AVAILABILITY OF PHOSPHATES IN SOILS AS A FUNCTION OF THE STATE AND TRANSFORMATION OF ORGANIC-MATTER

The energy accumulated in soil organic compounds is partially spent on the transformation of difficultly soluble forms of mineral phosphates into biologically available ones. This transformation is accompanied by an increase in the number of microorganisms and intensity of soil r espiration, and by a change in Eh and pH. Soil acidification does not always play a vital role in increasing the availability of mineral pho sphates. An increase in the mobility of phosphates remains stable in m ineral soils with high humus content and in organic soils.