Living mulches of legumes in imidazolinone-resistant corn

Living mulches of legumes are permanent cover crops that can fix atmospheric N and improve soil quality. The objectives of this study were to determine effects of living mulches on corn (Zea mays L.) yield and N fertilizer response and on soil quality. In this split-plot design, living mulches were main plots and N rates (0-225 kg ha^-1 N) subplots. Living mulches were crownvetch (Coronilla varia L.) cultivars Penngift and Pennmulch, flatpea (Lathyrus sylvestris L.) cultivar Lathco, birdsfoot trefoil (Lotus corniculatus L.) cultivars Empire and Steadfast, hairy vetch (Vicia villosa Roth), and galega (Galega officinalis L.). The crop was rainfed imidazolinone (IMI)-resistant corn on a Murrill silt loam (Typic Hapludult) in central Pennsylvania. Only crownvetch, flatpea, and birdsfoot trefoil (BFT) cultivars survived the herbicide program. Living mulches did not reduce corn yields, except in the dry year of 1995. The average N fertilizer equivalency of Penngift, Pennmulch, Empire, Steadfast, and Lathco was 71, 45, 44, 13, and 50 kg ha^-1 yr^-1, respectively, at 0 N rates. Their N fertilizer equivalency decreased to zero, however, with increasing N fertilizer rates. Bulk density, soil organic C content, and infiltration rate were not significantly improved after 10 yr of Penngift living mulch. When suppressed severely, crownvetch, BFT, and flatpea can be managed without yield reduction to IMI-resistant corn, but then N contribution to corn and soil quality benefits will be limited. For maximum corn yield, full N rates are required with these living mulches.