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Conservation Agriculture and soil erosion

Dr Johann Strauss
Senior Scientist , Directorate Plant Sciences Research and Technology Development Western Cape Department of Agriculture
One of the most important benefits of Conservation Agriculture ( CA ) is the protection of our soil against water erosion . To understand this benefit we must first understand how soil erosion is caused by water .

The erosion is caused by water that did not infiltrate into the soil but has run of the field . The impact of a raindrop on a bare soil surface as well as information on mechanisms of water infiltration dates back to the 1940 ’ s . Soil erosion and runoff is often seen as the nature of agriculture , especially on sloping land , but the truth is that this is just not the truth . Soil loss by erosion through runoff is avoidable . According to Lal ( 1982 ) the occurrence of erosion on cultivated land is merely a symptom of land misuse for that ecological environment - to put it bluntly : inappropriate farming practices .

The process Runoff and erosion start with the impact of a raindrop on a bare soil surface . In an article , published in the conference proceedings of the American Society of Agricultural
Engineering in 1967 , Meyer and Mannering explained the explosive power of raindrops . Raindrops hitting a hectare of bare soil in one year is the impact energy equivalent of 50 tonnes of TNT . The impact of the falling drops disaggregates the soil into very fine particles . These particles , dissolved in the water , clogs the soil pores and thus causes a sealing off of soil at the surface and impedes infiltration . The result is that water runs off the field and takes the soil particles along for the ride , causing erosion ditches while the sediment is deposited elsewhere . This “ elsewhere ” could be streams , rivers or dams , eventually resulting in loss of productive topsoil and unnecessary expenditure for the farmer and / or Government . When the soil dries out after the sealing has occurred ( called crusting ), it could be very detrimental to germination of
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