OCCURRENCE AND MINERALIZATION OF ORGANIC PHOSPHORUS IN SOILS, WITH PARTICULAR REFERENCE TO ASSOCIATIONS WITH NITROGEN, CARBON, AND pH

Abstract

In 25 pairs of virgin and cultivated soil samples, organic P was correlated positively with organic C and total N. Organic P mineralized during 25 days'' laboratory incubation at 40[degree]C was correlated positively with N and C mineralized concurrently. Amounts of organic P mineralized ranged from -4 to 45 ppm. These results constitute circumstantial evidence for the importance of organic P as a source of P in plant nutrition. The quantities of organic P, N, and C were greater in virgin soils than in corresponding cultivated soils. Moreover, the rates of mineralization were greater in virgin soils. Apparently, a fraction of each constituent in the virgin soils was relatively more susceptible to mineralization than was the remainder after cultivation. The ratios of organic C to organic P and of total N to organic P were associated positively with soil pH. Where the content of organic P was held constant, the quantity of organic P mineralized during laboratory incubation was likewise associated positively with soil pH. For C and N, however, pH and mineraliza- tion were not significantly associated independent of the quantities of these constituents present. These results indicate that organic P mineralization increased with soil pH not only during laboratory incubation but also during soil development in the field.