The Impacts of Cover Crops and Tillage on Nitrate-N Concentrations in Soil Water in Southern Illinois Row Crop Agriculture

Nitrate, as a water contaminant, can have many detrimental impacts on ecosystem and human health. With agriculture as one of the largest contributors to nitrate pollution in streams, the need to adapt agricultural practices that are less harmful to the environment is crucial. Furthermore, the need for optimizing agriculture production, while decreasing the impacts of nitrate leaching, becomes more critical as the world population grows. The purpose of this research was to evaluate methods for reducing nitrate leaching from agricultural fields and to determine the effectiveness of cover cropping systems for providing plant-available nitrogen that coincides with cash crop demands. Reductions of nitrate leaching have been documented from the incorporation of cover crops into field rotations, but more research is needed to understand what cover crops (legume vs. non-legume) along with what tillage system (conventional-till vs. no till) are the most effective at reducing nitrate losses. The four treatments for this two-year study were as follows: cover crop, no till; cover crop, conventional-till; no cover crop, no till; and no cover crop, conventional-till. The crop rotations for Season 1 were hairy vetch followed by corn, oats/radish followed by corn, no cover crop followed by corn. The crop rotations for Season 2 were cereal rye followed by soybean and no cover crop followed by soybean. Two tension lysimeters were installed in spring 2015 in each of the 18 treatment plots at 0.46 m deep and 0.91 m deep. Lysimeters were sampled every two weeks throughout the year except during January and February, where they were only sampled once a month. Impacts on soil health were also monitored. Soil samples were collected three times over the course of this study, in the spring of 2015, fall of 2015, and spring of 2016. Soil bulk density, infiltration rates, net nitrogen mineralization, and corn yield were also compared among treatments