Phosphorus content in sediment and eroded soils in the southeastern part of West Siberia

Water erosion as a result of spring snowmelt damages agricultural land and is accompanied by great losses of plant nutrients, including a considerable amount of phosphorus. The main objectives of this study are as follows: (1) to examine the distribution of total phosphorus (TP) and plant available phosphorus (K₂SO₄-P) in deposited sediment; and (2) to evaluate the phosphorus pool of eroded and drift soils by TP and fractional mineral phosphorus (FPₘᵢₙ) content. This study was carried out on Haplic Chernozem (non-eroded, moderately eroded, and strongly eroded) and stratified, slightly drift Colluvic Regosol in the southeastern part of West Siberia on slopes under both virgin and 5-year natural fallow conditions. Soils and deposited sediment were analysed for total, plant-available and fractional mineral phosphorus. The mineral phosphorus forms were classified into the following groups: fraction PI – phosphate of alkaline metals and NH₄, acid and fresh-precipitated Ca (Mg)-P, Fe²+; fraction PII – base-different Ca (Mg)-P, Fe²+; fraction PIII – Al-P; fraction PIV – Fe-P; fraction PV – Ca-P apatite type. The distribution and content of the TP and K₂SO₄-P in the deposited sediment was similar in character and was accumulated in the fine soil particles. The content (mgPkg⁻¹) of total phosphorus decreased and the sum of all mineral phosphorus fractions increased in the soils situated on the slope in the following order: non-eroded (1308 TP, 249 FPₘᵢₙ) to moderately eroded (785 TP, 279 FPₘᵢₙ) to strongly eroded (567 TP, 344 FPₘᵢₙ). The approach of A, AB and B horizons to the soil surface enriched the 0–20-cm layer of the eroded soils with calcium phosphates of the apatite type hardly available to plants. The drift soil exhibited the maximum content of total phosphorus (916 TP) and the sum of all mineral phosphorus fractions (414 FPₘᵢₙ), especially were enriched in the first two fractions.