Comparison of P-sorption selected indices in soils with different physico-chemical properties

In laboratory investigations, 9 methods of sorption ability against phosphorus in 36 soils of southern Poland (loam 7-71% , Corg 0.41-2.0%, Alox 14.7-64.8 mmol kg -1 and Feox 15.7-174.5 mmol kg-1) were compared. Evaluation of the maximum P sorption (Pmax) as well as two ways of buffering capacity against P (PBC) was estimated from multipoint curves according to the data of the Langmuir and Freundlich equation. The indices of P sorption obtained were compared with the single-point indices received by the addition to the soil of one P concentration (PSI1500, IPEC, and PRI200). All the indices of P sorption determined were highly correlated, being the evidence of the usability of the single-point indices in the evaluation of phosphorus sorption in routine soil tests. A significant correlation was found between the indices compared of Alox, Feox, loam concentration and CEC in the soil. The saturation of the soil with phosphorus, estimated by the Pox / (0.5(Feox + Alox ) was low and was in the range in 0.7-8.6 %.