HUMAN INTERFERENCE WITH SOILS


Conserving soil People employ different methods of preventing or reducing soil erosion.


Some of these methods of soil conservation are described here.


Contour ploughing The traditional way to plough a hill is to plough up and down the slope. But this method allows water to flow freely down through the ploughed furrows. The flowing water can carry soil with it and result in destructive gully erosion. Contour ploughing is a technique that is used to prevent such gully erosion. In this


Some soil conservation methods l contour ploughing l terracing l stone lines l windbreaks


type of ploughing the furrows and ridges go across a slope, following the contours of the hill. They therefore act like miniature dams or barriers that prevent water rushing down the slope. They hold back the water long enough for it to infiltrate (soak) into the ground. This improves soil fertility and leads to more vegetation growth, which further protects the soil from gully erosion. Although troublesome to carry out, contour ploughing can reduce soil erosion by up


to 50 per cent. It is practised widely in the Midwest of the United States where hydraulic equipment on tractors makes the technique less difficult or dangerous.


Terracing Terracing can be used to prevent soil erosion on slopes that are too steep for contour ploughing. A series of walls are built one above another across a hillside. Behind each retaining wall a wide ‘step’ or terrace of land is flattened and farmed. The top of each retaining wall forms a little barrier called a ‘bund’ across the front of each terrace (see the photograph). The terraces and the bunds combine to trap water that would otherwise flow rapidly down-slope. They thus prevent gully erosion and allow water to enrich the soil by soaking slowly into it. The building and maintenance of terraces is very labour intensive. Nevertheless,


terracing is very common in China, Vietnam and other parts of East and Southeast Asia. Terraces there help to prevent heavy monsoon rains from severely eroding hill slopes. They retain enough water to support the intensive cultivation of rice, which is the staple diet of most people in East and Southeast Asia.


Terraced rice cultivation in China. These terraces prevent serious gully erosion on steep slopes during periods of torrential monsoon rainfall. They retain sufficient water to allow the cultivation of rice.


Terraces Bunds 193


Original slope


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