Production traits of garden mums subjected to various substrate water contents at a commercial production farm

Improving water use and nutrient efficiency can play a pivotal role in ensuring sustainable production of horticultural crops. This study aimed to investigate the optimum moisture level that best management practices need to ensure for high-quality garden mum production, and also determine the feasibility of using a soil moisture sensor-based automated fertigation system for water and nutrient management for high-quality garden mum production. We used 20 5TE (Decagon Devices, Pullman, WA, USA) sensors to monitor and control fertigation based either on the substrate volumetric water content (θ, v/v) at 0.25, 0.35, 0.45, and 0.55 m³·m⁻³, or conventional greenhouse management culture practices. At harvest, most vegetative growth parameters were not significantly different across the treatments, but the leaf relative water content of plants under the 0.25 m³·m⁻³ treatment was lower than that of plants under other treatments, indicating that the plants were drought stressed. Although flower diameters and peduncle lengths were similar across the treatments, the number of flowers of plants under the 0.25 and 0.35 m³·m⁻³ treatments were 25–37% less compared to that of plants under the 0.45 and 0.55 m³·m⁻³ treatments, and the conventional culture practice, which suggested decreased quality of garden mums under water stress. Water savings without a decrease in product quality by adopting the automated fertigation system with the threshold θ values of 0.45 and 0.55 m³·m⁻³ were 34.2% and 42.7% of the conventional cultural practice, respectively. The soil moisture sensor-based automated fertigation system can therefore save a considerable amount of water and fertilizer and ensure efficient water and nutrient management for practical production of high-quality garden mums.