Impact of grazing on soil physical properties in the east African highlands

Taddese, G.; Peden, D.; Ayalnenh W.; Jobre Y. 2007. Impact of grazing on soil physical properties in the east African highlands. Ethiopian Veterinary Journal 11(2):163-173.

The impact of grazing on soil physical properties in the east African highland was studied from 1996 to 1998. The study was conducted at two sites with 0-4 % and 4-8 % slopes at the International Livestock Research Institute (ILRI) Debre Ziet Research Station, 50 km south of Addis Ababa, Ethiopia. The grazing regimes were; light grazing stocked at 0.6 animal-unit months per hectare (AUM) h-1, moderate grazing stocked at 1.8 (AUM) h-1, heavy grazing stocked at 3.0 (AUM) h- 1 very heavy grazing stocked at 4.2 (AUM) h-1, very heavy grazing on plowed soil stocked at 4.2 (AUM) h-1; and a control with no grazing. The grazing pressure has no impact on total nitrogen of the soil. Since manure is not collected from grazing plots the soil organic matter content did not decline, it was rather stable and slightly increasing. Grazing has improved the plant available-P compared to nongrazed plots at both slopes in all soil depths. Soil bulk density and total porosity did not show significant differences among different grazing pressures. At both sites the soil water content was high in heavily grazed plots as compared to the rest of the treatments. The steady state infiltration rate was significantly different only in light grazing treatment at 4-8 % slope. Finally livestock grazing with good management and manure recycling to the grazed plots could not degrade soil physical and hydrological properties. Hence, over utilization of the available grass herbage by livestock and removing manure from grazed plots is responsible for soil degradation.