Methodological progress in the measurement of agricultural greenhouse gases

Fossil fuels, land use, and agriculture are the three major sources contributing to the rise in atmospheric greenhouse gases (GHGs). Agricultural activities including the production of rice, animal raising, and aquaculture directly contribute to GHG emissions. Approximately one fourth of all GHG emissions are attributable to agricultural operations primarily as a result of unsustainable farming practices. The GHG emissions from agriculture include carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4). However, measurements of GHGs are laborious, expensive, and technically challenging but are crucial to select the most appropriate and feasible system. Since it is difficult to find a comprehensive overview of the variety of techniques, including latest technologies, in one article, this review aims to provide details of available methodologies, their benefits and drawbacks, with a focus on those that have been extensively tested in various ecosystems and regions. This paper is a purely methodological one which, on purpose, tried to familiarize the reader with the vast range of different developments. Our analysis is not exhaustive and is not intended to be a systematic review. The article summarizes that micrometeorological approaches are suitable for measurement from broader footprints, whereas chamber techniques measuring gases from point sources, are more appropriate for high spatio-temporal resolutions in diverse ecosystems. Stable isotope techniques are the most accurate methods and allow a process-specific quantification of GHGs but require sophisticated equipment.