Journal of Experimental Agriculture International

Hydroponic cultivation offers a resource-efficient alternative to conventional soil-based crop production by enabling controlled water and nutrient delivery. This study designed and developed a dual-module Internet of Things (IoT)-based smart Dutch Bucket hydroponic system for cherry tomato cultivation under a naturally ventilated polyhouse. The system used ESP32 microcontrollers as the central processing units and the ThingSpeak cloud platform for real-time data logging and visualisation. The irrigation module incorporated capacitive substrate moisture sensors, water flow sensors and a DHT22 temperature and relative humidity sensor. Irrigation was automated using threshold-based control, in which the solenoid valve was activated when the substrate moisture level fell below 40% and deactivated when it reached 70%. The nutrient management module integrated electrical conductivity (EC), pH, nutrient solution temperature and water level sensors with dosing pumps for nutrient solution A, nutrient solution B and pH adjustment. Nutrient regulation was programmed according to crop growth stage, with EC maintained at 1.2-1.8 mS cm-1 during the vegetative stage and 2.8-3.5 mS cm-1 during the fruiting stage, while pH remained within 6.7-6.9. Sensor calibration improved measurement performance, with the maximum pH deviation after calibration recorded as 2.49%, EC deviation reduced from 7.93% to 0.35% and flow sensor deviation reduced from +/-7.0% to +/-1.0%. The calibrated system was installed within the nutrient reservoir and linked to dedicated ThingSpeak fields for continuous acquisition of environmental, irrigation and nutrient solution data. The developed system enabled remote access to real-time readings through graphical visualisation. The results indicate that the integrated dual-module approach can support automated hydroponic management while reducing dependence on manual monitoring.