Using Cover Crops in Wheat-Corn Rotations to Provide Forage While Improving Soil Health.

The time window after wheat harvest in a corn-wheat rotation sequence could potentially be used to grow cover crops that provide harvested forage while protecting soil from water and wind erosion and other damaging factors, but the impact of forage harvest on soil improvement under cover crops is not well quantified. We are conducting a two-year randomized complete block design experiment (n=4) to look at the consequences of partial removal of cover crop biomass on soil improvement and crop yield in a wheat-corn rotation sequence. Treatments are in a split plot arrangement with cover crop as the main plot fallow negative control, red clover positive control, alfalfa, cowpea, sunn hemp, radish, oat/field pea mixture, BMR sudangrass, BMR sudex, and teffgrass and forage harvest (harvested or not harvested) as the subplot. Wheat was planted in October 2013, harvested in July 2014, and followed immediately with no-till planting of cover crop treatments. Half of each cover crop plot was mechanically harvested six weeks after planting and allowed to regrow. Corn was planted in spring 2015. First-year results were strongly impacted by unusually cool, wet weather in 2014 which delayed wheat harvest and cover crop planting by almost a month and was not favorable to growth of warm-season cover crop species. Wheat yield was uniform but low across all plots (4.09 Mg/ha). Forage dry matter yield (Mg/ha) ranked greatest for red clover (4.39) > oat-pea (3.03) > sudangrass (2.32) > sudex (1.83)  > all other treatments (avg 0.66) (P < 0.001). Nutritive composition of harvested cover crop was generally adequate for haylage production, but low dry matter concentration at harvest would require wilting. Corn will be harvested in fall 2015 with results presented. The unusual growing conditions in 2014 represented an extreme for cover crop growth in the first year of this trial.