Effects of aerobic composting on transformation of rock phosphate

Organic acid substances produced during dairy manure (DM) composting could transform rock phosphate.The effects of composting on increasing rock phosphate solubility were studied by mixing ground phosphate rock into DM during the composting process.Compared to DM treatment,P1DM treatment increased the active organic phosphate by 120.99%,moderately active organic phosphate by 34.86%,moderately stable organic phosphate by 27.74% and highly stable organic phosphate by 21.38%.Treatment with P2DM increased the active organic phosphate by 125.32%,moderately active organic phosphate by 38.64%,moderately stable organic phosphate by 30.84% and highly stable organic phosphate by 20.06%, compared with DM treatment alone.The increase was positively correlated with the quantity of phosphate rock added.At the final stage of composting,scanning electron microscopy revealed cavities on the phosphate rock surface,which suggested that DM composting could provide a biological approach to increasing phosphate solubility and improving the efficiency of phosphate fertilizer.