A field experiment was carried out from 1990 to 1994 in the experimental area of the Soil Department at the Federal University of Santa Maria, State of Rio Grande do Sul, Brazil, on an Hapludalf to evaluate the potential of some winter legumes as N suppliers to no-tillage corn. A completely randomized block design with split-plots was used, with the winter crops in the main plots and the N rates for corn in the split-plots. In the main plots, the legumes common vetch (Vicia sativa L.), field pea (Pisum sativum var. arvense (L.) Poir), wild winter pea (Lathyrus sativus L.) and blue lupine (Lupinus angustifolius L.) and the graminea black oat (Avena strigosa Schieb.) were implanted every winter. A treatment with fallow was used as a reference. The rates of N for corn were 0, 80 and 160 kg ha-1, applied as urea. On average for the four years, the two specie that produced the greatest amounts of dry matter were blue lupine (5,228 kg ha-1) and black oat (4,417 kg ha-1), followed by wild winter pea (3,047 kg ha-1), field pea (2,754 kg ha-1), common vetch (2,527 kg ha-1), and winter fallow (1,197 kg ha-1). Among the legumes, the blue lupine was the specie that accumulated the largest amount of N in the aerial part (113.7 kg ha-1 of N). The treatments that added the smallest amounts of N to the soil for the phytomass were black oat (41.7 kg ha-1 of N) and weeds under fallow conditions (20.5 kg ha-1 of N). Aproximately, 60% of the N accumulated by the above ground legume biomass was decomposed during the first 30 days after legume management. When N fertilization was not used, corn grain yield was greatest after legumes than after oat or winter fallow. The legumes differed in their potential as N suppliers to corn. The largest values of equivalent mineral N were obtained with common vetch (137 kg ha-1 of N) and blue lupine (122 kg ha-1 of N), evidencing the possibility of reduction of the amounts of mineral N to be applied to corn when cultivated in succession to these two legumes.
legumes; no-tillage; green manure; decomposition