Phosphorus sorption-desorption characteristics of soils under different land use patterns of eastern India

Abstract

The phosphorus adsorption-desorption behaviour of soils from four land use patterns of eastern India was studied. Sorption isotherms were described by Langmuir and Freundlich equations. Phosphate adsorption maximum was the highest in orchard soils followed by cultivated land and forest soils, and was the least in tea garden soils. The variation in different phosphate sorption parameters among the land use patterns was attributed to the variation in the physico-chemical properties, which were evidenced by significant correlations with organic carbon, oxides of iron and cation exchange capacity. The fraction of sorbed phosphate recovered in desorption run followed almost the same trend as phosphate sorbed, but neither with phosphate bonding energy (K) nor with phosphate buffering capacity (Kb). Soils of orchard and cultivated land having less bonding energy and relatively less buffering capacity contained a higher amount of equilibrium solution P at any given labile P content than the others but would not be able to sustain the concentration for a longer period and the need for P fertilization earlier than forest and tea garden for long-term sustainable crop production. Phosphate buffering capacity seems to play a key role in determining the agronomic and environmental threshold levels of available P content in the soils.