The Optimum Substrate Moisture Level to Enhance the Growth and Quality of Arugula (Eruca sativa)

Abstract

Arugula (Eruca sativa Mill.) is a nutritious vegetable, commonly used in salads, known for its high glucosinolate content and various health benefits and flavors. However, arugulas may contain -excessive nitrate levels, potentially harmful to human health. We aimed to examine the effect of substrate moisture levels on the growth and quality of arugula under controlled irrigation conditions to investigate a proper irrigation practice for the quality production of arugula. The plants were cultivated using a sensor-based automated irrigation system to maintain the substrate volumetric water content (VWC) levels at 0.20, 0.30, 0.40, and 0.50 m3·m−3 over three weeks (vegetative stage). The treatment with VWC of 0.20 m3·m−3 resulted in reduced shoot growth, primarily attributed to drought-induced constraints on leaf expansion. Despite the initial reductions in stomatal conductance in arugulas subjected to lower VWC treatments, they eventually recovered and exhibited similar stomatal conductance levels across all VWC treatments 15 days after treatment, indicating acclimation to drought stress. The VWC treatment did not affect the nitrate and total glucosinolate contents of arugula, except for a decrease in glucoerucin content observed in the lowest VWC treatment. Maintaining a VWC level at 0.20 m3·m−3 could impair both the growth and quality of arugula due to severe drought conditions. Alternatively, maintaining the VWC at 0.30 m3·m−3 would ensure a high water use efficiency while securing the growth and quality of arugula.