Impact of grazing around a watering point on soil status of a semi-arid rangeland in Ethiopia

The influence of long-term livestock grazing on the soil status of a semi-arid rangeland was studied along a grazing gradient from a watering point in southern Afar Region of Ethiopia for two seasons. The soil samples were analysed for organic carbon (OC), total nitrogen (N), available phosphorus (P), exchangeable cations (Ca2+, Mg2+, K+ and Na+), acidity (pH), cation exchange capacity, and particle size distribution (clay, silt and sand). No significant differences (P > 0.05) were observed for particle size distribution, OC, N, P and K contents along the grazing gradient further than 1500 m from the watering point. Ca2+ and Mg2+ were found to be dominant cations particularly in the severely degraded area contributing about 74% to the exchangeable cations. The study has also recognized high concentrations of Na+ and more than 11% exchangeable sodium percentage. Total exchangeable bases significantly declined (P < 0.05) along the grazing gradient and were indicative of the exchange complex of the soil being saturated with Ca2+ and Mg2+ ions. Thus this study concluded that there are soil differences in the grazing gradient caused by impact of grazing, particularly in the severely degraded area.