Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author.

THE EFFECTS OF DRILL COULTER DESIGNS

ON S O IL PHYS ICAL P ROPERT IES AND PLANT

RESPONSES IN UNTILLED S EEDBEDS .

A The s i s presen ted in partial fulfillment

of the requirement s for the degree of

Doctor of Philosophy a t

Massey Univers i ty

Palmers ton North

New Zealand

by

TRAN VAN MAI

July 1 9 78

· tto_ a (

in Vietnam

ABSTRACT

CHAPTER

TABLE OF CONTENTS

1 . GENERAL INTRODUCTION

2 , THE INTERACTION OF SOIL AND DRILL COULTER PASSAGE

2 . 1 Introduction and review o f literature

2 . 1 . 1 Soil water and conipact ion

2 . 1 . 2 Soil air and compact ion

2 , 1 . 3 Soil temperat ure and comp act ion

2 . 1 . 4 Soil bulk dens ity , compact ion and pore sys tem

2 . 1 . 5 Soil s trength and compact ion

2 . 1 . 6 Soil s tress and compact ion

2 . 1 . 7 Draft

P AGE

1

4

6

7

9

10

1 2

1 4

2 . 1 . 8 Visual assessments o f mac rostructural changes i n soils 16

2 . 1. 8 . 1 Thin sect ions 1 6

2 . 1 . 8 . 2 Scanning electron micros cope techniques ( S . E . M . ) 18

2 . 1 . 9 Func t ional requirement s o f drill coul ters 1 8

2 , 2 Experimental methods 2 3

2 . 2 . 1 Soil b in experiments 2 3

2 , 2 . 1 . 1 S i te and soil type selection 2 3

2 . 2 . 1 . 2

2 . 2 . 1 . 3

1 . Fie ld capacity and soil dry b ulk density

2 . Permanent wil t ing point

3 . Availab le water capac ity

4 . Soi l porosity

Soil b in collect ion procedures - post col lection

preparat ion of turf blocks

Experimental desi gns

24

24

25

25

29

30 V

2 . 2 . 2 Drilling o f turf blocks

2 . 2 . 2 ,1 Pre drilling

2 ,2 . 2 . 2 . Drilling operat ion s

2 . 2 . 3 Fiel d experiments

2 . 3 Measurements

2 . 3,1 Measurement of soil compact ion b y soil bulk density

2 . 3 . 1 . 1 Core sampling method

2 . 3 . 1 . 2 Small core sampler

2 . 3 . 1 . 3 Procedures

2 . 3 . 2 . Mechanical res istance of soil

2 . 3 .2 . 1 Des crip t ion of the measur�ng equipment

2 . 3 . 2 . 2 . Procedures

2 . 3 . 3 The ins t ant aneous zone of influence (soil pressures )

2 . 3 . 3 . 1 Des cription of the measuring equipment

2 . 3 . 3 . 2 . Procedures

35

35

35

36

39

39

39

40

40

4 1

4 1

4 5

4 8

48

49

2 . 3 . 4 The assessment of macros tructural changes by visual methods 5 3

2 . 3 . 4 . 1 Materials and methods 5 3

a . Thin sect ioning - impregnat ing 5 3

b . Electron micros copy 5 7

2 . 3 . 5 Dra f t Measurements 59

2 . 3 . 5 . 1 Des cription of the measuring apparatus 59

2 . 3 5 . 2 Procedures 62

2 . 3 . 6 Assessment of the zone of disturbance on the soil surface 62

3 . THE RESPON SE OF PLANTS AND ROOTS TO CHANGES IN SOIL PHYS ICAL 66 CONDITIONS WITHIN A SEED BED

3 . 1 Introduct ion and revi ew 66

3 . 1 . 1 The e ffects of soil bulk density on roo t growth 69

3 . 1 . 2 The e f fect of mechanical soil s trength on root growth 7 1

3 . 1 . 3

3 . 1 . 4

3 . 2

3 . 2 . 1

3 . 2 . 2

3 . 2 . 3

3 . 3

4 .

4 . 1

5 .

