Effect of Poultry Manure and Its Derived Biochar at Different Temperatures on Phosphorus Adsorption in a Calcareous Soil

Biochar is one of the organic matter sources and it can be effective in improving P adsorption in the soil. This experiment was conducted to investigate the effect of poultry manure (PM) and its derived biochar at temperatures of 200, 300 and 400 °C on P adsorption capacity in a calcareous soil. Poultry manure and its derived biochars were mixed with 400 g of the soil and incubated at appropriate temperature and humidity for 90 days. Phosphorus adsorption isotherms were measured by the modular method at the concentration range of 0 to 90 mg.L-1 of P, and adsorbed P was calculated. The results showed that the P adsorption rate decreased with increasing P concentration in the equilibrium solution in all treatments. Adsorption data were fitted with Long Muir model. In biochar-treated samples, average P adsorption gradient at the low and high P concentrations in equilibrium solution was, respectively, 56% lower and 116% higher than the control. Biochar produced at 300 and 400 °C had, respectively, the minimum and maximum impact on the amount of slope and maximum P adsorption. The maximum adsorbed P in B300 and B400 treatments were 144 and 246 mgkg-1, respectively. At low P concentration in equilibrium solution, P adsorption gradient in B300 and B400 was, respectively, 5.42 and 10.1 mgkg-1 for each unit change of P concentration, and it was 1.50 and 4.59 mgkg-1 at the high P concentration. The behavior of B300 in P adsorption indicates the higher possibility of using it in agricultural lands to improve P availability, compared to the other studied biochars, while B400 behavior indicates the possibility of using it to remediate P-contaminated soil.