Sustaining Soil Nitrogen for Corn Using Hairy Vetch Cover Crop
- M. Utomo,
- W. W. Frye and
- R. L. Blevins
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.
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