Change in the Phosphate Status of Western Siberian Forest-Steppe Soils through the Continuous Use of Fertilizers

Abstract

A comparative assessment of the effect of long-term agricultural use of gray forest and meadow chernozemic soils on their phosphorus status is performed in stationary field experiments in the western Siberian forest steppe. The content of different phosphorus compounds in the soils of extensive and intensive agrocenoses is determined. The soils under study are characterized by higher total phosphorus concentrations (0.15–0.21% in the gray forest soils, 0.15–0.17% in the meadow chernozemic soils). The continuous use of phosphorus fertilizers significantly increases the level of highly mobile forms of this mineral element in the arable layer of gray forest soils to 12.5–14.6 mg/kg and meadow chernozemic soils to 22.1–26.6 mg/kg. The fractional size distribution analysis of inorganic phosphates showed a steady increase in the reserves of its compounds with a long-term positive balance. Phosphorus applied in excess of the removal was distributed among the first four fractions, where it was available to crop uptake both in action and in afteraction. All changes in phosphorus concentrations (both with a decrease and with an increase) are less pronounced on the initially more fertile meadow chernozemic heavy clay loam soils than on the gray forest soils, indicating its higher buffering capacity. The largest relative changes in the values of diagnostic indices are characteristic of the most mobile fractions of phosphorus compounds.