Soil and water loss data under natural rainfall in Lages, Santa Catarina State (Brazil), from November 1992 to October 1998, were utilized to calculate the soil loss ratio (SLR) and C factor for the Universal Soil Loss Equation (USLE) under three soil tillage systems for corn and oat in rotation with other crops. The studied treatments were: plowing followed by disking twice (P + D), chiseling plus disking (C + D) and no-tillage (NT)/direct sowing, cultivated with corn (Zea mays) and oat (Avena sativa) in rotation with other crops and compared to a check plot: plowing followed by double disking without crops (PDW), on an Inceptisol with an average slope of 0.102 m m-1. The culture cycle was divided in five crop stages with equal time intervals. The SLR and C factors varied remarkably among the soil tillage systems, crop cycle stages, cycle stages for same crops, and between crops, indicating a strong effect of soil management, season, crop and rainfall on these variables. The SLR values for corn were 0.1189, 0.0888 and 0.0611 (Mg ha-1) (Mg ha-1)-1 for the P + D, C + D and NT soil tillage systems, respectively, while for oat the SLR values for the same tillage systems were 0.0783, 0.0655 and 0.0760 (Mg ha-1) (Mg ha-1)-1. For the above mentioned soil tillage systems, the C factors were 0.1097, 0.0809 and 0.0610 (Mg ha-1) (Mg ha-1)-1 for corn and 0.0671, 0.0409 and 0.0372 (Mg ha-1) (Mg ha-1)-1 for oat.
universal soil loss equation; water erosion; conservation tillage