Abstract
Drought stress represents a considerable environmental challenge, exerting a deleterious effect on plant growth and productivity. In order to address this issue, the use of biostimulants, such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF), has gained increasing attention in recent years. The present study, conducted in 2022, sought to evaluate the effects of biological and chemical fertilizers under drought-stress conditions on sesame yield and water-use efficiency. The research was conducted at two farms, Dashthouz and Sarkahnan, which are located approximately 80 km apart in Rodan city, Hormozgan province, Iran. The research was designed as a factorial experiment using a randomized complete block design (RCBD) with three replications. The study examined two main factors: fertilizer application, with eight levels (bacteria (B), mycorrhizal fungi (MY), chemical fertilizer (NPK), bacteria + mycorrhizal fungi (B+MY), bacteria + chemical fertilizer (B+NPK), mycorrhizal fungi + chemical fertilizer (MY+NPK), bacteria + mycorrhizal fungi + chemical fertilizer (B+MY+NPK), and a control), and drought stress, with two levels (normal irrigation without drought stress and drought stress). The results indicated that the main effects of location, irrigation, fertilizer application, and their interactions significantly influenced the leaf area index (LAI), number of branches, number of capsules, number of seeds per capsule, seed yield, biological yield, harvest index, oil yield, meal yield, and water-use efficiency. However, there was no significant effect on thousand-seed weight. This indicates that all measured traits were influenced by the experimental factors. Regarding seed yield, the lowest value of 95.3 g/m(2) was recorded in the control treatment under normal irrigation conditions at Dachthouz, while the highest value of 325.5 g/m(2) was achieved in the control treatment under normal irrigation conditions at Sarkahnan. The findings revealed that the application of mycorrhizal fungi (MY) and bacteria (B) as substitutes for phosphorus and nitrogen, respectively, produced seed yields comparable to those achieved with NPK fertilizers under normal irrigation conditions. However, under drought stress conditions, water scarcity disrupted the symbiotic interactions between the microorganisms and the crop, reducing the effectiveness of MY and B treatments in enhancing crop growth and yield. These results contribute to advancing sustainable sesame production systems by minimizing the reliance on chemical fertilizers and enhancing crop resilience to drought stress. Further research and practical implementation of these strategies could lead to more efficient and environmentally sustainable sesame cultivation practices.