Corn yield and soil nitrogen following winter annual cover crops interseeded into soybean

Nitrogen demand for corn (Zea mays L.) production is high, and winter annual cover crops (WCC) can be an alternative source of plant-available N. Common corn-soybean [Glycine max (L.) Merr.] rotations in the Mid-Atlantic region leave fields fallow after soybean, providing a niche for WCC. The objective of this research was to evaluate the effect of rye (Secale cereale L.), hairy vetch (Vicia villosa Roth subsp. Villosa), and rye-vetch mixture WCC interseeded into soybean on soil N, corn grain yield, and fertilizer N replacement from cover crops. Eight different field sites were seeded into standing soybeans in Virginia from 2012-2014. The experiment was a split-plot design with WCC species as the main plot in a full factorial arrangement with N rate (0 or 45 kg N ha(-1) as starter fertilization at planting, and sidedress rates of 0, 45, 90, 135, and 180 kg N ha(-1)) as subplots. Maximum corn grain yield following hairy vetch WCC was 0.7 and 0.6 Mg ha(-1) higher than when following rye at 0 and 45 kg ha(-1) starter N, respectively. At one site where hairy vetch biomass was >2 Mg ha(-1), corn grain yield increased beyond levels attributable only to the addition of legume N. Instead of decreasing the sidedress N requirement, optimum N rates with hairy vetch were similar to other WCC, only with higher yields. Hairy vetch WCC generally resulted in higher soil N than other WCC at the V4 stage of corn, but no differences after corn harvest.