Effects of Biological Fertilizers on Some Physiological Traits of Sweet Basil under Water Deficit Stress

Today, the use of biological fertilizers in sustainable agriculture is an appropriate alternative to chemical fertilizers because the former can improve the quantitative and qualitative performance of plants, especially under stressful conditions. Therefore, this study aims in greenhouse conditions to investigate the effects of plant growth-promoting rhizobacteria on antioxidant enzyme activities and some physiological traits of sweet basil under water limitation. For this purpose, a factorial experiment was conducted based on a completely randomized block design with three replications. Three levels of water deficit stress factor involved W0 = 100% of field capacity, W1= 60% of the field capacity, and W2 = 40% of the field capacity. Also, biofertilizers factor included nine levels of F1: Pota Barvar-2, F2: Phosphate Barvar-2, F3: Azeto Barvar 1, F4 (the combination of F1 and F2), F5 (the combination of F1 and F3), F6 (the combination of F2 and F3), F7 (the combination of F1, F2, and F3); F8 (100% chemical fertilizer as a positive control) and F9 (without any fertilizer as a negative control). Results showed that water limitation increased the activity of ascorbate peroxidase (193.55%), peroxidase (416.258%), polyphenol oxidase (48.21%) enzymes, and essential oil yield (135.48%). Meanwhile, the chlorophyll index, carotenoid, and yield decreased under water deficit stress. The use of biofertilizers improved these traits under water limitation conditions and normal irrigation. Also, applying a combination of 3 biofertilizers (F7) led to an increase 29.88% in the yield compared with negative control under severe water limitation. Therefore, the use of biofertilizer can be recommended for profitable basil production under water limitation conditions.