Abstract
Soil erosion is a serious challenge for sustainable crop production. Alfisols in Nigeria are easily prone to soil degradations which have significantly reduced soil productivity, crop yield and increased cost of production. The use of soil conservation measures are vital interventions for sustainable crop production against the effects of erosion. The impacts of soil conservation on erodibility of an Alfisol was investigated in a tropical alfisol in Southwestern Nigeria. The study utilized four-soil conservation measures - Irvingia wombulu, Irvingia garbonensis, paddock and Cynodon plectostachyus was established on 20.4 ha land for 25 years, and replicated thrice based on land area. Empirical soil erodibility factor using Universal Soil Loss Equation (USLE) and Water Erosion Prediction Project (WEPP) erodibility factor models was determined. Analysis of variance analysis was done using R statistics to ascertain response patterns of the soil conservation measures to erodibility. Correlation was conducted for the conformity and relationship between erodibility models and soil properties. I. garbonensis soil conservation measure gave the least erodibility factor (K = 0.07), among paddock (K = 0.09), I. wombulu (K = 0.11) and C. plectostachyus with the highest erodibility factor (K = 0.17), indicating that I. garbonensis has the highest potential for soil conservation. Soil conservation measures significantly (p ≤ 0.05) influenced soil properties. Wischmeier and Mannering's USLE erodibility and WEPP's rill and inter-rill erodibility were not significantly (p ≥ 0.05) different across the soil conservation measures. Elswaify and Dangler's USLE erodibility correlated best with Wischmeier and Mannering USLE erodibility (r = 1.00) and WEPP's rill (r = 0.8) and inter-rill (r = 0.8) erodibility. Sand, silt, organic carbon, available phosphorus and aggregate stability significantly (p ≤ 0.05) correlated with USLE erodibility factor. Elswaify and Dangler USLE erodibility gave higher precision in erodibility determination of the soils. I. garbonensis was more efficient in reducing soil erosion, indicating that it is the best soil conservation measure for sustainable agriculture in alfisols in the tropics.