Legume Cover Crops as a Nitrogen Source for No‐Till Corn and Grain Sorghum

Abstract

AbstractIncreasing use of conservation tillage has brought about a renewed interest in growing winter legume cover crops. Field experiments were conducted to determine the fertilizer N equivalency of hairy vetch (Vicia villosa Roth), bigflower vetch (Vicia grandiflora W. Koch var. Kitailbeliana), and rye (Secale cereale L.) to no‐tillage corn (Zea mays L.) and grain sorghum [sorghum bicolor (L.) Moench]. A fallow treatment, consisting of stalk residue only, was used as a comparison. Fertilizer N rates for corn were 0, 50, or 100 kg N ha−1 for 1980 to 1983 and 0, 85, or 170 kg N ha−1 for 1984 to 1987. Hairy vetch produced the most cover crop dry matter with the highest percentage of N. During 1980 to 1983, corn grain yields were significantly higher with the vetch treatments than with rye or fallow treatments at the 0 and 50 kg N ha−1 rates with a tendency toward higher yields at the 100 kg N ha−1 rate. During 1984 to 1987, corn yields from the vetch treatments were significantly higher than the other cover treatments at all N levels. Grain sorghum, like corn yields, were greater with the vetch treatments than with the rye or fallow treatments, although the bigflower vetch treatment was not significantly higher than the fallow treatment at the 170 kg N ha−1 rate. The estimated fertilizer‐N equivalency of the hairy vetch‐N in the corn experiment was 75 kg N ha−1 and bigflower vetch was 65 kg N ha−1. Fertilizer N equivalency values in the grain sorghum experiment were estimated to be 125 kg N ha−1 for hairy vetch and 135 kg N ha−1 for bigflower vetch.