ON THE RELATION OF SOIL-EROSION TO RAINFALL EROSIVITY IN SOUTHEASTERNNIGERIA

Concern over soil improvishment and water quality problems associated with runoff and erosion from agricultural lands led to a combination o f laboratory simulation and field study aimed at further understanding rainfall-runoff-soil loss relationships and also to improve the metho ds of predicting sediment loss and escape of pollutants during rainfal l-runoff events. The paper presents a relation for assesing erosivity from rainfall characteristics especially in conditions with limited fa cilities for rainfall intensity monitoring. Regression analysis show t hat soil loss can be predicted from rainfall intensity using exponenti al function. Some improvement in correlation between soil loss and dai ly rainfall depth, P was achieved with the erosivity equation: EImin = (3.64 x 10(-3)logP - 6.3 x 10(-5))P-2 This relation offers a simple, straightforward and reliable method of predicting soil loss when only daily rainfall data is available. In the study area, the contribution of rainfall to runoff on sandy loam and sandy clay loam textures varie d from 21% to 28%. High intensity short duration storms produced detri mental effects on the soil. An inverse relationship between soil loss and rainfall data on seasonal basis demonstrate that other factors are needed to completely characterize soil erosion by rain.