Pertanika 9(3), 323 - 330 (1986)

Classification of Acid Sulfate Soils of Peninsular Malaysia*

S. PARAMANANTHAN and NOORDIN DAUD 1

Soil Science Department,Faculty of Agriculture,

Universiti Pertanian Malaysia,43400 Serdang, Selangor, Malaysia.

Key words: Classification; acid sulfate soils; Pen. Malaysia.

ABSTRAK

Tanah-tanah asid sulfat adalah salah satu kumpulan tanah yang penting di SemeiwnjungMalaysia, khususnya di Pantai Barat. Tanah-tanah tersebut terbentuk daripada bahan-bahanendapan marin estuarin dan air payau. fa boleh dibahagikan kepada duo, kumpulan mengikut sistempengelasan Taksonomi Tanah - tanah potensi asid sulfat dan tanah asid sulfat yang sebenarnya.Pengelasan tanah-tanah mengikut sistem pengelasan di Malaysia juga dibincangkan. Walaupunsistem pengelasan di Malaysia berasaskan kepada konsep-konsep Taksonomi Tanah, tetapi ia telahdiubahsuaikan mengikut keadaan tempatan. Duo, jujukan tanah asid sulfat telah dlperkenalkan diSemenanjung Malaysia. Satu kunci untuk menentukan siri-siri tanah asid sulfat juga disampaikandalam kertas ini.

ABSTRACT

A cid sulfate soils form an important group ofsoils in Peninsular Mai<Lysia, particularly on theWest Coast. These soils developed over marine, estuarine and brackish water deposits can be dividedinto two groups - the potential acid sulfate soils and the true acid sulfate soils using the definitionsestablished in Soil Taxonomy. The classification of these soils in accordance to the Malaysian system isdiscussed. The Malaysian system though based on the concepts ofSoil Taxonomy has been modified tosuit local conditions. Two sequences ofacid sulfate soils have been recognized in Peninsular Malaysia.A key to the identification of these acid sulfate soils is also presented in the paper.

INTRODUCTION

The west coast of Peninsular Malaysia isdominated by clayey deposits of marine andbrackish water origin. These coastal clays extendas an almost continuous block along the westcoast and are only broken by occasional islandsof sedimentary and igneous rocks. This coastalplain which varies in width from about 10 to 50km often grades into peat swamps. The coastal

plain averages in height from 0 - 15 m abovemean sea level and is used extensively for agri­culture after the construction of a coastal bundto prevent inundation by the sea, and the con­struction of drains to lower the waterable. Thecrops commonly grown on these areas include oilpalm, coconut, cocoa, rubber and rice. Thedrainage of these coastal clays created problemsin many areas and were often associated with thedevelopment of acid sulfate soils.

*A paper presented at the Workshop on Acid Sulfate Soils organised by the Malaysian Society of Soil Science and held on 31stJanuary 1983 at Universiti Pertanian Malaysia, 43400 Serdang, Selangor, Malaysia.

I Rubber Research Institute, P.O. Box 12644, 50784 Kuala Lumpur, Malaysia.

S. PARAMANANTHAN AND NOORDIN DAUD

LITERATURE REVIEW

The lack of details given in many papersand the lack of an accepted definition of acidsulfate soils makes it difficult to decide whenacid sulfate soils were first recognized inPeninsular Malaysia.

Pratt (1911) reported that in the Krian ricegrowing area patches of soil'gave very poor yieldsdue to lack of drainage. He added that the distri·bution of these patches was irregular but that thewaterlogging caused the development of sournessand that the rice plants turned yellow. This ispossibly due to the formation of acidity. Dennett(1933) recognized that soils with high concentra­tions of acid were associated with the nipah palmand Wilshaw (1940) reported the occurrence ofacid conditions on draining coastal soils. Coulter(1952) referred to soils containing considerableamounts of pyrite as gelam (Melaleuca leuco­dendron) soils.

