A field experiment was carried out at the experimental área of the Soil Department, Federal University of Santa Maria, RS. Brazil, in a Yellow Redish soil, to evaluate the potential of Winter and Summer soil cover species to supply nitrogen to corn and the corn grain yield during 1992/93 to 1994/95 growing seasons. The Winter treatments were: (a) black oat (Avena strigosa) + common vetch (Vicia sativa) + 130kg ha-1 of mineral N for corn and b) blue Lupinus (Lupinus angustifolius) + 65kg ha-1 of mineral N for corn. The Summer treatments were: (a) gray mucuna (Stizolobium cinereum) and (b) pig bean (Canavalia ensiformis), seeded between corn rows about 100 days after corn seeding, with 65kg ha-1 of mineral N applied to corn. The control plots were Winter fallow without nitrogen for corn and Winter fallow with 130Kg.ha-1 of mineral N for corn. The Summer species accumulated the double of nitrogen in the biomass, with pig bean distinguishing over the gray mucuna, conparing to Winter species. The biomass of these Summer species and the corn, however, did not correspond to this superiority in relation to nitrogen accumulation. Corn grain yeld were 4927, 5191, 5405 and 4752kg ha-1 after Lupinus, mucuna, pig bean and uinter fallow + N, respectively. Those results demonstrates that the cover plants with half of mineral N fertilization reached yields similar to fallow +130kg ha-1 in the corn, which indicate the efficiency of these species in the fixation of atmospheric N2 and the partial supply of nitrogen to corn.
green manure; nitrogen; corn; no-till
