Introduction: Sesame (Sesamum indicum L.) is one of the oldest oilseed crops widely grown in Africa and Asia and well adapted to harsh environments. Among the oilseed crops in the world, sesame is one of the most important because of its high-quality nutritional seeds and oil. Different soil additives including fertilizers and microorganisms are extensively applied in agricultural systems to enhance soil fertility and crop productivity. Recently, the application of effective microorganisms (EM) and arbuscular mycorrhiza fungi (AM) have been considered an eco-friendly way in increasing nutrient and fertilizer use efficiencies and minimizing the harmful environmental effects of fertilizers. However, findings are inadequate regarding the effects of adding vermicompost alone or in combination with AM and EM on the sesame plants. Therefore, this study aimed to investigate the effect of their integrated application on the agronomic efficiency of vermicompost (AEV), AM and EM inoculation effect (AMIE and EMIE), yield and yield components, and nutrient use efficiency (NUE) of sesame.
Materials and Methods: A field experiment with the aim of evaluating the effect of different vermicompost levels (no application, application of 50% of the recommended amount; 5 t ha^-1, and 100% of the recommended amount; 10 t ha^-1), EM application (without EM inoculation, and EM inoculation) and AM inoculation (no-inoculation and inoculation with Funneliformis mosseae) was conducted as split-split plot experiment at Rudbar-e Jonoub region, Jiroft, Iran, during the growing season of 2021-2022. Sesame seeds were procured from the local farmers and sown on August 11, 2021. When the plants were established, the plants were thinned and a final density of 20 plants per m² was obtained. At the end of the growing season (November 21, 2021), plants were harvested and various traits including plant height, number of branches, number of capsules per plant, number of seeds per plant, 1000-seed weight, and seed yield were measured. NUE, AEV, AMIE, and EMIE were also calculated.
Results and Discussion: The results showed that vermicompost application, EM, and AM inoculation interaction effect significantly affected yield components, seed yield, and NUE of sesame and AEV. While the use of microorganisms in no application of vermicompost showed no significant effect on the mentioned characteristics, combined application of AM and EM in the application of 5 t ha^-1 vermicompost, and individual application in the application of 10 t ha^-1 vermicompost, led to a significant increase in the number of capsules per plant, the number of seeds per plant, seed yield (2124, 2637, and 2741 kg ha^-1, respectively), and nitrogen, phosphorus, and potassium use efficiencies (between 49 to 95 percent compared with the control). The highest AEV was also obtained from the reduced level of application (5 t ha^-1) and integrated inoculation of AM and EM. In general, the application of microorganisms in both vermicompost application levels led to an increase in vermicompost use efficiency. On the other hand, the use of different vermicompost levels increased the efficiency of microbial inoculation and the highest inoculation efficiency was obtained at the highest application level. Even though the highest yield and NUE were obtained from the application of 100% vermicompost, the integrated application of microorganisms with 50% of vermicompost did not show a significant difference with the 100% application and no microbial inoculation. In fact, this treatment combination led to achieving the highest agronomic efficiency of vermicompost, which can be considered in the management of fertilizer resources, especially in the limited availability of nutrient resources.
Conclusion: Overall, the integrated application of vermicompost and inoculation with AM and EM could be considered as an effective strategy to improve the growth, yield, nutrient use efficiency, and sesame productivity. Furthermore, the use of microbial inoculants improved the agronomic efficiency of vermicompost. Such information might help in decision-making to improve nutrient management in the fields.