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 H₂SO₄‐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, NaHCO₃‐P_i, and NaHCO₃‐P_o). These changes in P chemistry must be considered for a sustainable management of landscapes with Histosols and associated peat derived soils.