A New Non-Inserted and Portable FDR Instrument for Measuring Surface Soil Water Content

Yunfeng Qiao,Bo Li,Shanbao Liu,Fadong Li,Qi Li,Hao Zhang,Kun Du,Qiuying Zhang

doi:10.3390/w13192712

Abstract

Soil water content (SWC) is a vital parameter for understanding crop growth and the soil nutrient water cycle. Monitoring SWC without inserting sensors into the soil, which can break the soil structure, has previously been a significant challenge for scientists. In this study, we developed a non-inserted portable frequency domain reflection (NIP-FDR) instrument to monitor SWC continuously and automatically. The working technique of this instrument was based on the improved adjustable high-frequency oscillation method originating from the frequency domain reflection principle. Compared to the control SWC measurement instrument, the difference in SWC at 0–10 cm, 10–20 cm, and 20–30 cm depth was within 1%, 3%, and 15%, respectively, and the mean variation of SWC was less than 5% in the indoor measurements. In the field verification experiment conducted in the summer of 2020, the mean error of SWC measurements at a depth of 0–20 cm was 5%, while we failed to compare SWC at a depth of 20–30 cm due to low variability in the SWC measurement at this depth during the summer measurement period. This pioneer NIP-FDR was able to effectively monitor surface SWC, especially at depths of 0–20 cm.

Highlights

Soil water content (SWC) has an important impact on rainfall runoff, transpiration, and vegetation ecosystems in ecological environments [1]
The results showed that SWC at depths of 0–10, 10–20, and 20–30 cm measured by the non-inserted SWC monitor were consistent with the 5TE SWC sensor (Figure 3)
We developed an non-inserted portable frequency domain reflection (NIP-frequency domain reflection (FDR)) instrument to measure SWC, and the indoor and field verification work proved that it was possible to monitor SWC at depths of 0–20 cm during a short time frame and easy to move due to it being light-weight

Summary

Introduction

Soil water content (SWC) has an important impact on rainfall runoff, transpiration, and vegetation ecosystems in ecological environments [1]. Excessive soil water inhibits root growth, leading to root disease and subsequent crop death [8]. A number of methods at different scales have been proven useful for measuring. Among them, monitoring SWC at a point scale (less than 0.01 cm2 ) has advanced with various in-situ sensors, and the FDR method has been widely used [16]. The FDR method can measure the soil apparent dielectric constant using method has been widely used [16]. The FDR method can measure the soil apparent di lectric constant using the electromagnetic pulse principle, according to the frequency

Objectives

Methods

Results

Discussion

Conclusion