The use of open-source, affordable hardware in soil gas research

The development of new affordable sensors and hardware, and the ability to log high-resolution data for long periods of time can enhance the ability to capture soil gas process-related heterogeneity. The use of novel open-source sensors, defined as hardware whose design is made publicly available, lowers the cost dramatically compared to commercial solutions and allows implementing higher spatiotemporal resolution sensor grids that are imperative for modeling and mechanistic understandings. Here, I will present the basic concepts, advantages, and challenges of using open-source, low-cost, do-it-yourself hardware for soil gas monitoring (mainly O₂, CO₂, CH₄, and N₂O), including examples in which this type of sensors was utilized to solve soil-related research questions. For example, the development of a low-cost wireless underground sensor network for O₂/CO₂ monitoring under waterlogged conditions using the relatively new low-power long-range (LoRa) communication protocol. Another example is a portable, low-cost incubation chamber for quantifying soil microbial activity using in-situ sensors for measuring O₂, CO₂, CH₄, and air temperature at high temporal resolution (<1 min). In all the presented studies, only readily buyable hardware is used, and complete technical guides on design, assembly and installation are provided. By doing so, the adoption and cost barriers can be reduced, allowing easier reproducibility and opening the technology for new applications in soil gas monitoring studies.