manure tea were analyzed on IS day

(Zweeks) of extraction as well as on 21 day (3 weeks) of extraction. Since the Nand P were

higher in the poultry manure tea extracted on the IS day steeping (Table II), we use this manure

tea in the experiment and that extracted on 21 day steeping was discarded.

Field experiment

Experiment location and design

The field trial was conducted in the Organic Vegetables Research and

Development Experimental Station, Vegetable Division of Maejo University, which is located 10

km north of Chiang Mai City, Thailand. The elevation of the experiment area is 300 m above sea

level in Chiang Mai Province of Thailand located at latitude 17° 15' N - 20° 16' N and longitude

98° 03' E - 99° 33' E. The soil type of field was sandy clay and the field had been under

continuous organic farming for last five years . The preceding crop in the trial field was loose

lettuce and it was left fallow for 3 months before conducting this trial. The experiment in the field

was carried out from mid November 2008 till the end of January 2009. The trial was conducted in

conformity to the basic standards and requirements laid down in Organic Agriculture Certification

of Thailand-2003 (ACT, 2003) and International Federation of Organic Movement-2000

(IFOAM, 2000) for the organic plots. The inorganic plots were treated according to standard

conventional agricultural practice including the use of inorganic fertilizers . The organic and

conventional plots were separated by 5 m buffer strip of brinjal plants (Solanum melongena) but

both were located in similar microclimatic conditions with the same soil properties as practised by

2Murphy et al. (2007). There were 21 plots in the experiment and total area of the trial was 63 m :

54 m 3

for organic and control plots consisting of 18 plots and 9 m2

for inorganic plots with 3

3plots. The size of each plot was 3 m (3 x I m) and each plot had 20 plants in 2 rows. The in-field

variability for fertility, moisture and sunshine gradients were considered in laying the

experimental design . The longer length of each plot was oriented in north-south direction. The

cabbage seedlings were transplanted on November 15, 2008 at a spacing of 50 em (between rows)

51

by 30 ern (between plants). The experiment was laid out in randomized complete block design

(RCBD) consisting of7 treatments with three replications and as outlined below:

Treatment 1: Cattle Manure Compost (CMC) @ 18.35 ton/ha FW

Treatment 2: Poultry Manure Compost (PMC) @ 17.11 ton/ha FW

Treatment 3: [email protected] ton/ha FW + Poultry Manure Tea (PMT)@ 18900 L/ha

Treatment 4 : PMC @ 8.53 ton/ha FW + PMT @ 18900 L/ha

Treatment 5: PMC @ 4.28 tonlha FW + PMT @ 28400 L/ha

Treatment 6: Control

Treatment 7: Chemical fertilizers [urea @ 270 kglha +triple superphosphate @ 190 kg/ha

+ Muriate of Potash (KCI) @ 310 kg/ha]

Field preparation and application of fertilizers

The first ploughing up to 35-40 em depth was done with Kubota power-tiller.

This was followed by the application of total quantity of composts in organic plots (23.82 kg

CMC and 27 kg PMC), and total dose of triple superphosphate (171 g), total dose of Muriate of

Potash (281 g) and half dose of urea (122 g) in the inorganic plots as broadcast. Then the shallow

ploughing was performed to incorporate the composts and inorganic fertilizers into the soil. The

clod crushing and raising of the field beds was done manually with spade. The field preparation

was completed with racking to remove weeds and levelling of the plots. Black plastic sheet was

used for mulching in all the plots before transplanting the seedlings. The seedlings were

transplanted in the field after 1 week of land preparation on 15/11/2008. The poultry manure tea

in organic plots was applied in 4 equal splits as side drench, 25% (14 litre) applied during

transplanting and remaining doses at one week interval. The remaining quantity of urea (50% of

N) was applied 1 month later as topdressing.

mailto:[email protected]

52

Table 10 Amount of fertilizers applied in the experiment (composts applied on FW basis).

2 2Treatment Rate /m Rate/plot (3 m ) Rate/hectare

I (IOO%CM) 1.835 kg CMC 5.189 kg CMC 18.35 ton CMC

2(100%PMC) 1.711 kgPMC 5.132 kg PMC 17.11 ton PMC

3 (50% CMC + 50% PMT) ( I) 0.917 kg CMC (I) 2.752 kg CMC ( I) 9 17 ton CMC

(2) 1.89 litre PMT (2) 5.68 litre PMT (2) 18,900 litre PMT

4 (50%PMC + 50% PMT) ( I) 0.855 kg CMC (I ) 2.566 kg PMC ( J) 8.53 ton PMC


5 (25% PMC + 75% PMT) ( I) 0.428 kg PMC (I ) 1.285 kg PMC ( I) 4.285 ton PMC


6 (Control)

7 (Inorganic = Urea 46% N + Urea = 27.17 g Urea = 81.51 g Urea = 270 kg

GTSP 46% Pp,+ MoP GTSP = 19.02 g GTSP = 57.06 g GTSP = 190 kg

50% KP) MoP = 3 1.26 g MoP = 93.78 g MoP = 3 10 kg

Note: CMC = cattle manure compost, PMC = poultry manure compost, PMT = poultry manure tea

GTSP = granulated triple superphosphate, MoP = muriate of potash, FW = fresh weight.

Crop management

During the entire experiment period, the mean temperature was 22.2° C and the

accumulated rainfall in the entire cropping period was 50 mm (Appendix C). The equal amount

of supplementary irrigation water was provided to all the experimental plots from transplanting to

harvest. The first irrigation was applied immediately after transplanting and the subsequent

irrigations were applied when need ed, mostly at 4-5 days interval till the crop was harvested. The

irrigation was applied directly to the base of the plants through flexible pipe . The weeds

appearing on the furrows in between the plots were removed twice by hand s, first at 25 DAT and

the last at 50 DAT.

53

Insect pest control

At the time of head formation of cabbage a few larvae of diamondback moth

(Plutella xylostella Linn.) appeared in about 25 plants in all organic and control plots which was

controlled by 3 sprays of Bactguard F.C.™ (Bacillus thuringiensis var. kurstaki 10600 IU/mg SC)

@ 5 cc/litre of water at the interval of3 days. [I cc = I cubic em = I em = 1/1000 litre = I mL].

Measurement of plant height and leaf number per plant

Ten plants from each plot (5 plants from each row) as shown in Figure (10) were

selected as sample plants for measurement of leaf number per plant and plant height on weekly

basis. These ten plants in each plot were also used later for determination of frame leaves, stem

diameter, wrapper leaves, head width, head height, biological yield and economic yield at harvest.

The border plants located at the end of the rows were not included in sampling. The plant height

was recorded by measuring from the base of the plant stem at ground level to the tip of the tallest

leaf with a calibrated plastic ruler. The leaf number per plant was recorded by counting all the

leaves in a plant including the dead and dry leaves. However, after fifth week (35 OAT) the data

collection on leaf number was discontinued as the head formation started from 35 days after

transplanting and any new leaf produced was confined only to the head as wrapper leaf of the

head. This made the counting of leaves number without destroying the head impossible.

Figure 10 Location of sample plants (denoted by letter S) in rows and plot.

54

Measurement of yield and yield components

Measurement of stem diameter

The stem diameter was measured at the middle of the stem length with Mitutoyo

digital vernier caliper at the harvest of the crop. The same ten plants from each plot which were

earlier included in the sampling for measurement of plant height and leaf number per plant , were

selected for determination of stem diameter.

Measurement of frame leaves and wrapper leaves of cabbage head

The frame leaves were recorded at harvest by counting all the loose leaves in a

plant that did not form head. The frame leaves of all 30 sample plants were counted and recorded.

However, only three heads of cabbage were randomly selected from 10 plants in each plot at

harvest to count wrapper leaves. The wrapper leaves were recorded by removing all the leaves in

a head, starting from the outermost and finishing at the innermost core of head consisting of only

miniature leaf primordium.

Measurement of head width and head height

The head width was measured with Mitutoyo digital vernier caliper at the mid

point of the head by keeping the head in horizontal position. The head height was measured from

the base of the head in contact with the frame leaves to the tip of the head by keeping the head in

upright position with a calibrated plastic ruler. In total, 10 heads from each plot were measured

for height width and head height.

55

Determination of head firmness of cabbage

The firmness (solidity) of the head of 30 samples plant was measured by Hand

Held Penetrometer using 8 mm (\12 cm2

) plunger tip. First, the penetrometer reading was set at

zero kg by adjusting its knob. The cabbage head was firmly held horizontally with left hand on

the table and the plunger was placed against the surface of the head. Then a steady downward

pressure at right angle was applied until the plunger just penetrated the flesh of the cabbage head.

The plunger was removed from the cabbage and the reading on the penetrometer dial was noted.

Then the process was repeated on the opposite side of the cabbage head after first setting the

reading on penetrometer at zero. The average of two readings was used for recording the head

firmness.

Determination of biological yield and economic yield of cabbage

The cabbage was harvested on January 24 , 2009 when all the heads in the trial

field were mature which was determined by the hardness of the heads when they were pressed

with fingers. The same ten plants from each plot which were earlier included in the sampling for

measurement of plant height and leaf number per plant on weekly interval, were selected for

determination of biological yield and economic yield of cabbage yield. The plants were harvested

by cutting the stems at the ground level where the stems were in contact with the soil. After

determination of stem diameter, the stem from the head was removed by cutting the stem at the

base of the head below the frame leaves.

The biological weight (weight of head + weight of frame leaves) of the cabbage

on fresh weight basis was determined by weighing both frame leaves and head together in a

portable Camry platfonn weighing scale. Similarly, the economic weight (head weight) of

cabbage on fresh weight basis was determined by removing all the outer frames leaves and loose

leaves on the head and only the weight of intact head with firm wrapper leaves was recorded as

economic yield in a portable Camry platform weighing scale.

56

Determination of quality

Determination of dry matter content and total soluble solids

Three heads of cabbage were randomly selected at harvest from 30 sample plants in each

treatment to determine dry matter content (% DM) and total soluble solid (TSS) content (% Brix)

of the cabbage head. The three selected heads from each treatment were chopped into slices and

mixed together. Thus, in total there were seven mixtures of sliced cabbage, each mixture

representing one treatment. The three samples from each treatment were created and they were

accurately measured to 200 g in digital weighing scale at Department of Soil Resources and

Environment Laboratory, Maejo University and the readings were recorded as fresh weight of

cabbage. Then the samples were placed in paper bags, each sample bag was labelled and kept in

Hot Air Oven (Mernmert) at 70°C. The samples were weighed after every 12 hour by taking them

out from the oven. The constant weights of all the samples were observed at 90 hours after

keeping them in the oven at 70° C and the dry matter content (% DM) of the samples were

recorded subsequently.

