Determination of Manure P Source Coefficients in Ontario Soils.

Manure varies in P forms and contents, which can result in significant differences in P losses after land application, depending on the sources. Weighting factors must be determined to reflect the differences in risk of P loss from various types of manures. The objective of this study was to determine the P source coefficients (PSC) of major types of manures for Ontario soils using an incubation approach. Treatment factors included six predominant soil series distributing in the major manure production areas of Ontario, four types of manure P sources (solid beef, liquid swine, solid poultry, and liquid dairy) with 3 sources of each collected across the province, an inorganic fertilizer P control, a zero-P control, and four incubation stages (2 days and 2, 8 and 26 weeks). PSCs were determined using the measurement of water extractable P. The values of PSCs varied, depending on manure and soil types, as well as the incubation period. PSCs for liquid swine manures were very high and often exceeded 100%, but decreased in most soils with the prolonged incubation time, while they remained consistently the highest amongst the four types of manures. The temporal changes in PSCs for solid beef, liquid dairy, and solid poultry manures were with less fluctuation, relative to those for liquid swine manures. The values of PSCs for four types of manures averaged across six soils for the entire incubation period of 26 weeks were 97.8, 45.4, 45.0, and 25.0% for liquid swine, solid beef, liquid dairy, and solid poultry, respectively.