CHARACTERIZATION OF RUNOFF GENERATED UNDER VARYING COWPEA (VIGNA UNGUICULATA) COVER

Abstract

Erosion is one of the commonest environmental hazard that has rendered useless millions of hectares of arable soils in the tropics. This study was aimed at determining the runoff characteristics of soils planted with cowpea at different densities. Treatments were based on three densities: A (Bare soil) which serves as the control, B (13 stands/rn-) and C (26 stands/rn-). Soil moisture content was monitored using gravimetric method. Precipitation, runoff, drainage depths and sediment yields were measured during the experiment which was replicated twice. Rainfall-sediment yield model was established for ease of prediction of runoff that could occur from different precipitations. The water balance equation was used to compute the evapotranspiration for each plot. Results indicated that runoff depth was least in Treatment C (26 stands/m-) and was highest on the bare soil. There were significant difference in the sediment yield between the bare soil and the soil planted with 26 stands/rn- of cowpea with the bare soil having the highest value of sediment yield. Rainfall-sediment yield model show R2= 0.9665 in bare soil and 0.9085 in well covered soil in the second experiment respectively, an indication that plant density is a determinant of the sediment yield from rainfalls at any period or time. The result of this research work is useful in the prediction of future runoffs based on the available' storm data for a period.