S06 - Session P18 - Proper irrigation threshold level for growing sweet basil via subirrigation systems

Authors: Jongkyun Kim *, Seong Kwang An, Jongyun Kim

Many growers apply subirrigation systems for efficient and high-quality production of potted plants in commercial greenhouses. However, they usually depend on their experience or a timer scheduled irrigation with a lack of quantitative determination of the substrate moisture levels. The objective of the study was to investigate the proper subirrigation threshold substrate volumetric water content (VWC) levels for sweet basil production based on FDR soil moisture sensors, with analyzing the growth and physiological responses. Sweet basils were grown with a customized ebb and flow system, irrigated when the substrate VWC decreased below the setpoints (0.30, 0.45, 0.60 m 3 ∙m -3 ) through an FDR soil moisture sensor-based automated irrigation system. When irrigation occurred in a subirrigation box, the water level was 2.5 cm from the base of the pot, and the retention time was one hour. The frequency of irrigation application was recorded, and general growth and physiological parameters of the plants were measured two weeks after treatment. We also measured leaf relative water content and specific leaf area at harvest. On average, irrigation was applied 7, 9.8, 15 times under the treatment at 0.30, 0.45, 0.60 m 3 ·m -3 , respectively, during the experiment. Although irrigation was applied more frequently at 0.60 m 3 ·m -3 than the lower VWC treatments, there were no significant differences in most general growth and physiological parameters among the different setpoint treatments. However, the plants of the treatment at 0.30 m 3 ·m -3 had lower plant width, shoot fresh weight, leaf relative water content, and specific leaf area than those of the treatment at 0.60 m 3 ∙m -3 , indicating a potential decrease in sweet basil quality. These results were different from the results of the similar VWC research with drip irrigation systems. Overall, irrigating at 0.45 m 3 ·m -3 would provide efficient irrigation with quality of sweet basil under subirrigation system. This work was supported by RDA Korea (PJ016184).