Phosphorus Adsorption and Desorption as affected by Long-Term Fertilization under Rice-Rice Cropping System in an Acidic Inceptisol

Phosphorus (P) underpins global food security by ensuring soil fertility and sustainable crop production. Phosphorus adsorption-desorption under long-term nutrient management practices can shed light on availability and environmental fate of P. Our aim was to study the effect of super-optimal dose of P fertilization, liming and manuring on soil properties and its adsorption-desorption behavior in acidic Inceptisol under rice-rice cropping system. In this investigation, soil samples from selected seven treatments from a long-term (14 years) experiment viz., control, 100% of recommended dose of nitrogen (N), N and phosphorus (NP), N, P and potassium (NPK), 150% NPK, NPK+farmyard manure (NPK+FYM) and NPK+Lime were used to study the adsorption and desorption characteristics. The results revealed that P fertilization along with manuring or liming improved available P. The adsorption and desorption data was well fitted in Langmuir and Freundlich equation, respectively. The adsorption maxima ‘a’ decreased in NPK+FYM (324 mg kg^-1), 150% NPK (341 mg kg^-1) and NPK+Lime (352 mg kg^-1) treated plots compared to NPK treated plots (403 mg kg^-1) in surface soil. Moreover, the decrease in adsorption maxima and bonding energy coefficient due to manuring or liming with NPK suggest improved release of P. In P desorption study, NPK+FYM treated plots showed highest cumulative P desorption of 38.4% and 31.1% at 0-15 cm and 15-30 cm soil layers, respectively. Thus, long-term application of NPK+FYM can result in saturation of P adsorption sites and cause potential leaching loss of P and eutrophication in light textured acid soil. However, formation of insoluble P compound cannot be overlooked.