As in many countries where such soils occur,the lack of uniform definitions makes interpreta­tion of published work very difficult. A mixtureof circumstantial and intrinsic soil properties wasoriginally used to distinguish potential andactual acid sulfate soils from soils not showing ornot expected to develop extreme acidity ondrainage and cultivation. Thus in PeninsularMalaysia, the presence of acid sulfate soils in anarea can often be suspected by the presence ofgelam tree (Melaleuca leucadendron) or by anipah (Nlpah fruticans). If the area has beencleared, a sedge grass (scleria family?) and thegrass fimbristylis are common (Kanapathy,1976). The presence of reddish brown deposits(iron-organic complex) is also common along

drains in acid sulfate areas. Subsequently anacid sulfate layer as a diagnostic horizon wastaken to be one with a pH of about 3.3 or less (airdried soil) and which has soluble sulfate contentin the air dried soil exceeding 0.1 % (Coulter,1967). The introduction of the Soil Taxonomy(Soil Survey Staff, 1975) and its earlier draftsproposed more rigid definitions for sulfidicmaterials and the sulfuric horizon. These weretested for Malaysian conditions when systematicsemi-detailed mapping of the coastal plain areas

was initiated by the Soil Survey Section of theDepartment of Agriculture in West Johore.These studies (Gopinathan, 1973; Joseph andMaarof, 1975 and Paramananthan, 1976) pro­vided a better understanding of acid sulfate soilsin the country. Thus soil sequences of acidsulfate soils on both marine and brackish waterdeposits were proposed (Paramananthan, 1976;Paramananthan and Gopinathan, 1981). Sincethat time more data has been collected. Detailedstudies (Noordin, 1980, 1981) of the acid sulfatesoils in the coastal plain of Perak provided someimportant information pertaining to the genesis,classification, mineralogy and micromorphologyof acid sulfate soils in the country. The objectiveof this paper is to present the current status ofthe criteria used for the mapping and classifi­cation of acid sulfate soils in PeninsularMalaysia.

DEFINITIONS

As mentioned earlier, the major difficultyin interpreting published data is the lack of uni­formity of the definitions of acid sulfCl:te soils.Today the criteria used in Peninsular Malaysia isbased on those given in Soil Taxonomy (SoilSurvey Staff, 1975).

Sulfidic Materials

Sulfidic materials are waterlogged mineralor organic soil materials that contain 0.75% ormore sulfur (dry weight) mostly in the form ofsulfides and have l~ss than three times as muchcarbonate (CaCO 3equivalent) as sulfur.

Sulfidic materials accumulate in a soil thatis permanently saturated, generally withbrackish water. The sulfates in the water are bio­logically reduced to sulfides. Sulfidic materialscommonly occur along the coastal areas whichare inundated by sea-water; the pH, which maybe near neutral before drainage may drop to aslow as 2.5. On drainage the sulfides are oxidizedto form sulfuric acid which then reacts with thesoil to form iron and aluminium sulfates (e.g.yellow jarosite). This oxidation can take placewithin a few years. Often yellow jarosite mottlesmay occur in sulfidic materials along old root

324 PERTANIKA VOL. 9 NO.3, 1986

CLASSIFICATION OF ACID SULFATE SOILS OF PENINSULAR MALAYSIA

traces where localized oxidation has taken place.However, such materials still have a high In'value or are 'unripe'.

As the definition of sulfidic materials ismainly chemical, total analysis for determiningthe sulfur content is by far the most reliablemethod. However, this determination is not onlylaborious but seldom carried out as a routineanalysis in laboratories in Malaysia. In the field,a few criteria can be used to recognise the pre­sence of sulfidic materials. Material which is richin sulfides often give off a smell of rotten eggs(H 2 S) and the soil materials often changes blackon exposure due to the formation of some inter­mediate oxidation product. With time thisblack coating turns yellow Uarosite) if thematerial is allowed to dry for about two weeks.On a pit face sulfidic material often may alreadyshow yellow jarosite deposits along old rootchannels. Another quick field test is to oxidizethe soil sample by boiling it in concentratedhydrogen peroxide and measuring the drop inpH. This test however is dangerous especially ifhigh amounts of organic matter are present. Inthe laboratory, a sample is left in an open soilsample bag placed under shade. This sample ismoistened regularly as it dries in the shade. Ifthe material is sulfidic, after about a monththere should be a drop in pH by more than oneunit. It must be pointed out, however, that adrop in pH per se may not be sufficient to classifythe soil as sulfidic. This is particularly true if thematerial is rich in organic matter.

