The aim of this study was to identify corn production systems using green manure crops showing characteristics of sustainability. The experiments were carried out on a Yellow-Red Podzolic soil, 5.5% slope, at Federal University of Santa Maria, State of Rio Grande do Sul, Brazil, from 1991 to 1993. Plot dimensions were 3.5 m by 22.0 m, as defined by the methodology of natural rainfall erosion plots. The treatments consisted of: (i) bare soil, (ii) black oat (Avena strigosa) + common vetch (Vicia sativa)/corn, (iii) blue lupine (Lupinus angustifolius)/corn, (iv) wild winter pea (Lathyrus sativus)/corn, (v) gray "mucuna" (Stilozobium cinereum)/corn, (vi) pig bean (Canavalia ensiformis)/corn and (vii) natural grass. Green manure crops and corn were sowed on no-tillage system. Soil cover and erosion rates were evaluated in all production systems. After 18 months, chemical, physical and biological soil characteristics were analysed in order to assess any alteration induced by the different treatments. Soil cover was high in all systems; particularly in black oat + vetch/corn, gray "mucuna"/corn and pig bean/corn, which showed effective erosion control, with soil and water loss reductions higher than 98 and 85%, respectively. Incorporation of green manure crops into corn production systems resulted in a high carbon addition, leading to an increase of carbon content in the soil top layer (0-2.5 cm). Comparing to bare soil, soil infiltration (measured by a rainfall simulator) and microbiological activity (0-5 cm) were also increased. The use of legumes made possible to reduce 50% of the mineral nitrogen fertilization, with grain yield superior to double the State average. Considering the reduction of soil and water losses and changes in the biological, physical and chemical soil attributes, it can be concluded that these systems have characteristics of sustainability.
sustainable systems; nitrogen; soil and water losses; organic carbon; green manure