The Effect of Long-Term Use of Nitrogen, Phosphorus and Potash Fertilizers on the Content of Forms of Phosphorus Compounds in the Sod-Podzolic Soil of the Urals

The effect of long-term use of mineral fertilizers on changes in the content of total phosphorus, its organic, mineral and mobile compounds in soddy-podzolic heavy loamy soil (Albiс Retisol (Abruptic, Aric, Loamic)) was studied. The studies were carried out in a long-term stationary experiment established in the Perm region in 1978. Options – 0 (without fertilizers), N90, P90, K90, N90P90, N90K90, P90K90, N90P90K90, N30P30K30, N60P60K60, N120P120K120, N150P150K1 50. Ammonium nitrate or urea, double or simple superphosphate and potassium chloride were used in the experiment. It was established that long-term use of superphosphate during five rotations of a field eight-field crop rotation (P90, P90K90, N90P90, N90P90K90) led to a significant increase in the total content of phosphorus in the arable soil layer (0–20 cm), its mineral part by 1.3–1.8 times, mobile connections by 1.9–2.7 times. The use of nitrogen fertilizers (N90, N90K90, N90Р90 N90Р90K90) influenced the accumulation of organic phosphorus compounds in the soil. A significant increase in the soil content and reserves of both mineral and organic phosphorus compounds was observed only when using complete mineral fertilizer N90P90K90. Different combinations of superphosphate with nitrogen fertilizers and potassium chloride, as well as the dose of fertilizers, influenced the intensity of accumulation of mobile phosphorus compounds in the soil by rotation and changes in its amount along the profile. The application of low doses (NPK) 30–60 led to an increase in mobile phosphorus compounds mainly in the arable soil layer; when higher doses (NPK) 90–150 were used, changes were noted in the 0–80 cm layer. Long-term use of nitrogen and potassium fertilizers over time led to an increase in mobile phosphorus compounds in the arable soil layer.