8342937100

Perianika 14(1). 43-51 (1991)

Mineralogy, Morphology and Classification of Acid Sulfate

Soils in Pulau Lumut, Selangor

EDGARDO A.AUXTERO,J. SHAMSHUDDIN AND S. PARAMANANTHAN

Department of Soi l Science, Faculty of Agriculture Universiti Pertanian Malaysia 43400 U PM, Serdang, Selangor Daru lEhsan, Malaysia.

Keywords: Acid sulfate soils, aluminium, jarosite, Sulfaquept, Tropaquept.

ABSTRAK

Tanah asid sulfat, yangsa ngat meluas di kawasan pan tai di pan tai barat Semenanjung Malaysia, dicińkan oleh pl I yangrendah dan Afyangboleh diekstrakyangtinggi. Sala kajian telah dijalankan untuk mencińdan mengelas tanah asid sulfat di Pulau Lumut, Selangor, Malaysia. Keputusan kajian menunjukkan tanah-tanah ini mempunyai sifat morfo logi ya ng berbeza. Motel kuningjarosit ialah sala sifat lazirn didapati di dałam lapisan tanah yang teroksid. Bahagian lempung tanah ini dipenuhi oleh kaolin i t, smektit dan mika, dengan sejumlah kecil lapisan bercampur-mika, jarosit, halóisit dan gibsit. Bergantungkepada kedalaman lapisan jarosit, tanah ini boleli dikelaskan kepada Sulfik Tropakuept atau Tipik Sulfakuept.

ABSTRACT

Acid sulfate soils, which are very widespread in the Coastal plains of the west coast of Peninsular Malaysia, are characterized by IowpH and high extractable Al. A study was carried out to characterize and classijy acid sulfate soils in Pulau Lumut, Selangor, Malaysia. The study showed that these soils were morphologically yańable in naturę. Yellowish jarosite mottles were a common feature in the oxidized layer of the soils. The clay fraction of the soils was dominatedby kaolinite, smectiteand mica, with minoramounts of mica-mixedlayers, jarosite, halloysiteandgibbsite. Defjendingon the depth of the jarosite layer, the soils can be classified as Sulfic Tropaijuepts or Typie Sulfai/uepts .

INTRODUCTION

Acid sulfate soils are those soils with a pl l <3.5 and with a water-soluble sulfate eon lent of >0.1%. Acid sulfate soils in Malaysia are developed byoxidation of pyrite (FeS₉) in the soils when the soils are drained for agricultural production. There are approximately 110,000 ha of these soils in the Coastal plains of Peninsular Malaysia (Kanapathy 1973). In Selangor, these soils occurin the Coastal plainsespeciallyin Pulau Carey and in thenearby island of Pulau Lumut. Acid sidfate soils are characterized by Iow pH ( < 3.5) and very high

extractable Al. with distinct yellowish jarosite

(S0₄)₂(0H)₆) mottles, occurringeither in the A or B horizon. According to Van Breemen (1982) this jarosite is usually found under conditions of IowpH (2-4) andstronglyoxidisingenvironments (Eh >400 mV) .

In some acid sulfatesoilsin Peninsular Malaysia, jarosite mottles are found near thesurface. These

acid sulfate soils are classified as Typie Sulfaquepts (Paramananthan and Noordin 1986). Otherswhere jarosite mottles are found below 50 cm depth are classified as Sulfic Tropaquepts. Preliminary inves-tigation showsthat the twosoil typesoccurin Pulau Lumut. Selangor; the deposits forming the soilsare of Holocene age.

Some acid sulfate soils in Peninsular Malaysia have been reclaimed for oil palm (Poon 1977; Poon and Bloomfield 1977), cocoa and coconut (Chew et al., 1984) cultivation by proper water management practices (Tob and Poon, 1982). Reclamation proceduresalso include application ofappropriate organie and inorganicamendments such as limę (Chew et al 1984) and bunch ash (Yeow etal. 1977). Detailed changes in soil Chemical properties resulting from these reclamation procedures are notavailable. Thus, there isa need to further study and classify t hese soils so that their agricultural potential is known. A study was con-ducted with the followingspecificobjectives: