Impact of Fall-Planted Cover Crops on Greenhouse Gas Emissions and Corn Growth and Yield.

Two increasingly popular cover crops among Midwestern farmers are radish (Raphanus sativus L.) and annual ryegrass (Lolium multiflorum Lam.). Radish’s rapid growth and large biomass production allow it to take up residual soil N while outcompeting weeds and decreasing the potential for soil erosion. Annual ryegrass provides similar benefits. However, there are concerns with regard to the use of these cover crops to manage N. Radish has a relatively low C:N ratio and does not survive the winter. The potential thus exists for the N in the radish biomass to leave the system before cash crop planting. The N may be lost to surface runoff, leaching, or as part of greenhouse gas emissions. On the other hand, annual ryegrass has a relatively high C:N ratio; in spite of its name, it is winter-hardy. It is possible that N taken up by annual ryegrass may be immobilized in the soil after cover crop termination and thus not immediately available to a following crop. Planting a mixture of radish and annual ryegrass may help retain N in the system while improving N synchrony.

The purposes of this two-year, two-site study were to a). determine the quantity of N lost to greenhouse gas emissions in a cropping system that utilizes fall-planted cover crops and b). evaluate the impact of the cover crops on field corn growth and yield. Treatments included radish, annual ryegrass, radish + annual ryegrass, and a bare fallow control. Cover crops were drilled following wheat harvest and terminated the following spring. Field corn was then planted. Neither fertilizer nor irrigation was applied over the course of the study. Data collected included gas samples, fall and spring cover crop and weed biomass, and corn growth and yield measurements. Data from both years of the experiment are presented here.