Abstract: Surface soil properties are more susceptible to water erosion. Planting vetiver grass hedges (VGH) across the slope could protect surface soil from being washed away and allow meaningful cultivation of crops. A field experiment was carried out to assess the effects of VGH spaced at surface intervals of 5 m (VGH5), 10 m (VGH10), and control (no-VGH plot) on surface soil properties, runoff and sediments, and maize yields for five growing seasons on 6% slope in Southwest Nigeria.
Vetiver grass hedges and growing season interaction had significant effects on some physical (bulk density and moisture content) and chemical (N, C, P, and K) properties. Nutrient enrichment ratio for N, C, P, and K was highest in control plot, followed by VGH10, and least by VGH5 plots. In addition, VGH and growing season interaction had significant effects on runoff, soil loss, and soil loss/crop yield ratio. Average runoff (in millimeters) per five growing reasons obtained from control, VGH10, and VGH5 plots was in the ratio of 6.5:3:1, respectively. Corresponding soil loss was 8:2:1, respectively. Soil loss/crop yield ratio was significantly higher in control plot (9.69) than VGS10 (1.84) and VGH5 (0.74). The mean grain yield values during the five growing seasons obtained from VGH5 and VGS10 plots was higher than the control by 21.4 and 6.8%, respectively. The reduction of runoff nutrient losses on plots with VGH demonstrated the beneficial effects of protecting surface soil from being washed away on this sloping farmland.