The faster the water moves, the more soil is carried. This causes the top soil, the most productive layer, to be carried away. The top soil is where most of the organic matter is found. This organic matter contributes greatly to the productivity of the soil. Therefore, when top soil is carried away or eroded, the remaining soil is not as productive as before and crops do not grow as well.
Farmers can protect their soil from erosion in several ways.
They can build terraces on sloped land which slow down the water and move it off the field in a controlled manner. They also use contour plowing which means that, instead of plowing up and down the slope, they plow across, or at right angles to the slope. This allows water to soak in and not run off. Most farmers use a combination of terraces and contour plowing. When farmers harvest their crop they leave the stubble, or crop residue, on the surface of the soil.