Residual Effects of Interseeded Hairy Vetch on Soil Nitrate‐Nitrogen Levels

Abstract Increased use of winter legume cover crops has renewed interest in legume N mineralization patterns. This study was conducted to monitor the residual effect of a hairy vetch ( Vicia villosa Roth) cover crop and fertilizer N on surface soil NO 3 ‐N concentration in no‐till and conventional‐till corn ( Zea mays L.) in northeastern Nebraska on a Nora silty clay loam (fine‐silty, mixed, mesic Udic Halplustoll). The experimental design was a split‐split‐split plot with three replicates. Main plots of conventional tillage and no‐till were split into 0, 67, and 134 kg N ha −1 with and without hairy vetch. Soil samples were taken from the 0− to 7.5− and 7.5− to 15−cm depths five times during the 1987 growing season and three times in 1988. Inclusion of a hairy vetch cover crop interseeded during the previous growing season increased soil NO 3 ‐N concentration in the surface 7.5 cm between 50 and 64 d after corn planting and in the 7.5‐ to 15‐cm soil layer between 50 and 78 d after corn planting during 1987. In 1988 (a dry growing season), hairy vetch did not significantly increase soil NO 3 ‐N concentration in the 0‐ to 7.5‐cm soil layer at any sampling time, but did increase soil NO 3 ‐N concentration in the 7.5‐ to 15‐cm depth 103 d after planting. This increase in soil NO 3 ‐N concentration occurred in hairy vetch plots after silking, which probably resulted in the additional N not being available for plant growth in 1988. Increased available N resulting from a legume cover crop like hairy vetch may be beneficial in N management programs in lower rainfall areas of the USA when amounts of precipitation are adequate for plant growth and N mineralization.