Estimated net application of ammoniacal and organic N from manure, and potential for mitigating losses of ammonia in Canada

Manure nitrogen (N) includes what can be generalized as organic N, which includes undigested N from the feeds; ammoniacal and easily hydrolysable N, which includes urea and uric acid; and nitrate/nitrite species, which are the least abundant. From excretion to landspreading, the largest change in N concentration occurs because of volatilization of ammonia (NH3) from the ammoniacal and easily hydrolysable fraction. This process can be highly dependent on manure management, and some management strategies such as manure injection are largely designed to decrease NH3 loss. This paper utilizes recent models of NH3 emission from beef, dairy, swine and poultry production to estimate the net organic and ammoniacal N content of manure in Canadian Ecoregions before and after land spreading. Confinement versus grazing for beef is a major factor for overall net manure N application, and slurry versus solid manure is next most important. There are distinct differences among Ecoregions in the proportions of organic and ammoniacal N, so that generic assumptions are not appropriate. The estimates are mapped for all of Canada based on 2006 animal census. Several best management practices (BMPs) are evaluated using recent costing information (dollars per kg of NH3-N saved from emission). Relatively low-cost BMPs related to slurry manure applied nation-wide could save 16 Gg NH3-N year−1 for an estimated cost of $13 M. Other low-cost BMPs could increase this to a saving of 79 Gg NH3-N year−1 or 26% of present emissions.