Adsorption of added phosphorus as influenced by the application of lime and gypsum in an acid alfisol of Himalayan Region

A bulk soil sample of acid Alfisol (pH 5.8) was used for adsorption studies in the laboratory and the data for plotting phosphate adsorption isotherms were obtained as per the procedure of Fox and Kamprath (1970). The adsorption maxima and the index of bonding energy were calculated in accordance with the Langmuir adsorption equation. Phosphate adsorption studies showed that the experimental soil had a greater affinity for P as the P adsorption continued to rise with increase in equilibrium P concentration. The lime applications (1.5 and 3.0 t ha⁻¹) increased and gypsum application (2.7 and 5.4 t ha⁻¹) decreased the P adsorption. The lower level of gypsum application was superior in declining the P adsorption to its higher level. The values of P adsorption maxima (b) and index of bonding energy (k) were 2186 μg g⁻¹ and 0.015 mL μg⁻¹ under control (no lime, no gypsum) and 2381 μg g⁻¹ and 0.029 mL μg g⁻¹, respectively under lime (3 t ha⁻¹) which were reduced to 2041 μg g⁻¹ and 0.007 mL μg g⁻¹, respectively under 2.7 t ha⁻¹ gypsum application.