Continuous monitoring of greenhouse gas emissions from rice paddies using automatic flux chambers

Rice paddies are among the most important cultivated areas globally both in terms of food security and greenhouse gas (GHG) emissions. Rice paddies are estimated to contribute approximately 10% of anthropogenic CH₄ emissions and are also potential hot spots for N₂O emissions. However, emission estimates are highly uncertain as observational data consist primarily of manual, static closed chamber measurements combined with gas chromatography. This methodology is highly time consuming and sets limitations on the number of observations over time, which is problematic due to the highly variable temporal nature of both CH₄ and N₂O fluxes with respect to water table fluctuations and fertilisation. The temporal dynamics of CH₄ and N₂O emissions from rice paddies are therefore not well understood.

Here we present the methodology and initial results from a novel automatic chamber setup with continuous GHG measurements on rice paddies under varying agricultural practices, including water regimes. The concentrations of all three major GHGs, i.e. CO₂, CH₄ and N₂O, are continuously measured using state-of-the-art automatic chambers operated in both light and dark mode. The automatic chamber setup is designed to accommodate changes in both water table, plant height and crop types. GHG fluxes are estimated using both linear and non-linear (Hutchinson and Mosier model) regression.

This setup will provide the most detailed GHG measurements on rice paddies to date and improve our understanding of the GHG dynamics on rice paddies under varying agricultural practices and water regimes.