Cover crops are literally "crops that cover the soil" and are primarily used for erosion control. For most of the Midwest where com and soybean are grown, cover crops would have to be grown between harvest and planting. Unfortunately, in the upper Midwest (especially north of I- 80) the potential growing season for cover crops is usually short and cold, thus limiting their growth and effectiveness. This problem can be partly solved by overseeding cover crops into either com or soybean in mid-August to early September. Additionally for crops that are harvested relatively early, such as silage com, seed com, or early-maturing soybean, a winter-hardy small grain cover crop can be planted with a grain drill or incorporated with shallow tillage before late October.