1 WAITE INSTITUTE
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THE EFFECT OF GYPSUM ON THE CIT]IMICÂL AND PIITSICAL PROPERTIES OF À RANGE OF R}ID BROIüN EÀRTHS
Thes is sul-¡mit,t,ed by
I.To GRIETìSON B.Ag.Sc, (ttons)
f or t,he rlegree of
MASTER OF ÀGRICULTURAL SCIENCE
in t,lle
UNIVERSITY OF ÀDELAIDE
Nort,hfie It[ Rcsearch Laboratories Department, of Agriculture
ADELAIDE.
Àugust. 1975
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CONT],T{TS
SiIM}IARY iJTÂTEMEßJT
¡.CKNO\/LEDGEMENTS
CIlÀPTER 1. Introduction
CFiÀPTER 2. Literature Review 2"1 Definit,Lons
2.2 Clay Water Interact,ion 2.2.1 ÂtLs orpt,i on o f l¡a,ter
sh/e I ling
2.2.2 Effect of electrolyte concentration
2.2.3 Effect of catiorl va,lency
2.2.4 Monovalent ancL d.ivalent, Syst ems
2.) Stabilizing Forces 2.3.1 Organic Matter
2.3.2 Electrostat,ic attraction 2.3.3 Mac[eIung forces
2.).4 Iron and. Aluminium Oxid-es
and Hydroxid.es
2.4 Effect, of Different Cations on the SoiIs Physical Properties 2u5 Á.rnend.ments used. to d.isplace
exchangeable sod.ium
2.6 Effect of Gypsum on Soil
Physi cal Prcrperties in Aust,ralia 2.6.1 New South lrrales
2.6.2 Yíctoria
2.6.3 l{est,ern Aust¡alia 2.6o4 South Australia 2.7 Summar
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CH¡,PTER 3
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CHÄPTER 4.
Method s
3.1 Mechanical Properties 3.2 Chemical Properties
3.2.1 Tota1 So1uble Salts ancl PH
3.2.2 Calcium Carbonate 3.2.3 Organic Carbon
3.2.4 Cation Exchange measurements
J.3 Physical Properties
3.).1 Bulk DensitY and SoiI
Water Content,
3.).2 Âggregat,e Cohesion
3.3.3 Aggregate StabiIitY ).3.4 Rai.nf aIl Simulation J"3.5 Crust Shearing Strengt,h
Initial Survey
4"1 Experiment,al 4.1 .1 Soils
4.1 .2 Sampling 4.1.3 AnalYsis
4.2 ResuIt,s and. Discussl-on
4.2.1 Relation between ind ivitlual soil tests antl propert,ies
4.2.2 Effects of Interact,ions of soil propert,ies on
physical t'ests
4.2.2.1 Àggregat,e StabilitY 4.2.2.2 Cohesion
4.2.2.3 Bulk DensitY 4.3 Comparison rrit,h ot,her work
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CHAPTER 5.
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Fielcl Experiments 53
5.1 Experimental 53
5.2 Sampling 54
5 .2.1 S oi Is 54
5 .2.2 Herbage 55
5.3 AnalYsis 55
5.).1 Mech¿rnical ÀnalYsis 55 5.3.2 Chemical AnalYsis 55 5.3.3 Physieal AnalYsis 55 5.4 Results antL Discussion 56
5.4.1 Eff ect,s of GYPsum on Soil
Chemical Prõþerties 56
5 .4.1 .1 pH 56
5.4.1 .2 Totat Soluble Satts 58
" 5.4.1 .3 Organic Carbon 59 5.4.1.4 Exchangeable Cations 59
5.4.1 .5 Sotuble Salts 65 , 5.412 Effect of GYPsum on SoiI
, Physical PiõPerties 65
5.4.2.1 Àggregate StabilitY 65
5 '4'2
'2 lîå"f,:i*'iiä"å:lilT* 68
,.4.2.3
Dry shearing strength 71' 5.4.2.4
BulkDensit'Y
715.4,3 tflå;ilr.t
GYPsum onDrY
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5.5 Conclusions 73
CTIAPTER 6. Fielcl Test
6"1 Experimental
6.2 Methocl
6.2.1 Calculation of the Dispersion rndex (or)
6.3 Results and Discussion
6.4 Comparison with other work
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79 79
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CHAPTER 7. Conclusions
CHÂPTER 8. Bibiography
ÀPPENDICES À, B.
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LTST OF TABLES
The tl ickness of the clouble layer of Clays saturated with monovalerrt cations in a
scrLution of 121 electrolyte of various matric potentials.
Rainf al I intensity f or dif f erent' apert'ures, water pressures and nozzle sizes,
Uniformity "oefficient, for d-ifferent aperatures
w¿lt,er pressures and. nozzles sizes.