For determination of TSS, three head selected from each treatment were sliced

into fine pieces and a sample of 200 g from each treatment was ground in electric grinder. The

juice from the ground cabbage was extracted by squeezing it in muslin cloth. The juice, thus

obtained was further filtered through cotton wool in funnel and collected in sample vials. The

LCD Digital Hand Refractometer (Atago, PAL-I, Japan) used in the determination of TSS was

first calibrated to zero reading by putting several drops of distilled water on the prism surface and

the corresponding reading was adjusted to zero. The prism surface was dried by wiping with

tissue paper. 2-3 drops of filtered cabbage juice was placed on clean and dry prism plate of LCD

Digital Hand Refractometer and the corresponding reading was recorded. Three readings were

taken for each treatment sample. The prism plate of LCD Digital Hand Refractometer was

washed with distilled water and dried with tissue paper every time before placing the sample

juice. The room temperature during the determination of TSS with Refractometer was set at 20° C.

The experiment was conducted at the Postharvest Laboratory, Pomology Division of Maejo

University.

57

Figure 11 LCD Digital Hand Refractometer (Atago, PAL-I, Japan) used in the determination of

TSS of cabbage.

Figure 12 Hand Held Penetrometer (Wagner FDK Force Gage FT 10) used for the�

determination of head solidity of cabbage.�

Figure 13 Spectrophotometer (NICOLET Evolution 300 LC, England) used for determination

of nitrate concentration of cabbage leaves.

58

Determination of vitamin C contents in cabbage

Three heads of cabbage randomly selected from each treatment at harvest were

chopped and mixed together. From this mixed slices, one representative sample of 300-400 g for

each treatment was constituted. The samples were packed in airtight poly bags and they were

randomly provided with code numbers as below before sending to the laboratory for

determination of nitrate concentrations:

Treatment No. 1 2 3 4 5 6 7

Sample code No. S-7 S-l S-2 S-5 S-4 S-3 S-6

The vitamin C concentration of cabbage head leaves was determined at the

Laboratory of Faculty of Agro-Industry, Chiang Mai University by AOAC Official Method

976.21 (AOAC, 2000a) which is reproduced as below:

1. Preparation of extraction solution (metaphosphoric acid-acetic acid solution).

15 g of HP03 pellets was dissolved in 40 ml CH and 200 ml Hp by3COOH

shaking. The solution was then diluted to 500 ml with distilled water and filtered through fluted

paper into glass-stoppered bottle.

2. Preparation of ascorbic acid standard solution (1 mg/rnl).

50 mg USP Ascorbic Acid Reference Standard was dissolved in 50 ml HP03

before use. CH 3COOH

3. Preparation of indophenol standard solution.

50 mg of 2,6-dichloroindophenol Na salt was dissolved in 50 ml H20

by shaking

vigorously. The solution was diluted to 200 ml with distilled water and filtered through fluted

paper into glass-stoppered bottle.

4 . Preparation of sample.

109 of sample cabbage was ground in pestle and mortar by adding 25 ml of

before grinding. The solution obtained was filtered first through absorbent HP03CH3COOH

cotton and then through folded filter paper. This solution was diluted to 100 ml with HP0 3

CH 3COOH.

59

5. Determination of vitamin C (ascorbic acid) in sample.

5.1 2.0 ml of ascorbic acid standard solution was mixed with 5.0 ml

HP0 in 50 ml Erlenmeyer flask and then titrated rapidly with 50 ml indophenol3CH3COOH

solution from burette until rose pink colour persisted for more than 5 seconds.

5.2 3 blanks composed of 7.0 ml HPOJCHJCOOH solution was

titrated with 50 ml water from burette.

5.3 10 ml each of three test solutions (cabbage juice) was titrated

with 50 ml of indophenols solution.

Where:

X = average ml of test solution titration, B = average ml for test blank titration,

E = number of g assayed, V = volume initial test solution,

F = mg ascorbic acid equivalent to 1.0 ml indophenols standard solution,

Y = volume test solution titrated .

Determination of nitrate contents in cabbage

Three heads of cabbage randomly selected from each treatment at harvest were

chopped and mixed together. From this mixed slices, one representative sample of 300-400 g for

each treatment was constituted. The samples were packed in airtight poly bags and they were

randomly provided with code numbers as below before sending to the laboratory for

determination of nitrate concentrations :

Treatment No. 1 2 3 4 5 6

Sample code No. S-4 S-2 S-3 S-7 S-6 S-5 s-i

The nitrate content of cabbage head leaves was analyzed at the Institute of

Product Quality and Standardization, Maejo University by In-house AOAC Official Method

976.14 (AOAC, 2000b) as described below:

7

60

I. Sample preparation.

The coded sample was blended in electric grinder until it was finely ground. 109

sample was transferred to 200 ml volumetric flask . 70 ml of de-ionized water (DI), 10 ml

ZnS0 and 12 ml NaOH were added to the flask containing 10 g sample. To the recovery4.7Hp

flask 1 ml of standard sodium nitrate solution was also added in addition to the reagents used for

sample. After keeping these two flasks in water bath at 50° C for 10 minutes, they were cooled at

room temperature and diluted to 200 ml with D1. Then the solutions were filtered through

Whatman No 1 filter (125 mID diameter) into volumetric flasks . The first 20 ml each of filtrate

from two flasks was discarded. After that 80 ml of each filtrate were collected in Erlenmeyer

flasks and their mouths were covered with parafilm of4 inch x 125 feet dimension.

2. Coating of cadmium with copper in modified Jones Reductor.

30 g of 5-20 mesh cadmium was first washed with 6N HCl and then with water.

After that the cadmium balls were kept in 100 ml of 2% CuS04 for 5 minutes with constant

stirring till blue colour of CuS04 disappeared. The CuS04 solution was discarded and new CuS04

solution was added until brown precipitate was obtained. Then the cadmium coated with Cu was

washed 10 times to remove CuS04 precipitates.

3. Determination of nitrate in sample

30 g of cadmium balls was placed in Jones Reductor column and 15 ml of 0.1 N

HCI passed through the column. The column was further cleaned by running IS ml of DI water

for 2 times followed by 15 ml buffer solution. The solution thus collected was discarded. The 5

ml buffer solution followed by 5 ml sample solution and 25 ml DI water were run through the

column and collected in 50 ml volumetric flask . To the collected solution. 2 ml sulfanilamide and

I ml NED (N-I-naphthyl ethylene diamine dihydrochloride) were added and left for 20 minutes.

The final solution was then diluted to 50 ml with DI water and the optical density of the solution

was measured by UV Spectrophotometer (NICOLET evolution 300) at 540 nm wavelength.

NO (rug/kg) = V x C x D 2 W

Where: C = concentration of nitrite from standard curve (ug/rnl),

V = volume of solution before dilution (rnl),

D = dilution factor,

61

Where: C = concentration of nitrite from standard curve (ug/ml),

V = volume of solution before dilution (rnl),

D = dilution factor,

W = weight of sample (g).

NO) (rng/kg) = (A-B) x 1.348

Where: A = quantity of nitrite in sample passed through column (mg/kg),

B = quantity of nitrite in sample,

1.348 = N02 to NO ) conversion factor.

Data analysis

All the data collected in the experiment were statistically analyzed with SAS

(Statistical Analysis System) Version 9.0 statistical software program. Analysis of Variance

(ANOVA) was used to determine significant differences between treatments in each experiment.

Duncan's Multiple Range Test (DMRT) and Least Significant Difference (LSD) at 5%

probability were applied for treatment means comparison when treatments had significant effect.

Pearson Correlation Coefficient was used to find out the correlation among different variables

like yield and yield components.

Chapter 4

Results

Plant nutrients in composts and manure tea

The nutrient contents in the composts were analyzed after 51 days of their

preparation. The poultry manure had higher nitrogen (N) content (1.13%) compared to that in

cattle manure compost (1.07%) but the cattle manure was better in potassium (K) content

(0.682%). The poultry manure compost was more acidic than cattle manure compost (Table II)

but there was no noticeable difference in CIN ratio between these composts.

The NPK nutrients content in poultry manure tea were analyzed on IS day (2

weeks) of extraction as well as on 21 day (3 weeks) of extraction. The Nand K contents were

higher in manure tea extracted on IS days of extraction but phosphorus (P) was higher in manure

tea extracted on 21 day (Table II and Figure 14). The pH started decreasing when the extraction

period was extended beyond IS days. For this reason, we used poultry manure tea extracted on IS

day of steeping in the crop experiment.

1.80 1.64 1.64

[JOloN 1.60

- 1.40r::: Cl>

1.20-r::: 1.13

0 (J 1.00 ~ a. 0.80 Z ~

0.60 0

0.40

0.20

0.00

PMC CMC PMT(150) PMT (210)

Organic fertilizers

Figure 14 NPK nutrients content in compost and poultry manure tea.

63

Table 11 NPK nutrients content and other physico-chemical properties of composts (dry

weight basis) and poultry manure tea.

Organic Fertilizers pH % DM % N % P % K % C ClN Ratio

Poultry Manure Compost (PMC) 6.48 64.65 1.13 1.640 0.646 15.87 14 .04

Cattle Manure Compost (CMC) 6.87 63.67 1.07 1.640 0.682 15.80 14.77

Poultry Manure Tea (PMT 15 D) 5.97 0.33 0.074 0.676

Poultry Manure Tea (PMT 21 D) 5.90 0.30 0.097 0.608

No te: DM = dry matter content, 15 D = extracted on 15 day, 2 1 D = extracted on 2 1 day.

Stock of plant NPK nutrients in the soil

Th e stock of plant nutrients like N, P and K and other phys ico-chemical

propert ies of the field soi l were studied by analyz ing the field so il from of 0-25 ern depth both

before planting the crop and after the harvest of the crop. The organic matter (OM) content of the

field soil before harv est was 1.71% (Table 12). As shown in Table 12 and Figure 15, there was an

increase of OM content after the harvest of the crop in most treatment soils including the control.

However , there was a slight decrease in OM content in Treatment 7 (inorganic) and Treatment 5

where the highest and second highest yield were recorded respect ively. The highest incre ase in

OM was observed in the soil of Treatment 1 (2.82%) followed by Treatment 2 (2 .8 1%). The least

increase in OM content was recorded in the soil of the control plot with 1.80%.

