SMALL GRAIN COVER CROPS FOR CORN AND SOYBEAN

Authors: Singer, Jeremy; Kaspar, Thomas; PEDERSEN, P - IA STATE UNIVERSITY

Submitted to: Meeting Abstract
Publication Type: Experiment Station
Publication Acceptance Date: 7/8/2005
Publication Date: 7/12/2005
Citation: Singer, J.W., Kaspar, T.C., Pedersen, P. 2005. Small grain cover crops for corn and soybean. Fact Sheet:PM 1999. Meeting Abstract. Available: http://www.extension.iastate.edu/pubs/Masterlist4.html#1800

Interpretive Summary:

Technical Abstract: Cover crops cover the soil and may be used to reduce soil erosion, limit nitrogen leaching, suppress weeds, and increase soil organic matter. Small grain cover crops increase surface cover, anchor corn and soybean residues, increase water infiltration, and reduce both rill and interrill erosion. A three-year study in Iowa reported that rye cover crops over-seeded into no-tillage soybean reduced interrill erosion by 54 percent and rill erosion by 90 percent compared with no-tillage without cover crops. Oat cover crops reduced interrill and rill erosion by 26 percent and 65 percent, respectively. Nitrogen remaining in the soil after harvest is a significant source of nitrate contamination for groundwater, wells, streams, and lakes. During the late fall and early spring, small grain cover crops accumulate nitrate that would otherwise leach out and potentially contaminate water supplies. Nitrate accumulated by cover crops is recycled into the soil in plant residues. In Iowa, field studies conducted over three years have shown that rye cover crops reduced nitrate losses by 96 percent while oat cover crops reduced losses by 75 percent. Small grain cover crops can also reduce the number of early season weeds and provide a mulch for continued weed suppression. Species Selection Winter-hardy cultivars of rye, wheat, and triticale planted in the fall offer the best erosion protection because they provide fall and winter cover and regrow in the spring. Oat and spring cultivars of wheat, rye, and triticale can be planted in early fall, but will winter kill. A three-year study in Iowa reported fall average oat dry matter production of 410 lb/acre compared to 365 lb/acre for rye. In spring, rye dry matter prior to corn production was 1666 lb/acre. Information for oat, wheat, and triticale cultivar selection can be obtained from Iowa State Extension at the following website: http://www.extension.iastate.edu/pubs/cr.htm. Contact your local seed dealer to find out which cultivars of winter and spring rye are available in your area. Oat Oats are the primary small grain planted in Iowa. When planted as a grain crop, they are planted in early spring. They will not overwinter in Iowa. If planted in the fall as a cover crop, they winter kill, and will not regrow in spring. If planted in early spring as a cover crop, they need to be killed with tillage, cutting, rolling, or herbicides. In Iowa, seeds of adapted oat cultivars are widely available and the least expensive of all small grains. Rye Rye cultivars are available as either spring or winter types. Winter rye is the most winter-hardy of the small grains and usually has excellent winter survival in Iowa. If planted as a fall cover crop, rye will overwinter, regrow vigorously in the spring, and need to be killed with tillage, cutting, rolling, or herbicides. Spring rye cultivars used as cover crops are managed the same as oat. Winter rye seed is available in many locations in Iowa, but usually the cultivar is unnamed or unknown. Spring rye seed is not readily available in Iowa. Wheat For grain production, spring wheat is adapted to the northern third of Iowa and winter wheat to the southern third of Iowa. Spring wheat is the hard red type and winter wheat is hard or soft red. The presence of snow cover dramatically improves winter wheat survival in Iowa. Generally, hard red wheats are more winter-hardy than soft red wheats. Even adapted cultivars of hard red winter wheat will have severely reduced stands because of winter damage in one out of five years. Winter wheat cultivars used as cover crops are managed the same as winter rye and spring wheat cultivars are managed the same as oat. Named cultivars of winter wheat are available in Iowa. Triticale Triticale cultivars are crosses between wheat and rye and have both spring and winter types. The winter-hardiness of