Efficient irrigation system using a combined wireless sensor network based on LoRaWAN and IEEE 802.15.4 technologies and photosynthetically active radiation measurements

• Combined wireless sensor networks to address all types of agricultural scenarios. • Low-cost low-power sensors monitor proximal in-field information for a precise management of crop growth and the watering process. • PAR sensor calibrated by intercomparison with a reference equipment considering precipitable water vapour and zenith angles. • Hardware and software design strategies for achieving robust nodes, a self-sustainable WSN, and reliability and security in the communications. • The automatic irrigation system is designed for easy operation, simple deployment, scalability, and nearly maintenance-free operation. To address the demands of wireless communication, small amount of transmission, low power consumption, and cost-effectiveness in agricultural Internet of Things (IoT) applications, this paper introduces a hybrid information monitoring approach. It combines a low-data-rate personal area network based on IEEE 802.15.4 with a low-power wide-area network utilizing LoRaWAN. This method employs a communication architecture comprising a central node, multiple subnodes, and end devices to support the needs of large-scale information monitoring. Specifically, the main node is designed using LoRaWAN communication technology and performs in-field measurements of photosynthetically active radiation (PAR) using a device calibrated through intercomparison with reference radiometers. The subnodes or cluster heads incorporate LoRaWAN, sensor technologies, and IEEE 802.15.4. End devices also utilize IEEE 802.15.4 and sensor technologies. A control terminal manages sensor data and transmits the collected information to a web application for further processing. The advantages of this approach are that combining IEEE 802.15.4 and LoRaWAN at the device level enhances the spatial variability of agricultural fields, since tree and star network topologies are integrated to collect detailed information about specific crop areas, while providing low-power, long-distance network services and reducing the operating costs of the wide-area network information monitoring system. Additionally, hardware and firmware strategies were applied to further extend the system autonomy, and it can be self-powered. System testing revealed that, in a challenging environment, the maximum communication range reaches up to 60 m for IEEE 802.15.4 and 2 km for LoRaWAN. The average energy consumption is only 0.55 mAh, supporting real-time monitoring with latency under 100 ms, and the packet loss rate is approximately 2.5%. Overall, the system operates reliably, and the data collected are accurate. The findings indicate that the proposed method effectively fulfills the needs for data gathering, transmission, storage, and processing across large areas. Furthermore, it proves to be valuable for implementing strategies aimed at improving both irrigation systems and the cultivation process of strawberry crops.