The N stock in the field soil also increased in all the treatments except Treatment

5 and Treatment 7 where there was slight decrease in N stock in soil. The highest increase in N

stock was observed in the soil of Treatment 1 (1410 ppm) which was followed by Treatment 2 at

1405 ppm. Th e high est decrease in N stock to 760 ppm was recorded in Treatment 7 (inorganic).

The P stock decreased in all the treatm ent soi ls and the grea test decrease was found in control plot

at 183 ppm followed by inorganic plot with 186 ppm . The decrease of K stock in the so il was

observed in Treatment 5, Treatment 6, and Treatment 7 where the highest decrease was recorded

in control plot at 123 ppm.

64

Table 12 Stock of NPK nutr ients in 0-25 cm depth of field so il befo re and after cro pping.

Treatment % O M N (ppm) P (pp m) K (p pm) % C C/N Ratio

Before Planting

Soi l 1.71 853 289 160 0.85 10.03

After Harvest of Crop

1 0 00% CMC) 2.82 1410 200 289 1.41 10.00

2 (100% PMC) 2.81 1405 199 234 1.41 10.00

3 (50% CMC + 50% PMT) 2.36 1180 199 183 1.18 10.00

4 (50 % PMC + 50% PMT) 2.14 1070 199 165 1.07 10.00

5 (25% PMC + 75% PMT) 1.57 785 196 149 0.79 10.12

6 (Co ntro l) 1.80 900 183 156 0.90 10.00

7 (Inorganic, NPK fertilizers) 1.52 760 186 123 0.76 10.00

Note: CMC = catt le manure compos t, PMC = poultry manure co mpost, PMT = poult ry manure tea , OM = organic matt er content.

1600-E 0. 1400 0.

lJ) 1200 -CIl e tV 1000 J:: I:3N ... CIl 800 ~ tV liP

·0 600 lJ) I!IIK e 400 e -CIl 200 l:

CJ 0 -~

zn, 2 3 4 5 6 7

Treatment soil

Figure 15 Stock of NPK nutri ents in trea tment soil after the harvest of cabbage.

0

65

Vegetative growth

Leaf numbers

Data pre sented in Ta ble (13) and Figure (16) showed the effect of different

treatments on leaves number per plant before the formation of head. Initi ally the different

treatments had no effect on the formation of leaves though the combined application of poultry

manure compos t and poultry manure tea in 1:3 ratio (Tre atment 5) produced the highest number

of leaves both at 7 OAT (6.3) and 14 OAT (8 .8) . The co mbined application of PMC and PMT in

equ al proportion (T rea tme nt 3) also showed the same result (8.8) at 14 OAT. Th e application of

different typ es of fertili ze rs sta rted giving significa nt effec t on leaf nu mber from 28 OAT

(P<0.05). Th ou gh the ino rganic plot produ ced lowest leaf number initiall y, from 2 1 OAT it

co ntinued to produce the highest leaves num ber till 35 OAT. The lowest number of leaves was

consecut ively observed in control plot afte r 14 OAT to 35 OAT.

Table 13 Effects of organ ic and inorganic fertilizers on the formation of cabbage leaves.

No. of Leaves in Plant Treatment

7DAT 14 DAT 21 DAT 28DAT 35DAT

1 (100% CMC) 6.0 8.7 12.2 15.0 a 16.5 ab 2 (100% PM C) 6.0 8.5 12.1 14.8 a 16.4 ab 3 (50% CMC + 50% PMT) 6.1 8.8 12.2 15.3 a 16.7 ab 4 (50 % PMC + 50% PMT ) 6.2 8.5 12.3 15.0 a 16.2 b 5 (25% PMC + 75% PMT) 6.3 8.8 12.5 15.2 a 16.7 ab 6 (Control) 6.2 8.5 10.9 13.5 b 15.1 c 7 (Inorganic) 5.6 8. 1 13.0 15.6 a 17.2 a F test ns ns ns * * LSO at 0.05 0.6 0.6 1.2 1.2 1.0

CV % 5.3 3.8 5.6 4.4 3.3

Note: Means havin g the same lettert s) do not di ffer significantly by OMRT at 5% level. LSO = least significant difference, CV= coe ffic ient of variance , OA T= day after transplanting, ns = not significa nt at P <0.05; * = significant at P < 0.05

66

Plant height

The pattern of plant growth from transplanting to harvest is presented in Table

(14) and Table (15) as well as in Figure (17). The treatments had no significant effect on plant

growth till 28 DAT though at 7 DAT the highest plant height (14 .8 ern) was observed in

Treatment 3 (50% CMC + 50% PMT) and Treatment 4 (50% PMC + 50% PMT). The highest

plant height was observed in Treatment 5 (25% PMC + 75% PMT) both at 14 DAT (17.1 em) and

at 21 DAT (21.7 em), The plant heights were significantly different among treatments after 35

DAT. At the beginning, the inorganic treatment had the lowest plant height, even lower than the

control plot. However, starting from 28 DAT, the inorganic treatment continually produced the

tallest plant among the treatments till the harvest of crop. In contrast, the minimum plant height

was recorded in control throughout the plant growth period starting from 21 DAT. In general , the

application of inorganic fertilizers produced taller plants than inorganic fertilizers . However, there

was no significant difference between application of compost alone and compost combined with

manure tea in promoting plant height. Similarly, no significant difference was found between

CMC and PMC when they were applied alone without combining with PMT .

20.0

18 .0

16.0

14.0 L. _ 1. CM C (100%) Ql 12.0 ~

_ 2. PM C (100%) E ::J 10 .0 z

_ 3. CMC (50%)+PMT (50%) 111 -Ql 8.0 -' _ 4. PMC (50%)+PMT( 50%)

6.0 ____ 5. PMC (25%)+PMT (75%)

4.0 _6.Conlrol

2.0 --+- 7. Inorganic (urea-TSP+KCI)

0.0

7 OAT 14 21 28 35

Age of plant (day after transplanting)

Figure 16 Weekly leaf number of cabbage as influenced by organic and inorganic fertilizers.

67

Table 14 Effects of organic and inorganic fertilizers on plant height before head formation.

Plant Height (em)

Treatment 7 OAT 14 OAT 21 OAT 28 OAT 3S OAT

1 (IOO%CMC) 13.7 16.3 20.2 22.1 23.4 be

2 (100 % PMC) 13.7 16.0 19.7 22.7 24 .1 abc

3 (50 % CMC + 50% PMT) 14.8 17.0 21.3 23.0 24.4 abc

4 (50 % PMC + 50% PMT ) 14.8 16.9 2 1.1 23.7 24 .5 ab

5 (25% PMC + 75% PMT) 14.3 17.\ 21.7 23.4 24.7 ab

6 (Control) 14.1 15.6 17.6 19.4 2 1.3 c

7 (In organic) 13.7 14.8 18.9 240 26.9 a

F test ns ns ns ns *� LSD at 0.05 level 1.4 1.9 2.9 2.8 2.9� CV % 5.6 6.5 8.0 6.9 6.7

Note : Means having the same letter(s) do not differ significantly by DMRT at 5% level.

DAT = day after transplanting, ns = not signi ficant at P <0.05 , * = significant at P < 0.05

Table 15 Effects of organic and inorganic fertilizers on plant height afte r head formation .

Plant Height (em)

Treatment

42 OAT 49 OAT S6 OAT 63 OAT 70 OAT

1 (IOO%CMC) 24 .5 b 25.4 b 26.1 b 26 .7 b 27 .5 b

2 (100% PMC) 25 .1 b 26 .0 b 26.9 b 27.4 b 28. 1 b

3 (50 % CMC + 50% PMT) 25.3 b 26 .1 b 26 .8 b 27.3 b 27.9 b

4 (50 % PMC + 50% PMT) 25 .8 ab 26.8 b 27.5 b 28.0 b 28 .8 b

5 (25 % PMC + 75% PMT) 25 .8 ab 26 .5 b 27. 2 b 27.7 b 28.3 b

6 (Control) 23.0 b 24.0 b 24 .8 b 25.5 b 26.4 b

7 (Inorganic) 28.4 a 29.5 a 30.4 a 31.0 a 31.7 a

F test * * ** ** LSD at 0.05 2.8 2.6 2.6 2.5 2.3

CV % 6.2 5.4 4.65.6 5.1

Note : Means having the same letteris) do not differ significantly by DMRT at 5% level.

LSD = least s ignifi cant di fference , CV = coeffic ient of variance, DAT= day a fter transplant ing ,

* = sign ificant at P < 0.05, ** = sign ificant at P < 0.0 I

68

35

30

E ~ ... .c t10

'Qj :J:... s::::

25

20

15

r L-rr-----..------

_1. CMC (100%)

__ 2. PMC (100%)

.......- 3. CMC (50%)+PMT (50%)

_4. PMC (50%)+PMT(50%) 11lc:: I _ 5. PMC (25%)+PMT (75%)

10 t -··· _6. Control

5 L.---- _7. Inorganic (Urea+TSP+KCI)

I 0

I-i - - - _·- r ·_- ···- - --,- - - -,- - - - ,.- - --,

14 28 42 56 70

Age of plant (Day after transplanting)

Figure 17 Effects of organic and inorganic fertilizers on fortnightly plant height of cabbage.

Yield components

Stem diameter

The stem diameter of the sample plant was measured at the middle of the stem

length with Mitutoyo digital vernier caliper at the time of the harvest of the crop. The stem

diameter was s ignificantly different among the treatments (Table 16). However, no significant

difference was observed between organic and inorganic fertilizers in their influence on promoting

the stem diameter thou gh the plant with biggest stem diameter was recorded in inorganic plot

(26.1 mrn) . This inorganic treatment was followed by organic Treatment 5 (24 .1 mm) where the

nutrients were supplied through PMC and PMT in 1:3 proportion. The third biggest stem diameter

(23.9 mm) was recorded in Treatment 4 where PMC and PMT were applied in 1:1 ratio. This

indicated that the application of both poultry manure compost alone and poultry manure compost

in combination with poultry manure tea were more effi cient in promoting stem diameter

compared to cattle manure compost. The lowest stem diameter was found in control at 2 1.6 mm .

69

Table 16 Effects of organic and inorganic fertili zers on the yield components of cabbage.

