Boron Desorption Kinetics in Inceptisols representing Benchmark Soils of Punjab

Boron (B) desorption is one of the most important factors in deciding the efficiency of B fertilization and its management in intensively cultivated soils. A study was conducted in benchmark soils of Punjab to ascertain the rate of B release in relation to soil properties. Four mathematical models viz. Integrated second approximation rate equation, Elovich, power function and parabolic diffusion were used to describe B desorption kinetics. The total desorbable B was higher in coarse textured soils as compared to the fine textured soils of Punjab. Maximum desorbable B of 13.36 mg kg⁻¹ soil was in Tulewal, while minimum of 9.04 mg kg⁻¹ in Chamror soil series. The integrated rate equation indicated two types of pseudo-first order reactions in B desorption from soils and the rate coefficients from both sites were positively and significantly correlated with organic carbon content (r=0.82** and r=0.76**) while these had negative association with soil pH (r=0.69* and r=−0.74**) and clay content (r=0.67*). The power function and Elovich kinetic equations were found to be successful in describing B desorption data in all the soils. The Parabolic diffusion kinetic model could not describe the B desorption satisfactorily in all the soils. The total desorbable B was negatively correlated with clay content (r= −0.93**), CEC (r= −0.84**) and organic carbon (r= −0.65*) while it was positively associated with sand content (r= 0.75*). Soil pH, EC, organic carbon, CaCO₃, clay content and CEC together explained 97% of variation in Elovich desorption rate coefficient and 96 and 92% variation in rate constants of power function and parabolic diffusion model.