Sulfuric Horizon

The sulfuric horizon is composed either ofmineral or organic soil material that has botha pH of less than 3.5 (1: 1 in water) and jarositemottles (the colour of fresh straw that has a hueof 2.5 Y or yellower and a chroma of 6 or more).A sulfuric horizon forms as a result of artificialdrainage and oxidation of sulfide-rich mineralor organic materials. It is necessary to addanother criteria to the two already given in SoilTaxonomy i.e. that the In' value must be less than1.0. The 'n' value refers to the relation betweenthe percentage of water under field conditionsand the percentage of inorganic clay and humus.

The In' value can be estimated in the field bysqueezing a sample of the soil in the hand. It thesoil flows with difficulty between the fingers, theIn' value is between 0.7 and 1.0 and if it flowseasily between the fingers, the 'n' value is 1 ormore. The In' value is necessary to exclude sulfi­dic materials which may have jarosite mottlesalong old root channels.

During field mapping in Malaysia, when asoil has an 'n' value of less than 1.0 and if jarositeis readily recognised in a horizon, then thehorizon is taken to be sulfuric. Only in some isthe pH determined. Thus even if the pHhappens to be more than 3.5, it is stilI mapped asa sulfate soil. This is done to avoid the estab­lishment of a number of soil series depending onthe pH (Paramananthan and Gopinathan, 1981)and to facilitate field mapping.

CLASSIFICATION OF ACID SULFATESOILS

From the definitions given above, it can beseen that two groups of soils can be defineddepending on the diagnostic horizon present. Ifa soils is waterlogged, has no profile develop­ment, and has sulfidic materials within 50 cm ofthe surface it would be a potential acid sulfatesoil - potential in the sense that if it is drained,it would develop into soils with a sulfurichorizon. Soils which have been drained and havea sulfuric 'B' horizon would be true acid sulfatesoils.

Classification According to Soil Taxonomy

The Soil Taxonomy is a morphogeneticclassification. It therefore attempts to separatesoils using their profile morphology and theirgenesis. Hence the potential acid sulfate soils i.e.those with snlfidic materials within 50 cm of thesoil surface are separated from soils having asurfuric horizon.

Since sulfidic materials may occur both inmineral and organic soils, two great groups arerecognized viz. Sulfaquents and Sulfihemists.Mineral soils which have sulfidic materialswithin 50 cm of the soil surface are classified as

. /

PERTANIKA VOL. 9 NO.3. 1986 325

S. PARAMANANTHAN AND NOORDIN DAUD

Fig. 1: Soils with sulfuric materials in PeninsularMalaysia

Oroanlc/SulfldlcHigh/Law'n' valut

A/e Profile

o

L1NAU

~ Organic Soli~ MOI.rlols

MERBOK

Low 'n' yolueA/C Profll.

Sulfidic Moltrlall

P'77/l Sulfidic~ Mot.rloll

KRANJI

32

_A horizon

120 48HIOh 'n' volu.A/C Profll.

Sulfidic Mot.rlols

In the case of organic soils with sulfidicmaterials, we prefer to deviate somewhat fromthe Soil Taxonomy. In Soil Taxonomy, allorganic soils having sulfidic materials within 100em are placed into ·the Sulfihemists irrespectiveof the nature of fibres. Our thinking in Penin­sular Malaysia is that we should have three GreatGroups i.e. Sulfifibrists, Sulfihemists and Sulfi­saprists. It is our opinion that in addition to thepresence of sulfidic materials, the stage of

Soils with Sulfidic Materials A soil is con-sidered to be a potential acid sulfate soil if it hassulfidic materials within 50 em of the soilsurface. These potential acid sulfate soils arethen sub-divided using the 'n' value and presenceof an organic soil layer (histic epipedon) at thesurface. Only three mineral soils which arepotential acid sulfate soils have been identifiedto date (see Figure 1).