No of No of Wrapper Frame

Treatment Stem Leaves Leaves Head Head Plant Diameter per per Height Width Height (mm) Head Plant (em) (em) (em)

I (100% CMC) 22 .7 b 35.0 a 12.8 16.5 b 11.8 d 27 .5 b

2 (10 0% PMC) 23.7 ab 37 .2 a 13.0 17.4 ab 12.2 bed 28.1 b

3 (50% C MC+50% PMT) 23 .1 b 35 .8 a 12.9 17.0 ab 12.0 cd 27 .9 b

4 (50% PMC+50% PMT ) 23 .9 ab 38.7 a 12.6 17.6 ab 12.4 be 28.8 b

5 (25% PMC+75% PMT) 24 .1 ab 38 .9 a 12.6 17.8 ab 12.7 ab 28.3 b

6 (Control) 21.6 b 28 .9 b 13.5 14.5 c 9.9 e 26.4 b

7 ( Inorganic) 26.1 a 40.0 a 13.0 18.3 a 13.0 a 31.7 a

F test * NS* ** ** **

LSD at 0.05 2.3 5.6 1.6 1.3 0.5 2.3

CV % 5.4 8.6 7. 1 4.4 2.5 4 .6

Note: Means ha vin g the same letterts) do not differ significantly by DMRT at 5% level. LSD = lea st significant di fference , CV = coefficient of vari an ce, DAT = day after transplanting, NS = not signi fica nt a t P <0.05, * = significant at P < 0.05 , ** = significa nt at P < 0.01

Wrapper lea ves per head

The wrapper lea ves that contributed in form ation of head in cabbage were counted at the

time of harvest of sample plants. From the dat a presented in Table (J 6) and Figure (J 9) , it is

clear that the wrap per leaves in cabbage head were significa n t different onl y be twe en control

plot and fertili zed plots . Th ere was no signi ficant effect on wrapper leaf number from

application of di fferent types of fer tili zers. Nevertheless, the h ighest numb er of wrappe r leaves

was found in inorganic (40.0) followed by Treatment 5 (38.9) that was fertili zed with 25% PMC

and 75% PMT. T he third highest number of wrapper leaves among treatment s wa s recorded in

Treatment 4 {38.7) wh ere PMC and PMT were applied in I: I proportion to supply the nutrients.

70

Cabbage plants in the field at the early stage (before head initiation)

Cabbage plants in the field at head formation stage

Cabbage plants in the field at harvesting stage

Figure 18 Cabbage plants in the field at different stages of the growth.

71

mStem Dia (mm)� III Wrapper Leaf No.�

45 mFrame Leaf No.�

40

35 .... Q) .c 30E ::J t:- 25 co Q)�

...J 20�::::.. E

15E-.... Q)... 10 Q)

E co 5 Cl

0

o\~ 1;)1;)

". (i~v~

Treatment

Figure 19 Stem diameter , frame leaf numb er and wrapper leaf number at harvest of cabbage.

Frame leaves in plant

As presented in the Table (J 6), the frame leaves in plan t were statistically not

signific ant among the treatm ents. Nonetheless, the highest numb er of frame leaves ( 13.5) was

found in control plot and this was follo wed by Treatment 7 (inorganic) and Treatment 2

(ino rganic). The lowes t number of frame leaves (12.6) was observed in Treatment 4 and 5.

Head height

The head height was statistically s ignificant among the treatments (Ta ble 16) as

the head height was influenced significantly due to the applica tion of different types of

72

fertilizers. The longest head was found in the inorganic plot (18.2 em), However, this was

statistically not different from the second longest head (17 .8 ern) recorded in Treatment 5

fertilized with PMC (25%) in combination with PMT (75%). The second longest head among

organic treatments (17.6 em) was found in Treatment 4 where the nutrients were supplied

through PMC and PMT in equal proportion. The lowest head length (14.5 ern) was observed in

control plot.

Head width

The treatments had significant effect on the width of the head (Table 16). The

highest head width was found in inorganic plot (13.0 ern) followed by Treatment 5 (12.7 em).

The third highest head width among treatments was found in Treatment 4 (12.4 em) though this

value was statistically not different from that of treatment 5. The lowest head width was found in

control plot (9.9 ern),

Il!IHead Height (ern)

BHead Width (cm)

35.0 I:llPlant Height (cm)� .-..�5 30.0 '-'

£ 25.0 "0

~ 20.0 '<,

:c 15.0 ell

.~

::t 10.0

5.0

0.0 ~,,-., ,,-" ,,-" ~-., If'~o ,,~ <I,

<I. <I. ' ~~ <I.~ . ~.\. . \. .\. . \. e."'''> <:0' ~~ n~ n~ \o~

C,x C,x C,x~'" ~ ·v ~ ,<>"'~

C,~" <I,1::-" <I,~ ,,\.\. . \" . \" ~~ e 0'"

", . l>' ~.

Treatment

Figure 20 Effects of organic and inorganic fertilizers on plant height, head length and head

width of cabbage.

73

Yields

Head yield (economic yield)

The result presented in Table (17) showed that all treatments significantly

promoted the fresh weight of cabbage head, as the head yield was statistically different among the

treatments. The highest head yield among treatments was produced by the inorganic plot (664.67

g) fertilized with urea, triple superphosphate and potassium chloride (KCl). Among organic

treatments, the application of PMC in combination with PMT in 1:3 proportion (Treatment 5)

gave the highest head yield (601.33 g) and this organic plot was not significantly different from

inorganic treatment in term of head weight. The second highest head weight among organic

treatments (588 .33 g) was recorded in plot fertilized with PMC and PMT in I: 1 ratio (Treatment

4). However, these two organic plots (Treatment 5 and Treatment 4) were statistically similar in

terms of head weight. The lowest head weight (189.67g) in the trial was found in control plot.

The cabbage plants in all the organic plots matured I week earlier than those in

inorganic and control plots did . Therefore, at the time of harvest (70 DAT), most cabbage heads

in organic plots were split and cracked open (Figure 22) . In contrast, leaf senescence was more

developed with pale-yellow colour in inorganic plot at harvesting time.

Plant biological yield

As presented in Table (17), the plant biological weights (weight of head +

weight of frame leaves) were significantly different among the treatments. The biological weight

among treatments differed in the same manner as observed in the case of head weight. As in the

head weight, the highest plant biological weight was recorded in the inorganic plot (963.67 g)

followed by organic plot fertilized with PMC and PMT in 1:3 ratio (Treatment 5) with mean

biological weight of 899.33 g per plant. These two inorganic and organic treatments were

statistically similar. The second highest mean plant biological weight among organic treatments

applied (Treatment 4) . The lowest plant biological weight (351.33g) was found in control plot.

74

664.67 700�

600�

:§ 500...s: bll '0; 400 s "C 300 11l QI

J: 200 e 11l QI 100:2

0

.\~",,,, ~

~(, c;

v

Figure 21 Effects of organic and inorganic fertilizers on head weight of cabbage.

Biological yield per hectare

The biological yield per hectare (ton/ha) was calculated by multiplying the mean

plant biological weight with 66,666 (total plants population in an area of I hectare at a plant

spacing of 50 x 30 em), As presented in Table (J 8), the biological yield per hectare differed in

the same manner as observed in the case of plant biological weight. The highest biological yield

was recorded in inorganic plot with yield of 64.24 ton/ha. However, this yield was statistically

similar to that of organic treatment (59.96 ton/ha) where PMC and PMT in 1:3 ratio were used

for fertilization (Treatment 5). The third highest biological yield among treatments was given by

Treatment 4 (55 .31 ton/ha), while the lowest biological yield was observed in control.

Head yield (economical yield) per hectare

The mean head weight was multiplied with 66,666 (total plants population in an

area of 1 hectare at a plant spacing of 50 x 30 ern) to obtain economic yield per hectare (ton/ha) .

In doing so, the economic yield per hectare differed in the same trend as observed in the case of

75

head weight (Table 18). Among all treatments , the highest economic yield was recorded in

inorganic plot with head yield of 44.33 tonlha. However, this yield was statistically similar to

40.11 ton/ha recorded in organic plot fertilized with PMC and PMT in 1:3 proportion (Treatment

5). The second highest economical yield among organic treatments (37.24 ton/ha) was produced

in plot fertilized with PMC and PMT in equal ratio (Treatment 4). The lowest economical yield

was observed in control with yield of 12.65 tonlha.

Table 17 Effects of organic and inorganic fertilizers on different yie lds of cabbage.

Biological Weight Mean Head Head Weight

Treatment (head + frame leaves) Weight 2

per m

(g) (g) (g)

1(100% CMC) 725 .33 c 468.33 c 3123 .8c

2 (100 % PMC) 744 .33 c 497 .67 c 3319.4c

3 (50% CMC + 50% PMT) 738.33 c 494.33 c 3297.2 c

4 (50% PMC + 50% PMT) 824.67 be 588.33 be 3724.1 be

5 (25% PMC + 75% PMT) 899.33 ab 601.33 ab 4010.9 ab

6 (Control) 351.33 d 189.67 d 1265.1 d

7 (Inorganic) 963.67 a 664 .67 a 4433.3 a

F test ** ** **

LSD at 0.05 132.22 98.08 654 .2

CV % 9.9 11.1 II. I

Note: Means having the same letterts) do not differ significantly by DMRT at 5% level. LSD = least significant difference, CV = coefficient of variance, ** = significant at P < 0.01

76

Table 18 Effects of organic and inorganic fertilizers on the yield of cabbage.

Head Yield Head Yie ld Biological Yield (Economic Comparison

Treatment (head+frame leaves) Yield) to Inorganic (ton/ha) (ton/ha) Yield (%)

1(100% CMC) 48 .36 b 31. 24 c 70 .5

2 (100% PMC) 49 .62 b 33 .19 c 74 .9

3 (50 % CMC + 50% PMT) 49 .22 b 32 .97 c 74.4

4 (50 % PMC + 50% PMT) 55.31 ab 37 .24 bc 84 .0

5 (25% PMC + 75% PMT) 59.96 a 40 .11 ab 90 .5

6 (Control) 23.4 2 c 12.65 d 28.5

7 (Inorganic) 64 .24 a 44.33 a 100.0

F test ** **

LSD at 0.0 5 8.8 6.5

CV % 9.9 11.1

Note: Means having the same lettert s) do not differ sign ificantly by DMRT at 5% level. LSD = least significant difference, CV = coefficient of variance, ** = significant at P < 0.01

Head yield com parison between inorganic and organic cabbages

To see how much yield reduction had occurred in organic and control cabbage s,

the economic yield (head yield) obtained in inorganic treatment was con sidered as 100%

(maximum yield potential) and the economic yields of organic treatments and control were

compared with this inorganic yield . The highest % eco nomic yield among organic treatments was

recorded in Treatment 5 that was fertilized with PMC and PMT in 1:3 ratio with yield 90 .5% that

of the inorganic cabb age and this was followed by 84% yield produced by Tre atm ent 4 where

PMC and PMT were used in I: 1 ratio for organic fertilization (Table 18). Treatment I , Treatment

2 and Treatment 3 produced yield 70 .5%, 75 .9% and 74.4 % respectively. The lowest %

economic y ield was found in control with yield 28.5% that of inorganic cabbage.

