Validation and field application of a low-cost device to measure CO₂ and ET fluxes

Abstract. Mitigating the global climate crisis and its consequences, such as more frequent and severe droughts, is one of the major challenges for future agriculture. Therefore, identifying land use systems and management practices that reduce greenhouse gas emissions (GHG) and promote water use efficiency (WUE) is crucial. This, however, requires accurate and precise measurements of carbon dioxide (CO₂) fluxes and evapotranspiration (ET). Despite that, commercial systems to measure CO₂ and ET fluxes are expensive and thus, often exclude research in ecosystems within the Global South. This is especially true for research and data of agroecosystems in these areas, which are to date still widely underrepresented. Here, we present a newly developed, low-cost, non-dispersive infrared (NDIR)-based, CO₂ and ET flux measurement device (~200 Euro) that provides reliable, accurate and precise CO₂ and ET flux measurements in conjunction with manual closed chambers. To validate the system, laboratory and field validation experiments were performed, testing multiple different low-cost sensors. We demonstrate that the system delivers accurate and precise CO₂ and ET flux measurements using the K30 FR NDIR (CO₂) and SHT31 (RH) sensor. An additional field trial application demonstrated its longer-term stability (> 3 months) and ability to obtain valid net ecosystem C balances (NECB) and WUE. This was the case, even though environmental conditions at the field trial application site in Sub-Saharan Africa were rather challenging (e.g., extremely high temperatures, humidity and intense rainfall). Consequently, the developed low-cost CO₂ and ET flux measurement device not only provides reasonable results but might also help to democratize science and close current data gaps.