Browse Theses

Soil erosion and nutrient loss as a result of lack of ground cover in conventional corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] cropping systems in the U.S. Midwest warrant use of cover crops to provide improved protection to the soil. There are needs for alternate cropping systems and management practices capable of protecting our resources without sacrificing existing and future crop yield goals. Field pennycress (Thlaspi arvense L.) and winter camelina [Camelina sativa (L.) Crantz] are short season annual oilseed crops having the potential to be integrated into corn and soybean systems as cash cover crops. Alfalfa (Medicago sativa L.) also has the potential to be intercropped with corn to accelerate its establishment period compared to conventional spring seeding while acting as a cover crop in fall following corn harvest. We interseeded pennycress, camelina, and winter cereal rye (Secale cereale L.) in corn and soybean at late reproductive stages. Soybean was relay planted the next year with an objective to (i) determine the effect of cover crops on row crop grain yield, (ii) assess the survival, biomass and seed yield of cover crops, and (iii) determine the effect of cover crops on soil moisture and weed density. In another study, corn was intercropped with alfalfa with and without the application of prohexadione with an objective to (i) determine the effect of intercropped alfalfa on corn grain yield, (ii) estimate the survival and biomass production of intercropped alfalfa, and (iii) determine the overall productivity of the intercropping system. Corn and soybean yields were not affected by interseeding cover crops from mid-August to late Sept. but soybean yield when relay planted into oilseed cover crops was reduced by 12 to 32%. Overall seed yield of pennycress and winter camelina was 218-880 kg ha-1 and 15-770 kg ha-1, respectively. Corn yield was reduced by 23-26% when intercropped with alfalfa in a dry year whereas intercropped alfalfa stand density was reduced by 36-68% in the establishment year. Despite the reduction in corn yield, the overall productivity of a corn and alfalfa intercropping system was greater than the conventional system where alfalfa is spring seeded following corn harvest.