Nitrogênio total de um solo submetido a diferentes métodos de preparo e sistemas de cultura

Low N availability is one of the main limiting factors of crop yield in degraded soils. A five-year experiment established on a Paleudult soil at the Experimental Station of the University of Rio Grande do Sul, Eldorado do Sul (State of Rio Grande do Sul, Brazil) was sampled after five years to determine the recovery capacity of total soil nitrogen (TN) by tillage methods and crop systems. The treatments consisted of three soil tillage methods (conventional, reduced and no tillage), three crop systems (oats/corn, oats + clover/corn, oats + clover/corn + cowpea) and different nitrogen rates (0 and 120 kg ha -1 ) applied to corn. Native grassland was sampled as the natural condition of the soil. The reduction of tillage and the addition of N by legumes in the crop systems increased TN in the top layers of the soil (0-2.5 and 2.5-7.5 cm). The crop system oats + clover/corn + cowpea under no-tillage contained, after five years, 490 kg ha -1 more TN in the 0-17.5 soil layer than oats/corn under conventional tillage, representing a relative difference of annual accumulation of 98 kg ha -1 year -1 .