Important considerations in the management of soil erosion [Malaysia]
1995
Ghulam M Hashim (Mardi, Kuala Lumpur (Malaysia))
Soil erosion in agricultural slopeland conditions was investigated in an area with shale-derived soils in eastern Peninsular Malaysia. Detailed soil loss and hydrological data associated with contrasting surface cover management practices were analysed to gain insights into the physical processes operating on the soil surface. These provide pointers for conservation planning. Four plots of 0.1 ha were equipped with stilling basins, Parshall flumes, height recorders and suspended load sampling devices. Two plots supported dense surface vegetation whilst two were clean-weeded. Gliricidia-shaded cocoa was grown in all plots. Contact cover and surface geometry greatly influenced soil loss. In 1991-1992 well-developed flow pathways in a clean-weeded area contributed to a soil loss of 77.2 tonnes per ha per yr in contrast to 33.9 tonnes per ha per yr in another clean-weeded area with less well-developed pathways. Where dense vegetation protected the soil surface, soil loss was 10 tonnes per ha per yr. An increase in leaf litter through time did not reduce soil loss as overland flow tended to shift dry leaves along flow pathways. Wet spells accounted for a high proportion of annual soil loss and need to be considered in conservation planning. Long slopes allowed bed load to be deposited and increased the proportion of suspended load. Suspended load, unlike bed load, is highly enriched in nutrients and organic matter. For one particular area its N content was six times greater and its organic C content was five times greater than in bed load. Estimates of nutrient loss therefore need to consider the different contributions of bed load and suspended load
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