Studies in soil fertility with special references to organic manures. IV. Effects of glucose on phosphate availability

Abstract

The results of pot culture experiments, laboratory incubations, and soil chemical studies on phosphate availability are reported for a neutral loam from Griffith, N.S.W. Phosphorus-free organic matter (glucose) was incubated aerobically and anaerobically in soil to which known, relatively unavailable phosphorus sources had been added. These included rock phosphate, strengite (FePO₄.2H₂0), and variscite (AlPO₄. 2H₂O). Native soil phosphate and added strengite became more available following anaerobic incubation. This effect was sometimes but not always increased when glucose had been incubated with the soil. Added rock phosphate and variscite were rendered less available following anaerobic incubation. These effects were prevented when glucose had been present. The organic acids produced during the anaerobic incubation of glucose in the soil seem to have played little part in determining the availability of phosphate in these experiments. Anaerobic conditions as such appear to have played a major role.