Ivled.ian clrop d.iameter f or d-if f erent apertures, water pïessures and nozz\e sizes
Summary of results of Physical tests and'
Chemica.l- Ànalyses for 28 sites
The significance of coefficient's between
phys j ca.ì- tests.
The significs,nce of coefficients bet'ween
chemica t and mechanical proper-Uies.
The significance of coefficients between physical tests on soils ancl their mechanical
and. chemical ProPert,ies.
coefficients of Iinear regïession of chemical
and mechanical propert'ies on result's of physical tests.
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Effect of physical
percentage of organic carbon on test,s.
Ef f ect,s of exchangeable s od-ium percentage on physical tests.
SoiI si-te numbers in relation to ESP range antl EMgP range
Analysis of the seed gypsum used.
Effect of d.ifferent, gypsum epplication rates on the exchangeable soclium percentage '
to a d.epth of 3Ocm by 1973 (18 months
after application).
Effect of tlifferent gypsum application rates
on the exchangeable soclium percent'age t'o
a, depth of 3Ocm by 1974 (3O months after apptication).
Effect of clifferent gypsum application rates on the exchangeable ma,gnesium percentage t'o
a, clepth of 3Ocm by 1973 (18 months af ter application).
Effect, of ttifferent, gypsum applicat'ion rates
on the exchangeable magnesium percent'age to
a, ctepth of 3Ocm by L27! (30 months after application).
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Aggregate stabilitv (rtn) for sites showing response in 1973 to gypsum adclition
(18 months previously)
Effect of gypsum on aggregate stability in
1974 in t,he Soil Prof i le 30 months after applicat,ion (responsive sites only).
Effect of gypsum treatment on the total
amount of run-off fronr rainfall simulation (responsive sites only).
Effect of gypsum treatment on vater content,
in the sc¡iI profile (responsive sites only) on the
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Effect of gypsum treatment,
strength of the soil crust sites onty) 1973-74.
dr)- shearing
re spons ive
The response to gypsum application at the
f ieltt sites.
The effect of tlj.fferent gypsum applicat,ion rates on the responses to specific test,s f or the d.iff erent f ie.[d sites.
Yalues f or the Dispersion Ind,ex (DI ) f or each site, calculat,ecl from the ranked. d-ispersion
at the air clry and remoulded (lOOcm surction) stagés.
VaIues f or lLovedayt s I regression ecluations to predict penetrometer resist,ance and seedLing emergence f or sit,es 1 t,o 10.
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1 Structure of the lamellae of a 1 :1 layer clay mineral (kaolinite ) ancl a 221 layer
cJ-ay mineral (mont'morillonite) from HilIeI
(1971\
The difference in concent'ration of the
positive and- negative ions in solution from the surface of a, clay la'mella bearing
net negative charge. No is the Ionic concentrat,ion in the bulk solution (Uiffef
1971)
3 Schematic tliagram of SPraY Unit
Map of t,he Mict antl Lower North regions of
South Australia showing the locat'ion of the
survey sampling sit,es.
Relation of exchangeable sod'ium percentage
to aggregate stability in red'-brown earths Map of the Mid ancl Lower North regions of
South Àust,ra'Iia showing locat'ion of Fieltl Experimental Sit'es.
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7 Layout of GYPsum Fielct Trials
Effect of t,he ÀcLctition of Gypsum on pH in the
soil profile by 197) (f g mont'hs after applicat'ion) 56
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9 Effect of the Àcttlition of Gypsum on pH in the soil profile by 1973 (18 months after applicat,ion).
Effect of the Attdition of Gypsum on pH in the
soil prcif ile by 1974 (30 months after application).
Effect of the Atltlit,ion of Gypsum on pH in the Soil Profile by 1974 (3O months aftev
ap¡,lication),
12 Ef f ect of Gypsum on Dry lvfatter Yield'.
After Da,se
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SUMMARY
Á.pplicat,ion of gypsum has Iong be en I.ecommend.ecl f or recl-brown earths with structural problems. HoweveÏ't
resurlts obtainecl- in Sout,h Aust,ral ia have proved' inconclusive indicating t,he need to ilefine the structural problems more clearly before recommencling the use of gypsum'
A survey was conducteil throughout the Mid and- Lor+er Nortli regions of South Aust,ralia to select and- sample red-brown
earths with surface struct,ural problems. samples weI.e taken from 28 sit,es for chemical ancl physical analysis to
determine factors responsible for the physical conilitions oI the s oiIs.
Aggregate stability was found to be relatecl t'o
organic carbon content and exchangeable sodium and- magnesium
percentages by the following equation:
Àggregate stability = O.82 + 2.1) organic carbon - (0.6 ESP + 0.3 EMgP)
Sites with a history of regular harroving hacl soils with Iouer oggrcgotc stability and. higher aggregate cohesion than soils from sites not subjectecl to harrowing.
