Eects of erosion-induced degradation on soil chemical quality, plant nutrient loss in runo water and water quality were related to slope length for a 5-year study from 1984 through 1988 conducted on tropical Al®sols under maize (Zea mays)± cowpeas (Vigna unguiculata) rotation. A total of 13 ®eld runo plots involved six slope lengths (i.e. 60 m, 50 m, 40 m, 30 m, 20 m, and 10 m), two tillage methods (i.e. conventional till and no-till), and an uncropped control of 25 m length. Slope length eects on soil chemical quality diered among tillage methods. Decrease in slope length had a favorable eect on soil chemical quality in the conventional till treatment for exchangeable Ca 2 , cation exchange capacity (CEC) and Bray-P. The soil organic carbon (SOC) increased with decrease in slope length at the rate of 0 . 007 per cent m À1 for 0±5 cm depth and 0 . 015 per cent m À1 for 5±10 cm depth, and soil pH decreased with increase in slope length. Soil concentration of Bray-1 P generally increased with decrease in slope length. For the no-till treatment, however, there were no consistent trends in soil chemical quality with regard to slope length. Further, soil chemical quality was superior under no-till than conventional till treatment for 0±5 cm and 5±10 cm depths. All soil chemical properties declined with cultivation duration, with the rate of decline being more in conventional till compared with the no-till treatment. The rate of decline for the conventional till treatment was 0 . 396 per cent year À1 for SOC, 0 . 21 unit year À1 for pH, 0 . 053 per cent year À1 for total soil N, 0 . 375 cmol kg À1 year À1 for Ca 2 , and 0 . 41 cmol kg À1 year À1 for CEC. The rate of decline in soil quality with cultivation duration was consistently more for longer than for shorter slope lengths especially for SOC and soil pH. Temporal changes in soil chemical quality for the no-till treatment were not well de®ned. The total loss of plant nutrients in runo ranged from 8 . 4 kg ha À1 to 17 . 8 kg ha À1 for season 1, and, in general, the nutrient loss decreased with decrease in slope length. The total loss of plant nutrients in season 2 was lower than that in season 1, and lower with no-till compared with conventional till treatment. Total nutrient loss in runo decreased with increase in slope length for conventional tillage, and increased with decrease in slope length for the no-till treatment. Concentration of plant nutrient in runo diered among elements, tillage methods and slope length treatments. Concentration of bases and NO 3 -N in runo followed a U-shape response over time during the year, with relatively high concentrations toward the beginning and end of the rains. The concentration of PO 4 -P in runo generally decreased with time after application of fertilizer. For the conventional till treatment, the concentration of PO 4 -P, K, and Fe decreased with decrease in slope length.