Influence of Tillage and Vetiver Grass Strips Spacing on Soil Physical and Chemical Properties from Eroded Soil in Southern Guinea Savanna, Nigeria

Abstract

Field studies were conducted to evaluate changes in soil properties on eroded soil under vetiver grass strips and different tillage practices. Split plot experiments with a randomized complete block design were established on a 6% slope in Ogbomoso. Main plot treatments consisted of manual tillage (MT), plough tillage (PT), and conventional tillage (CT). Subplot treatments were vetiver grass strips (VGS) spaced at 5 and 10 m intervals and no- vetiver (NV). Soil samples from the plots were, in the laboratory, analysed for bulk density, macroporosity, microporosity, saturated hydraulic conductivity (Ks), soil pH, organic carbon, N, P, K and exchangeable cations after the first, second and third growing seasons. Data were analysed using Analysis of Variance at p = 0.05. Physical properties: bulk density, macroporosity, microporosity, and saturated hydraulic conductivity were neither significantly affected by tillage nor VGS in all the growing seasons. However, PT and CT compared to MC respectively, reduced soil bulk density (4 and 1%), macroporosity (2 and 9%) but increased microporosity (4%) and Ks (6 and 10%). Ks on 5 m VGS was higher than NV by 10%. Organic carbon was significantly (p<0.05) higher on CT compared to MT, available phosphorus increased on PT and CT than MT, while PT had higher exchangeable Ca than MT in the second year. Vetiver grass spaced at 5 m interval had higher Ks, and significantly higher organic carbon than NV. Thus, deterioration of soil properties caused by erosion on a sloping land through conventional tillage can be ameliorated by planting vetiver grass strips.