Soil and water losses in different soil tillage systems on a hapludox under simulated rainfall

Soil management has an impact on soil cover and roughness, and, together with other variables, affects water erosion. In Sao Jose do Cerrito, State of Santa Catarina, Brazil, three simulated rainfall tests were evaluated during the soybean cycle March 2000 through June 2001 in combination with the five tillage systems: plowing + disking (bare soil) (BS); plowing + disking and soybean crop on dry oat residues (PD); chiseling + disking and soybean crop on dry oat residues (CD); soybean crop and no-tillage on desiccated natural pasture (NTD); and soybean crop and no-tillage on desiccated and burned natural pasture (NTDS). The experiments were carried out in two replications under field conditions, in a clay loam structured soil (Hapludox) with 0.18 m m(-1) average slope, under a constant rainfall intensity of 64 mm h(-1). There was a remarkable impact of the tillage systems on soil losses, while water losses were moderately influenced. The CD treatment reduced soil and water losses by 85 and 34 %, respectively, in relation to the PD treatment. Under the BS treatment, this reduction was 96 and 40 %, respectively, in the mean of the simulated rainfall tests. Treatments NTD and NTDS presented very similar soil and water losses. Soil losses were 88 % lower than in the CD treatment and, in the case of water losses, practically identical to the CD treatment.