Measurement of greenhouse gas fluxes in agricultural soils with a flexible, open-design automated system

Abstract. Over the last decades and due to the current climate change situation, the study of the impacts of human activities on climate has reached great importance, being agriculture one of the main sources of soil greenhouse gas. There are different techniques to quantify the soil gas fluxes, such as micrometeorological techniques or chamber techniques, being the last one capable to assess different treatment at the same site. Manual chambers are the most common one. However, due to the low sampling frequency, this approach cannot resolve short-term emission events, like fertilization or rewetting. For this reason, automated chamber systems are an opportunity to improve soil gas flux determination, but their distribution is still scarce due to the cost and challenging technical implementation. The objective of this study was to develop an automated chamber system for agricultural systems under Mediterranean conditions and compare measured GHG flux rates to those derived using manual chambers. A comparison between manual and automated chamber systems was conducted to evaluate the soil gas fluxes obtained by the automated system. Moreover, over a period of one month the soil gas fluxes were determined by both systems to compare their capabilities to capture the temporal variability of soil gas emissions. The automated system reported higher soil GHG fluxes compared to the manual chamber system. Additionally, the higher sampling frequency of the automated chamber system allowed for the capture of daily flux variations, resulting in a more accurate estimation of cumulative soil gas emissions. The study emphasises the importance of chamber dimension and shape, as well as sampling frequency, in the development of chamber systems, especially when using the manual chamber system.