2019 ASHS Annual Conference

Water management is becoming an increasing concern in agriculture, whether dealing with too much or too little. Finding tools and methods to better manage water is critical to future success. Precision irrigation can help growers conserve important resources, such as water and fertilizers, and increase crop water-use efficiency. Previous research has demonstrated that tomato yields, biomass, and water-use efficiency increased when irrigating based on soil moisture sensor reading. Thus, the objective of the current study was to determine the effect of precision irrigation set points on the physiological performance of kale grown in a greenhouse. Kale plants were grown in 3 gal. plastic grow bags in soilless (Metro Mix 360; Sun Gro Horticulture, Agawam, MA) medium and fertilized with a 15N-3.9P-9.9K controlled release fertilizer. The fertilizer was incorporated at a rate of 5.93 kg·m^-3. Substrate volumetric water content (VWC) was measured using capacitance sensors (Terros 12; Meter Group) and a datalogger (CR1000x; Campbell Sci.) was used to record data and control solenoid valves when bags reached 0.15, 0.25, or 0.35 m³·m³, corresponding to well-watered, intermediate drought, and drought stressed conditions. Kale physiological performance parameters, such as net CO₂ assimilation rate (A) and stomatal conductance (g_s) were measured with a LI-6800 (Li-Cor Biosciences) photosynthesis system under each VWC treatment over 31 d. There were significant differences in kale fresh mass (FM), dry mass (DM), transpiration (T), CO₂ assimilation (A_n), internal CO₂ (C_i), and water use efficiency (WUE). There were also significant differences in the relationship between stomatal conductance (g_s) and C_i. Additionally, there were significant differences in the transpiration (T) of kale leaves. Reducing the VWC in soilless medium, thus conserving water, from 0.35 to 0.25 does not affect kale’s physiological performance, FM, and DM.