Effect of livestock grazing on soil micro-organisms of cracking and self mulching vertisol

The impact of grazing on physical properties of Vertisol was studied from 1996 to 2000 in the Ethiopian highlands. The study was conducted at two sites with 0-4 % and 4-8 % slopes at Tero Jemjem watershed in Ginchi, 80 km west of Addis Ababa. The main objective of this work was to study effect of livestock on soil microorganisms of the cracking and self-mulching Vertisol. The stocking rate was moderate grazing 1.8 animal-unit months per hectare (AUM) ha-1, heavy grazing 3.0 animal-unit months per hectare (AUM) ha-1 (3.0 AUM) ha-1 and a control treatment with no grazing. Soil bacterial content was high in medium grazed treatments at 0-4% slope in alls sampling seasons. In contrast the soil fungal content was high in non-grazed plots. Soil nitrifying bacteria was high in clipping treatments as compared to the rest of the treatments. The soil fungal quantity differed significantly with sampling seasons; highly significant correlation coefficient was observed between soil fungal quantities and sampling seasons. There was also highly significant correlation between soil fungal and soil bacteria quantity.