Global Research Alliance N2O chamber methodology guidelines: Introduction, with health and safety considerations

Authors: DE KLEIN, CECILE - Agresearch; HARVEY, MICHAEL - National Institute Of Water And Atmospheric Research (NIWA) Ltd; CLOUGH, TIMOTHY - Lincoln University - New Zealand; PETERSEN, SOREN - Aarhus University; CHADWICK, DAVID - Bangor University, Wales; Venterea, Rodney - Rod

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2020
Publication Date: 7/23/2020
Citation: De Klein, C.A., Harvey, M.J., Clough, T.J., Petersen, S.O., Chadwick, D.R., Venterea, R.T. 2020. Global Research Alliance N2O chamber methodology guidelines: Introduction, with health and safety considerations. Journal of Environmental Quality. 49(5):1073-1080. https://doi.org/10.1002/jeq2.20131.
DOI: https://doi.org/10.1002/jeq2.20131

Interpretive Summary: Non-steady state (NSS) chamber techniques are used to measure fluxes of nitrous oxide (N2O) from agricultural soils. Nitrous oxide is an important greenhouse gas that is produced when nitrogen is applied to soil in the form of manure or fertilizers. Chambers are widely used because they are relatively inexpensive, easy to adopt, versatile and adaptable to varying conditions. While easy to adopt, use of NSS chambers requires decisions regarding multiple aspects, each of which may significantly impact the results. Variation in these details can lead to challenges in comparing results between studies and assessment of reliability and uncertainty. Therefore, the New Zealand Government, in support of the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases (GRA), funded an international project to develop standardized guidelines on the use of NSS chambers. This introductory paper summarizes a special collection of papers representing the work of an international team of scientists who have been refining these guidelines for several years. Each article summarizes existing knowledge and provides guidance and recommendations for key aspects, including design, deployment, sample collection, storage and analysis, automated chambers, flux calculations, statistical analysis, emission factor estimation and data reporting, modeling approaches, guidelines for ‘backfilling’ missing measurements, and health and safety considerations, which are included in this introductory paper. Each paper defines minimum requirements; however, these are not meant to be highly prescriptive, but instead to provide researchers with guidance on best practice and factors that need to be considered. This collection of papers provides guidance and recommendations that will be useful to researchers across the world in generating reliable data to support regional, national and global estimations of agricultural N2O emission inventories.

Technical Abstract: Non-steady state (NSS) chamber techniques have been used for decades to measure nitrous oxide (N2O) fluxes from agricultural soils. These techniques are widely used because they are relatively inexpensive, easy to adopt, versatile and adaptable to varying conditions. Much of our current understanding of the drivers of N2O emissions, efficacy of mitigation practices, as well as estimations of agricultural N2O emission inventories, are based on chamber measurements. While easy to adopt, use of NSS chambers requires decisions regarding multiple methodological aspects including chamber materials and geometry, sample replication, timing and frequency, sample analysis, use of ancillary information, and data analysis and statistical methods, each of which may significantly impact the results. Variation in these methodological details can lead to challenges in comparing results between studies and assessment of reliability and uncertainty. Therefore, the New Zealand Government, in support of the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases (GRA), funded an international project to develop standardized guidelines on the use of NSS chambers. This introductory paper summarizes a special collection of papers representing the work of an international team of scientists who have been refining these guidelines for several years. Each article summarizes existing knowledge and provides guidance and recommendations for key aspects, including design, deployment, sample collection, storage and analysis, automated chambers, flux calculations, statistical analysis, emission factor estimation and data reporting, modeling approaches, guidelines for ‘backfilling’ missing measurements, and health and safety considerations, which are included in this introductory paper. Each paper defines minimum requirements; however, these are not meant to be highly prescriptive, but instead to provide researchers with guidance on best practice and factors that need to be considered.