No-Till Drilling Cover Crops after Wheat Harvest and their Influence on next season’s corn (E2897)
Over the past five years, Michigan has seen a 22 percent decline in wheat acres (Mich. Ag Stats, 2000-01).This decline is primarily because the markets for wheat have not been competitive with those for other field crops.
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Over the past five years, Michigan has seen a 22 percent decline in wheat acres (Mich. Ag Stats, 2000-01).This decline is primarily because the markets for wheat have not been competitive with those for other field crops. Wheat is a very important rotational crop. Integrating wheat or rye into a corn-soybean rotation can increase corn yield by 10 percent (Copeland, personal communication, 1997).A small grain can also disrupt winter annual weed populations. Developing a more diverse crop rotation that includes a small grain will disrupt pest cycles and enhance soil quality.
We have known for a long time that growing one continuous crop ultimately results in yield reductions, pest problems and high fertility needs. For example, continuous corn requires a soil insecticide, herbicides and a high amount of nitrogen each year. If grown continuously, soybeans will likely develop a soybean cyst nematode problem. Because of this, most field crop farmers in Michigan have adopted a corn-soybean rotation system. Evidence now suggests that two-year rotations may not be long enough to break all pest cycles, however. Recent long-term two-crop rotations of corn and soybean have resulted in the development of variant behavior in female western rootworm beetles. These beetles will deposit eggs into standing soybean fields. When corn is planted in this soybean field next season, western corn rootworms (CRW) are ready and waiting. A corn-soybean rotation used to confuse the CRW, but now the CRW has adapted to this rotation. The end result is that farmers may need to use a soil insecticide even with a two-year corn-soybean rotation.
Using small grains as a third crop in a rotation provides farmers a better long-term soil, insect, weed and disease management system. Wheat is seeded after the Hessian fly-free date, usually into soybean stubble. Wheat and rye are winter annuals that are established in the fall and mature in Michigan in July. Because these small grains are seeded in the fall and harvested in midsummer, a window of opportunity exists to seed cover crops and further increase crop diversity.
Many farmers used to frost seed red clover into wheat. This seeding practice usually occurs in March when the ground is frozen in the morning and thaws in the afternoon—the freeze-thaw action shallow incorporates the clover seed in the soil. Most of the initial growth of the red clover plant is root development. The wheat grows aggressively in the spring and early summer, shading the red clover’s top growth. In July, wheat is harvested, and the red clover now receives full sunlight and, with adequate moisture, grows. At KBS we have demonstrated that frost-seeded red clover can reduce common ragweed populations (Mutch et al., 2003). Red clover, a biennial that acts like a perennial, allows the farmer to mow weeds and clover, which decreases weed populations and stimulates red clover growth.
Many farmers stopped seeding red clover when herbicides became available for wheat. The same herbicides that control broadleaf weeds also controlled the red clover. Therefore, red clover frost-seeded acreage has dramatically declined.
Because small grains are harvested in mid-July, farmers can usually no-till cover crops into the harvested fields. A study was initiated in late summer 1999 to evaluate four cover crops no-till drilled into harvested wheat stubble and their influence on weeds, nitrogen and corn yield.
In 1999, wheat was harvested July 6 and the straw was baled. On July 8, four cover crops and a control (no cover crop) were established. Crimson clover, oilseed radish, hairy vetch and soybeans were seeded at 15, 20 and 30 pounds per acre (lb./A) and 1 bushel/A, respectively. The cover crops grew and a biomass sample was taken October 20. Weeds and cover crops were separated, dried and weighed. Two biomass samples from 4 square feet were taken for each treatment.
Oilseed radish and hairy vetch resulted in the highest cover crop biomass in the fall. All cover crop treatments reduced weed biomass compared with the control (no cover crop) (Table 1A).
Spring biomass samples showed that hairy vetch and crimson clover (both legumes) had doubled their fall biomass weights (Table 1B).
Corn was planted into the cover crop treatments May 8 at 28,000 plants/A. The field was prepared by a chisel plow and disked. A broadcast herbicide treatment of 2.1 qt. of Bicep II Magnum™ was used to control weeds. The corn plots received nitrogen at either 0, 60 or 120 lb./A. Ammonium nitrate was side-dressed to evaluate the nitrogen effect of the cover crops.
In spring 2000, a presidedress nitrogen test (PSNT) was taken for each cover crop treatment.
Hairy vetch provided the greatest N credit. Crimson clover had a significantly greater N credit than oilseed radish, soybean or the control (Table 2).
Corn was harvested and yield of the plots with the cover crops and three nitrogen rates compared.