Use of the 15 N gas flux method to measure the source and level of N2O and N-2 emissions from grazed grassland

作者：Baily Anne^*; Watson Catherine J; Laughlin Ronnie; Matthews Dave; McGeough Karen; Jordan Philip

来源：Nutrient Cycling in Agroecosystems, 2012, 94(2-3): 287-298.

DOI：10.1007/s10705-012-9541-x

• Grazing intensity
• Denitrification
• N-15 gas flux method
• Nitrous oxide
• Dinitrogen
• Mole fraction
• Denitrifier community composition

Understanding the contribution of nitrification and denitrification to production of nitrous oxide (N2O), a potent greenhouse gas, is important in devising effective mitigation strategies to reduce emissions. In this study the N-15 gas flux method was used to investigate N2O and N-2 emissions following an application of N-15 labelled ammonium nitrate (0.71 mol N m(-2)) to intensive grassland swards (grazed at 2.74 or 2.05 livestock units ha(-1) year(-1)) at a site in Southern Ireland. The N-15 labelled fertiliser (NO3 moiety N-15 labelled at 60 at. %) was applied to designated soil areas in the field, enclosed by static chambers, in June 2009, September 2009 and March 2010. Fluxes of N2O and N-2 were determined over 12 days on each occasion. N2O and N-2 emissions were significantly (P %26lt; 0.001) lower in March 2010 than in June or September 2009. There was little difference between the two swards grazed at different stocking rates on N2O or N-2 emissions. Mean cumulative N2O emissions over 103 h were 212.9, 279.5 and 62.06 mg m(-2) for June 2009, September 2009 and March 2010, respectively. Mean cumulative N-2 emissions for the three time periods were 818.8, 893.8 and 87 mg m(-2), respectively. The N2O mole fraction averaged 0.21 and 0.23 in June 2009 and September 2009, respectively, but increased to 0.41 in March 2010 which may have been due to changes in denitrifier community composition or due to N2O reductase being sensitive to low soil temperatures. The results point to denitrification of nitrate as the major source of N2O at this site which may have implications for choice of fertiliser in moist temperate climates.

• 出版日期2012-12