Effect of the size and stability of soil aggregates on germination, emergence, establishment and subsequent growth of wheat

Effect of the size

^and

stability of soil

^aggregates

on

germinationr

emergencer establishment ^{and subsequent} growth

of

^wireat.

A Thesis submitted ^bY

SMAIL ANSER

B. Ae. Sci. UniversitY of Algiers

The

UniversitY of Adelaide for the

^degree

of

Master

of Agricultural Science'

DePartment

of

^AgronomY

tlaite Agricultural Research Institute'

The

UniversitY of Adelaide

to

June 1982

TABLE OF ^CONTENTS

LIST OF ^TABLES

LIST OF FIGURES

L]ST OF PLATES SUMMARY

DECLARATION ACKNO!¡LEDGEMENTS

SECTION

1 -

INTRODUCTION SECTÏON 2 LITERATURE ^REVIEhI

2.1 2.2

GENERAL

PROPERTIES AND BEHAVTOUR OF DIFFERENT SIZED AGGREGATES

Organic

matter

content Clay content

Bulk density

and PorositY Aggregate

stabilitY

Erosion and

surface crusting 2.3

ENVTRONMENTAL CONDITIONS

IN

SEED-BEDS

Aeration

Irilater

Temperature

2.4

^{AGGREGATE S]ZE AND PLANT GROWTH}

Germination

Emergence

Dry matber production Root growth

Nutrient avallabilitY

^{and uPtake}

SECTÏON 3 FIELD STUDIES

Page No.

1

IV v v1

4 6 6

I

6 9 10 13 13 15 1T 18 1B 1g 21 22 22 x x1

1

2.2.1 2.2.2 2.?.5 2.2.3 2.2,4

2.3.1 2.3.2 2.3.3 2.4.1 2.4.2 2.4.3 2.4.4 2.4 .5

3.1 3.2

INTRODUCTION

MATERIALS AND ^METHODS

26 26 26 2T 28 28 28 29 29 30 30

3.2.1 3.2.2 3.2.3

Site

Design and treatments Procedures

Preparation

of soil

Sowing and management

of the

experiment

3.2.4

Measuremenb

of soil structure

Collecbion of

^samPles

Method

of

^measuring

soil strucfure SoiI

penetrometer

resistance

^and

soil bulk

^density

3.2.3.1

3.2.3.2

3.2.4 .1

3.2.4 .2

3.2.4.3

TABLE 0F CONTENTS Contd.

SECTION 3 FIELD STUDIES Contd.

3.2.5 Soil

temperature and

soil

water

Measurement

of soil

temPerature Measurement

of soil

water

Meteorological

^data

3.2.6 Plant growth measurements

Germination and emergence

Dry weight measurements

Nitrogen measurements Root

length

measurement 3.3 ^{RESULTS AND DISCUSSION}

3.3.1 Soil- structure 3.3.1.1

^Resul-ts

3.3.1.2

^Discussion

3.3.2 Soil

temperature and

water potenlial

3.3,2.1

^Results

3.3.2.2

^Discussion

3.3.3

^{P1ant Growth}

3.3.3.1

^Results

3.3.3.2

^Discussion

SECTION

4 -

GLASS-HOUSE AND LABORATORY EXPERII'IENTS

4.1

LEACHING AND MTNERALISATION OF ^NTTROGEN

4.1.1 Introduction

4.1.2 Materials

and methods

4.1.2.1

Leaching exPeriment

4.1.2.2 Incubation

exPeriment 4. 1

.3

Results

Leaching experiment

Incubation

experiment

4.1.4

^Discussion

Leaching experiment

Incubation

experiment

4

.2

^{CRUST STRENGTH, I/'IATER} CONTENT, AND SEEDLING ^EMERGENCE

Introduction

Material-s and methods Results

Discussion 3.2.5.1

3.2.5.2 3.2.5.3

3.2.6.1

3,2.6.4 3.2.6.2 3.2.6.3

30 30 31 31 32 32 32 34 34 34 34 34 40 42 42 46 49 49 55

5B 58 59 59 60 61 61 69 72 72 74 77 T7 7B 79 81 4

4

3.1 3.2 4.1.4.1

4 .1 .4.2 4.2.1

4 .2.2 4.2.3

4 .2.4

SECTION 5 GENERAL DISCUSSION AND CONCLUSTONS

].

