ASSIMILATION OF PHOSPHORUS BY A MIXED SOIL POPULATION AND BY PURE CULTURES OF SOIL FUNGI

Abstract

During the early periods of decomposition of organic matter, inorganic phosphate is transformed by microorganisms into organic forms of P, the rate and extent of transformation depending on the supply of energy-yielding material and available P; an increase in these leading to increased synthesis. As long as the supply of these constituents persists, conversion of inorganic phosphate to organic P continues. During the biol. decomposition of organic matter the course of changes is reversed sooner or later, depending on the supply of energy-yielding material. Depletion of this material is attended by mineralization of the organic P, whereby these are used as a source of energy. As long as the P requirement exceeds the amt. derived by the organisms from the organic compounds, synthesis exceeds mineralization. When these organic P compounds provide more P than is required for synthesis, the excess is liberated as inorganic phosphate. Some phosphate is liberated during autolysis of microbial cells. Addition of soluble phosphate greatly stimulates the rate of decomposition of straw and cellulose. Speed of decomposition is increased by increasing the amt. of phosphate.