Effect of Long-Term Use of Nitrogen, Phosphorus, and Potassium Fertilizers on the Contents of Phosphorus Compounds in Soddy-Podzolic Soil of the Urals.

The effect of long-term use of mineral fertilizers on changes in the content of total phosphorus and its organic, mineral, and mobile compounds in soddy-podzolic heavy loamy soil (Albiс Retisol (Abruptic, Aric, Loamic)) was analyzed. The studies were performed in a long-term stationary experiment initiated in Perm krai in 1978. The variants were: 0 (without fertilizers), N90, P90, K90, N90P90, N90K90, P90K90, N90P90K90, N30P30K30, N60P60K60, N120P120K120, and N150P150K150. 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 eight-field crop rotations (P90, P90K90, N90P90, and N90P90K90) resulted in a significant increase in the contents of the total phosphorus, mineral phosphorus (by 1.3–1.8 times), and mobile phosphorus (by 1.9–2.7 times) compounds in the plow layer (0–20 cm). The use of nitrogen fertilizers (N90, N90K90, N90Р90, and N90Р90K90) affected the accumulation of organic phosphorus compounds in the soil. The increase in the content and reserves of both mineral and organic phosphorus compounds was significant only in the case of using complete mineral fertilizer N90P90K90. Different combinations of superphosphate with nitrogen fertilizers and potassium chloride, as well as the rate of fertilizer application, affected the accumulation intensity of mobile phosphorus compounds in the soil during rotations and the changes in their contents in the soil profile. The application of low fertilizer rates ((NPK)30–60) resulted in an increase in the content of mobile phosphorus compounds mainly in the plow layer, whereas higher rates ((NPK)90–150) caused changes in the 80-cm-thick soil layer. Long-term use of nitrogen and potassium fertilizers resulted in an increase in the content of mobile phosphorus compounds in the plow layer over time. [ABSTRACT FROM AUTHOR]