Determination of soil CO2 Concentration With Two Newly Developed Mobile Measuring Devices

Abstract

Background

Carbon dioxide concentration in soil air is an important indicator of carbon turnover and the soil's aeration status. However, measuring CO₂ in soil air using a gas chromatograph (GC) is time-consuming and expensive.

Aim

This study presents two newly developed CO₂ measuring devices. The first one is a mobile device with an infrared sensor (MiCO2), which enables time-efficient soil air analyses up to a depth of 25 cm. The second device is a mobile profile probe equipped with CO₂ sensors at four different depths (MaCO2).

Methods

The four built-in sensors (8, 22, 42, and 62 cm depth) operate on the photoacoustic measuring principle and record temperature and soil air moisture in addition to CO₂ concentration. MiCO2 offers a cost-effective and rapid method for assessing the aeration status of the topsoil, enabling quick diagnosis of aeration problems. Conversely, MaCO2 allows for monitoring up to a soil depth of 60 cm, facilitating analysis of the entire aeration situation in the main rooting zone.

Results

Comparative tests with a GC have shown that the measuring accuracy of the newly developed CO₂ measuring devices is comparable under laboratory and field conditions. Only in highly compacted soils with CO₂ concentrations above 5%, that the MiCO2 measurements were lower than those of the GC.

Conclusion

The MaCO2 even showed a clear advantage over the GC and MiCO2: Since measurement can be achieved by diffusion, there is no risk of drawing in and measuring soil air from soil layers besides the measurement depth.