New Sensor Technology for Field‐Scale Quantification of Carbon Dioxide in Soil

Abstract

Core Ideas This new technology is suitable for field‐scale quantification of CO2 in soil. The measurement scale ranges from decimeters up to decameters. The concentrations from the soil water and air phases are averaged. Transient CO2 production and transport reflect plant growth. Biological activity in soil causes fluxes of O2 into and CO2 out of the soil with significant global relevance. Hence, the dynamics of CO2 concentrations in soil can be used as an indicator for biological activity. However, there is an enormous spatial and temporal variability in soil respiration, which has led to the notion of hotspots and hot moments. This variability is attributed to the spatiotemporal heterogeneity of both plant–soil–microbiome interactions and the local conditions governing gas transport. For the characterization of a given soil, the local heterogeneities should be replaced by some meaningful average. To this end, we introduce a line sensor based on tubular gas‐selective membranes that is applicable at the field scale for a wide range in water content. It provides the average CO2 concentration of the ambient soil along its length. The new technique corrects for fluctuating external conditions (i.e., temperature and air pressure) and the impact of water vapor without any further calibration. The new line sensor was tested in a laboratory mesocosm experiment where CO2 concentrations were monitored at two depths during the growth of barley (Hordeum vulgare L.). The results could be consistently related to plant development, plant density, and changing conditions for gas diffusion toward the soil surface. The comparison with an independent CO2 sensor confirmed that the new sensor is actually capable of determining meaningful average CO2 concentrations in a natural soil for long time periods.

Short‐term effects of nitrogen source on soil properties and plant growth

“…Throughout the entire experiment (ORG‐N = UAN‐32 > no‐N), mean accumulated soil CO 2 fluxes were 48.2, 37.0, and 24.8 mol m −2 , respectively (Figure 2). Increases in accumulation rates (shown as steeper gradient lines in Figure 2) were attributed to larger plant (autotrophic) contributions stemming from increased production, which increases root and rhizosphere respiration (Amos et al., 2005; Lazik et al., 2019; Sainju et al., 2008). Overall, ORG‐N and UAN‐32 accumulated significantly higher (93 and 49%, respectfully) soil CO 2 than no‐N.…”

A New Principle for Measuring the Average Relative Humidity in Large Volumes of Non-Homogenous Gas

“…As discussed in [30], C-turnover in soil can result in elevated concentrations of CO 2 of up to 10%, which can according to the comparatively high permeability of CO 2 (Table 1) influences the measurement. But in these cases water must be abundant, i.e., RH ≡ 100%.…”

“…Both processes will lower the difference of the soil gas composition with respect to air. Nevertheless, further investigations will be appropriate with respect to influences due to varying gas composition on the measurement and for compensating techniques, e.g., in analogy to those developed in [30].…”

“…The method has the advantage of providing an average of fluctuating local concentrations within the dynamically changing, heterogeneous multi-phase system soil over an area in the order of 100 to 103 m 2 [26,27,28]. The combination of a self-calibrating sensor design [29] with a specially constructed water vapor compensating membrane [30] allowed the determination of small CO 2 concentrations due to soil respiration in face of a temperature-dependent varying water vapor pressure in humid soils. Such membrane-based sensors can be used to analyze various gases as shown by computer simulations [31] and experiments, e.g., [32].…”

IoT-based data logger for weather monitoring using arduino-based wireless sensor networks with remote graphical application and alerts

“…This sensor gives the simple voltage that corresponds to a specific climatic factor. Subsequently, the Arduino integrated microcontroller will convert this voltage into numerical values [23][24][25] .…”