It, was d.eclucecL that' a struct'ure improvement'
progranme for the harcl setting red-bror,¡n eart,hs should- be
aimed. at, red.uct,ion in harrowing, improved management
techniques t,o increase the organic carbon Ievel, addition of gypsum to reduce the exchangeable sod-ium percent'age (IlsP)
Il.
ÍInd exclìB.ngeable magnesium percenlage (nMgp) or a
combination of them alI.
To enable d.ccisions to be nracle regarding whicll hard setting red-brown ear1,hs woúIcl be improved by gypsum application ten fielcL trial si.tes we¡e used. The trials
were carried out on a range of harcl setting red-brown earths with ESP ranging from gleater than 17.5 to less
tlran 5 and EMgP from greater than 20 I'o below 1).
Gypsum rates of O r 2.5 , 5 ancl 12.5 f,/ha were applied- in
March 1972 and, the physical and chemical changes resultin6¡
from these applications'\^¡ere examined, in Oct'ober 1973 and 0ctober 1974. St,ructural measurements includ'efl crust shearing strength ancl the use of a portable rainfall sjmulat,or for examining changes in rainfall run-off.
Gypsum application resr¡lted in recluct,ions in soil
pHr ESP and EMgP, the amount and clepth to which these reductions occurrecl clepend-ing on t he rate of gypsum appliect. Gypsum application.was also founcl to improve rainfall run-off in 4 sites in 197) and J sites in 11974 and'
red,uce crust shearing strength at, 3 sites in 1973 and 1974'
Dr.y matter yieIcI increases from 5BO kg/ha to 1660 Xg/ha were
also obtainecl and. at,tributec[ to improved, r+at,er penetration
ancl redu cecl crust, strength.
From these resuilts it was prectictecL that hard. setting
red-brown eart,hs with ESP abov e 17 .5 would give bot,h
structural ancL yieltl responses to appliect gypsum and red- brown earths with moc'erate ESP (l-lo) antt EMgP values
greater than 20 would. show improved struct,ure after
acLclition of gypsum.
Because determinat,ion of ESP ancl EMgP requires laboratory vork a field- test, was evaluat,ed. on the basis of being able to tListinguish which soils woultl give yietcl and'/
or st,ructural responses to gypsum applicat,ion. The
f ielct t,est basetl on di.spersioh of air clriecl eggregates in water, selectecl sites with high ESP values but showed. pool
egreement, with the results from the field. trials.
It was conclud.etl, that gypsum applicat,ion shoultl not be regard.ed. as a panacea f or aII surface struct,ural problems of red-brown eart,hsl, a,nd that ESP and EMgP values shoulil be
used, to preclict, those sit,es which woulcl benef it from gypsum application.
IV,
STATEN{U{T
This t,hesis contai.ns no mat,elial which has been accepted f or the award of a,ny other degree or d.iploma
in any university antl, to the best, of my knowleclge and
belief, it contains no material pleviously publishecl or
written by another per.sonr except when due reference is
made in the text,.
ACKNOWLEDGEMENTS
This work was carried out as part of my official
tlr,Li,cs a.s & rcsearch officer in the South Àustra,lian Dcpartment of r\griculture.
I r+ould, Iike to expres,s my grat,itucte to Dr. J.Il.
Oadcs of the Department of Á.gr icult,ural Biochemistry antl Soi.I Science at the l{aite .A.gricult,ural Research Institute, for lris grridance and critism throughout, the proiect,. I
am also indebtetl to my senior officers Mr. J.A. Beare and
lnlr. R.,J. Frcnch f or their help in the planning and.
arìministration of this ploiect. I voulcl like t,o also express my thanks to Mr. R.J..French for his valuable ccmnents and sì.rggestions given d-uring the writ,ing up of
l,his thesis.
I would like to thank my colleagues within the
South Äustralian Depart,ment, of Àgriculture for their help in various ways. In particular Mr. D. Heanes for his aclvice and help wjth the laboratory t,echniques, Mr. G. Young an'd-
Mr. W. Mathcson in the selection of the experimenta,l sites
and Messrs. R. Lehmann and. T. Rothe (f ormerly f ielcl
assistant at Nuriootpa) for their assist,ance in carrying
ou-t; the f ietd measurement,s.
I woulct also like to expïess my sincere t'hanks
to Mrs. J. And.erson for her work in clrawing the f i.gures and.
especially the effort ancl help given by Mrs. D. Green
for the typing of this thesis'
The assistance and. keen interest of the farmers
on vl.ose properties the experiments we¡'e ccnduct'ecl is gratef u Ily acknowledged..
