Cover crops are sown once the harvest is complete. They germinate, cover the soil, and hold it in place during the fall and winter. In the spring, they are allowed to die and contribute nutrients back to the soil. The use of cover crops has really caught on in Iowa where the acreage of corn and soy bean fields using cover crops is 1.2 million acres (16% of the land used for these purposes). Farmers utilizing cover crops routinely see an increase in yield per acre while using lower levels of fertilizer. Use the link at the end of this article to learn more about cover crops.