Contour farming Soil erosion can be a major problem for farmers in Africa. It results in a loss of top soil and a decline in land productivity. Contour farming is a simple, cheap method used to prevent soil erosion and conserve rainwater. A simple A –frame is made using three sticks and a rock hanging down the middle from a piece of string. This is then walked along a plot of land to find the contour lines which are marked with sticks and string. These lines are used as a guide to dig trenches and barriers that redirect and slow down water run-off down a slope.