5 . 1

5 . 2

5 . 2 . 1

5 . 2 . 2

5 . 2 . 3

5 . 3

5 . 3 . 1

5 . 3 . 2

5 . 3 . 4

5 . 3 . 4 . 1

The e ffect of interactions amongs t s oil mois ture ,

s oil compact i on , s oil s trength on r oot growth

The e ffe ct of direct drill ing on crop yie lds

Experimental methods use d in root studies

Lab orat ory tillage bin experiment s

B ox experiments

Fiel d e xpe riments

Seedl ing emergence

THE INFLUE NCE OF SOIL FAUNA IN DIRECT DRILLED SOIL

Review

OBJECT IVES AND RESULTS OF INDIVIDUAL EXPERIMENTS

General objectives

a .

b .

Lab ora tory expe riments

Field expe riments

Expe rimen t 1 .

Obj ect ive s

Re sul t s and discus s i on

a . Bulk density (pe rmanen t de f ormation)

Resul ts

b .

c.

d .

e .

Discuss ion

S oil strength (permanent de formation)

Re sults

Dis cussion

S oil press ure ( instan tane ous de formation)

Results

Di s cussion

Draft force

Results

Discussion

Root studies

Re sults

Dis cussion

Brie f summary of Expe riment 1 .

Experiment 2 .

Obj e c t ives

Resul ts and discus s i on

Macros truct ural chan ges of s oil unde r compre ssion

Resul ts and discus s i ons

7 6

77

78

78

81

81

81a

82

82

83

83

83

83

85

85

86

88

94

101

103

107

108

108

108

1 1 7

1 1 7

a . Thin sectioning

b . Electron micros cop ic technique

5 . 3 . 5 Root responses

Results

Discuss ion

5 . 4 Experimen t 3.

5 . 4 . 1 Object ives

5 , 4. 2 Resul t s and discuss ions

a . Bulk dens ity and soil streng th

Result s

Discuss ion

b . Soil surface dis turbance

Resul t s

Discus s ion

c. Root responses

Resul ts

Dis cus s ion

5 . 4 . 3 Brief summary

5 .5 Experiment 4 .

5 . 5 �1 Obj e c t ives

Result s

Discus sion

5 . 5 . 2 Brief summary

5 . 6 Exper iment 5 . ( f ield experiment )

5 . 6 ,1 Obj ect ives

Result s

Discussion

5,7 Experiment 6 . ( f ield exper iment )

5 . 7 . 1 Obj e c t ives

1 1 7

1 2 3

1 30

1 35

1 35

1 36

1 36

1.39

1 43

1 5 2

1 5 4

1 5 4

162

163

1 6 3

1 6 9

169

5 . 7 . 1 ( cont inued)

Results

6 .

7 .

8 .

Dis cuss ion

a . Root and herbage dry we ights

b . Seedling emergence

c . Earthworms

d . Yields

SUMMARY AND DI SCUSSION

A. Equipment arid measuring technique

B . Soil physical changes and plant and root response

a. Permanen t deformat ion data

Bulk density

So il s t rength

b, Coult er operat ional forces

c . Instantaneous dis s ipat ion of soil s tress

d . Interact ions

e . The e f fects o f coul ter shapes on root growth

CONCLUS IONS

REFERENCES

ACKNOWLEDGEMENTS

APPENDICES

1 8 4

184

1 8 5

186

1 8 7

1 8 7

1 9 2

1 9 2

1 9 5

1 9 7

200

2 0 0

206

2 0 9

LIST OF FIGURES

1 . Soi l mo ist ure content an d s uct ion curve of

Toko rnaru s il t loam

la . Th e pos i t ionin g o f t reatmen t b ins on the

lb .

l e.

3 .

4 .

5 .

6 .

7 .

8 .

9 .

10 .

11 .

1 2 .

1 3 .

14 .

testing ri g

Th e expe riment layout

The randomised blo ck de s i gn

Turf block ext raction procedure - Part 1 .

Turf b lock ext ract ion procedure - Part 2.

Turf blo ck ext raction p rocedure - Part 3 . .

The expe rimental design o f 1 2 bins

The chi s el coul ter assembly

The t ri ple disc coul te r assembly

The mul t i point pene t rome t e r

The meas uring pos i t ions o f the pene t romete r

The mul t i po int penet romete r a t work

Ty pical soil st ren gth curves obtained with the

mul t i po int penet rome t e r a ppa ratus

Hol ding magnet s with adj us table clamp

The so i l pressure s ens ing tube assembly

The po sit ioning of the press ure tube in the

t urf block

15a , b & c . Equipment used in thin sec�ioning

1 6.

1 7 .

1 8 .

19 .

20.

21 .

22.

