Submitted to: Integrated Crop Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/6/2001
Publication Date: 12/6/2001
Citation: KASPAR, T.C., PARKIN, T.B., KOHLER, K.A. SMALL GRAIN COVER CROPS FOR IOWA. INTEGRATED CROP MANAGEMENT CONFERENCE PROCEEDINGS. 2001. P. 85-89.
Technical Abstract: Small grain cover crops in a corn-soybean rotation have the potential to reduce erosion, prevent nitrate leaching, increase soil organic matter, and suppress weeds. Unfortunately, in the upper Midwest the potential growing season for cover crops is between harvest and planting of the primary crops and is usually short and cold, thus limiting their growth and effectiveness. This problem can be partly solved by overseeding small grain cover crops into either corn or soybean in mid-August to early September. Additionally for silage corn, seed corn, or early-maturing soybean, a winter-hardy small grain cover crop can be planted with a grain drill until late October. A three-year study in Iowa showed that over-seeded rye cover crops in no till reduced interrill erosion by 54% and rill erosion by 90% compared with no till without cover crops. Our studies also showed that over three years rye cover crops reduced nitrate losses by 96% while oat cover crops reduced losses by 75%. Unfortunately, corn yield reductions of up to 28 bu/acre and with an average of 21 bu/acre over seven years have been observed in Iowa following a rye cover crop that was killed at corn planting. Corn yield reductions have not been observed following an oat cover crop, which winterkills. We are continuing to work on the management of winter rye cover crops to reduce the risk of corn yield reductions. Additionally, we have begun searching for winter rye and wheat varieties that don't reduce corn yield. In the meantime, an oat cover crop can be used without fear of reducing corn yield and provides most of the benefits of a winter hardy cover crop.