EFFECT OF FIELD SLOPES AND MULCH RATES ON RUNOFF AND SOIL LOSS IN OWERRI, NIGERIA

Abstract

Simulated rainfall was used to determine quantitatively the effect of field slopes and mulch rates on runoff and soil loss in Owerri, Nigeria. The results obtained show that soil loss and runoff significantly increased with increase in field slope, and were reduced with successive increase in mulch application. The bare plot yielded 0.22t/ha soil loss and no runoff on 2% slope; 12.58t/ha soil loss and 564m3/ha runoff on 9% slope and 18.42t/ha soil loss and 870m3/ha runoff on 15% slope. The possible minimum desirable mulch (Panicium maximum) cover required to protect the soil at 2% slope is St/ha. The 5t/ha mulch cover reduced soil loss by 76% and runoff by 64% on 9% slope, and by 76% and 56% respectively on 15% slope when compared to the bare plots. Better results were achieved with 10t/ha mulch cover on each slope. However, based on the generally recommended mulch rate of 4-6t/ha for the tropics, the study recommends 5t/ha mulch cover as the desirable and most cost effective rate for controlling erosion on sloping loamy sand soil of Owerri, Nigeria.