The s ide view o f d raft measurin g apparatus

Rea r view of moving gan t ry and tool tes ting

a ppa ratus

Pen-et rat ion of s oul te r assemb l i es by dead

we ights

The ins t rumentat ion fo r moni t o ring the zone

o f in fluences around co ulye rs

The inte rrelat ionships o f soi l phys ical

parameters an d root g rowth unde r

compact ion

Ext ract ion of samp les fo r roo t s t udies with

pe rplex pin boards

So il resistan ce at eight s i de of the t ri ple

disc and

PAGE

28

3 0e

30f 3�

31

3 2

3 3

34

38

38

44

45

4 6

4 7

50

50

5 2

54

61

61

64

65

68

7 9

9 1

di s coulter grooves

2 3 . Variat ion o f s oi l resistance a t wither s ide of the t riple

2 4.

2 5 .

2 6 .

d i!sc and chisel coulters

Sidewall p ressure detected a t 30mm away from the groove

Pressures detected at 50mm away from the base o f the groove

The effects o f direct drilling coulter designs on lupin and

dry weigh t (Expt 1 . )

9 2

9 7

9 8

104

2 7 . The e ffec t s o f d i rect drilling coul ter designs on lupin root 105

length (Expt 1 . )

2 8 . The e ffects o f direct drilling coul t e r designs on wheat root 1 0 6

2 9 .

30 .

3 1 .

32 .

33 .

34.

35 .

36 .

3 7 .

38.

3 9 .

40 .

dry weight ( Expt 1 . )

Soil resis t ance a t ei ther s i de of the t riple disc and

chisel coulters

Variat ion o f s oil resi stance at ei ther s ide of the t riple

d js c and chisel coul ter

Thin section s amp ling sites

Sect ions o f soil in the ir original condition

Soil sect ions t aken at lOmm from the s oil/ trip le d is c

coulter interface

Soil sect ions taken at lOmm from the soil/chisel coulter

interface

Soil sect ions t aken at 20mm from the soil/ triple dis �

coulter interface

Soil sect ions t aken at 20mm from the soil/chisel coulter

interface

Soil sections t aken at 30mm from the soil/ triple disc

coulter in terface

Soil sect ions t aken at 30mm from the soil/chisel coulter

interface

Subsampling posit ions for elect ron micros copic s t udies

Mic rograph (xl70) of soil in "undisturbed" condition

1 12

1 1 3

1 18

1 1 8

1 19

1 19

1 2 0

1 2 0

1 2 1

1 2 1

1 2 5

1 2 5

4 1 .

42 .

Micrograph o f soil / t riple disc coulter interface

Micrograph o f soil/ chisel coulter int erface

43 . Micro graph taken a t 10-20mm away from the soil/

trip l e disc coulter interface

44. Micrograph t aken at 10-20mm away from the soil/

chisel coul ter interface

45 . Micrograph taken a t 20 -30mm away from the soil/

tripl e d isc coul te r interface

46 . Micrograph taken at 20-30mm away from the soil/

chisel coulter interface

47 . Micrograph taken at the base o f the t riple dis c

coulter

48 . Micrograph taken at the base o f the chisel coult e r

49 .

50 .

created groove

The e ffects o f direct drilling coulter desi gns on

lupin root dry wei ght (Exp t 2 . )

The effects o f direct drilling coulter desi gns on

lupin root length ( Expt 2 . )

5 1 . The e ffect s o f direct drilling coulter designs on

wheat root dry weigh t

5 2 . The e f fec ts o f direct drilling coulter designs on

soil s ur face disturbance

5 3 . The t riple disc coul ter has a greated longi tudinal

soil/ coulter contact

5 4. The chisel coulter sha t ters soil abruptly on both

sides of the coul ter

55 . Dis torted roo t growth o f a lup in seedling in the

triple disc groove

56 . A lupin roo t which has been deflected at the base o f

a triple disc groove

5 7 . Lupin root c ross-section grown in uncompacted soil

126

1 2 6

12 7

12 7

12 8

1 2 8

1 2 9

12 9

132

133

134

1 40

1 42

1 42

1 48

149

150

58 .

5 9 .

60 .

61.

62 .

63 .

64 .

65 .

