Repercussions of Agro-Pastoralism on Soil Condition in Western Serengeti, Tanzania

Abstract

Overgrazing of rangeland and continuous cultivation of cropland are among human activities contributing to the deterioration of soil properties. To elucidate the effect of agro-pastoral activities on soil properties in western Serengeti, we examined soil properties in four land use types, namely fallow land, communal grazing land, mixed grazing land and wildlife dominated grazing land. The soil sampling sites were along the landscape from village lands towards protected areas while crossing all four land use types. Soil pH was not significantly different (p≥0.05) although it was relatively low in fallow and communal grazing lands. Clay content in soils was not affected by land use types whereas sand and silt contents were significantly different (p≤0.05) among land use types. In terms of soil nutrients, OC, CEC and soil P showed a significant difference (p≤0.05) among land use types but land use did not affect TN and Ca²⁺. Bare land within quadrats was highest in communal grazing lands (1233 cm²/quadrat) and lowest in wildlife dominated grazing lands (906 cm²/quadrat). Protected areas represented by wildlife grazing sites had the highest soil stability expressed in terms of soil structure stability index. Soil quality declined with increase in bare land. Further, high density of grazing animals caused a decline in soil properties. The study demonstrated that the four land use types had negative influence on soil properties. It was further noted that the current practices of livestock grazing and cultivation had higher negative effects on soil properties than the other land use types. Long term monitoring study on impacts of agro-pastoralism in western Serengeti is needed so as to establish proper stocking rates to avoid reaching an irreversible soil properties deterioration situation.