Analysis of Evapotranspiration using a Load Cell and Precise Irrigation Amounts for Strawberries in a Coir Slab Hydroponic System

초록

Strawberries in Korea hold significant economic value, and their cultivation in hydroponics is progressively expanding. This study explored the weighted evapotranspiration (WETc) of strawberries grown on coir substrates, with the goal of optimizing irrigation volumes for improved water management. 'Sulhyang' strawberries were transplanted at a plant density of 7.5 plants per m(2) on September 15, 2022 into three different substrate types: V40D10 (40 L, dust: chip (v/v) = 10:0), V30D10 (30 L, dust: chip (v/v) = 10:0), and V20D5 (20 L, dust: chip (v/v) = 5:5). The nutrient solution was administered through an ISR-automated irrigation system. The schedule concentrated irrigation from sunrise to 2 p.m. (accounting for 78-95% of the total daily irrigation volume), resulting in higher drainage rates from 11 a.m. to 2 p.m. (50-70% of the day's total drained volume). The drainage rate for V20D5 was higher, at 40-50%. Total fruit weight per plant varied significantly across the substrates, with V30D10 producing the highest weight (428.4 g) and V40D10 the lowest (315.5 g). Despite lower dust ratios, V20D5 achieved performance comparable to that of V30D10, with a total fruit weight of 350 g. An analysis of WETc on sunny days showed a pattern of February > January > December, with hourly WETc revealing significant differences among the substrates. On cloudy days, WETc remained below 5 g<middle dot>plant(-1), with cumulative values ranging from 41 to 75 g<middle dot>plant(-1). Overall, the results suggest that the optimal daily irrigation volumes per plant should be between 90 to 150 mL<middle dot>plant(-1) depending on the substrate volume and ratio. These findings underscore the potential to minimize drainage and optimize irrigation in strawberry hydroponics through precise, WETc-based scheduling, providing valuable insights for sustainable cultivation practices.

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