Cortex p ortion of lup in root cross-sect ion

flat ten ed because of hard s oil

P oor s eedling es tablishment in the t rip le

disc c oult er t reat ment

Better s eedling es tablishmen t in the chise l

coul t er t reatment

The chara c t eristic shaped groove of the t rip l e

d i s c c oul t er

The characteri s t ic s ubsurface sha t t ering of the

chisel coul t er

Cl os e- up s eedling emergence with the smeared

V-shap ed gr oove

E ff ect s of smearing on se edling per formance

from various shap es of gr ooves

The interrelat ionship between s oil moisture

c ontent , s oi l bulk density and

count er t yp e in direct drill ed silt

l oa m

15 1

15 3

15 3

15 6

15 6

15 9

15 9

2 01

LIST OF TABLE S

PAGE

1. The me chani ca l p ropert ies of soi l 2 6

2. Values o f p robe pressure at which roo t e longat ion ceas ed 7 5

3 . The sequence o f roo t related measurements 80

4. The effe c t s of dri l l coulter des igns on soil bulk dens i ty

at groove base

5 , The effects of coulter des i gns on soil st rength around the

groove

6 . The e f fects of coulter des igns on soil s tr •ngth on e i ther

s i de of the groove

7 . The e f fec ts o f coulter designs in maximum oil pressure at

the base of the dril led groove

8. The effects of coul ter des igns on maximum soil pressure

at the sidewa l l of the dril led groove

86

88

9 0

9 4

95

9 . Draft forces required by two dri l l coul ter designe in a s i l t

loam a t 2 3% w/w mois ture content 10 1

1 0 . The effects of drill coul ter des i gns on soil density around

th8 groove (Expt 2 . )

11. The e f fects of drill coulter des igns on soi l stre�gth

12. The e ffects of d r i l l coul ter des igns on soil strength on

e i ther side of the groove

109

1 10

1 1 1

1 3 . The e f fects of d r i l l coul ter designs on maximum soil press ure

at the base of the dri l led groove (Expt 2 . ) 1 1 4

14. The e f fects o f dri l l coul ter des igns on maximum s oi l press ure

a t the s i dewa l l s of the groove

15 . The e ffects of d r i l l coulter designs on draft force

1 14

1 16

16. The �ffects on s oil compact ion of mult iple runs with

17.

18,

vibrat ion rollers

The e f fects of dri ll coulter des igns on bulk density

The effects of drill coulter des igns on soil strength

19. The e f fe c t s of drill coulter des i gns on root propert ies of

lupin seedl ings sown in we t and dry soil

20. The e f fe c t s of dri l l coulter des i gns on wehat seed lings a t

day 4 i n we t soil

21. The e f fects of direct drilling groove fo rmation techniques

on seed ling emergence

22. The e f fects of shape , smear, compact ion and cover of d irect

dri lled grooves on wheat and lup in plants

23. The e f fects of s o i l and drill coulter des igns on lupin

and wheat roo t d r y wei ghts in f ield condit ions

24. The interaction o f soil and coult e r on lupin and wheat

root dry wei ght in field cond i ti ons

25. The e f fects of d r i l l coult e r des igns and soil on root and

shoo t growth of wheat and lupin crop s at 3 weeks

(ma in t rea tmen t ef fec ts )

26. The interact ion of direct dri ll ing coulter designs and soi l

135

137

138

146

147

160

161

167

168

171

compac t ion on root and shoot growth of wheat and lupin 172

crop at 3 weeks ( interac t ions )

27. The ef fects of d r i l l coult e r des i gns and compac t i on on root

and shoo t growth of wheat and lupin crops at 5 weeks 173

( main t rea tment ef fec t s )

28. The e f fects of d i rect dri l ling coul ter des igns and soil

compact ion on roo t and shoot growth of wheat and

lupin crops at 5 weeks ( interac t ions )

29. The ef fec ts o f d rill coulter des i gns and soil compac t ion on

174

root and sho.o t growth o f wheat and lupin crops at 7 weeks 175

(main t reatment effe c t s )

30. The e f fects of drill coulter designs and soil compact ion on roo t

and shoot growth o f wheat and lupin crops at 7 weeks

( interac t ions )

31 . The effects of drill coulter desi gns and soil compact ion on

seedling emergence of wbeat and lupin (main t �eatment

e f fect s )

32. The e ffec t s o f drill coulter des igns and soil compac tion o f

wheat and lupin ( interact ions )

3�. The e f fects o f drilling coul ter desi gns and soil compact ion

on Earthworm populat ion (main treatment e ffects )

34. The e f fects of drill coulter designs and soi l compac tion on

Earthworm popula tion (interact ion effects)

35, The e ffects o f drill coulter des igns and soil compact ion on

Wheat yield

36, The effects of drill coulter des igns and soi l compaction on

lupin yield (main trea tment e ffects)

37. The e ffects of drill coulter des igns and soil compaction on

lupin yield (interac tions )

38. Summary o f the effects of drill coulter des igns on bulk

dens ity , poros ity and soil s t rength

39. Summary o f forces req uired for coul ter penetra t i cn of two

direct drilling coul ters

40. Summarized e ffec ts of di rect drilling coulter de�igns on soil

pres s ure

-ooOoo -

176

177

178

179

180

181

182

18:

19·

19

1S

1.

