Losses of nutrients and organic matter due to hydric erosion are highly affected by soil management. Inadequate management systems may cause pollution and eutrophication of surface waters, fertilization cost increase, and ecosystems degradation. Nutrient and organic matter losses due to erosion were evaluated during six years on a very clayey Dusky Red Latosol, with a 0.03 m m-1 slope at Dourados, Mato Grosso do Sul, Brazil under natural rainfall conditions, and different soil management systems. The treatments applied in the crop succession wheat/soybean, were: (a) chisel plowing + levelling disk harrow; (b) heavy disk harrow + levelling disk harrow; (c) no-tillage; and (d) disk plowing + twice levelling harrow, without plant covering. Runoff water was collected daily and the supernatant was separated from the sediment in the laboratory. Ca2+, Mg2+, and K+, and available P were determined both in the sediment and in the solution. Organic matter was determined only in the sediment. Ca2+ and Mg2+ concentrations were higher in the solution than in the sediment, and P and K+ were higher in the sediment than in the solution. No-tillage system showed the highest P concentrations in the sediment and the highest Ca2+ concentrations in the solution, as well as P highest enrichment rates in the sediment. The no-tillage system, however, was more effective in the control of total nutrients and organic matter erosion losses than the other tested systems. Among the cropped systems, the heavy disk harrow + levelling disk harrow was the least efficient, followed by the chisel plowing + levelling disk harrow. The heavy disk harrow + levelling disk harrow system, when compared to the no-tillage system, lost 6.5 times more K+, 6.0 times more P and organic matter, 5.0 times more Ca2+, and 4.0 times more Mg2+. Losses of Ca2+, Mg2+, and K+, total and in the solution, and organic matter in the sediment, were correlated with water and soil losses and adjusted to a mathematical potential model. The nutrient losses followed the sequence: Ca2+ > K+ > Mg2+ > P.
Oxisol; no-tillage; chisel plow; disk harrow; soybean; wheat