SOIL LOSS RATIO AND C FACTOR FOR CORN MANAGEMENT SYSTEMS FOR THE UNIVERSAL SOIL LOSS EQUATIONSoil loss data from research plots at three Experimental Stations of the Instituto Agronômico, State of São Paulo, Campinas, Pindorama and Mococa, were tabulated to determine C factor for corn management systems. Data for 7 -year periods and three soils, Typic Haplortox, Petrofenic Tropudult and Oxic Argiudoll were collected from plots cropped to continuous corn and corn following legumes and pastures. Treatments were continuous corn, buried residue; continuous corn, burned residue; continuous corn, residues left on surface; corn after soybean; and corn after pasture. Crop stage periods were defined as F - from tillage to planting (rough fallow); SB - planting to 35 days after planting (seedbed); 1-35 to 60 days after planting (establishment); 2-60 to 80 days after planting (development); 3-80 days to harvest (maturing crop), and 4 - harvest to tillage (residue). Soil loss ratio (SLR) for the individual crop stage periods varied greatly between years and locations. For each management system SLRs were calculated as weighted average of the values obtained for each location. The SLR for the crop stages F, SB, 1, 2, 3 and 4 were 0.24, 0.34, 0.14, 0.09, 0.06 and 0.01 , respectively, for continuously cultivated corn crop with incorporated residues. The SLR obtained here were substantially lower than those reported by Wischmeier & Smith for all crop stage periods of corn. The annual C-values obtained for different management systems and different locations ranged from 0.025 to 0.156 t ha t-1 ha-1.
Index terms
universal soil loss equation; C factor; corn; water erosion