Sustaining Soil Nitrogen for Corn Using Hairy Vetch Cover Crop

Abstract Nitrogen fertility management is often complicated by inadequate supply, low efficiency, high losses, and the potential of polluting water resources. This study was conducted in 1984 and 1985 on a Maury soil (fine, mixed, mesic Typic Paleudalfs) in Kentucky to determine the role of a hairy vetch ( Vicia villosa Roth) cover crop in sustaining soil N for corn ( Zea mays L.) under no‐tillage and conventional tillage. Winter cover treatments of hairy vetch, rye ( Secale cereal L.), and corn residue were combined factorially with N rates of 0, 85, and 170 kg ha −1 in the two tillage systems. Total soil C and N in the 0‐ to 7.5‐cm depth, averaged across treatments and sampling dates, were 21.8 and 2.07 g kg −1 , respectively, in no‐tillage and 16.6 and 1.70 g kg −1 in conventional tillage. Values were 19.8 and 1.99 g kg −1 , respectively, with hairy vetch and 18.8 and 1.80 g kg −1 with rye. Conventional tillage caused rapid mineralization of soil N, as indicated by greater inorganic N approximately 6 wk after plowing. Nitrate apparently leached deeper into the soil under no‐tillage than conventional tillage. Grain yield without N on the vetch treatment was essentially equal to yields with 170 kg N ha −1 on the rye or corn residue treatments—6.75, 6.75, and 6.65 Mg ha −1 , respectively. Grain yield with vetch and 170 kg N ha −1 was 7.85 Mg ha −1 . Although vetch provided a substantial amount of N, results suggested that to obtain optimum corn yields N fertilization should be reduced little, if any, with a vetch cover crop. Vetch appeared to add grain yield instead of reduce the need for N fertilizer.