Abstract

Adsorption and desorption behaviour of phosphorus was studied in soil samples collected from long term fertilizer experiment adopting rice monoculture continuously since 1975. The soil samples from eight treatments differed widely in their P adsorption and desorption behaviour. The extent of P adsorption was relatively higher in the control plot soil (75.0 to 787.5 mg kg-1) than the P added plots. Similarly adsorption of P was found to be lower in the manure added soils than the unmanured ones. The rate of desorption of sorbed P was relatively higher in the manure treated soils than the unmanured ones. Among the organic manures, addition of urban compost reduced the rate and amount of adsorption of added P (50.0 to 252.5 mg kg-1). The sorption data for all samples were found to fit best the Classical Langmuir isotherm equation. The values of P sorption maxima (b) (812 mg kg-1), and bonding energy constant (k) (0.378 L mg-1) were the highest for control plot soil than the P and manure added soils.

Keywords: Phosphorus, adsorption, desorption, manure, fertilizer