In principle, the definition of sulfidicmaterials used in Peninsular Malaysia is similarto that used in Soil Taxonomy. As mentionedearlier, although we accepted the definition ofthe sulfuric horizon used in Soil Taxonomy, inpractice when we see jarosite in a horizon weassume that the pH in that horizon is less than3.5

100 40

On the other hand, if the soil has jarositemottles within 50 em of the mineral soil surfacebut the pH is between 3.5 and 4.0 and thereforedoes not qualify for a sulfuric horizon, then thesoil is classified at the Sub-Group level as a SulficTropaquept. Also placed into this Sub-Groupare soils where jarosite mottles occur between50 - 150 em and which also has a pH of less than4.0. Organic soils which have a sulfuric horizonwhose upper boundary is within 50 em of thesurface, are classified as Sulfohemists.

Classification in Peninsular Malaysia

In general the classification of acid sulfatesoils in Peninsular Malaysia follows closely thatused in Soil Taxonomy. However, some slightmodifications were found necessary in order tofacilitate field mapping and the interpretationsof the soils for agricultural use. In the classifi­cation discussed here, the organic soils are notconsidered as our knowledge of these soils is stillinadequate.

In the case of soils with.a sulfuric horizon,the depth at which these occur is used at diffeentlevels in Soil Taxonomy to reflect the severity ofthe acid sulfate conditions. Mineral soils, whichhave a sulfuric horizon whose upper boundary iswithin 50 em of the mineral soil surface, areclassified into the Great Group of Sulfaquepts.These are soils which have some profile develop­ment, have an aquic moisture regime and asulfuric horizon within 50 em of the mineral soilsurface.

Sulfaquents. These are recent or young mineralsoils which due to their high water table arepoorly drained and show no profile develop­ment. They have sulfidic materials within 50 emof the soil surface. All organic soils which arepoorly drained and which do not have a sulfurichorizon, whose upper boundary is within 50 emof the soil surface but have sulfidic materialswithin 100 em are classified as Sulfihemists. Inmineral soils, if the sulfidic materials arepresent, between 50 to 100 em, it is considered atthe sub-group level.

326 PERTANIKA VOL. 9NO. 3,1986

CLASSIFICATION OF ACID SULFATE SOILS OF PENINSULAR MALAYSIA

F£g. 2: Soils with a sulfuric horizon within 50 em inPeninsular Malaysia

IDENTIFICATION OF ACID SULFATESOILS

cm Inl PARIT BOTAK0 0

~=~-'.=~ A,20 B

II40 16 B

60 24

BO 32

100 40

120 4BLiQhl Gray

AnQular BlockySlicky

Cm SEOU0

~.=.=-

__~A

20 B

I40 16 I60 24

80 32

100 40

120 4BBrown

SUbon~~:~~I:loCky

[ITJ Jorolile ~MorineMollies Cloy

I B

GUAR

I

~ A horizon

KUALA PERLIS_A

Inside the bund drainage produces soils whichhave a sulfuric horizon at varying depths (seeFigure 4). Further inland where the coastal plainmerges with the peat swamps, the soils are en­riched in organic matter and this results in soilswith a friable consistence, moderate structuresand generally brown colours. Near the peatswamps, the soils are undeveloped potential acidsulfate soils with a surface organic layer. Awayfrom the peat swamps where drainage has beeneffected, the soils have a sulfuric horizon at vary­ing depths (Figure 4).

As a means of assisting soil surveyors andagronomists to understand the properties of acid

Soils with a Sulfuric Horizon In Soil Taxo­nomy, if a sulfuric horizon occurs within 150 cmof the soil surface, it is taken into considerationin the classification of the soil. If the sulfurichorizon occurs within 50 cm, then it is used atthe Great Group level e.g. Sulfaquepts or Sulfo­hemists. On the other hand when the sulfurichorizon occurs between 50 to 150 cm then it isused at the sub-group level e.g. Sulfic Tropa­quept.

