Dynamics of ryegrass P in red soils

An investigation on the dynamics of transformation of P from 32P-labelled rye-grass in red soils was conducted in laboratory. The results showed that the rapid increase in flush 32P related with biomass P was accompanied with the decrease in extractable 32P on the first 3 d of incubation in both sandy and clayey soils, and afterwards, it displayed great fluctuation in sandy soil, but had little fluctuation in clayey soil during 3∼20 d of incubation. At the later stage of incubation, the increase in extractable 32P was accompanied with decrease in flush 32P. The opposite changes in content of extractable 32P and flush 32P suggested transformation of ryegrass P was closely related to its utilization and its release from microorganisms in red soils. It can be concluded that addition of organic matter accelerated the release of soil native P according to the changes in the extractable soil P during incubation