Phenology-driven dynamic threshold iot control for hydroponic garlic sprout production

Abstract To address the problem that traditional facility agriculture environmental control relies on fixed environmental thresholds and cannot adapt to the dynamic environmental requirements of crops at different growth stages, a crop phenology-based Crop Growth Dynamic Threshold Strategy (CGDTS) was proposed. An Internet of Things (IoT)-based intelligent greenhouse control system was developed, which integrates multi-source sensing, Programmable Logic Controller (PLC) control, edge computing, and cloud coordination. The proposed strategy incorporates real-time Growing Degree Days (GDD) as an indicator of crop developmental status into the greenhouse closed-loop control system. The crop phenological stages are automatically identified through cumulative GDD, and the environmental setpoints are switched according to the identified phenological stage, achieving coordination between environmental regulation and crop growth. A 24-day comparative cultivation experiment was conducted on hydroponic garlic sprouts. The results demonstrated that the proposed system achieved stable environmental monitoring, stage-based control, and remote management. Compared with the conventional fixed-threshold strategy, the CGDTS treatment was associated with an 11.7% higher marketable fresh weight, an 11.6% higher average plant height, and a 51.2% lower coefficient of variation of plant height in this single-cycle experiment, along with a lower observed developmental deviation ratio. These preliminary results suggest that the application of CGDTS in hydroponic garlic sprout production is feasible, and that stage-switching environmental regulation based on crop developmental status has the potential to improve crop growth performance and population uniformity; further studies with independently replicated treatments are needed to confirm these findings.