Phosphate Regime of Soils with Long-Term Application of Fertilizers in Siberian Agriculture

The phosphate stock of Siberian arable soils reflects the uniqueness of the genetic features of soil formation and the unequal phosphate enrichment of soil-forming rocks of various geomorphological structures. Among the mineral phosphates that serve as the main factors of soil fertility, loosely bound (Ca-PI) and polybasic forms (Ca-PII) are of crucial reserve importance for plant nutrition. Siberian arable lands in half of the surveyed area (>10.5 million hectares) are insufficiently supplied with available phosphates to produce sustainable yields of high-quality products. The use of phosphorus fertilizers, having a positive effect on the productivity of field crops, significantly improves the qualitative composition of mineral phosphates in soils. The degree of influence of fertilizers on the fractional composition of phosphates is determined by the type of soil, duration and doses of their application. With the systematic application of fertilizers, the main quantitative changes occur in the first 4 groups of mineral phosphates – the content of P2O5 increases by 1.4–2.2 times. Their total share in sod-podzolic and chestnut soils is 15–20%, in chernozems and meadow-chernozem soils it increases to 25–34%.