Phosphate Sorption-Desorption Characteristics of some Ustifluvents of Punjab

A laboratory study conducted on 19 soils collected from flood plain areas of Punjab showed that the amount of phosphate sorption and desorption increased with increase in amount of P added and it varied with various soil properties viz. clay, CaCO3, Fe and Al oxides etc. Most of these soils were adsorbing more than 150 mg P kg−1 soil. Sorption parameters such as sorption maxima, buffering capacity and bonding energy constant related mainly to CaCO3, free Fe oxides, silt, clay and exchangeable Mg. The values of mobility constant (Kd) correlated significantly with clay (r = 0.467*), exchangeable Ca (r = 0.503*) and exchangeable Mg (r =0.648**). Organic carbon (r = 0.870**) and exchangeable Fe (r = 0.680**) showed highly significant relationship with maximum phosphate desorption (Dm). Supply parameter, maximum buffering capacity and bonding energy constant are important sorption parameters which control P availability to berseem in these soils.