Technical Abstract: Cover crops have many potential benefits for both soil and water quality in annual grain cropping systems, like the corn-soybean rotation. Studies in Iowa have shown that rye and oat winter cover crops can reduce erosion and nitrate leaching in corn-soybean rotations, which improves both water and soil quality. Cereal winter rye and oat cover crops reduced interrill erosion by over 33% and rill erosion by over 53%. Similarly, rye and oat cover reduced nitrate leaching in a tile drained field by over 50% and 40%, respectively. These studies on nitrate leaching and soil erosion demonstrate that winter cover crops can have substantial effects on both soil and water quality by keeping plants growing in corn and soybean fields during the normally fallow months between harvest and planting.