In Peninsular Malaysia, if the sulfurichorizon occurs below 100 cm it is not consideredin the classification. This is because in ouropinion, any soil feature below 100 cm seldomaffects soil suitability. Like in Soil Taxo­nomy, the soils are separated initially on whetherthe top of the sulfuric horizon occurs within 50cm or between 50 to 100 cm. Th~se two broadgroups are then sub-divided using the depth atwhich the marine clay, the C horizon occurs andthe nature of the B horizon. Humus rich Bhorizons have friable consistence and are wellstructured while others are sticky, weaklystructured and low in organic matter (see Figure's2 and 3). In the case of soils having a sulfurichorizon within 50 cm of the surface, four soilseries viz. Kuala Perlis, Parit Botak, Guar andSedu have been identified (Figure 2). When thesulfuric horizon occurs between 50 to 100 cm,then another four soil mapping units viz. Telok,Tongkang and Jawa (shallow) and Jawa havebeen identified to date (Figure 3).

decomposition of the organic material is alsoimportant.

Soil Sequence ofA cid Sulfate Soils Soilsurveys carried out in Peninsular Malaysia indi­cate that these soils form a drainage sequence.This was first recognized by Paramananthan(1976). Subsequent work and redefinition of soilseries made it possible to improve the sequence.Generally two sub-sequences occur in thesecoastal plains. Near the coast soils which arepoor in organic matter and which have coarseangular blocky structures, sticky consistence andlight gray matrix colours are common. Thesequence begins with the areas outside thecoastal bund which are inundated by sea water.

PERTANIKA VOL. 9 NO.3, 1986 327

S. PARAMANANTHAN AND NOORDIN DAUD

It must be pointed out that many workersconsider the Lubok Itek Series mapped on theKelantan Plain to be an acid sulfate soil. Thissoil has a massive clay overlying an organicdeposit with its upper boundary between 50 to100 cm from the soil surface. This organic layeroften has a pH of less than 3.5 and hence it hasbeen assumed to be a sulfuric horizon. However,as this soil is often under water, no jarositemottles have been reported. Thus it is possiblethat this layer contains sulfidic materials butsince it is a mineral soil and the sulfidic materialsoccur below 50 cm, it is not considered to bediagnostic and therefore not even a potentialadd sulfate soil. Furthermore, no sulfur deter­minations have been reported to confirm if thematerials are sulfidic. It is possible that the lowpH is due to organic acids.

sulfate soils in Peninsular Malaysia, Parama­nanthan (1981) has prepared a "Key to the Iden­tification of Soils ~n Marine, Estuarine andBrackish Water Deposits". This Key includesboth acid sulfate and non-acid sulfate soils. Anidentification table for the acid sulfate soilsextracted from this Key is given in Table 1.

B,

/ B2/

I

JflWA

B,

TONGKANG

!///'//, r.Liqht Groy

Anqular BlockyS!icky

Brown, SubonQulorBloCky, Frlobl.

l777/l Marine~cloy

40- ·16

20- 8

0- 0

80- - 32

60- -24

cm Inl0 0

20- 8

40- 16

60 24

80 3?

100 40

120 46

120- 48

'00- 40

I"j71I Jorelitel!...!-J Matt In

B,

TELOI(

B,

I I B2

I/ B2

LiQhr GrayAnouior Blocky

Sticky

Brawn, SubonqulorBlocky, Friable

~ A horizon

Fig. 3: Soils with a sulfuric horizon between 50 to100 cm in Peninsular Malaysia

aUND em i~s

SEA --IL 0A A A A A A A

II20 8

8B, 8, 8, 8,

40 16

C 60 Z4

C

,I

Bz B2 80 l2

40

C C

lON~G48

KRANJI MERBOK KUALA PARIT TELOK BERNANPERUS BOTAK

ills0

A A

0B, S,

'6

24

82 32C

40

C 120 48SELANGOR JAWA JAWA SEOU GUAR LINAU ORGANIC

(sholIow) SOil

m Orqanlc Materials cz::zJ Jarosite Mot"" ~ Sulfidic Materials

Fig. 4: A dd sulfate soil sequences in Peninsular Malaysia

328 PERTANIKA VOL. 9NO. 3,1986

'i:ItTl:;:tl...,;l>:2~;l>

<:or<.0

:2o!;.>O.....<.000O'l

(jON)<.0

TABLE 1Table for the identification of acid sulfate soils of Peninsular Malaysia

Horizonation A/C or 01A/C AlBIC AlBIC

Diagnostic Sulfidic material Sulfuric Cambichorizonlmaterial

'n' value or depth tosulfuric horizon High on' value Low 'n' value Less than 50-100cm No sulfuric

