**MA LA**  **YSI AN PE** **AT CHA** **RA CTERISTICS** 
**Introduction** Of the major groups of marginal soils in Malaysia, peat is by far the most widespread. Malaysian peatland had been usedfor agriculturefor avery long time ago. Many problems encountered by the farmers in using this land had been solved through intensive research carried out on peat. Government involvement by providing financial and technical support also has help in the successful of annual and industry crops cultivation on peat. Nevertheless, extensive exploitation ofthe peatland is not encouraged andwhere such land is being developedfor agriculture, a high level of management is emphasized to minimise the occurrence of undesirable consequences which can lead to the drastic subsidence and rapid disappearance of the peat. **Classification** The three major regions of Malaysia (Peninsular Malaysia, Sarawak and Sabah) use different systems of soil classification. The system in Peninsular Malaysia and Sarawak is based on the USDA Soil Taxonomy (Soil Survey Staf f 1990) but with some criteria being modified to suit the local conditions while Sabah uses the FAO/UNESCO Legend (1974). **Distribution** Peat soils occur both in the highlands and lowlands, however, the highland organic soils are not extensive. The lowland peat occurs almost entirely in low-lying, poorly drained depressions or basins in the coastal areas. In Peninsular Malaysia,they arefound inthe coastal areas ofthe east andwest coasts of the peninsula. Most of peat land is found in the coastal areas of West Johore, Kuantan and Pekan districts, the Rompin-Endau area, northwest Selangor and the Trans-Perak areas in the Perak Tengah and Hilir Perak districts. In Sarawak, peat occurs mainly between the lower stretches of the main river courses (basin peats) and in poorly drained interior valleys (valley peats). They are found in the administrative divisions of Kuching, Samarahan, SriAman, Sibu, Sarikei, Bintulu, Miriand Limbang. In Sabah, the organic soils are found on the coastal areas of the Klias peninsula, Krah swamp in Kota Belud, Sugut and Labuk estuaries and Kinabatangan floodplains.2

**Extent** There are about 2.43 million ha of peat and organic soils in Malaysia accounting for about7% of the total land area of the country. Sarawak has the largest area of peat in the country, covering about 1.59 million ha and constituting 13% of the state. This is followed by Peninsular Malaysia which has about 716,944 ha, comprising 5% of its total area, while Sabah has 121,514 ha, representing2% of the state (Figure 1 and .Table 1) About 80 % of peat in Sarawak are deep peat. No estimates onthe depths of peat are available for Sabah and Peninsular Malaysia. Other type soils associated with peat are organic clayand muck.

Figure 1: Location of peatlands i n Peninsular Malaysia, Sabah and Sarawak Table 1: Area of peatland in Malaysia **Region Ar** **ea (ha)** Peninsular Malaysia 716,944 Sabah 121,514 Sarawak 1,588,142

**Total 2,426,600** 3

**Characteristics of peat Landscapes**  The peat swamps are usually situated 2to4 km fromthe coast. In Peninsular Malaysia and Sabah, the general topography ofthe peat land tends to beflat whereas in Sarawak, the basin peat swamps are dome-shaped. On the west coast of Peninsular Malaysia, the peat swamps are formed in depressions consisting predominantly of marine clay deposits which are either sulfidic in nature, or consist of an admixture of marine and riverine deposits especially in areas along river courses. On the east coast of the peninsula, particularly in the states of Kelantan and Terengganu, peat swamps arefound between the young and old BRIS (Beach Ridges Interspersedwith Swales) landscapes. In Pahang and eastern Johore, the peat swamps are situated immediately adjacent to the BRIS landscape, approximately 5 to 10 km from the presentday coastline. In Sarawak, the coastal and deltaic peat swamps have convex surfaces with the convexity of the swamp surfaces becoming more pronounced with distance from the sea. Maximum heights recorded in the Daro Forest Reserve and Loba Kabang Protected Forestwere 4 m. The swamp surface is like that of an inverted saucer with almost flat bog plain at the centre. **Morphological characteristics** Morphologically, the lowland peat in the three regions is quite similar. In the natural state, the lowland virgin peat consists of dark reddish brown to black, loose, partly decomposed leaves, branches, twigs and tree trunks with a low mineral content. The water table is always high and occurs at or near the surface. In drained areas, the peat is transformed to a compact mass consisting of partially and well-decomposed plant remains with large wood fragments and tree trunks embedded in it, as a result of decomposition, shrinkage and consolidation of the virgin peat. In the west coast peat of Peninsular Malaysia and most of the peat in Sarawak, the underlying materials consist of sulfidic marine clay, while in the east coast of the peninsula, the peat is underlain by riverine alluvium, colluvium and sand. The common soil profile morphology in the drained peat consists of three distinct layers; an upper layer of 20-30 cm thick consisting of welldecomposed organic materials ofthe sapric type, a middle layer of 30-40 cm thick containing semi-decomposed organic materials belonging to the hemic type and a lower layer of fibric peat which is made up of a large quantity of4

