When farmers plant a single crop, whatever nutrients that crop needs will be absorbed from the soil. This will result in a depleted soil if the same crop is grown year after year. Soil is considered to be a natural resource as it takes hundreds of years to form from bedrock, by the process of weathering as well as the decomposition of organic matter. Instead of a single crop, farmers can alternate rows of different crops. This prevents nutrients from becoming depleted as quickly. If they leave older stalks and other organic matter to decompose, that allows the soil to recover and prevents erosion as well.