Wireless Powered Moisture Sensors for Smart Agriculture and Pollution Prevention: Opportunities, Challenges, and Future Outlook

Purpose of Review

The ability to monitor soil moisture wirelessly can deliver immense benefits to annual crops. Real-time soil moisture monitoring allows for accurate and on-demand irrigation to achieve optimal growth and avoid overwatering. It is also an effective pollution prevention method, eliminating excessive run-off to prevent soil erosion, sediment discharge, and the dispersion of key water pollutants such as nitrogen and phosphorus to natural waterway. Current soil moisture sensors require constant a power supply or battery. Wiring can be used for soil moisture sensing of perennial crops but is also not suitable for annual crops that require significant tillage. This review aims to delineate the readiness of moisture sensors and wireless power transfer technology for developing a wireless soil moisture sensing network.

Recent Findings

Of the many types of soil moisture sensors, only a few are compatible to a wireless network. They either are too expensive, have unreliable measurement accuracy, or require too much power. This review shows that capacitive sensor is a potential candidate for underground sensor networks in terms of affordability, measurement reliability, and power consumption. In addition, among all currently available wireless power transfer technologies, inductive power transfer has the potential to supply adequate power for wirelessly charging underground sensors and meet other requirements of an underground sensing network.

Summary

This review evaluates available soil moisture sensing and wireless power transfer techniques for wireless underground moisture sensing. The combination of capacitive sensing and inductive power transfer technologies has been identified as a potential solution for wireless underground sensor networks. Future research should focus on improving the calibration and post-processing algorithm for capacitive sensor while the misalignment and impact of soil need to be considered to enhance the performance of the inductive power transfer system.