TabIe ñIñ6ãr

3.0 3.1

3.2 3.3 3.4

3.5

3.6

3.7 3.8 3.9

3.11

3.12 3. 13.

3. ¹⁴

LIST OF TABLES

Title

Meteorological data

recorded

at the Ìlaite

AgricuJ-tural Research

Institute

^between

14

^{Lo 25}

JuIy

^.1979.

Temporal change

in Ìinear macro-porosity as affected

by aggregate

size

and

P.V.A.

treatment.

Temporaì- changes

in

mean

intercepted pore lenglh

as

affected by

^aggregate

size

^and

P.V.A.

treatment.

Temporal changes

in

^mean

intercepted

aggregate

length

as

affected by

aggregate

size

and

P.V.A.

treatment.

Temporal changes

in intercepted

^pore

length distribution

expressed

as the proportion of intercepted

macropores

larger than

Xmm, as

affected by

^aggregate

size. All

aggregates were

treated with

P.V.A.

Temporal chânges

in intercepted

^pore

length distribution'

expressed

as the proportion of

macropores

larger

than X mm,

as affected by P.V.A. treatments.

Aggregates sj-zes

were4-Bmm

Bulk density

and penetrometer

resistance as affected

by aggregate

size

and

P.V.A. treatment.

^Both measurements were done on 27

JuIy

(Emergence).

SoiÌ

temperature

at 4

cm

depth.

^Mean

of

temperature recorded

at

0630 and 1500

hours from

17 Lo 25

Jufy

1979.

SoiI

temperature

at

B cm

depth.

^Mean

of

temperature recorded

at

0630 and 1500

hours from

14 Lo 25

July

1979.

Vrlater

potential of different

^seed-beds

at 4

cm depth.

Mean

of

water

potential

recorded

at

0630 and 1500 hours

from

14

to

25

July

1979.

Germination emergence and

survival of

wheat

as affected by soil

aggnegate

size

afrd

P.V.A.

^treatment.

Effect of

aggregat,e

size

^and

P.V.A. treatment

^{on mean} day

of

^emergence.

Effect of

^aggregate

size

^and

P.V.A.

treatments

on total-' dry matter production of

wheat

at tÍtlening

^{( 17 September)}

and strat+ and

grain

yieJ-ds

at harvest (5

December)'

Effect of

^aggregate

size

^and

P.v.A. treatment

^{on seminal}

root length

and diameter

at

emergence

(27

,Suty) and

total root length at tillering

⁽¹⁷ September).

Nitrogen concentration

^and

total nitrogen in tops of

^wheat

plantã at tillering

⁽¹⁷ September) and

maturity (5

^December)

3. 15

LI

LIST 0F TABLES Cont.

Table

Ñu-m-rer

4.1 4.2

4.3

4.4 4.5 4.6 4.7

4.8 4.9

4. 10

4.11

4.12 4.13

4 .14

Title

Percolation of water

through

soil

columns

in relation to the quantity

and frequency

of water

applied.

Percolation of water

through

soil

^col-umns

with

surface

layers of different sized

aggregates

as affected

^by treatment

with

P.V.A.

Total percolation of water

through

soil

columns as

affected

by aggregate

size, P.V.A. treatment

^{and bhe}

quantity

and frequency

of water application.

Summary

of the analysis of variance for total

^amounts

of

water

percolated during the four

week period.

Mineral nitrogen content in dj-fferent sized

aggregates

before leaching

^and

incubation

experiments.

Concentration

of

^(NH/,)-N

and

(N0")-N

in leachates

^from

soi-l

columns,

in retätion to

the-volume

of water

appJ-ied.

Concentration

of

^(NH

columns

with

layers and

nol treated with

L)OI P

-N,

(NO")-N

in leachates

^from

soil differdnt sized

aggregates, treated

.V. A.

Amounts

of

^(NH,)-N

and

(N0-)-N leached from

soils

columns,

in relation toqthe

volume

Ef water

applied.

Amounts

of

^(NH,

)-N and

^{(NO^)-N} leached from

soil

^columns

containing diflerent

sizedJaggregates

treated or

^not

treated

wi-th P.V.A.

Total

amounts

of

^(N0.

+

NH^)-N leached from

soil

^columns

as affected by aggre[ate size, P.V.A. treatment

^and

quantity

and frequency

of water application.

