Effect of incubation period of different levels of apple and grap biochars on the adsorption behavior of phosphorus in a calcareous soil

Organic manures can affect on phosphorus sorption and its availability. Biochar as a renewable organic source of phosphorus could have a significant role in increase phosphorus availability in calcareous soils. In this study, phosphorus sorption was performed in a calcareous soil treated with two types of of biochar prouduced from apple and grape pruning at 400 ° C at different rates (0, 10 and 20 g/kg soil, w/w) and three incubation periods (40, 80, 120 days). Phosphorus adsorption data were fitted to langmuir and freundlich and temkin models. The results showed that the use of biochar reduced phosphorus adsorption in the soil and increased the release of phosphorus. Based on coefficient of determination (R2) and the standard error of estimation (SE), all three models Langmuir, Freundlich and Temkin fitted well with the experimental data. High values of Langmuir (qmax) was observed (850 mg/kg) in untreated soil and low values was observed (415 mg/kg) at the 2% levels of grape biochar. The binding energy (Kl) declined from 0.03 to 0.175 (l/kg). Capacity parameters (KF) of freundlich was variable from 14-90.5 (l/kg) in the apple and grape biochar treated soil and was (95 l/kg) in the untreated soils .The intensity adsorption (n) parameter of freundlich was variable from (0.1-1.5 ) in the apple and grape biochar treated soil and 1.25 in the untreated soil. The parameter of (kT) of temkin declined from 139 to 122 (l/kg). Phosphorus adsorption declined in all treatments over time. The value of soil buffering indices declined in the apple and grape biochar treated soil as Comparied to the untreated soil. It can be concluded that use of apple and grape biochar reduse the phosphorus places adsorption in calcareous soils and increase solution phosphoruse soil.