Effect of balanites glabra canopy cover on soil organic matter, soil moisture and selected grass species production in Isinya, Kajiado, Kenya

Abstract

This study was conducted to determine the scasoual effects or Balanites glabra (Mildbr. & Schlecht.) canopy cover on soil organic matter, soil moisture content and selected grass species production in Isinya, Kajiado, Kenya. The study was conducted to capture both the dry (June-September) and the wet (October-December) season during the year 1999. Eight B. glabra trees from the dominant size-class; canopy height :::;2111c,rown diameter :::::6m, and growing under similar conditions (same soil type ami terrain) were selected [or this study. Around each tree, three zones were marked in concentric rings at equal intervals. Based on the distance from the tree trunk, the zones were designated as midcanopy (0-2m), sub-canopy (2-4111) and open grassland (4-6111). Soil samples for organic matter and moisture determinations were taken at 0-30 and 0-60cm depths at [our equidistant points within each zone. Soil organic matter and moisture contents were determined using Walkley-Black and gravimetric method, respectively. Samples for grass species composition determination were obtained using four a.25m2 quadrats in each zone. Grasses from the same quadrats were clipped and analyscd [or aboveground biomass production. Soil organic matter content in the mid and sub-canopy zones was 2-3 times higher than in the adjacent open area during both dry and wet season. This phenomenon may be mainly attributed to the general accumulation of litter and its relatively slow mineralisation under tree canopies compared to the open grassland areas.