A significant amount of phosphorus (P) is present in animal manure. Land application of animal manure can benefit crop production by providing P and other nutrients. However, P runoff from agricultural soil due to over-application of animal manure may cause surface water degradation. Best management strategies are needed to optimize recycling manure P while minimising adverse consequences of manure land application. The chemical composition of P in animal manure is one of the critical factors controlling P transport and bioavailability in soils. In the last decade, efforts have been made to increase basic knowledge of manure P chemistry by applying novel and/or modified advanced analytic methodologies. This book discusses research on characterisation of P forms in animal manure.