Forage Dynamics in the Face of Rainfall Variability across Pastoral Plains of Kajiado, Kenya

Abstract

The study aimed to examine forage changes and change dynamics relative to rainfall variability in Kajiado county of Kenya. Forage was examined as a key factor influencing pastoral productivity. Rainfall data from Ngong Divisional Office, Mashuru and Magadi Soda Works Meteorological Stations, representing different ecozones, were analyzed through standard deviation, mean, range and coefficient of variation (C.V.) over the period 1964 - 2011. Data on forage levels for the period 1982 – 2004 were processed in the form of Normalized Differential Vegetation Index (NDVI) for sampled areas within the four ecozones. Time series of these data were then averaged into dekadal means and annual averages then regressed and correlated with corresponding rainfall data at lags 0 and 30days. Findings for this research suggested that rainfall over Kajiado had overtime revealed high variability; spatially, seasonally and inter-annually. Spatial variations revealed that Mashuru to the East had exhibited higher variability (C.V. = 26%) compared to areas around Ngong in the North (C.V. = 24%) and areas around Lake Magadi in the West (C.V=21%). Similarly, there was higher variability during the short-rain seasons as compared to long-rain seasons over the three stations. The results indicated that forage indices strongly correlated to rainfall amounts at Magadi Soda Works Meteorological Station, accounting for 74% of forage at onset and 92% at peak vegetation performance, while at Mashuru Meteorological Station it accounted for 48% at onset and 89% at its peak.