Biofertilizers effect on Satureja bachtiarica Bunge. traits under irrigation stress at various growth stages

Deficiency or excess of any growth factor leads to morphological, anatomical, physiological, and growth disorders in plants. Drought stress means a lack of water in the plant. This situation occurs when the amount of transpiration exceeds the amount of water absorption. Low irrigation (watering less than the optimal water requirement of the plant) is a strategy to save water, but it affects the plant at a particular stage of growth or the entire season. Biofertilizers develop the root system, changing host plant water relations and plant metabolism. They also activate the defense system, improving access to minerals and tolerance to drought in the host plant, making it environmentally friendly and natural. To manage the prevailing water crisis, one should look for solutions such as reducing water consumption and stopping irrigation at all stages of growth. This is without harming the plant's final performance. In addition, due to the importance of medicinal plants and increasing their biomass, biological fertilizers and the adjustment of drought stress effects have a special place. This experiment was carried out to investigate the effectiveness of Satureja bachtiarica Bunge. against dehydration at different stages of growth. It also investigated the consumption of mycorrhizal fungi and growth-stimulating bacteria to manage plant production with high quality and quantity.

The experiment was carried out in the form of split plots in the form of a randomized complete block design in three replications in the research farm of Islamic Azad University, Tabriz branch, in 2018. The main and sub-factors were included in 4 water stress (I1: without stress, I2: cut irrigation in stem elongation stage, I3: cut irrigation at the budding stage and I4: cut irrigation at 50% flowering stage) and 5 biofertilizer levels (b1: without inoculation, b2: inoculation with Funneliformis mosseae, b3: inoculation with Rhizophagus irregularis, b4: Funneliformis mosseae + Rhizophagus irregularis and b5: Azosprillium+Pseudomonas+Azetobacter), respectively. The harvest was in full flowering stage.

The comparison of the average of irrigation interruptions showed that the most number of leaves, stem diameter, canopy extent, root weight, leaf yield, flowering stem yield, and flowering branch yield belonged to the irrigation interruption at the 50% flowering stage. Inoculation with Funneliformis mosseae mycorrhizal fungus achieved the highest leaf yield (912.06 kg/ha), flowering stem yield (1071.25 kg/ha) and flowering branch yield (1983.32 kg/ha) in inoculation with Azosprillium + Pseudomonas + Azotobacter was observed. The highest percentage of essential oil was found in inoculation with Funneliformis mosseae with an average of 1.76%. The maximum average yield of essential oil at 30.50 kg/ha was observed in the inoculation treatment with Azosprillium + Pseudomonas + Azotobacter. The results of the comparison of the average of the interaction effect showed that the maximum height of the plant and the number of inflorescences with an average of 61.72 cm and 30.46 per plant were found in the interaction effect of the treatment of interruption of irrigation at the stemming stage and inoculation of Rhizophagus irregularis + Funneliformis mosseae, which is about 31 and 39 The percentage increased compared to their lowest value. Stopping irrigation in the budding stage ×Funneliformis mosseae had the highest percentage of essential oil with an average of 2.33%. Stopping irrigation in the stemming stage ×Rhizophagus irregularis had the lowest essential oil percentage. The highest leaf yield (1212.83 kg/ha), flowering stem yield (1494.75 kg/ha), flowering branch yield (2707.58 kg/ha) and essential oil yield (44.39 kg/ha) in the interaction effect of cutting × Azosprillium + Pseudomonas + Azotobacter irrigation was observed at the 50% flowering stage, which increased by 70, 82, 81 and 87% compared to the lowest ones.

The correct management of soil fertility, improvement, and maintenance of soil fertility in modern agricultural systems will provide the nutrients needed by the plant and thus enhance the yield. Therefore, in recent years, many studies have been conducted on biological fertilizers. Mycorrhizal fungi are essential factors in the stable plant-soil system, which coexists with more than 85% of plants. Drought stress is one of the most influential environmental factors in plant growth and causes morphological, physiological, and metabolic changes. In addition, biofertilizers increase plant access to nutrients and produce and direct hormones involved in the growth of the root environment. They also increase stress tolerance and enhance yield. Considering the arid and semi-arid conditions of the country and the increase in demand for medicinal plants and Satureja bachtiarica spices, it is recommended to stop irrigation at the 50% flowering stage and use Azotobacter, Azospirillium, and Pseudomonas biofertilizers to obtain the maximum yield of leaves, flowering branches, and essential oil.