Influence of lime and organics on phosphorus sorption-desorption kinetics in red-lateritic soils of West Bengal

Purpose Iron- and aluminum-dominated red-lateritic soils suffer from poor phosphorus (P) use efficiency due to the fixation of added P.Methods The present investigation was conducted to study P sorption-desorption kinetics and to minimize the hysteresis indices of three acidic red-lateritic soils of West Bengal by amending with lime and/or organics like vermicompost or biochar either singly or in combination @ 10% (w/w).Results Except for the rate constant for slow sorption (k(2)), the application of lime or organics in general significantly decreased all the kinetic parameters over their respective control during sorption but increased during the desorption process. About 75% of P adsorption occurred within the first 2-h period of investigation. In limed soils, more than 70% of P adsorption occurred by fast sites. The highest rate constant values (k(1)) for fast sorption sites were associated with the treatment receiving biochar. Irrespective of soil and treatment, more than 50% P desorption occurred from fast desorption sites. In general, the highest initial desorption rate was observed in the treatment receiving biochar either alone or in combination with vermicompost and with or without lime. In all the cases, the highest hysteresis index (> 82%) was observed in the control treatment, indicating the extent sorbed P remained in a non-diffusible form in non-amended soil.Conclusion Application of organics in the form of biochar with the recommended dose of lime caused a maximum reduction in the hysteresis index value and thus can be regarded as the best P management strategy for acidic red and lateritic soils.