Design and Evaluation of a Smart Greenhouse Control System for Hemp (Hemp plant) Seed and Fiber Production

บทคัดย่อ

This study aimed to design and evaluate the performance of a smart greenhouse control system for hemp (Hemp plant) cultivation for seed and fiber production, based on the principles of Controlled Environment Agriculture (CEA) and Good Agricultural Practices (GAP). The experiment was conducted in a closed greenhouse measuring 3 meters by 6 meters, containing 72 hemp plants cultivated in pots with one plant per pot defined as the experimental unit, evaluated using a completely randomized design (CRD) with $n = 24$ independent biological replicates per treatment. An automated control system was employed to regulate key environmental parameters, including lighting, irrigation, and air circulation. Because lighting duration, irrigation volume, and air circulation were manipulated simultaneously across treatments, this study evaluated the combined synergistic effects of these microclimatic factors rather than isolated individual main effects. The experimental design consisted of three treatment levels: low (L1–W1–A1), medium (L2–W2–A2), and high (L3–W3–A3), under a controlled light intensity ranging from 5,000 to 7,000 lux. Data were analyzed using one-way analysis of variance (ANOVA), and mean comparisons were performed using Duncan’s Multiple Range Test (DMRT) at a significance level of less than 0.05. The results demonstrated that the medium-level treatment (L2–W2–A2), consisting of 8 hours per day of lighting, 20 minutes per day of irrigation, and 8 hours per day of air circulation, was statistically identified as the best-performing combination condition among the tested set. Under this treatment, plants achieved an average stem height of 165 ± 10 centimeters, an average total leaf area per plant of 320 ± 25 square centimeters, and the highest average seed yield of 62 ± 7 grams per plant, along with superior fiber quality (tensile strength of 385 ± 28 MPa and fiber yield of 14.2 ± 1.1 g/plant). In contrast, the low-level treatment (L1–W1–A1) induced physiological stress and resulted in a substantially lower seed yield of 28 ± 5 grams per plant. Although the high-level treatment (L3–W3–A3) produced the greatest stem height (180 ± 12 centimeters), it significantly reduced seed yield to 45 ± 6 grams per plant, likely due to imbalanced vegetative growth and etiolation. In conclusion, the balanced regulation of light, water, and air through a statistically validated automated control system plays a critical role in optimizing hemp growth performance and seed productivity. These findings provide a scientifically grounded guideline for precision-controlled environmental management in small-scale smart greenhouse systems.