Glutamic Acid Improves Yield and Phytochemical Properties of Strawberry (Fragaria x ananassa) Under Deficit Fertigation

Excessive use of chemical fertilizers in agricultural production, especially in hydroponic cultivation, wastes fertilizer and water and thus increases production costs. Therefore, reducing the amount of nutrient solution in greenhouse production systems is essential. This study aimed to evaluate the effect of glutamic acid on strawberries under deficit fertigation conditions. In the present study, different concentrations of glutamic acid (0, 200 mg/l, and 300 mg/l) were sprayed on strawberry cv. Albion under deficit fertigation conditions (100 ml, 140 ml, and 180 ml) based on a completely randomized design with four replications to evaluate the yield and phytochemical characteristics of fruits. The obtained results showed that glutamic acid increased the yield at all levels of fertigation. The highest yield (550.5 g) was recorded in the plants that received 180 ml of nutrient solution with glutamic acid (300 mg/l). Most of the parameters measured in response to the normal fertigation (180 ml) decreased, and glutamic acid ameliorated these adverse effects. The highest amounts of total flavonoids (139.45 mg quercetin per 100 g FW), antioxidant capacity (94.68%), and catalase enzyme activity (4.32 units g/min) were recorded in plants treated with severe deficit fertigation (100 ml). Also, the highest amount of total anthocyanin (38.58 mg cyanidin-3-glucoside per 100 g FW) and ascorbate peroxidase enzyme activity (13.68 mu mol per min/v g FW) was observed with mild deficit fertigation treatment (140 ml). In conclusion, the results showed that increasing the fruit quality and yield of strawberries grown in hydroponic conditions is possible with deficit fertigation and glutamic acid treatments.