The characteristics of phosphorus in animal manure composts

Phosphorus (P) in animal manure compost (AMC) is one of the most important resources of P for crop production. The P characteristics in AMC are affected by animal type, feed, additive, and composting method, among others. Clarifying the P characteristics in AMC is necessary to utilize P effectively and eco-sustainably. Several approaches exist for characterizing P in AMC. The chemical method (extraction) is widely used and can evaluate P according to solubility. Other methods include non-destructive methods like X-ray diffraction (XRD), 31P nuclear magnetic resonance (NMR) spectroscopy, and X-ray absorption spectroscopy (XAS), which can determine P compounds or speciation in AMC. In this paper, we review recent studies relating to the P characteristics in AMC. The chemical P composition or solubility was differed by animal types. The ratio of labile P (water and 0.5M NaHCO3 soluble P) to total P (T-P) was highest in cattle manure compost, followed by swine and poultry. This difference in P solubility was explained by the kind of P compounds in each AMC determined by non-destructive analysis. Struvite (MgNH4PO4·6H2O) was contained in all types of AMC and considered to be the main source of labile P. The relative efficiency of struvite P was higher than commercial chemical P fertilizer, increasing the P recovery rate of AMC. Poultry manure compost had a higher ratio of organic P (Po), mainly phytate P, than others. However, there were few studies which demonstrated the accumulation of Po in AMC-applied soils, indicating the mineralization of Po in soils. Finally, we suggested the best management of P derived from AMC.