Twin Cities WRS Seminar
Mitigating Nitrate Leaching on Irrigated Sandy Soils with Nitrogen Management and Rye Cover Crop
Nearly 500,000 acres of Minnesota farm land are irrigated sandy soils and produce impressive corn yields when supplemented with N fertilizer; however, the majority of these acres are prone to NO 3 - - N leaching that pose high risk for groundwater contamination and reduced return on fertilizer investment. Recent studies determined that the majority of NO 3 - -N leaching takes place early in the growing season when precipitation is frequent and there is little to no plant biomass to take up excess soil water and nutrients. Research also suggests that cover crops could be a solution to mitigate NO 3 - -N leaching but the research is limited to fine-textured soils. The objectives of this study were to 1) evaluate the impact of a rye cover crop on crop yield and N requirements, and 2) measure the effect of N rate and rye cover on season-long NO 3 - -N leaching losses below the root-zone. Extensive data was collected to answer these questions including weekly soil water NO 3 - -N concentrations using permanently- installed porous-cup suction lysimeters. The results suggested that rye cover had no effect on corn yield and can have inconsistent effects on N requirements. In a corn-soybean rotation rye reduced the economic optimal N rate (EONR) by 52 lbs N ac -1 in 2016 but increased it by 47 lbs N ac -1 in 2017, while there was no difference in continuous-corn. Additionally, rye had no impact on leaching in continuous-corn but reduced leaching in corn-soybean. These preliminary results are encouraging and revealed opportunities for improved nitrogen management for these productive yet high risk soils.