Vegetation Dynamics in Relation to Grazing Management Practices in Semi-arid Grazing Lands of Makueni County, Kenya

Abstract

Livestock grazing practices in rangelands are being recognized as management tool for environmental protection and increased livestock productivity. Continuous grazing has been largely reported to reduce pasture productivity and increase environmental degradation. Rotational grazing is an alternative to continuous grazing and is considered to reduce negative environmental effects and provide quality pastures and browse ensuring availability of quality feed for animals while conserving the environment. This study was conducted in a semi-arid grassland in the south eastern rangelands of Kenya which is primarily used for cattle production to establish how grazing management system affects herbaceous biomass yield, cover, plant species richness and diversity (in 2016). Quadrat method was used to collect vegetation samples. In each plot, a 100 m² sub- plot was demarcated and five 1×1m quadrats laid out. A quadrat was placed at each of the four corners of the 100m² plot and the 5th quadrant placed at the center of the plot. Herbaceous biomass production was significantly higher (p≤0.05) in rotationally grazed areas compared to both continually grazed and ungrazed areas with average values of 7037, 2478 and 2390 Kgha^-1 respectively. Similar trend was obtained for vegetation cover. Vegetation cover of herbaceous plants was significantly higher under rotationally grazed areas compared to both continually grazed and ungrazed areas with average values of 55, 37 and 27%, respectively. There was no significant difference for plant species richness and diversities and between the three sampling blocks. However, the highest values of both latter traits were obtained in rotationally grazed areas, followed by continually and ungrazed areas. Improved biomass yields and high species diversity in rotation grazed areas was largely attributed to the flexibility in the management in which grazing frequency, durations and the rest periods are efficiently controlled compared to continuous grazing areas. This study concludes that rotation grazing allows flexibility of animal utilization of pastures resulting to enhanced soil water retention, increased species diversity; richness and vegetation cover which increase biomass yields.