Chamber Measurements of Soil Nitrous Oxide Flux: Are Absolute Values Reliable?

Abstract

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 soil 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.

Quantifying soil carbon stocks and greenhouse gas fluxes in the sugarcane agrosystem: point of view

“…Consequently, several precautions need to be taken to avoid biased flux estimates when using chambers (Rochette and Eriksen-Hamel, 2008). …”

“…Criteria to evaluate chamber methodology in studies on N 2 O Considerable variation can be observed in the chamber methodology used to measure soil N 2 O fluxes in recent literature (Rochette and Eriksen-Hamel, 2008). These authors performed a literature review to evaluate criteria were determined for assessing the quality of soil N 2 O flux measurements made using chambers.…”

“…The score of each characteristic to the quality of N 2 O emission data is based on estimated impact of each characteristic on the measurement error. Adapted from Rochette and Eriksen-Hamel (2008 ber with 0.70 × 0.45 m size. These dimensions are associated with sugarcane row-space, which in most of the areas is 1.5 m between planting rows.…”

“…Rochette and Eriksen-Hamel (2008) estimated that incubation periods greater than 40 min are likely to result in significant negative impacts on chamber conditions. To assess N 2 O emissions in sugarcane fields, it is recommended an incubation period of 20 min, in which four samples should be collected.…”

N2O emissions from a cultivated mollisol: optimal time of day for sampling and the role of soil temperature

“…The current global estimate of agricultural N 2 O emissions has an uncertainty ranging from -60 to 170 % of the mean estimate (Venterea et al, 2009). Rochette & Eriksen-Hamel (2008) concluded that 50 -60 % of the N 2 O data measured using field chambers is unreliable, usually due to the use of inappropriate methods. This makes the minimization of experimental errors during field sampling a key concern to improve confidence levels of N 2 O measurements (Schindlbacher et al, 2004;Venterea et al, 2009).…”