Integrated soil moisture and water depth sensor for paddy fields

• A wireless, integrated moisture sensor was designed for paddy fields.
• This soil sensor is capable of measuring soil moisture content and water depth.
• A sensor package was designed for convenient installation in paddy fields.
• The sensor was calibrated with various soil samples.
• The performance of the sensor was tested.

This paper reports the development of a wireless, integrated, frequency-domain soil moisture sensor for paddy field applications. This soil sensor is able to measure soil moisture content and water depth at the same time and transmit the collected data wirelessly to a target receiver. The sensor consists of five parts: Probes, Sensor Acquisition Module, Processor Module, Communication Module and Power Supply Module. A sensor package was designed as well for convenient installation and practical deployment in paddy fields. The sensor was calibrated with various soil samples. The performances of the sensor were tested on measurement range, stability, system error, energy consumption and transmission distance. Results indicated that the optimum range of the soil moisture content was from 30% to 50%, and the measurement range of water depth was from 1 cm to 8 cm. Within these ranges measurement errors were less than 5% for soil moisture content and 0.5 cm for water depth. The sensor could transfer reliably 60 m and work continuously for at least 4 months using a 2100 mAh/3.6 V battery. It is suitable for monitoring soil moisture content and water depth in paddy fields.