77

Figure 22 Size and condition of cabbage heads as influenced by organic and inorganic

fertilizers.

Quality aspects of cabbage

Head solidity of cabbage

As shown in the Table (19), the cabbage head solidity (head firmness) was

significantly different among the treatments (P<O.05). However, no significant difference was

78

observed between organic and inorganic treatments. The highest head solidity among treatment

(0.563 kg/crn) was observed in Treatment 5 where PMC was combined with PMT in 1:3 ratio for

?

fertilization. This value was followed by head firmness of 0.551 k/cm" recorded in Treatment 2

that was fertilized solely with poultry manure compost. The third and fourth highest head solidity

were found in Treatment 7 (inorganic) and treatment 4 (50% PMC + 50% PMT) with values of

0.535 kg/em and 0.500 kg/ern' respectively. However, these four treatments were statistically not

different in terms of head solidity. The lowest head solidity was observed in control plot at 0.426

2kg/cm.

Total soluble solid content of cabbage

As presented in Table (19), total soluble solid content (TSS) was significantly

different among treatments (P <O.O I) . The inorganic plot that produced the cabbage head with

highest TSS (6.17 % Brix) was significant different from other organic and control plots. The

organic plot fertilized with PMC and PMT in 1:3 proportion (Treatment 5) produced the second

highest value at 5.80% Brix. The third highest TSS was found in Treatment I at 5.63% Brix and

the lowest content ofTSS was found in Treatment 4 with 5.20% Brix.

Dry matter content of cabbage head

As shown in Table (9), the dry matter content (% DM) was affected by

different treatments . The % MD was statistically different among the treatment (P<O.O I) but there

was no significant difference between organic and inorganic cabbages. The application of PMC

and PMT in 1:3 ratio (Treatment 5) and the control plot produced the highest dry matter content

(7.6%). This was followed by inorganic plot at 7.5%. The lowest content of dry matter was found

in Treatment 3 at 6.8%, whieh was fertilized with CMC and PMT in I: I proportion.

79

Vitamin C content of cabbage bead

The concentration of vitamin C in cabbages was influenced by the application of

different types of fertilizers (Table 20). As a whole, the plants produced higher concentration of

vitamin C in all the organic treatments (I06 mg/l00 g to 139 mg/l 00 g) than inorganic (I03

mg/lOO g) and control (96 mg/l00g) treatments. It was also observed that among organic

treatments, those plots fertilized with higher proportion of liquid organic fertilizer (poultry

manure tea) produced higher vitamin C than the plots where only solid fertilizer (compost) was

applied. The highest vitamin content in the head leaves of cabbage (139 mg/l OOg) was found in

Treatment 5 that was fertilized with PMC in combination with PMT in 1:3 proportion. This value

was followed by Treatment 3 (50% CMC + 50% PMT) with vitamin C content of 123 mg/IOO g.

The inorganic plot with vitamin C content of 103 mg/l 00 g was better than the control that

produced the lowest vitamin C content (96 mg/I 00 g) among the treatments.

Table 19 Effects of different treatments on head solidity, TSS and dry matter contents.

Treatment Head Solidity (kg/em2) TSS (% Brix) DM(%)

1 (100% CMC) 0.479 b 5.63 be 7.3 abc

2 (100% PMC) 0.551 a 5.07 d 7.0 cd

3 (50% CMC + 50% PMT) 0.491 ab 5.50 c 6.7 d

4 (50% PMC + 50% PMT) 0.500 ab 5.20 d 7.1 be

5 (25% PMC + 75% PMT) 0.563 a 5.80 b 7.6 a

6 (Control) 0.426 b 5.27 d 7.6 a

7 (Inorganic) 0.535 a 6.17 a 7.5 ab

F test * ** ** LSD at 0.05 0.081 0.20 0.3

CV% 9.0 2.1 2.6

Note: Means having the same letterts) do not differ significantly by DMRT at 5% level. LSD = least significant difference, CV = coefficient of variance, TSS = total soluble solid, DM = dry matter content, * = significant at P < 0.05, ** = significant at P < 0.0 I

80

IlITolal Solub le Solid (% Brix)

(J Dry Matter Content (%) 8.00� )(� .;: 7.00 OJ ~ 0 6.00 ~

~ 5.00 e..... t: 0

:.;:; 4.00 ra...... t: 3.00 Q)� (.)� t: 0 2.00 o

1.00

0.00 .\;

~~ ~

~0 c v

T rea tment

Figure 23 Total soluble so lid (TSS) and dry matter content (% OM) of cabbage.

Table 20 Effects of organic and ino rganic fertilizers on vitamin C and nitrate contents of cabbage.

Treatment Vita min C( mg/I OOg) Nit r a te (mg/kg) Vit.C/Nit ra te Ra tio

I (100% CMC) 106 309. 1 3.4

2000% PMC) 106 300.5 3.5

3 (50 % CMC + 50% PMT) 123 202.9 6.1

4 (50% PMC + 50% PMT) 117 212 .5 5.5

5 (25 % PMC + 75% PMT) 139 163.3 8.5

6 (Control) 96 148.4 6.5

7 (Inorganic) 103 589 .2 1.7

81

Leaf nitrate content of cabbage head

The result presented in Table 20 and Figure 24 showed the differential influence

of different types of fertilizers on nitrate content in cabbage. In general, organic fertilizers were

found superior in reducing the nitrate concentration in cabbage, as all the organic treatments

produced lower concentration of nitrate than inorganic treatment. Among organic treatments, the

application of liquid organic fertilizer (PMT) resulted into lower accumulation of nitrate than

solid organic fertilizers (composts). The inorganic plot had the highest leaf nitrate (589.2 mg/kg)

among the treatments. This was followed by Treatment I (309.1 mg/kg) and Treatment 2 (300.5

mg/kg) in which the nutrients were supplied solely through CMC (100% CMC) and PMC (100%

PMC) respectively. The lowest nitrate content (148.4 rng/kg) was found in control plot.

Vitamin C/nitrate ratio in cabbage

The vitamin C in fruits and vegetables is a desirable compound as it helps in

reducing several ailments due to its antioxidant activity. On the contrary, nitrate in vegetables is

considered as undesirable chemical as its consumption leads to several health problems like

methaemoglobaenemia and possibly some cancers. Therefore, the ultimate nutritional quality of

vegetables does not depend solely on vitamin C or nitrate content but it is judged by vitamin

C/nitrate ratio; the higher the ratio the better the quality of the vegetable in question.

As in the case of vitamin C content, all the organic treatments and control

showed higher vitamin C/nitrate ratio than inorganic plot (Table 20). In this study, the highest

vitamin C/nitrate ratio (8.5) was found in Treatment 5 where PMC and PMT in 1:3 ratio were

used for fertilization. This was followed by control plot (6.5) and then by Treatment 3 (6.1) that

was fertilized with CMC and PMT in equal proportion. The inorganic plot had the lowest ratio at

1.7 (Table 20).

82

700 0($ ,-... 589 .2 i:).() 600 caVitamin C (mg/100 g)

0 0

• Nitrate (mg/kg),-... 500 ---i:).() i:).() je '-' ~ 400U ec '-'

~·S .... 300 ~ .... ~

l. .~ .-::

c 200... 0� cj� 100c 0 U 0

2 3 4 5 6 7

Treatments

Figure 24 Vitamin C and nitrate concentrations as affected by organic and inorganic fertilizers

Matrix of Pearson's correlation coefficient between yield and yield components

The coefficient of correlation analysis presented in Table (21) showed that the

head yield (weight of cabbage head) was significantly and positively correlated with all the

horticultural characters except frame leaf number and dry matter content. The head yield was also

positively correlated to total soluble solid (TSS) but it was not significant (r = 0.5506 ns), The

head yield of cabbage showed strong positive relationship with head width (r = 0.9971 **)

followed by wrapper leaf number (r = 0.9863**), head height (r = 0.9708**), stem diameter (r =

8783**), head solidity (r = 0.8073*) and plant height (r = 0.7893*). There was also strong

positively correlation (r = 0.9989**) between plant biological yield (head weight + weight of

frame leaf) and head yield. As for frame leaf number and dry matter content, there was negatively

correlation with head yield.

Table 21 Matrix of Pearson's Correlation coefficient among different parameters of cabbage as influenced by different types of fertilizers

Parameter Stem

Diameter

Biological

Yield

Head

Yield

Head

Solidity

Frame

Leaf No

Head

Height

Head

Width

Wrapper

Leaf No

Plant

Height

Dry

Matter TSS

Stem Diameter 1.0000

Biological Yield 0.8783 ** 1.0000 -

Head Yield 0.8872** 0.9989** 1.0000

Head Solidity 0.7817* 0.8044* 0.8073* 1.0000

Frame Leaf - 0.4230NS

- 0.7942* - 0.7829* - 0.5378NS

1.0000

Head Height 0.8723* 0.9642** 0.9708** 0.8876** - 0.7378NS

1.0000 -

Head Width 0.8779** 0.9948** 0.9971 ** 0.8372* - 0.7835* 0.9847** 1.0000

Wrapper Leaf 0.8 784** 09825** 0.9863** 0.8482* - 0.7835* 0.9891** 0.9910** 1.0000

Plant Height 0.9600** 0.7742* 0.7893* 0.601 7NS

- 0.2737NS

0.7643* 0.7729* 0.7703* 1.0000

Dry Matter 0.0848 NS

- 0.1036NS

- 0.1328NS

- 0.0725NS

0.2736NS

- 0.2292NS

- 0.1757NS

-0.1595 NS

0.0494NS

1.0000

TSS 0.6408NS

0.5660NS

0.5506NS

0.3007NS

- 0.2097NS

0.3819NS

0.5026NS

0.4283 NS

0.6269NS

0.4458NS

1.0000

NS N . ifNote : == ot sigru icant; * = Significant at 5% level; ** == Significant at I% level

VJ 00

Chapter 5�

Discussion�

NPK nutrients in poultry manure tea

The poultry manure tea extracted in 15 day of steeping poultry manure had

higher Nand K contents but lower P content than that extracted in 21 day of steeping. This result

showed that when the extraction period extended beyond 15 days, there was decrease in the

accumulation of Nand K in manure tea. Since, N is the most yield determining nutrient for leafy

vegetable like cabbage, the poultry manure tea prepared by steeping fresh poultry manure in

water in 1:1 ratio (weight of manure: volume of water) for 15 days was considered superior for

this experiment. Moreover, P and K are adequately supplied in plant available form by solid

organic fertilizers (composts) applied before planting as these nutrients are mostly present in

inorganic form in organic fertilizers (Leikam and Lamond, 2003 ; Gross et al., 2007). The soluble

nutrients in poultry manure dissolve in water during the process of fermentation of manure tea

preparation. The amount of nutrients released from organic materials depends on their

physical/chemical composition, nutrient content in them and the surrounding environmental

factors (Nhamo et al., 2009). The decrease in N accumulation in manure tea after 15 days of

steeping in this experiment can be ascribed to loss of inorganic N (NH 4 +) through volatilization in

gaseous form. This means, the rate of loss of inorganic N from the manure tea was more than the

rate of N released in manure tea from the poultry manure. Since phosphorus is not subject to

volatilization loss like inorganic manure nitrogen (Leikam and Lamond, 2003), the concentration

of P kept accumulation up to 21 days of extraction. However, we could not provide any suitable

explanation for decrease of K content in manure tea with increase of extraction time beyond 15

days. Assuming that it was not related to error limits of analysis, it is reasonable to believe that

the released K reacted with some organic compounds present in manure (i.e, K fixation) as the

extraction period extended beyond 15 days. Nonetheless, we suggest further research on this for

verification.

