Phosphorus Water Extractability in Major Ontario Soils Amended with Various Manures.

Water extractable P in soils amended with animal manures may be used as a tool to predict the potential for P loss in both surface and sub-surface runoff water. Water soluble P from six Ontario soils amended with four types of manure (liquid swine, solid beef, liquid dairy, and solid poultry) was determined after 2 and 14 days of incubation under controlled conditions with temperature 25^oC and 50% soil pore space water-filled. There were significant differences in soil total dissolved P (TDP) and dissolved inorganic P (DIP) amongst soil and manure types in different incubation periods, while same amount of manure P was added. Both TDP and DIP were the highest in soils added with liquid swine manure (13.09 mg DTP kg^-1 and 9.68 mg DIP kg^-1for liquid swine vs. 7.07 mg TDP kg^-1 and 3.44 mg DIP kg^-1 for other three types).  For soil type, contents of water extractable P followed the order of Fox sandy loam > Brookston clay, Conestogo loam > Perth clay loam > Listowel silt loam > Grenville loam, ranging from 4.26 to 15.17 mg P kg^-1 for TDP and from 2.17 to 11.63 mg P kg^-1 for DIP. Water extractability of P in soils amended with manures ranged from 1 to 63%. Water extractable P in soils started to decline after 14 days of application, relative to those after 2 days of application. The P source coefficients for four types of manure averaged across six soil types were 1.26, 0.67, 0.58, and 0.26 for liquid swine, solid beef, liquid dairy, and solid poultry manure, respectively.  The results indicated that the P extractability not only depended on manure type, but also on soil properties and reaction period.