relatively undecomposed organic materials consisting of tree trunks, large wood fragments and branches. The fibric materials are often submerged in water at a depth of 60-70 cm. The rubbed colours of these layers vary from very dusky red (2.5 YR 3/2) to very dark yellowish brown (5YR 3/2) depending on the stage of decomposition. In general, the thickness of the deep peat in Malaysia exceeds 5 m, although in Sarawak peat thickness exceeding 15 m has been recorded. **Phy sical characteristics**  Field moisture contentofthe peat rangesfrom about 100 to 1300 %, on a dry weight basis. The high water content results in high buoyancy and high pore volume leading to low bulk density and low bearing capacity. The ash content in most ofthe peat ofthe west coast of Peninsular Malaysia and in Sarawak is less than 10%, showing a very high content of organic matter. This is indicated by a loss of ignition value exceeding 90%. In the east coast of the peninsula, the organic matter content is highly variable as the mineral content rangesfrom 10% to as high as 65%. This variability is due to periodic disposition of mineral sediments by seasonal floods. The bulk density for the top 30 cm of the peat is low and varies from 0.1 to 0.2 g per cubic centimeters in peat of Peninsular Malaysia and Sarawak. Upon drainage and cultivation, peat decomposes and shrinks, resulting in subsidence and lowering ofthe ground surface. Inthefirst2years ofdraining the peat in the West Johore Integrated Project, the rate of subsidence is drastic and reaches a value of 50 cm. The sudden drop in the peat level is due to the collapse of the loose fibric materials followed by decomposition and compaction of resultant hemic and sapric materials. In subsequent years, as a result of the consolidation of the sapric and hemic materials, the rate of subsidence is only 2 to 3 cm per annum. In Sarawak, a subsidence rate of 6 cm per annum has been reported for peat with a water table at 75-100 cm. **Chemical characteristics** Organic soils in the three regions are very acidic with very low pH values ranging from 3.0 to 4.5. In some cases where sulphidic materials are found within the profile, pH values can drop below 3.0. The electrical conductivity values are generally low (less than 1 dS/m). However, in some coastal areas which are influenced by sea water, e.g. Tanjung Karang, values of up to 4.7 dS/m have been recorded.5

The organic carbon values are in the region of 30 to 40%. However,due to its high C/N ratio, very little nitrogen is mineralised unless large quantities of nitrogenous fertilizers are applied. Peat has high CEC values ranging from 40 cmol (+) per kg soil in the east coast of Peninsular Malaysia to 40 to 80 cmol (+) per kg soil in west Johore and 145 cmol (+) per kg soil in Jalan Kebun in Selangor. In Sarawak, values of 40 to 135 cmol (+) per kg soil have been reported. Variability in the CEC values of peat is due to the stage ofdecomposition and nature ofthe organic matter. Peat soils have low exchangeable bases and base saturation values. Micronutrients, particularly Cu, Bo and Zn, are also deficient. Iron is found to be high. Severe Cu deficiencies of maize, cassava and oil palm on peat have been observed

. The acid and hyper acid conditions of the peat are readily neutralised by liming and the use of oil palm bunch ash. The problems associated with micronutrient deficiencies are no longer serious threats to crop production as these have been overcome by intensive research.
**Profile characteristics** Based on field investigations carried out in Johore and Selangor, most ofthe cultivated peat had the sapric-hemic-fibric profile morphology

. This profile morphology was developed when the peat is drained and this encouraged decomposition of the peat

. Peat decomposition enhanced consolidation and compaction ofthe broken down organic materials resulting intheformation of the sapric and hemic layers. This process invariably leads to the subsidence of the ground surface. Generally, in draining the peat swamp, emphasis is focussed on controlled drainage which involves a gradual lowering of the ground water table to favour the formation of the sapric and hemic layers while ensuring that the subsidence is kept to a minimum. **Conclusion** While peat soils are not comparable to mineral soilsfor crop production, they are highly suitable for awide range of crops especially those with shallow rooting and fibrous root systems including oil palm, pineapples, vegetables, cassava, Liberica coffee, mulberry, banana, sago etc. In Sarawak, relatively large areas of the peat swamps are bearing species of valuable timber such as the "Ramin" (Contystylus bancanus).6

( Extracted from the Proceedings ofthe International Symposium on Tropical Peatland, 6-10 May 1991, in Kuching, Sarawak and Progress Report of Oil Palm Inventory, Joint Committee on Carbon Emission Dec. 2010 )