Total

amounts

of mineral nitrogen leached.

Summary

of the analysis of variance for the total four

week period.

Mineral

N

content of soil after incubation of different sized

aggregates

treated

wi.th P.V.A.

Mineral

^N

content of soil as affected by the

temperature and

water content of the soil during incubation.

Effect of

temperature,

P.V.A.

treatments and aggregate

sizes

on

net mineralisation of nitrogen in

Urrbrae red- brou¡n

earth during six

weeks incubation.

Net

mineralisation of nitrogen after six

^weeks incubation.

Summary

of the analysis of

variance.

4 .15

]-II ^.

LIST 0F ^{TABLES Cont.}

TabIe ffim-rer

4 .16

4 :17

Title

Effect of aggregate size, P.V.A. treatment

^{and water} regime on

tñe wát"r contenl of the cnust

and penetrometer

resistance of the soil.

EffecLofaggregatesize'P.V.A.treatmentandwater

regime on ^mean áay

of

emergence,

total

emergence, ^and

dry matter

Production.

Figure

Number

l_v.

LIST OF FIGURES

TitIe

Dry sieve analysis of

aggregates obtained

by rotary sieving into four size

ranges.

Typical thermistor calibration curve for the

determination

of

parame.ter

in

equatì-on 3.0.

Catibration curve for

gypsum bl-ocks.

SoiI water potential - soil water content relationship for

Urrbrae foam.

Distrj.bution of rainfal-I during three

^months

of

the growing season 1979 aL

the lüaite Agricultural

^Research

Institute.

!üater

potential at 4

^cm

depth

^(seed

Ìevel) in

seed-beds made

of

aggregates

4 - B/< 2

^mm

(-)

and

2 - 4/< 2

^mm

(----) at

0630

h

and 1500

h from

¹

4

Lo 25

JuIy.

^(Mean

of

^O 7" and

0.2

%

P.V.A.

treatments)

!üater

potential at 4

cm

depth

^(seed

level) at

0630 ^and 1500

h from

14 Lo 25

JuIy with (----)

^and

without (-) P.V.A. treatments.

^(Mean

of aII

aggregate treatments)

2

3 4

5

6

7

Plate

^Number

10

11

12

13 2

3

4

v

LIST OF ^PLATES

TitIe

Changes

in soil structure with

^time'

The

initial

^aggregate

size

range was

4 -

^B

mm'

^The

soiL

was

untreated with P.V.A.

^{Sampling was done}

from (top to

bottom)

at

sowing (11

July),

germination

(14

Jutyl'

^{emergence (20}

Juty)

^and

tillering

Qo September ) .

Changes

in soil structure with

^time'

The

initi-aì-

^aggregate

size

was

2 - 4

^mm'

Changes

in soil structure with

^time'

The

initial

^aggregate

size

^was

2 -

^{4 mm'}

ThesoilwastreatedwithP.V.A.Samplingwasdone

(from

top to

^bottom)

at

sowing (11

JuIy),

germination

itr* ¡rrvl,

^{emergence (25}

Jury)

^and

tilJ-ering

⁽²⁰

September ) ^.

General

layout of the field

experiment'

Completed

plot wifh thermistors

^{and resistance}

blocks in

^place.

Plots

made

of

aggregales

4 - B/2 -

^{4 mm untreated}

wÍth P.V.A., 5

^days

after

^sowing.

Plots

^made

of

aggregates

4 - B/2 - 4

^{mm treated}

with P.V.A., 5

^days

after

^sowing.

Ptots

made

of

aggregates

2 - 4/< 2

^{mm untreated}

with P.V.A., 5

^days

after

^sowing.

PLots made

of

aggnegates

2 - 4/< 2

^{mm treated}

with P.V.A., 5

^days

after

^sowing.

Plots

made

of

unsorted aggregates

4

^{B mm untreated}

with P.V.A., 5

^days

after

^sowing.

Plots

made

of

^unsorted aggregates

q

B mm treated

with P.V.A., 5

^days

aften

sowiñg.

Collecting of soil cores in steel

tubes wi-th ^a

hydraulic

^ram.

Set up

of the leaching

experiment

in the glass

house'

5 6

7

I

9

14

I i

I

VI

SUMMARY

The

effects of soil structure

^on

the

^growth

of

wheat were examined

in field

and glasshouse

studies.

