Effects of Surface Mulching and Velvet Bean Cover Crop on Runoff Generation and Soil Loss in a Sandy Loam Soil of Southeastern Nigeria

Abstract

Soil erosion remains a major environmental and agricultural challenge in southeastern Nigeria, particularly in Awka, Anambra State, where high rainfall intensity and fragile sandy loam soils accelerate land degradation. This study evaluated the effectiveness of surface mulching and velvet bean (Mucuna pruriens) cover cropping in reducing runoff generation and soil loss under field conditions. A randomized complete block design with three treatments—bare soil (control), maize stalks and husks mulch, and velvet bean cover crop—was employed with three replications. Runoff, soil loss, runoff coefficient, and infiltration characteristics were measured under natural rainfall conditions. Results showed a progressive reduction in runoff and soil loss across treatments. Soil loss values were 6.0 t/ha for bare soil, 2.7 t/ha for mulching, and 1.0 t/ha for velvet bean. Corresponding runoff coefficients were 0.54, 0.30, and 0.14, respectively. Analysis of variance revealed highly significant differences among treatments (F = 62.77, p < 0.001). Percentage reductions in soil loss were 55.0% for mulching and 83.3% for velvet bean relative to bare soil. Regression analysis indicated a strong relationship between runoff and soil loss (R² = 0.96). Velvet bean exhibited the highest infiltration rates and lowest erosion losses, demonstrating superior soil protection. The study concludes that vegetative cover, particularly velvet bean, is an effective and sustainable strategy for soil erosion control in the study area