The effect of humic acid on physiological characteristics, antioxidant activity and yield of Cape gooseberry (Physalis peruviana L.) under deficit irrigation

In order to investigate the effect of humic acid on the physiological characteristics, antioxidant activity and yield of Cape gooseberry (Physalis peruviana L.) under deficit irrigation conditions, a split plot experiment based on randomized complete block design with three replications was conducted in 2021. Treatments consisted of the arrangement of three levels of irrigation (starting irrigation at 100, 80 and 60% ETc (crop evapotranspiration)) and three levels of humic acid (0, 1.5 and 3 kg ha-1). The results showed that deficit irrigation significantly reduced fruit yield. The soil application of humic acid significantly increased leaf relative water content, antioxidant capacity, fruit yield, and decreased leaf electrolyte leakage under normal and deficit irrigation. The highest value of total phenol (18.1 mg gFW-1), flavonoid (0.47 mg gFW-1), antioxidant activity (90.06 %), proline (5.91 mg gFW-1) and catalase (0.81 μmol H2O2 g-1 FW min-1) and peroxidase (1.92 units g-1 FW min-1) enzymes activity were obtained with 3 kg ha-1 soil application of humic acid under deficit irrigation 60% ETc. The maximum fruit yield (4793.3 kg ha-1) was observed in plants treated with 3 kg ha-1 humic acid under 100% ETc irrigation. According to these results, the application of 3 kg ha-1 humic acid is suggested to improve the antioxidant capacity and fruit yield of Cape gooseberry under normal and deficit irrigation conditions.