Development of a Low-Cost Internet-of-Things (IoT) System for Monitoring Soil Water Potential Using Watermark 200SS Sensors

Abstract

Soil moisture monitoring is one of the methods that farmers can use for irrigation scheduling. Many sensor types and data logging systems have been developed for this purpose over the years, but their widespread adoption in practical irrigation scheduling is still limited due to a variety of factors. Important factors limiting adoption of soil moisture sensing technology by farmers include high cost and difficulties in timely data collection and interpretation. Recent developments in open source microcontrollers (such as Arduino), wireless communication, and Internet-of-Things (IoT) technologies offer opportunities for reducing cost and facilitating timely data collection, visualization, and interpretation for farmers. Therefore, the objective of this study was to develop and test a low-cost IoT system for soil moisture monitoring using Watermark 200SS sensors. The system uses Arduino-based microcontrollers and data from the field sensors (End Nodes) are communicated wirelessly using LoRa radios to a receiver (Coordinator), which connects to the Internet via WiFi and sends the data to an open-source website (ThingSpeak.com) where the data can be visualized and further analyzed using Matlab. The system was successfully tested under field conditions by installing Watermark sensors at four depths in a wheat field. The system described here could contribute to widespread adoption of easy-to-use and affordable moisture sensing technologies among farmers.

An Arduino-Based Wireless Sensor Network for Soil Moisture Monitoring Using Decagon EC-5 Sensors

“…The data sampling and communication system includes a Coordinator and several End Nodes following a Star Topology (Figure 2), similar to that described by [4], except that the End Node does not require a voltage divider to read the EC-5 sensors. Each End Node is identified by a unique address and is hardwired to the EC-5 moisture sensors.…”

“…Each End Node is identified by a unique address and is hardwired to the EC-5 moisture sensors. The End Nodes periodically sample the four EC-5 sensors and the data from the sensors is transmitted wirelessly to the Coordinator via radio communication [4]. The Coordinator then sends the received data to a website to be permanently stored in a Cloud server and visually displayed [4].…”

“…The line-of-sight distance range of the radio is over 2 km, using a wire quarter-wave antenna [4]. processor, which uses 3.3 V logic at 48 MHz.…”

“…Each End Node was built using a Feather 32u4 RFM95 LoRa Radio (RFM9x) (Adafruit Industries, New York, NY), which integrates an ATmega 32u4 microcontroller (Arduino-compatible), which uses 3.3 V logic at 8 MHz, and a Long Range (LoRa) packet radio transceiver [4]. The transceiver transmits or receives radio signals at 868 or 915 MHz frequencies, which can be specified in software.…”

“…Soil moisture sensing is one of the technologies farmers can adopt to properly schedule irrigation, which has been shown to potentially increase profits while protecting the environment [3]. Although many systems are commercially available for soil moisture monitoring, a number of factors still limit their adoption for irrigation scheduling among commercial growers [4]. Consequently, irrigation scheduling decisions in most commercial farming operations are still based on "the condition of the crop".…”