This result is in close similarity with that of Price and Duddles (1984). These

researchers reported that the increase of concentration of soluble nitrogen in chicken manure tea

85

was entirely due to increase of ammonium, which lost through volatilization after 2 weeks of

steeping 35 pound of chicken manure in 35 gallon of water. Yekutieli et al. (1996) noted that high

pH of manure tea and stirring (mixing) applied during extraction of manure tea enhanced N loss

through volatilization of ammonia. Gross et al. (2007) designed an experiment to entrap the

volatilized ammonia (NH 3) in order to measure the amount of ammonia lost via volatilization. In

their study, they found that 24% of poultry layer manure-N was released to the manure tea , of

which 12% (50% of total N released) volatilized as ammonia.

Stock of NPK nutrients in the soil and mineralization of organic fertilizers

In general, the organic matter content and nitrogen stock in 0-25 cm depth of the

field soil after the harvest of crop was closely related to the crop yield obtained . The N stock in

the field soil after crop harvest was positively correlated to the N released into the soil during the

cropping period from the fertilizers applied and negatively correlated to the N removed from the

soil by plants for their growth and yield . This was obvious from the presence of different levels of

lN stock in the treatment soils though the same quantity of N (i.e. 125 kg N ha· ) was applied in

every treatment before planting cabbage. The inorganic plot produced highest head yield (44.33

ton/ha) among all the treatments because all the N present in urea (chemical fertilizer) was

available to the plant during cropping season. Consequently, the lowest N stock (760 ppm) was

recorded in the soil of inorganic plot after harvest of crop. The slow plant growth rate and low

yield in organic treatments was due to the slow release of N from the organic fertilizers , which

was not sufficient to meet the N requirement of cabbage. The rate of nutrient release from basal

application of solid organic fertilizers depends on soil temperature (Nakano et al., 2003). As our

experiment was conducted in mid winter when the mean atmospheric temperature was 22.20

C

(Appendix C) , it is reasonable to assume that the soil temperature was not high enough for release

of nutrients from compost in adequate quantity in our experiment. Poultry manure tea (liquid

organic fertilizer) was found better in releasing N during the cropping period compared to

compost (solid organic fertilizers). This is obvious from the fact that the higher cabbage yield

with lower N stock was obtained in treatments where poultry manure lea was applied. The slow

N-releasing nature of solid organic fertilizers was revealed by the lower crop yield with high N

86

stock in the soil of treatments that were supplied with only compost as N source. The high stock

ofN at harvest in organic plots denotes that N was not released in sufficient quantity from organic

fertilizers both in early and mid crop growth stages, thereby plants were in short supply of N

during crop growth stage that caused early crop maturity in organic plots. The retardation of early

plant growth later affects the yield (Nakano et al., 2003). However, organic fertilizers continued

releasing N in large quantity at late crop stage (i.e. at harvest) when crop's demand for N was

low. This was the reason for cracking of cabbage heads in organic plots. Such cracking of

cabbage head was not ob served in inorganic and control plots . In the organic plots, more N

remained in the soil than in inorganic plot, suggesting that most of the applied organic materials

were stored in the soil. The higher N stock in control plot compared to inorganic plot might be

due to carryover N through compost and other organic fertilizers applied to previous crop because

the field where the experiment was conducted was under continuous organic cropping system for

last five years.

Gros s et al. (2007) stated that supplementary N side dressing is often required in

organic cropping system because the available N from solid composted manures is not adequate

for crop requirement. Xu et al. (2003) reported that the growth of two leafy vegetables , Brassica

rapa and Brassica campestris, at the early stage was weaker in organic treatment than in

chemical fertilization treatment, which was attributed to lower available nutrients in organic

fertilizers in early crop stage. Similarly, Jakse and Mihelic (1999) reported that N is the major

driving force for vegetables and they further reported that N released from compost was not

sufficient for economic vegetable production.

Vegetative growth

In this study, the vegetative growth of cabbage was indicated positively by

weekly leaf number (Table 13), weekly plant height (Table 14 and Table 15) and other

horticultural characteristics recorded at harvesting like number of wrapper leaf per head, number

of frame leaf per plant and stem diameter, which are presented in Table (16). The vegetative

growth of cabbage, especially after third week of growth, was highly correlated to both biological

and economic (head) yields. The growth of cabbage immediately after transplanting was slow and

87

weak in inorganic plot as shown by lower plant height and less leaves number. This could be due

to the stress caused by changing the root environments when seedlings solely grown in organic

medium were transplanted in the field where chemical fertilizers were used for supplying

nutrients. At this stage, the cabbage seedlings in inorganic plots had even shorter height than

seedlings in control plot. However, after third week of transplanting, plants in inorganic plot

recovered from transplanting shock, became acclimatized to the chemical fertilizers and

performed better with consecutively producing both higher leaf number and higher plant height

among all the treatments. The plants were dark-green in inorganic plot in early and mid stages of

growth as compared to pale-green plant of control and organic plots. At harvesting time, the

inorganic plot, which produced the highest yield, had highest plant height, highest stem diameter

and the highest number of wrapper leaves, suggesting that vegetative growth of plants was

sufficiently supported by inorganic fertilizers and plants did not face any nutritional stress during

their growth. Similarly, organic plot fertilized with poultry manure compost and poultry manure

tea in 1:3 proportion, also had favorable vegetative growth without any major nutritional stress.

Plants in other organic plots where only composts were applied greatly suffered from nutritional

stress during their vegetative stage. The control plot that produced the lowest yield among

treatments showed the least value with respect to vegetative growth. Early head maturity by one

week and cracking of heads in organic plots indicated that plants in organic plots faced nutritional

stress during early growth stage but the condition became more favourable for vegetative growth

later in harvesting stage. The possibility of cabbage head splitting due to excess soil moisture was

ruled out in this study since all the plots were supplied with equal amount of water. The active

vegetative growth in organic plots at head maturity stage producing more leaves in the core of the

head caused cracking of heads. This phenomenon can be attributed to slow release of N from

compost, which affected vegetative stage at early crop growth stage and induced early head

maturity but continuous N release from compost even at late crop stage brought vegetative growth

again. The more leaf senescence with pale-yellow colour in inorganic plot at harvesting time

indicated that nutrients were completely exhausted in inorganic plot by harvesting time.

Similar finding was obtained by Xu et al. (2003) where the growth of two leafy

vegetables, Brassica rapa and Brassica campestris, at the early stage was weaker in organic than

in chemical fertilization treatment but at the later stages both vegetables in organic plots grew

88

better and resulted in a higher final total yield than those in inorganic plot. Moreover, Nakano et

al. (2003) reported that the early growth of tomato was retarded in organic treatment due to which

the tomato yield was affected later.

Yield of cabbage

Yield responses of cabbage to fertilization were better on plot to which mineral

fertilizers had been applied. Chemical fertilizers instantly release nutrients once they are applied

to the soil provided the soil conditions are favourable. In inorganic plot, cabbage plants had

higher number of wrapper leaves, thicker stem diameter and longer head length and wider head

size. This indicated that plants supplied with chemical fertilizers did not suffer from nutrition

stress during their growth. The head yield obtained by application of chemical fertilizers (44.33

tonlha) was the highest among treatments. However, this head yield was statistically not

significant from yield (40.11 ton/ha) produced by organic treatment fertilized with PMC (25%) in

combination with PMT (75 %) . This fertilization gave head yield 90.5% that of inorganic plot.

The other organic plots where the proportions of PMT were lower than 75% gave yield 74-84%

that of inorganic fertilization . It is clear from the obtained result that the application of poultry

manure compost in combination with poultry manure tea had more favourable effect on

increasing the final head yield. This effect could be due to the increased availability of plant

nutrients from the combination of both sources. On the other hand, application of compost alone

to the soil did not show noticeable increase in head yield. Further, the substituted part of solid

organic fertilizers (composts) with any of the poultry manure tea level showed more production of

head weight. This result confirms that organic liquid fertilizers like PMT contains instant plant

nutrients and is suitable for short duration vegetable crops, whereas the solid organic fertilizers

like composts, FYM or manure have to undergo long process of mineralization to make the

nutrients contained in them available to the plant. Therefore, it is reasonable to believe that

poultry manure tea (liquid organic fertilizer) provided adequate nutrients to the plant at the early

crop stage while composts (solid organic fertilizer) provided nutrients to plants at the later crop

growth period as they undergone mineralization.

89

In the present experiment, higher yields among organic treatments were obtained

where higher proportion of poultry manure tea was applied as a nutrient source. Further, the

organic treatments fertilized with only poultry manure compost produced higher yield of cabbage

compared to plots fertilized with only cattle manure compost. This result prompted us to believe

that poultry manure, in addition to its higher nutrient content, releases nutrient faster than cattle

manure . Gross et al. (2007) stated that poultry manure has fine texture and smaller particle size

that enhances faster nutrient release as well as provides more surface area for microbial activity.

Similarly, Rasnake (2002) mentioned that poultry and liquid manures have higher percentages of

N as inorganic N, which increases N availability during the year of application but solid manures

from other animals have more organic N that is released slowly and carry over to the next year.

