Abstract

Introduction: Sesame, as the queen of oilseeds, is world-famous for its resistance to drought stress. This feature justifies its cultivation in arid and semi-arid regions and enables the production of high-quality oil. However, this crop, like other crop, is affected by drought stress and its yield decreases in severe drought conditions. Nevertheless, proper nutritional management can reduce the adverse effect of drought on sesame yield. In this regard, the use of biological fertilizers along with chemical fertilizers can improve soil quality, help to increase crop yield and reduce the negative effects of chemical fertilizers. Consequently, the use of biofertilizers in sesame farming has received significant attention in recent years.

Materials and Methods: A factorial experiment based on randomized complete block design with three replications was performed to investigate the effect of chemical and biological fertilizers application on yield and some agronomical traits under drought stress during the 2022-2023 season in two regions of Hormozgan province (Sarkahnan and Dashthouz). Treatments included two levels of drought stress (full irrigation (based on 90 mm evaporation from Class A evaporation pan) and drought stress (based on 150 mm evaporation from Class A evaporation pan)) and eight levels of fertilizer (bacteria (B), mycorrhizal fungus (MY), chemical fertilizer (NPK), bacteria + mycorrhizal fungus (B+MY), bacteria+ chemical fertilizer (B+NPK), mycorrhizal fungus + chemical fertilizer (NPK+MY), bacteria+ mycorrhizal fungus+ chemical fertilizer (B+MY+NPK) and control). In this experiment was utilized Pseudomonas putida bacteria and a mixture of Rhizophagos intraradices and Funneliformis mosseae fungi. All plots were evenly irrigated with a pressurized system until they reached the 3-4 leaf stage. After thinning, drought stress was applied by carefully controlling the amount of water based on evaporation rates measured using evaporation pans and meteorological stations.The traits measured in this research included days to flowering, days to poding, chlorophyll index, plant height, stem dry weight, leaf dry weight, oil content of seeds, oil content of meal, grain yield, biological yield. The relationship between these traits and grain yield was also examined. Finally, Statistical analysis of the collected data was conducted using ANOVA in SAS software. Significant differences between means were evaluated the probability level of 0.05 by Duncan 's test.

Results and Discussion: The results indicated an acceleration of phenology with the application of drought stress. Flowering and podding occurred 3 and 6 days earlier, respectively, in the stressed treatments. Drought stress also caused a decrease of 0.16%, 9.10%, and 3% in plant height, chlorophyll index, and oil percentage of the meal, and an increase of 4% in seed oil compared to the control treatment (full irrigation). The results also showed that the application of fertilizer treatments, especially the combination of bacteria + mycorrhizal fungi + chemical fertilizer, improved the traits under stress and non-stress conditions in sesame. The highest dry weight of leaves (390 g/m²), dry weight of stem (501 g/m²), seed yield (2960 kg/ha), and biological yield (20240 kg/ha) were observed in the Sarkahnan region under non-stress conditions and treatment with bacteria + mycorrhizal fungi + chemical fertilizer. The lowest seed yield, and biological yield were 953, and 4250 kg/ha, respectively, for crops under drought stress and no fertilizer application in the Dashthouz region. Correlation of traits also showed a high positive correlation of seed yield with dry weight of leaves (0.80**), dry weight of stem (0.75**), and biological yield (0.74**), and a small negative correlation with days to podding (-0.21*).

Conclusion: Based on these resultes, the combined use of biological and chemical fertilizers can be considered a suitable strategy to reduce the negative effects of drought stress in arid and semi-arid regions for sesame.