Technical Abstract: Water extractable P (WEP) in manure is increasingly used as an environmental indicator as it is correlated with P in runoff from soils recently amended with manure. Little information exists on WEP variability across livestock manures. A survey of 140 livestock manures was conducted to assess trends in WEP (dry weight equivalent) related to livestock types and manure storage. Manure WEP ranged widely (0.2 to 16.8 g per kg), with swine having the highest average concentrations (9.2 g per kg), followed by turkey (6.3 g per kg), layer chickens (4.9 g per kg), dairy cattle (4.0 g per kg), broiler chickens (3.2 g per kg-1) and beef cattle (2.3 g per kg). Varying positive correlations were observed between WEP in manure and water extractable Ca, Mg and Fe, or total P, depending upon livestock category. Results of this study show that livestock manure can be categorized by WEP, a key step toward differential weighting of agricultural P sources in P site assessment indices.