Fie1d studies

A

field

experiment was conducted on red-brov¡n

earth

^(Urrbrae loam)

to investigate the influence of the size

^and

stability of

^soil-

aggregates on

germination,

emergence establishment and growth

of

^wheat.

Stratified

seed,beds, B cm deep vrere prepared

in small plots

⁽⁵⁰

x

50 ^cm) frorn aggregates obtained

by dry sieving the soil.

The seed-beds

comprised two

layers

each

of 4

cm depth and

the

aggregate

sizes

^were

2-4

^{mm/< 2mm,}

4 -

^{B nm/2mm and}

4 -Brnm/Z - 4mm. Unstratified

seed-beds B cm deep were prepared from unsorted aggregates < B ^mm

diameter. HaIf the plots

were prepaned from aggregates containLng

0.2

%

poly (vinyl alcohoì-), P.V.A. to stabilise the structure.

^{One hundred}

wheat

grains

were sown

at 4

^{cm depth}

in

each

plot.

Germination

of the

wheat was

satisfactory (96.9 t 0.28)

and was

similar in all the plots.

The number

of plants

^which

finally

emerged

and become

established

was

not affected by

^aggregate

size or

^P.V.A.

treatments, but the rates of

emergence

of plants in

seed-beds ^made

of 2 - 4

r¡t(t/< 2 ^mm aggregates and

of

unsorted aggregates

<

B mm, were higher than

in other

seed-beds

(4 -

^B

mm/2-

^4mmand

4 -

^B

mm/<2mm).

The dry

weight of plants af tillerj-ng

^and

straw

and

grain yields at maturity

^were

Iower for plants

^gror¡rn

in

seed-beds

4 -Brnn/Z -

^{4mm and}

4 -

^{Bmm,/< 2mm}

than for ptants

^grov{n

in

seed-beds

2 - 4

^mm/<

2

^{mm and unsorted aggregates}

< B

mm.

^Treatment

of the soil with P.V.A.

decreased

dry matter

^production and

grain yield

although

the

decreases were

not

al-ways

significant at

P

< 0.05.

^The

plots

where

greater dry matter

and

grain yield

was obtained

þ

il_lr''I I

I I

vf ^l_

wet'e those which gave

the earliest plant

^emergencc and where fhc

ptants

had

the highest concentrations

^and

total content of nitrogen.

Geometrical

macro-structure of the surface layer of the soil

ü¡as measured

at

sowing,

germination,

emergence and

tillerJ-ng,

on sections

cut

through ^bJ-ocks

of resin

impregnated

soiI. Total

macroporosity and mean pore

size at 0.5

cm depth decreased

during the eight

weeks

following

sowing

of the

wheat

particularly

where

the soil

^had

not

^been

treated with p.V.A..

_The lowest macroporosity occurred

at

emergence,

3

^weeks

after sowing. Total porosity

^{and mean pore}

size

were

consistently higher in the surface soil of

seed-beds

with

aggregates

initialty 4 -

^{B mm}

Ín

diameter

than in

seed-beds

2 - 4

^mm

dianeter aggregates. SoiÌ treated with

P.V.A. had

greater porosity

and

greater

mean pore

size

than untreated

soil at aII times of

measurements.

Measurements made

at 4

cm and B cm depth

in the soil-

from

sowing

to

^emergence

of the

wheat showed

that soil

temperature blas

sirnilar in aII the plots. Soil water potential at 4

cm depth was

higher

^(less

negative) in plots

^made

of

aggregates

2 - 4

^{nn/Z rnm}

than in plots

^made

ofaggnegates 4 -Bnm/Z

mmand

4 -

^B

nn/Z- 4mmdiameter.

Meteorological

factors

had

a greater influence

on temperature and

water in the soil

^than

did the treatments.

Regression

analysis

showed

that soil

temperature was

most

cfosely related to the relative humidity of the air

and

to rainfall

which

soil water potential

was most

highly correlated with water

^pressure

deficit.

Surface

crusting

and seedlj-ng emergence

The

effect of surface crusting of the soil

on emergence

of

^wheat

was

investigated in a

glasshouse

experiment.

Seed-beds

consisting of

B cm depth

unsorted (<

B mm)

soil overlain by 4

^cm

of < 2, 2 - 4

^or

4 -

^{B mm diameter} aggregates were

prepared.

