US EPA

1564908 

Journal Article 

Chamber measurements of soil nitrous oxide flux: Are absolute values reliable? 

Rochette, P; Eriksen-Hamel, NS 

2008 

1 

Soil Science Society of America Journal
ISSN: 0361-5995
EISSN: 1435-0661 

72 

2 

331-342 

10.2136/sssaj2007.0215 

WOS:000254060200005 

The vast majority of soil N2O flux data reported in the
literature was obtained using non-flow-through non-steady-state (NFT-NSS) chambers. Considerable
variation in chamber methodology may influence N2O flux measurements, however, raising concerns
about the reliability and accuracy of these measurements. The objectives of this study were to
determine criteria for assessing the quality of soil N2O flux measurements made using NFT-NSS
chambers, to evaluate NFT-NSS chamber methodologies used in the scientific literature, and to
propose a minimum set of criteria for NFT-NSS chamber design and deployment methodology. We
identified 16 characteristics of chamber methodology and developed four factors contributing to
the quality of N2O flux measurements made using NFT-NSS chambers. We compiled a data set of 356
studies and evaluated the quality of each study against the set of characteristics and factors to
determine the confidence in the reported N2O flux. Confidence in the absolute flux values
reported in about 60% of the studies was estimated to be very low or low due to poor
methodologies or incomplete reporting. The confidence in flux measurements improved with time;
however, there were still about 50% of recent studies (2005-2007) with low or very low confidence
levels. This study has shown that the quality of sod N2O flux measurements reported in the
literature is often poor. While the flux data obtained may be valid for comparisons between
situations (e.g., treatments) within a given study, they are often biased estimates of actual
fluxes. We propose a minimum set of criteria for reliable soil N2O flux measurements using NFT-
NSS chambers.