Effects of Leguminous and Non-Leguminous Cover Crops and Tillage on Nutrient Leaching in a Corn/Soybean Rotation.

Agricultural practices like tillage and excessive fertilization can increase nutrient leaching especially nitrogen (N) leaching to ground water, in turn making it a major environmental concern. Tillage during autumn and early spring can stimulate N mineralization too early and increase the risk for nitrate leaching before subsequent crops have a chance to take up the nitrogen released by microbial activity. Cover crop establishment could provide an alternative measure to reduce potential nutrient leaching, nutrient loss via runoff, and soil profile accumulation of nutrients. The specific objectives included are; (a) to quantify the influence of cover crops (Hairy vetch or radish/oats or cereal rye) and tillage (till or no-till) on soil solution chemistry and soil nutrient content in corn/soybean rotation, (b) to evaluate the influence of cover crops on yield and biomass accumulation of corn and soybean. A field experiment was conducted in 2015 at agricultural research site adjacent to Southern Illinois University’s tree improvement center located on west side of the City of Carbondale, IL. Cover crop treatments with till and no till followed crop rotation of hairy-vetch/corn/cereal rye/soybean and radish-oats/corn/cereal rye/soybean and no cover crop treatments with till and no till followed crop rotation of corn/ soybean. Soil samples collected after corn/soybean harvest and after cover crop termination were used for analysis of standard soil fertility parameters. Soil solution nutrient concentration were measured through pan lysimeters installed below the ‘A’ horizon with depth varying from 15 to 25 cm. Soil solution samples were collected weekly or biweekly depending on the amount of precipitation received and were analyzed for pH, EC, anions (Br^-, Cl^-, F^-, NO₂^- , NO₃^-, SO₄^2-, and PO₄^3-), dissolved reactive phosphorus, total nitrogen and dissolved organic carbon. Preliminary results showed higher nitrate-N leaching in treatments planted with hairy vetch (Vicia villosa) under both tillage systems compared to all other treatments. Nitrate-N leaching decreased exponential to below 3 kg ha^-1 for all treatments up to termination of cereal rye in spring 2016. Long term soil solution monitoring is needed to discover temporal changes in nutrient leaching under these treatments. This research will help to better understand the interaction of cover crops with tillage and will help in decision making on selection of an appropriate cropping sequence for agricultural producers.