Phosphorus adsorption-desorption mechanisms in a typical alfisol soil under rice husk biochar application: a batch sorption study

The sustainable production of food is hindered by environmental issues caused by human activities, particularly the management of vast amounts of waste generated by modern agriculture. To address this, batch sorption studies were conducted to investigate the impact of varying levels of rice husk biochar (0, 10, 20, 30, and 40 tons ha-1) on phosphorus availability in a typical alfisol. The adsorption data was analyzed using Langmuir and Freundlich isotherm models. The results showed that the application of 10 tons per ha of rice husk biochar (Treatment B) had the highest phosphorus sorption capacity, bonding energy, and buffering capacity, with values of 24.39 mg kg-1, 23.23, and 566.7, respectively. The Freundlich model revealed high adsorption constants and slopes greater than 1, indicating unfavorable phosphate sorption. Both models showed high coefficients of determination (r2), with the Langmuir model providing a slightly better fit. The study concludes that the Langmuir isotherm model more accurately describes the adsorption process, suggesting that rice husk biochar can improve soil phosphorus availability, although other factors may influence the process. Keywords: alfisol, modern agriculture, phosphorus sorption, rice husk biochar, waste management