Water erosion on an hapludox submitted to different soil managements under simulated rainfall. I - Soil and water losses

Soil management influences surface cover and roughness, and it is the major factor that affects water erosion. A rotating-boom rainfall simulator operated at a constant rainfall intensity of 64 mm h(-1) and 0.2083 MJ ha(-1) mm(-1) kinetic energy was used to investigate water erosion and related parameters in six management systems of corn and bean crops. The experiments were carried out on a clayey loam structured soil (Hapludox) with 0.165 m m(-1) average slope, on the Southern Plateau of Santa Catarina State, Brazil, from March 2001 to April 2003. Three simulated rainfall tests were applied to the corn and three to the bean crop in the following treatments: plowing + disking (bare soil) (SSC), corn and bean crop after plowing + disking on desiccated residue (PCO), corn and bean crop under no-tillage on desiccated residue onpreviously prepared soil (SDI), corn and bean crop under no-tillage on desiccated residue on never tilled soil (SDD), corn and bean crop under no-tillage on burned residue on never tilled soil (SDQ), and improved native pasture (CNM). Soil losses were strongly influenced by the soil management while water losses were only slightly affected. Results showed that the SDI treatment reduced the soil loss 96 % in relation to PCO, while the water loss, equivalent to 22 % of the applied rainfall volume in the PCO, was reduced to 7 % of the above-mentioned volume produced in the SDI in crop means. The burning of crop residues increased the soil loss 21 -fold compared to no burning while the water loss, equivalent to 22.5 % of the applied rainfall volume in the SDD, rose to 26.5 % of the above-mentioned volume obtained in the SDQ in the crop means. Soil losses were exponentially correlated with the soil cover percentage by crop residues and with the soil cover percentage by canopy crops. D-50 index was also exponentially correlated with the soil cover-percentage by crop residue.