Furthermore, Leikam and Lamond (2003) reported that poultry solid manure contain 65% of total

N in manure in inorganic form (NH 4 ' ) as against only 45 % in dairy manure. All of the inorganic

anunonium N in any manure is potentially available to growing crop since it does not have to wait

for mineralization. Similarly, Havlin et al. (2005) stated that poultry manure contains 61% of total

manure-N as uric acid. Further, Gros s et al. (2007) reported that uric acid is readily degraded to

anunonia by bacteria within 14 days. In addition, the better growth and high yield in organic plots

might be due to higher photosynthetic activity in organic plots at later stages (Xu et al., 2003) .

Hendawy (2008) reported that manure tea contains microbes that produce plant growth hormones,

mineralize plant nutrients and fix nitrogen.

Such high yield by fertilizing with compost combined with poultry manure tea in

lettuce was obtained by Adhikari (2009) in his Master's Thesis. Further, Nakano et al. (2003)

reported that there was no significant difference between the yield of tomatoes grown under

organic and inorganic fertigation systems where com steep liquor (industrial byproduct of

cornstarch manufacture) was used as liquid organic fertilizer for fertigation. However, Xu et al.

(2003) reported that the accumulated yield of two leafy vegetables , Brassica rapa and Brassica

campestris were higher in organic farming than in conventional farming when their harvesting

periods were extended up to 120 and 140 days respectively by adopting leaf harvest method. They

had applied 30% more N through compost in organic treatment than in inorganic treatment

considering 30% N in compost would not be available during the cropping period. This result is

in partial agreement with the finding of Jakse and Mihelic (1999) where the yield of organic

90

cabbage was higher in inorganic fertilization. They reported that N released from compost was

not sufficient for economic vegetable production regardless of relatively now CIN ratio. Our

finding suggests that vegetable growers who want to take up organic vegetable production should

be aware of the N mineralization capacity of organic fertilizers and crop growth characteristics.

Nevertheless, one reason for lower yield in organic treatments compared to

chemically fertilized plot in this study could be due to the use of cabbage cultivar developed for

conventional farming. Murphy et al. (2007) warned that modem crop cultivars selected by plant

breeder under conventional systems do not accurately represent the conditions present in organic

farming system. Further, in their study they found that the highest yielding soft white winter

wheat genotypes in conventional systems are not the highest yielding genotypes in organic

systems. The other reason for lower yield in organic plots in the present study might be due to the

application of composts based on the assumption that 100% N in them would be available for

take up by plants through complete mineralization during the cropping season. In the study

carried out by Xu et al. (2003) obtained higher crop yield in organic plot compared to

conventional plot when the compost was applied assuming only 70% of total N would be

available during the cropping season

As shown in the result of the correlation coefficient matrix that several

horticultural characteristics like cabbage head width, head height, head wrapper leaf number,

plant height and head firmness are positively correlated to the final head yields. Therefore, these

parameters are important to include in cabbage production plan and most importantly, an effort

has to be made to maximize the value of these characters in order to obtain good cabbage yield.

Nutritional quality of cabbage

Although the dry matter content in cabbage was significantly affected by the

application of different types of fertilizers, there was no significant difference between organic

and inorganic fertilizers. This result is in partial agreement with that of Jakse and Mihelic (1999)

where it has been reported that control and other plots fertilized compost and FYM (farmyard

manure) gave higher dry matter content compared to inorganic plot. In a study carried out by

Sorensen (1999) it was found that at increased N supply, the concentration of dry matter of white

91

cabbage, broccoli and leek decreased significantly. Unlike dry matter, the total soluble solid

(TSS) was more favoured by inorganic fertilizers. As total soluble solid is the main constituent of

the dry matter, these two variables were closely correlated in the present study.

In this study, the nutritional quality of cabbage was positively indicated by the

concentration of vitamin C and negatively by the concentration of leaf nitrate. The result showed

that the concentration of vitamin C was higher but that of nitrate was lower in all organically

fertilized plots than in inorganic plot. The quality of vegetables is generally measured by vitamin

C/nitrate ratio since this indicator is more reasonable as the consumers consider not only the

nutritious substances but also the harmful compounds like nitrate and pesticide residue (Xu et al.,

2003). The concentration of vitamin C, which is wanted to be abundant in vegetables, is taken as

the numerator, and the concentration of nitrate, which is not wanted to be contained in vegetables,

is taken as the denominator. In the present experiment, vitamin C/nitrate ratio was higher in all

organic plots and control than in inorganic plot. The finding of the existence of a negative

correlation between the cabbage head weight and the vitamin C concentration in the present

study, is in agreement with Sorensen (1999). As the biosynthesis of vitamin C is enhanced by

exposing plant to light, the concentration of vitamin C is linearly related to the surface area of the

head (Sorensen, 1999; Lee and Kader, 2000). The several researchers have reported that increase

in potassium fertilization increases vitamin C while increased supply of nitrogen through

fertilizers decreases vitamin C in vegetables (Nagy, 1980; Mengel and Kirkby, 1982; Sorensen

1999). Similarly, Masamba and Nguyen (2008) found significantly higher vitamin C content in

organic Valencia oranges (51.8 mg/lOO g) as compared to conventional ones (43.4 mg/lOO g) on

fresh weight basis. In general, plants produce higher concentration of vitamin C when they are in

stress condition both from biotic and abiotic factors (Conklin and Barth, 2004; Davey et al.,

2006). Therefore, the high concentration of vitamin C in organic cabbage compared to inorganic

cabbage in our study might be due to low rate of N supply by organic fertilizers and/or nutritional

stress encountered by plants in organic plots.

Leafy vegetables like lettuce, spinach, cabbage and collard greens contain high

amount of nitrate than other vegetables. Nitrate accumulation in vegetables occurs when the rate

of nitrate uptake from the soil or translocation to other parts exceeds that rate of assimilation into

proteins, and applying N fertilizers in amount beyond the ability of crops to use them leads to

92

nitrate accumulation (Maynard and Barker, 1979; Prasad and Chetty, 2008). Organic fertilizers

release N very slowly as they have to undergo mineralization through microbial action, hence

they prevent nitrate accumulation in fruits and vegetables (Pascale et al., 2006). Also vitamin Cis

very efficient at preventing the nitrate to nitrite in plant and animal tissues (Chung et al. , 2003;

Nantachit and Winijkul, 2007).

The ingestion of nitrate is known to be harmful to human and animal health

when it changes to nitrite and other metabolites as these compounds are associated with

methaemoglobinaemia and certain cancers (Maynard and Barker, 1979; EFSA, 2008). Nitrate per

se is relatively non-toxic, but its reaction products like nitrite and N-nitroso compounds that form

endogenously in the stomach (at pH > 5.5) by bacteria after ingestion of nitrate are known to

cause gastric, colon and bladder cancers in human (Zhong et al., 2002; Chen et al. , 2004; Prasad

and Chetty, 2008). Nitrite causes methaemoglobinaernia in human and animal, in which nitrite

oxidizes blood's haemoglobin iron (Fell) to methaemoglobin (Felli), and unlike haemoglobin that

carries oxygen throughout our body, methaemoglobin is unable to transport oxygen (Mengel and

Kirkby, 1982). Nitrite is also a precursor of nitrosamines, as nitrite reacts with secondary amines

to form toxic and carcinogenic nitrosamine compounds (Shokrzadeh et al., 2007). Thus, reducing

nitrate content in vegetables can decrease a risk of human illness. In the present study all the

organic plots as well as control produced cabbage with lower level of nitrate than that of

inorganic plot.

Similar result was reported by Xu et af. (2003) in Brassica rapa and Brassica

campestris where vitamin C was higher but nitrate was lower in organic vegetables compared to

chemically fertilized vegetables. Furthermore, Pascale et al. (2006) also found similar result

where the carotenoid concentration was higher in organically grown tomatoes. Sorensen (1999)

reported that in white cabbage, the concentration of vitamin C decreased at increased N supply

and increased plant size but the concentration of N and nitrate in cabbage increased significantly

at increased N supply and increased plant size. Therefore, the lower concentration of nitrate in

organic cabbage compared to inorganic cabbage in our study might be due to slow rate of N

released by organic fertilizers. Therefore, the result obtained in this study clearly showed the

nutritional quality advantages for organically produced vegetables over the chemically fertilized

vegetables.

Chapter 6�

Conclusions and Recommendations�

Conclusions

This study compared the yield and nutritional quality between F I hybrid white

cabbages grown under organic and conventional (chemical) farming systems. The efficacies of

application of composts (solid organic fertilizers) alone as well as their combination with poultry

manure tea (liquid organic fertilizer) in promoting the growth, yield and nutritional quality of

white cabbage were evaluated in comparison to chemical fertilizers. In general, among all the

treatments, the growth of cabbage under organic fertilization was better with higher leaf number

and taller plant height. Similarly, organic plot fertilized with poultry manure compost and poultry

manure tea in 1:3 proportion also had favorable vegetative growth. Plants in other organic plots

where only composts were used considerably suffered from nutritional stress during their

vegetative stage. The cabbages in all the organic plots matured one week earlier than inorganic

and control plots and at the time of harvest, most cabbage heads in organic plots were split and

cracked. In contrast , leaf senescence was more developed with pale -yellow colour in inorganic

plot at harvesting time .

Yield responses of cabbage to fertilization were better on plot to which mineral

fertilizers had been applied. The inorganic plot fertilized with urea, triple superphosphate and

potassium chloride produced the highest cabbage head yield (44.33 ton/ha) in the study where

plants had higher number of wrapper leaves, thicker stem diameter and longer head length and

wider head size. However, this yield was not significantly different from the yield (40.11 ton/ha)

obtained in organic treatment fertilized with PMC in combination with PMT in 1:3 proportion.

This organic plot produced head yield 90.5 % that of inorganic plot. The other organic plots where

the proportions of PMT were lower than 75% produced head yield 74-84 % that of inorganic

fertilization. It is clear from the obtained result that the application of poultry manure compost in

combination with poultry manure tea had favourable effect on increasing the final head yield.

This result confirmed that the organic liquid fertilizer like PMT contains instant plant nutrients

94

and is suitable for short duration vegetable crops. whereas the solid organic fertilizers like

composts have to undergo long process of mineralization to make the nutrients contained in them

available to the plant. Further. the organic treatments fertilized with only poultry manure compost

produced higher yield of cabbage compared to plots fertilized with only cattle manure compost.

This result indicated that poultry manure, in addition to its higher nutrient content, releases

nutrient faster than cattle manure. The result of the correlation coefficient matrix showed that

several horticultural characteristics like cabbage head width, head height. head wrapper leaf

number, plant height and head firmness are positively correlated to the final head yields.