(> 1.0) ( <1.0) 50 cm horizon to 100 cm

SubsoilMatrix light gray, Kranji Merbok Kuala Perlis I Telok 2

angular blocky and sticky Parit Botak 2 Carey 2

Tongkang Bernam

SubsoilMatrix brown subangular Linau Guar I Jawa (shallow) 2-blocky and friable Sedu :1 Jawa Selangor

Taxonomy Typic (Typic) Typic Sulfic TypicSulfaquent Sulfaquent Sulfaquept Tropaquept Tropaquept

Notes: I marine clay within 50 cm a loamy textured soils2 marine clay 50 - 100 cm

()t""';l>~

~

:;;(3;l>...,o:2o'Tl;l>()

6~

c::t""''Tl;l>...,tTl~

Qt""'~

o'Tl""CItTlZZC/lc::l';l>:;:tl

3::;l>l';l>><:~

;;

S. PARAMANANTHAN AND NOORDIN DAUD

CONCLUSION

The knowledge of acid' sulfate soils ofPeninsular Malaysia has increased greatly overthe last few years. However, the mapping ofthese soils still presents a lot of problems as thesesoils often occur as pockets within areas of non­acid sulfate soils. The need for analytical data tosupport soil surveys cannot be over-emphasisedin the mapping of these soils. The distribution ofthese soils, however, cannot be assessed from theearlier maps as the definitions used for soils weredifferent or have since been modified.

REFERENCES

COULTER. J.K. (1952): Gelam Soils. Malayan Agric. j.35: 22 - 35.

COULTER, J.K. (1967): Acid Sulfate Soils in Malaya.Unpublished Report, Dept. of Agric. Malaya.

DENNET. J.H. (1933): The Classification and Proper­ties of Malayan Soils. Malayan Agric. j. 20: 298 ­302.

GOPINATHAN, B. (1973): The Semi-Detailed SoilSurvey of the West Johore Coastal Plain. Unpub­lished Report. , Dept. of Agric. PeninsularMalaysia.

JOSEPH. K.T. and N. MAAROF. (1975): A Field Studyshowing classicial changes in acidity over largeareas in the Parit Jawa area of Johor during thelast decade. Froc. Third ASEAN Soils ConJ.,383 - 391.

KANAPATHY, K. (1976): Acid Sulfate Soils. Soils andAnalytical Services, Division of Agric., Min. ofAgric., Bull. 6, 67 p.

NOORDIN WAN DAUD. (1980): Soil Genesis on theCoastal Plain of Perak (Peninsular Ma,laysia).D.Sc. thesis, State University of Ghent', Belgium.

NORDIN WAN DAUD. (1981): Characteristics of somemarine and riverine alluvial soils, Perak,Malaysia. Field Tour Guide Book, Soil Correla­tion Tour Perak, 23 - 27 November 1981, Mal.Soc. of Soil Science.

PARAMANANTHAN. S. (1976): Soils of the West JohoreArea. Soil Correlation Report 1/1976. Min. ofAgric. and Rural Dev., Malaysia.

PARAMANANTHAN. S. (1981): Keys to the Identifica­tion of Soils Developed on Sub-Recent, Recentand Estuarine Deposits in Peninsular Malaysia. Apaper presented at the Soil Correlation Tour ofPerak, Mal. Soc. of Soil Science.

PARAMANANTHAN. S. and B. GOPINANTHAN. (1981):Problems of classifying soils with sulfidic horizonsin Peninsular Malaysia. In: Froc. BangkokSymposium on Acid Sulfate Soils. H. Dost and N.van Breemem (Editors). ILRI Public. 31: 96­102.

PRATT. H.C. (1911): Padi Cultivation in Kerian.Dept. of Agric. Federated Malay States, Bull.No. 12, 19 p.

(Received 19 October, 1985)

330 PERTANIKA VOL. 9 NO.3. 1986