MALAYSIAN PEAT CHARACTERISTICS

Introduction 

Of the major groups of marginal soils in Malaysia, peat is by far the
most widespread. Malaysian peatland had been used for agriculture for a
very 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 of the
peatland is not encouraged and where such land is being developed for
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 Staff 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 are found in the coastal
areas of the east and west 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, Sri Aman,
Sibu, Sarikei, Bintulu, Miri and 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.

Extent

There are about 2.43 million ha of peat and organic soils in Malaysia
accounting for about 7% 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, representing 2% of the state (Figure 1 and
.Table 1) 

About 80 % of peat in Sarawak are deep peat. No estimates on the depths
of peat are available for Sabah and Peninsular Malaysia. Other type
soils associated with peat are organic clay and muck. 

Figure 1: Location of peatlands in Peninsular Malaysia, Sabah and
Sarawak

Table 1: Area of peatland in Malaysia

Region	Area (ha)

Peninsular Malaysia	716,944

Sabah	121,514

Sarawak	1,588,142

Total	2,426,600



Characteristics of peat

Landscapes

The peat swamps are usually situated 2 to 4 km from the coast. In
Peninsular Malaysia and Sabah, the general topography of the peat land
tends to be flat 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 are found between the young and old
BRIS (Beach Ridges Interspersed with 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 present-day 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 Forest were 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
well-decomposed organic materials of the 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 of 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.

Physical characteristics

Field moisture content of the peat ranges from 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 of the peat of the 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 ranges from 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 of the ground surface. In the first 2 years of
draining 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. 

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 of
decomposition and nature of the organic matter. 

Peat soils have low exchangeable bases and base saturation values.
Micro-nutrients, 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
of the 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 of the broken down organic materials
resulting in the formation 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 soils for crop
production, they are highly suitable for a wide 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).

(Extracted from the Proceedings of the 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)

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