HUMAN INTERFERENCE WITH SOILS


Overcropping Rapid population growth has forced many farmers to overcrop land (cultivate land excessively) in an attempt to provide sufficient food for themselves and their families. In such cases the soil is not allowed to rest or is not fertilised sufficiently between crops. The soil then becomes progressively more bare and barren. As overcropped areas become less productive,


farmers are sometimes forced to cultivate marginal land in order to feed their families. Marginal land is land that that is not fully fertile enough for agriculture. When cultivated, such land quickly becomes barren and bare.


International debt has also contributed to


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1970 5 1980 1990 20002010


overcropping in the Sahel. Countries such as Niger have gone into heavy debt to Western banks and governments. In order to raise foreign capital to repay such debt, the government of Niger has encouraged farmers to grow cash crops such as groundnuts (peanuts) for export. This has led to the following problems: l Groundnuts are usually not rotated with any other crop but are grown exclusively on the same ground year after year. This system is called monoculture. Groundnut monoculture exhausts the soil so much that after three years of cultivation the land needs to be left fallow for a six-year period. But most Niger farmers cannot afford to rest their land for such long periods. The land has therefore gradually become infertile.


l Many farmers were forced into personal debt in order to purchase the seeds and technology that they needed to grow groundnuts. To pay these debts, some farmers began to devote more and more land to groundnuts. This sometimes caused cattle herding and other land uses to be displaced and pushed into more ‘marginal’ semi-desert areas. During particularly dry years, marginal lands produce very little vegetation. They then quickly became overgrazed and barren.


A groundnut crop in Niger. What problems have been associated with the large-scale commercial growing of groundnuts in Niger?


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Rainfall levels at a village in Burkina Faso between 1970 and 2010. Do you think the rainfall trends shown here are suited to crop growing? Explain.


Annual precipitation (mm)


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