Improving ECH2O Field Performance
Decagon introduced the ECH2O-20 cm soil moisture probe in the spring of 2001. Since that time, the probe has been continually tested and modified to improve its performance in the field. Issues that have received considerable attention recently are the ECH2O probe's sensitivity to differences in electrical conductivity (EC), soil texture, and temperature.
Electrical Conductivity, Soil Texture, and Temperature
While the current ECH2O-20 and 10 cm probes are adequate for most field applications, some research and commercial project needs are not being met because of these issues. Thus, there has been considerable interest in developing a probe that has lower sensitivity to variations in electrical conductivity, soil texture, and temperature while maintaining the qualities that have made the ECH2O probe so widely accepted.
Increasing Measurement Frequency
There has been considerable discussion in the scientific literature regarding how increasing measurement frequency improves the salinity, soil texture, and temperature response of soil moisture sensors. With this in mind, we changed the measurement frequency of one of our current probes, (ECH2O-10cm) and two new 5 cm-long ECH2O probes (ECH2O-TE and ECH2O-5) to see if we could improve the response of the probes.
Figure 1 illustrates the improvement that increasing the measurement frequency has made in the ECH2O-10 sensor. The performance of the two new sensors (ECH2O-TE and ECH2O-5) is similar to that of the ECH2O-10 (Fig. 2).
Fig. 1. ECH2O-10 probe output running at two frequencies in sand and silt loam at several solution electrical conductivities and water contents.
Fig. 2. Two ECH2O-TE probes calibrated in four soil types at varying salinities up to 8.9 dS/m (S - sand, Sd L - sandy loam, Si L - silt loam, HBC - Houston black clay).