S06 - Session P8 - Low substrate moisture level may increase the nitrate content of arugula leaves (Eruca sativa)

Authors: Kiram Lee *, Seong Kwang An, Jongyun Kim

Arugula ( Eruca sativa ) is a popular leafy vegetable for a salad and pasta. It has high nitrate contents so that is regulated by legislation in some countries. Although some research to regulate the nitrate contents through environmental control, the effect of irrigation on the growth and nitrate contents was not quantitatively investigated yet. The current experiment was conducted to investigate the effect of substrate volumetric water contents (VWC) on the growth and nitrate content of arugula. Arugula seedlings were transplanted into a 10 cm plastic pot with a commercial growing mix with a controlled-release fertilizer. Plants were grown at an indoor farm with T5 LED light with 8/16 hours of light/dark, average temperature, relative humidity, and light intensity at the canopy level during the experiment were 24.6℃, 70.9%, 270 μmol·m -2 ·s -1 , respectively. FDR soil moisture sensors were used to monitor and maintain a specific substrate VWC with an automated drip irrigation system using a datalogger. The irrigation setpoints were determined at 0.3, 0.4, 0.5, and 0.6 m 3 ·m -3 , corresponding to -9.8, -5.1, -2.8, and -1.4 kPa, respectively. The experiment was conducted for 2 weeks and harvested weekly. At harvest, general plant growth and photosynthetic parameters were collected, and the nitrate contents of the fresh leaves were measured using a compact nitrate ion meter. As the result, general growth parameters and photosynthetic parameters did not significantly differ among VWC thresholds, regardless of the harvest week. This is likely due to a short period of experiment with a low light intensity indoors. However, nitrate concentration in the leaves in the lowest VWC treatment at 0.30 m 3 ·m -3 was significantly higher than those in the higher VWC treatments, indicating the low substrate VWC induced higher nitrate concentration. Therefore, controlling substrate VWC can be effective to control the nitrate concentration for arugula to regulating its nitrate contents for the market. This work was supported by RDA Korea (PJ016184).