Farm survey used to guide estimates of nitrogen intake and ammonia emissions for beef cattle, including early season grazing and piosphere effects.

Sheppard, S.C. and Bittman, S. (2011). "Farm survey used to guide estimates of nitrogen intake and ammonia emissions for beef cattle, including early season grazing and piosphere effects.", Animal Feed Science and Technology, 166-167, pp. 688-698. doi : 10.1016/j.anifeedsci.2011.04.048  Access to full text

Abstract

National inventories of N emissions to the atmosphere from cattle depend on reliable information about husbandry practices, with appropriate spatial and temporal resolution. A survey of ~ 1400 beef cattle farmers was used to quantify the prevalence of pasture and forage management practices that impact N intake and NH3 emissions, with implications for N2O emissions. These survey data were coupled to a mass balance model to inventory NH3 emissions by accounting for total ammoniacal (i.e., ammonia and ammonium) N (TAN) from excretion through to land spreading. As inputs, the model required excretion fractions, 2006 Canadian Census of Agriculture animal populations and detailed farm management practices from the survey. The N intake by grazing cattle was especially difficult to quantify. Early season grazing, when forages have elevated crude protein (>300 g CP/kg dry matter), indicated potential for elevated emissions in May and June. Such exceptional CP concentrations during spring grazing may be important for N emissions, especially NH3. Additionally, beef cattle were reported by producers to spend 7-30%) of their time congregated, such as around water sources, feed or shade trees. This level of piosphere activity was attributed in the model to ~ 20% increases in NH3 emissions relative to open pasture, and similar or higher effects would be expected for N2O emissions.

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