!'lheat v,Ias sovrn

at 4

cm depth

in air dry soil

^and

the water content of the soil

^{was then}

adjusted

^to

vIIl_.

20 % by v¡eight

by spraying

^{25 mm}

ofrrainr onto the soil

^strrface.

Different soil water

regimes were produced

by covering the soil in,

two

sets of pots with a plastì-c

^{mulch O atld}

3

^days

afLer the pots

^were

watered,

while the soil in the third set of pots

^was

left uncovered'

^As expected,

the strength of the soil

^{as measured}

by

penetrometer resistance

at the time of

^emergence

of

wheat i-ncreased

with

decreasing

water

content

of the soil-.

^The

strength of the crusl

^{which formed from}

small

^aggregabes

(<

2 mm) was

signi-ficantly greater than those

^{formed from}

the larger

aggregates. In

^some

instances, treatment of the soil with poly (vinyl

alcohol-)

significanbly

^lowered

the strength of the crust. In

^general

emergence

of the

wheat decreased

with

decreasing

soil water content

^and

with increasing crust strength.

^{Emergence was markedJ-y decreased}

or

no emergence occurred

as crust strength

increased from 90

to

341 kPa'

Production and ^movemen

t of mineral ni

trogen

in

beds

of different

^sized

soil

aggregates

Aggregates

< 2, 2 - 4

^and

4 -

^{B mm} dj-ameter were

subjected to aerobic incubation at

¹

2 or

²⁴ %

water content for up to six

^{weeks under}

two

fluctuating

temperature regimes

viz alternating

¹²

h periods at

⁵

and lOoC

or jZ

^and

24oC.

^Nel

mineralisation of nitrogen

vJas

higher at

24 % wa1er

content

and ¹ 2/24oC than

at lower water conlent

and lower temperature

regime.

^However

the

^amounts

of

^{ammonium and}

nitrate

^produced

during the six

^week

incubation period

^were

similar in

aggregates

of aII sizes,

and were

not affected by treatment of the soil wifh P.v'A"

Stratified

^beds

of

aggregates ^{(B cm deep)}

underlain

^by

undisturbed cores

of subsoil

^{(20 cm} deep) were

set up in leaching

^tubes' The'beds vrere

constructed as

^described

for the field

experiment described above and ^ammonium sulphate ^{was added}

to the lower layer of

aggregates

in

^each

tube.

The columns were leached

with rain water at various rates

and frequencies

of apptication

^and

the

vol-ume and

mineral nitrogen

^content

]-X

of the

leachates were detertnined

at

weekly

intervals for four

^weeks'

Treatment

of the

aggregates I^¡ith

P.V.A. permitted greater percolation of water

and

greater loss of mineral nitrogen

from

the soil

^columns'

partj-cularly

where

the surface layer of the

^bed comprj-sed coarse

aggregates.

^The

size of the

aggregates had

littte effect

^on

the total

amount

of

^{ammonium and}

nitrate

leached where

the

beds were

not treated with

^{P.V. A.}

Under

the conditions in

which

the field

experiment was

carried out

aggregate

size

had more

effect

^on

plant

emergence, establishment ^and growth

of

wheat

than stratification of aggregates.

^Aggregate

size

and

aggregate

stability affected nitrogen

^uptake

by the plants.

Aggregate

size

and aggregate

stability

^{may have had an}

effect

^on

leaching of

nitrogen in the field.

x

DECLARATION

This thesis contains

^no

material

which has been accepted

for the award of any other degree or diploma in any university. This thesis contains no material published previously or written by any other person, except where

due

reference is made in the text of the thesis.

May 1982. ^, Smail ^Anser

I

I

i I f

I

I

I I

xt

ACKNOVüLEDGEMENTS

I wish to

thank my

supervisors Dr.

^A.M.

Alston

^and

Mr.

^E.D.

Carter for their help

and guidance throughout

this project. I

^also

thank

other

^members

of the ltaite Agricultural Research Institute' in particular, Dr. J.M. Oades, Dr. J.S. Hewitt, Dr. D.l/ü. PuckrÍdge' J.A. Denholm, C.M. Rivers, steve challis, Mr.. Brian Palk and all the

I'laite library staff. This thesis

was

carefully

^typed

by Mrs. J. Howe.

The

financial-

support

of the Australian Development Assistance Bureau is acknowledgecl.