PHOSPHORUS CHANGES DURING LEACHING AND DECOMPOSITION OF HAYED-OFF PASTURE PLANTS

Ground samples of hayed-off pasture plants were decomposed in the laboratoryunder continuously moist, and intermittently moist and dry, conditions. During thecourse of decomposition they were leached at different frequencies and the resultingchanges in inorganic and organic phosphorus measured. The dissolution of superphosphateand its conversion to organic phosphorus were also studied under some ofthese conditions. Inorganic phosphate was readily leached from the samples when microbes wereinhibited. Microbial activity, on the other hand, largely prevented the loss of inorganicphosphate by leaching from a phalaris sample over a period of 3 months. Intermittentdrying increased the amount of phosphate leached from decomposing plants but theleaching frequencies examined had little effect. The percentage of the phosphorus leachedfrom plants varied with the type of material. In all cases less than half was recovered asinorganic phosphate, even after decomposition and leaching for 6 months. When superphosphate granules were leached in the presence of decomposingplants the conversion of fertilizer phosphate to organic phosphorus was small, but thedissolution of phosphate was sometimes retarded. The recycling of phosphate in hayed-off pastures is discussed in the light ofthese results. © 1969 CSIRO. All rights reserved.