MOVABLE FORMS OF COMPOUNDS OF PHOSPHORUS AND IRON IN CHERNOZEM-LIKE SOILS IN THE NORTH OF TAMBOV PLAIN
Factors determining the dynamics of the content of available phosphorus in chernozem-like soils under surface and ground waterlogging are moisture and redox conditions. With increasing humidity, and maintaining oxidizing conditions in soils of chernozem series with a high content of calcium phosphates take place their transformation from apatite fraction into more mobile - Ca-PI and Са-РII. In reducing conditions in chernozem-like soils with high content of iron phosphate with increasing moisture content increases phosphorus extracted by 0,1 n. H<sub>2</sub>SO<sub>4</sub> stretch by moving phosphates of iron in the mobile state. Rainfall saturating the soil with atmospheric oxygen promotes to increase the values of Eh and consequently lowering the mobility of iron phosphate.