Impact of highland utilization on soil erosion
1992
Nipon Tangtham (Kasetsart Univ., Bangkok (Thailand). Faculty of Forestry. Dept. of Conservation)
Effects of land-use practices by converting natural forest to upland agricultural crops have been studied since 1953. Results of investigation carried out by various institutes showed that soil erosion from natural forest even in the heavy rain areas is quite low. Fire induced soil erosion in the forest at about 2-10 times greater than that of unburned forest. Traditional upland crop cultivation such as rice, corn, bean and sesame on slopes steeper than 35 percent produced soil loss much higher than the tolerant limit (12.5 ton/ha/yr). Agroforestry and narrow terraced plantation keep soil on the site as well as that natural forests do. Conservation measures such as grass-strips, inter-cropping and hillside ditches can effectively reduce soil loss in the level of much less than tolerant limit. Rubber plantation on terraces in the South showed insignifacant average soil loss compared to that of moist evergreen forest and gradually decline to the same level within 5 years.
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