IoT-Based Sensor Monitoring and Automated Irrigation Control for Sustainable Smallholder Vegetable Production: A Case Study

Greenhouse vegetable cultivation in tropical regions is often affected by high temperature, unstable humidity, and irrigation management problems. This study presents a pilot-scale case study of Green Oak lettuce cultivation using an IoT-based sensor monitoring and automated irrigation control system in Phra Nakhon Si Ayutthaya Province, Thailand. The system used AM2315C, BH1750, NPK, and flow sensors connected to ESP32. Data were transmitted to the ThingsBoard platform for real-time environmental monitoring and irrigation control. The greenhouse temperature averaged 33.21 ± 3.61 °C, while relative humidity averaged 71.55 ± 9.66%. The average daytime light intensity was 16,976 ± 409 lux. Nitrogen (N), phosphorus (P), and potassium (K) concentrations remained within ranges of 62.42–74.57, 76.46–84.30, and 71.46–79.30 mg/kg, respectively. Economic evaluation demonstrated favorable feasibility, with a water use efficiency (WUE) of 0.63 kg/L, return on investment (ROI) of 40%, benefit–cost ratio (BCR) of 1.6, and payback period of approximately 2.5 years. The developed system demonstrates potential for supporting sustainable greenhouse agriculture and contributes to SDG 2, SDG 6, SDG 12, and SDG 13 under tropical agricultural conditions.