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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #292387
Title: Tracking short-term effects of 15N addition on N2O fluxes using FTIR spectroscopy

Author
item Phillips, Beckie
item GRIFFITH, DAVID - University Of Wollongong
item DIJKSTRA, FEIKE - University Of Sydney
item LUGG, GLENYS - Manildra Group
item LAWRIE, ROY - Department Of Primary Industries
item MACDONALD, BEN - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2013
Publication Date: 9/1/2013
Publication URL: http://handle.nal.usda.gov/10113/60284
Citation: Phillips, B.L., Griffith, D., Dijkstra, F., Lugg, G., Lawrie, R., Macdonald, B. 2013. Tracking short-term effects of 15N addition on N2O fluxes using FTIR spectroscopy. Journal of Environmental Quality. 42:1327-1340.

Interpretive Summary: Nitrogen to agricultural soils is in some part released to the atmosphere as nitrous oxide, but this amount is difficult to quantify without advanced techniques using stable isotopes of nitrogen. Here, we determined if a field-based, Fourier Transform Infrared (FTIR) spectrometer could be used to track gaseous emissions of nitrous oxide following nitrogen addition during the southern hemisphere summer of 2011-2012. We found this method effectively tracked nitrous oxide at very low levels of nitrogen addition (<5 lbs per acre) in the field with automated measurements. Peak emissions for all nitrous oxide fluxes followed rainfall events for 7-10 days. At low levels of nitrogen addition, approximately 1% of the added nitrogen was emitted as nitrous oxide. Future studies should investigate how agronomic additions of fertilizer-nitrogen affect the percentage emitted as nitrous oxide and the length of time emissions persist.

Technical Abstract: Anthropogenic nitrogen (N) additions to soils have significantly increased atmospheric nitrous oxide (N2O) concentration, and advanced methods are needed to track the amount of applied N that is transformed to N2O in the field. Here, we present a method for continuous measurement of N2O isotopologues (14N14N16O, 14N15N16O, 15N14N16O and 15N15N16O) following a light dose of 15N-labeled substrate as potassium nitrate (KNO3) or urea [CO(NH2)2] using a mobile Fourier Transform Infrared (FTIR) spectrometer. We evaluated this method using two 4-week experimental trials on a coastal floodplain site near Nowra, New South Wales, which is managed for silage production. We deployed an automated 5-chamber system connected to a multi-pass cell and low resolution FTIR spectrometer to measure N2O isotopologue fluxes. Emissions of all isotopologues were evident immediately following 15N addition. All isotopologues responded positively to rainfall events, but only for 7-10 d following N addition. Cumulative 15N-N2O fluxes (sum of the three 15N isotopologues) per chamber for the 14 d following 15N addition ranged from 1.5 to 10.3 mg 15N-N2O m-2. Approximately 1% (range 0.7 – 1.9%) of the total amount of 15N applied was emitted as N2O. Root mean square uncertainties for all isotopologue measurements were less than 0.3 nmol mol-1 for 1-min average concentration measurements, and minimum detectable fluxes for each isotopologue were <0.1 ng N m-2 s-1. The results indicate that the portable FTIR spectroscopic technique can effectively trace transfer of 15N to the atmosphere as N2O after 15N addition, allowing for powerful quantification of N2O emissions under field conditions.