Phosphorus sorption in relation to soil grain size and geochemical composition in the Simiyu and Kagera river basins, Tanzania

The phosphorus sorption characteristics of eight surface soil samples representative of the land use and landscape in the Simiyu and Kagera River basins were determined using the Langmuir equation. The Langmuir P adsorption maximum (Cmax) ranged from 109 to 802 mg kg-1, while Langmuir coefficient (K) ranged from 59 to 736 mg L-1. Cmax and were positively correlated to clay content, aluminium (Al), and iron (Fe) and negatively correlated to calcium (Ca). By using stepwise regression, the combination of Al, Fe, clay and Ca predicted more than 94% of the variation in the P sorption capacity of soils samples from Simiyu and Kagera basins. These four soil properties, which are strongly related to P sorption, could therefore be used as quick tests for predicting the P sorption capacity of soils in the two basins. Tanzania Journal of Science Vol. 31 (2) 2005: pp. 31-4