Phosphorus in organic combinations makes up as much as half or more of the total phosphorus found ill the surface layers of Iowa soils, and hence might be expected to furnish a significant proportion of the phosphorus used by crops. Since little was known about the relative amounts of different organic phosphorus compounds present, the conditions under which these compounds are stabilized in the soil, and the mineralization of soil organic phosphorus compounds, these problems formed the subject of the present investigations.

It was found that phytin and its derivatives, with the exception of the monophosphate, can be separated from nucleic acid by their precipitation as calcium salts under alkaline conditions. The organic phosphorus in alkali extracts of soils is separated into two fractions by this procedure. A major part of the soil organic phosphorus behaved like phytin in that it was precipitated by calcium, and the remainder behaved like nucleic acid in that it remained soluble. Dephosphorylation tests with alkaline sodium hypobromite and with enzymes from corn roots and wheat bran showed that the soil fractions behaved like phytin and nucleic acid, respectively.