'2.

3.

4 .

5 .

6.

7 .

8 .

9 .

10.

11.

LIST OF APPENDICES

a . Res ults o f soi l bul k dens ity measuremen t Exp t . 1.

b . Res ults o f soi l bulk den s i ty meas urement Expt . 2 .

c. Results o f soil bulk d en s i ty measur ement Exp t . 3.

Soil s tr ength data .

Dra ft force data .

Roo t dry weight p er p lan t basis .

Est ima t ion o f evapora t ion from t urf blocks under rain canop i es .

Cal ibra t ions .

Det ermination o f roo t p ercentage in soil co res .

��t eorological data .

Brief descrip t ions o f so il bins , tes t ing appara tus and coult er

designs .

E quipmen t .

Comput er lis tin gs .

-oo Ooo-

ABSTRACT

Dur ing the process of direc t drilling different shaped drill coul ters

have been ob served to creat e different micro-environments a t the seed

zone . This study has been to examine possible changes in soil

structure and the s tate of soil compact ion around the groove, which

in t urn might affect root penetrat ion .

Several methods and pieces o f equipment were developed to inve s t igat e

t h e influence o n the soi l of two contra sting coul ter shapes . These

were the commerc ially-avai lable triple disc coult er and an experimental

chise l coulter . To measure soil bulk density in the drilled groove

zone , a small core sampler was des igned and tested . Soil strength

wa s a ssessed using a modif ied mul t i-point penet rometer which could be

in serted vert ically into t he soil or normal to t he groove walls.

The instantaneous and permanent soil pressure zone of influence

around the groove , which wa s created by the passing of the coulters ,

was monitored using a l iquid-fi l led tub e with a terminal d iaphrapnand

a minipressure t ransducer .

Macro scopic visual asses sment of the compac t ion of soil a t the seed

l evel was undertaken using a free z ing sampl ing t echnique which

fac ilitated thin section subsamples to be studied by photographic

t echniques. In addi t ion, 3 mm3 subsamples were taken dire c t ly f rom

the grooves for electron microscopy study .

S upplementary measurements included draft force and the coulter­

p assage-disturbance-zone at the soil surface using a load cell and a

d i splacement t ransducer respec tively .

Wheat and lupin seeds were sown to s tudy the e ffec ts of so il changes

on root gro wth of a f ibrous and tap root system .

The data sugges ted that the triple disc coulter tended t o compac t

well-defined zones around the groove while the chisel coulter produced

no apparent compac tion .

Such soil compaction in a moist silt loam of init ial bulk dens ity less

than l . lg/cc d id not resul t in any apparent differences in plant r oo t

responses between the t wo coulter types . I n a drier , harder soil

ho wever (greater than 1 . 32g/ cc) there appeared to be a c lear

d i sadvantag� from use of the triple disc coul t e r in this respect .

With lupin , root growth was restricted-and deformed from use o f the

lat ter coulter, while in the case of wheat , seedl i ng emergence was

r e stricted in comparison with the chisel coul ter .

Smearing was found on the groove wall in moi s t so il with the triple

disc coulter but the experiments were not able t o show any mechanical

restriction to root and plant development arising from the smear .

In the f ield conditions , in contra s t to the laboratory conditions

( where seedling performance and root growth were bet ter with the

chisel coulter in almo s t all of the tested conditions except with

moist and loose soil where it was equivalent t o the triple disc) any

localised compaction o f soil by the triple disc c oulter (particularly

at and near t he base of the groove) appeared to be compensated by

o ther factors (weathe r , earthworms e tc . ) during the plan t 's full

g rowth cycle .

Compac tion and mechanical impedance i n isolation did not appear to be

solely responsible for the root and plant growth responses .

A physiological study o f soil moi sture transpor t proce ss and soil

water vapo ur availability in the see d zone should therefore be the

subj ect of f urther studie s.