In this study, the nutritional quality of cabbage was indicated positively by the

concentration of vitamin C and negatively by the concentration of leaf nitrate. The result showed

that the concentration of vitamin C was higher but that of nitrate was lower in all organically

fertilized plots than in inorganic plot. Similarly, vitamin C/nitrate ratio was higher in all organic

plots and control than in inorganic plot. This result clearly showed the nutritional quality

advantages for organically produced vegetables over the chemically fertilized vegetables.

Integrated results suggested that it is possible for organic farming to produce

high quality white cabbage with yield similar to that of conventional farming by using composts

(solid organic fertilizers) in combination with poultry manure tea (liquid organic fertilizer) in

organic farming. The application of liquid and solid organic fertilizers in combined package

supplies nutrients to the plant in early stage and advanced stage of crop growth respectively in

organic farming, thus avoiding nutrient stress during the entire cropping period.

Recommendations

From the findings of this study, the following recommendations can be made :

1. The poultry manure tea extracted by steeping poultry manure in water

for 15 days at 1: I weight/volume ratio (w/v) by Bucket Fermentation Method contains the highest

amount of total NPK nutrients.

2. The application of solid organic fertilizers in combination with liquid

organic fertilizer produces higher yield of cabbage than the use of solid fertilizer alone.

95

3. Liquid organic fertilizer like poultry manure tea is better than solid

organic fertilizer in promoting the early growth as well as the final yield of short duration crop.

This may be due to shorter mineralization period of liquid fertilizers or it may be due to higher

microorganism population in them that bring instant mineralization.

4. The use of poultry manure compost @ 4.28 ton/ha FW in combination

with poultry manure tea @ 28400 Llha can produce head yield of F I hybrid white cabbage as high

as 90% of that of conventional farming.

5. The concentration of vitamin C is higher in organically produced white

cabbage than the cabbage fertilized with chemical fertili zers.

6. The leaf nitrate content of organically grown cabbage is lower than that

of cabbage grown by conventional fanning.

7. Integrated results suggested that it is possible for organic farming to

produce high quality white cabbage with yield similar to that of conventional farming by using

solid organic fertilizers in combination with liqu id organic fertilizer in organic farming.

Suggestions for future research

As there were several limitations In our study, we would suggest further

investigations in future study on the following:

1. Use of organic seeds for organic crop while carrying out the yield

comparative study between organic and conventional farming systems.

2. Application of organic fertilizers based on their actual mineralization

capacity during cropping period is suggested for future study.

3. The study on the presence and the number of pathogenic organisms in

organic and conventional vegetables is suggested for future.

4. Analysis of cost and benefit ratio and the economic returns from organic

and conventional cabbage may be carried out in the future study.

5. The similar study can be undertaken to verify the effect of poultry

manure tea on yield and nutritional quality of other cole crops like cauliflower, broccoli, kale, etc.

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Appendices

109

Appendix A

Raw data of individual sample plants for head weight (gram)

III

Raw data of individual sample plants for head weight (gram)

Sample Pants Plot No Total Mean

1 2 3 4 5 I 6 7 8 9 10

Replication/Block -1

TlR1 550 150 690 540 220 390 680 850 200 300 4570 457

T2R1 270 300 510 370 630 430 640 780 570 410 4910 491

T3RI 300 150 670 480 370 750 600 740 210 520 4790 479

T4R1 420 230 680 490 630 570 690 420 860 640 5630 563

T5R1 320 560 480 420 390 400 550 420 520 410 4470 447

T6R1 50 160 100 240 60 20 80 160 390 180 1440 144

T7RI 650 720 510 830 780 480 580 540 750 530 6370 637

ReplicationlBlock - 2

T1R2 370 530 470 540 450 490 510 520 500 400 4780 478

T2R2 460 650 180 640 960 290 230 960 610 340 5320 532

T3R2 280 510 320 170 480 570 730 720 640 470 4890 489

T4R2 420 630 560 480 540 200 600 870 480 790 5570 557

T5R2 620 650 250 800 790 850 940 740 880 780 7300 730

T6R2 370 70 330 20 70 250 270 160 370 150 2060 206

T7R2 330 570 590 480 630 680 740 760 690 960 6430 643

ReplicationlBlock - 3

TlR3 390 440 140 620 570 540 460 660 280 600 4700 470

T2R3 400 380 140 340 440 730 200 870 700 500 4700 470

T3R3 670 150 880 320 570 560 690 260 590 460 5150 515

T4R3 560 650 71 0 440 560 490 590 480 320 750 5550 555

T5R3 430 240 670 480 700 650 880 71 0 850 660 6270 627

T6R3 90 10 130 240 10 370 330 50 600 360 2190 219

T7R3 550 320 650 860 1050 840 790 940 570 570 7140 714

Appendix B

The ANOVA Table and DMRT for cabbage head weight (gram)

113

The ANOV A Table and DMRT for cabbage head weight (gram)

The SAS System 14:16 Wednesday, March 3, 2010

The ANOVA Procedure

Dependent Variable: weight of head (gram)

R-Square Coeff Var Root MSE Head Wt. Mean

0.921563 11.10731 55.12929 496.3333

Source DF Anova SS Mean Square F Value Pr > F

Rep 2 14381.8095 7190.9048 2.37 0.1361

Trt 6 414118.0000 69019.6667 22 .71 <.000 1

Duncan's Multiple Range Test for weight of head (g)

Alpha 0.05

Error Degrees of Freedom 12

Error Mean Square 3039.238

Number of Means 2 3 4 5 6 7

Critical Range 98 .1 102.7 105.4 107.3 108.5 109.4

Means with the same letter are not significantly different.

Duncan Grouping Mean N Trt.

A 664.67 3 7

B A 601.33 3 5

B C 558.33 3 4

C 497.67 3 2

C 494.33 3 3

C 468.33 3

D 89.67 3 6

Appendix C

Weather recorded during crop period (November 2008 to January 2009)

115

Weather recorded during crop period (November 2008 to January 2009)

Temperature CC) Precipitation. MonthlYear MH(%)

Max. Min. Mean (mm)

November 2008 30.6 19.0 24.5 69.8 38.86

December 2008 28.4 15.4 21.2 67.4 11.68

January 2009 29.3 14.4 20.9 6 1.8 0.00

Average/Total 29.4 16.3 22.2 66.3 50.54

Source: http ://www.tutiempo.net/en/Climate/Chiang_Mai/lO-2008/483270.htm

Appendix D

Report of result of the vitamin C content in cabbage head leaves analysis performed at�

the Faculty of Agro-Industry, Chiang Mai�

University on February 03, 2009.�

117

mft1'l11mftl'Ul"ufll ':i ~\llI 'Ulf-l~vUltu<Yi

RW~f)(;\ 6{1'Vin-a-a3-1 bn'H(;\-a 3-I'Vi11't1t11im ihJ\1t'Via.i�•

1\JVl. . .4 l~t1\J T)~m~'Ufi VU'1. . .2552 .

1'UVl 3 L~'il'U T)Wn~\Jfi. ..Yol. Pl .2552 .

~"'11Y1m~I'.m,JtJl

"llUUlIi1'J'flth-3 n:;"'~ltl~ 91'U'}'U 7 ~,}t1l'h\l

..... .~

U11'fll'.J 1-3Y1 . ViLC(mg/100g)

1.n:;V1~htl~ S-1 106

2 . n:; V1~h tl~ S-2 123

3. n:; V1~ l tl~ S-3 96

4 . n:; V1~l tl~ S-4 139

5 .n :;V1~ltl ~ S-5 ' . 117

. .6.n :;V1 ~ ltl ~ 8-6 103. . .

7.n :;V1 ~ltl ~ S-7 106

Appendix E

Abstract of the research paper presented (oral presentation) in 16th

National Graduate�

Research Conference held on March 11, 2a10 at Maej 0 University,�

Sansai, Chiang Mai, Thailand�

119

Effects of Organic and Inorganic Fertilizers on Growth, Yield and Nutritional Quality of

White Cabbage (Brassica oleracea L.var. capitata cv. Cape Horn)

Ganja Singh Rai', Nippon Jayamangkala, Jiraporn lnthasan',

Anan Pintarak, Thawalrat RatanadachanakinJ

Abstract

The field trial with three replications was conducted at Maejo University, Thailand in 2008 to evaluate

the effect of composts with or without poultry manure tea on the vegetative growth, yield and the nutritional

quality of white cabbage (Brassica oleracea L.var. capitata cv. Cape Horn), which was further compared with

that of inorganic fertilizers. The experiment consisted of seven treatments: 5 organic, I inorganic and control.

The amount of added nitrogen was equal in all treatments except the control. Vitamin C and leaf nitrate

contents were used as the indicators of nutritional quality of cabbage. In this study, the highest cabbage head

yield (fresh weight) of 44 ton/ha was recorded in inorganic treatment followed by organic plot fertilized with

poultry manure compost and poultry manure tea in 1:3 proportion with the yield of 40 ton/ha. But these 2

treatments were statistically similar. The other organic treatments produced yields ranging from 31 to 37 ton/ha.

The lowest yield (12 ton/ha) was observed in control. The highest yield produced among organic treatments

was 90% of inorganic plot. As for quality, vitamin C was higher in all the organically fertilized cabbages (106

to 139 rng/I00 g) than in inorganic cabbage (103 mg/l OOg). Photospectrometric analysis of nitrate showed that

all organically fertilized cabbages had lower leaf nitrate (163 to 309 rug/kg) than inorganic cabbage (589

rng/kg). The control showed both the lowest vitamin C (96 mg/l 00 g) and the lowest leaf nitrate (148 rug/kg),

This integrated result suggested that it is possible for organic farming to produce high quality cabbage with

yield similar to that of conventional farming when compost is used in conjunction with poultry manure tea.

Keywords: White cabbage, organic farming, composts, poultry manure tea, vitamin C, nitrate

'Graduate student, M.Sc. Horticulture, Maejo University, Chiang Mai, Thailand; 2Faculty of Agricultural

Production, Maejo University, Chiang Mai, Thailand; 1. Faculty of Science, Maejo University, Chiang Mai,

Thailand

Appendix F

Curriculum Vitae

121

Curriculum Vitae

Name: Ganja Singh Rai

Date of Birth: August 03, 1976

Educational Background: 1996-2000 B.Sc. Agriculture

Marathwada Agricultural University,

Parbhani, Maharashtra, India.

2008-2010 M.Sc. Horticulture

Maejo University, Chiang Mai, Thailand

Work Experience: 2001-2005 Regional Manager

Druk Seed Corporation, Eastern Regional

Centre , Trashigang, Bhutan.

Under Ministry of Agriculture. Bhutan

2006-2008 District Agriculture Development Officer

Dzongkhag Administration, Samdrup

Jongkhar, Under Department of

Agriculture , Bhutan.

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