Vegetation and hydrologic responses to grazing Management in a south Kenya rangeland

Abstract

Title: Vegetation and hydrologic responses to grazing management in a South Kenya rangeland ~ J.K. Mworia A study was conducted to evaluate the effects of three selected stocking densities ./ on infiltration rate, bulk density, sediment production and animal performance in a south Kenya rangeland. The stocking densities used were 0, 4, 8, and 16 heifers/Ha, hereafter referred to as control (CL), light density (LD), medium density (MD) and high density (HD) respectively. Each treatment was replicated twice on plots measuring 0.5 Ha each. The study was done at National Range Research Center, Kiboko. The study site is classified as a bushed grassland with species of Acacia and Cornrniphoras the dominant woody plants, while Digitaria macroblephera and Chloris roxburghiana are the most dominant grasses. The texture of the soils at the site is sandy clay loam. The highest stocking density, HD, gave the highest animal output per hectare yielding a peak weight gain of 104 kg/Ha, which however declined after pasture deterioration. The HD treatment also produced the highest soil loss, lowest infiltration rate, and highest bulk,density. The LD treatment maintained the highest animal output per head and had the least negative impact on the pasture hydrologic conditions and vegetation. Infiltration rate after 30 minutes of simulated vi rainfall in HD plots was 4S% and 27% lower than in CL and LD plots respectively, making a significant difference (p<O.OS). Sediment production on the last sampling date was IllS kg/Ha in HD treatment, which was significantly (p<o.S) more than 226 and S17 kg/Ha for the CL and LD respectively. Bulk density, 0- Scm, in HD increased by lS% by the end of the experiment and was significantly higher (p<O.OS) than CL and LD. It can be concluded from this study that the effects of high stocking densities on the range were, increased land bareness, reduced infiltration rates, increased soil loss, and increased soil compaction. The linear relationship of stocking density to output per head developed in this study could vary from year to year due to climatic and other environmental variations; further studies are necessary to develop long-term relationships.