Sequentially extracted phosphorus fractions in peat‐derived soils

Phosphorus (P) forms were sequentially extracted from peat derived soils (Eutric Histosols and Gleysols) at eight sites in Saxony-Anhalt (Germany) to disclose general differences in P pools between mineral and organic soils and to investigate effects of peat humification and oxidation in conjunction with land use and soil management on the P status of soils. Overall 29 samples providing a wide variety of basic chemical properties were subjected to the Hedley fractionation. The Histosol topsoils contained more total P (P t ) (1345 ± 666 mg kg -1 ) than the Gleysol topsoils (648 ± 237 mg kg -1 ). The predominant extractable fractions were H 2 SO 4 -P (36-63 % of P t ) in calcareous and NaOH-P o (0-46 % of P t ) in non-calcareous Histosols. These soils had large pools of residual P (13-93 % of P t ). Larger contents and proportions of P o and of labile P fractions generally distinguished organic from mineral soils. Regression analyses indicated that poorly crystalline pedogenic oxides and organic matter were binding partners for extractable and non-extractable P. Intensive management that promotes peat humification and oxidation results in disproportional enrichments of labile P fractions (resin-P, NaHCO 3 -P i , and NaHCO 3 -P o ). These changes in P chemistry must be considered for a sustainable management of landscapes with Histosols and associated peat derived soils.