In the pursuit of sustainable agriculture, researchers are increasingly turning to biostimulants to boost plant growth, yield, and the production of valuable secondary metabolites. A recent study published in *Plant, Soil and Environment* (which translates to *Rostlina, půda a prostředí*) has shed light on the potential of combining nitrogen-fixing rhizobacteria and seaweed extract to enhance the growth and essential oil quality of Trachyspermum ammi L., commonly known as ajwain, an aromatic herb in the Apiaceae family.
Led by Aya H. El-Nagar from the Horticulture Department at Tanta University in Egypt, the study investigated the effects of two strains of nitrogen-fixing rhizobacteria (Azotobacter chroococcum and Azospirillum lipoferum) and three levels of seaweed extract on ajwain’s growth, fruit yield, and essential oil constituents over two winter seasons. The findings revealed that the application of these biostimulants significantly improved various growth traits, including plant height, number of branches, and fresh and dry weights, as well as fruit traits like umbel number, 1,000-fruit weight, and fruit yield.
El-Nagar noted, “The combination of Azospirillum lipoferum soil inoculation and foliar application of seaweed extract at 250 mg/L resulted in the highest growth and yield values.” This treatment led to a remarkable 27.6% and 32.7% increase in fruit yield per plant for the first and second seasons, respectively, compared to the control.
The study also delved into the phytochemical composition of ajwain’s essential oil, identifying γ-terpinene, p-cymene, and thymol as the major components. The applications used in the study altered the percentages of these main components. Notably, increasing the seaweed extract level reduced γ-terpinene while increasing thymol content. The highest conversion rate from γ-terpinene to thymol was observed in plants treated with Azospirillum lipoferum and seaweed extract at 250 mg/L.
The commercial implications of this research are significant, particularly for the energy sector, where essential oils like thymol are in high demand for various applications, including as a natural antiseptic and flavoring agent. The use of biostimulants not only enhances yield but also improves the quality of the essential oil, making it a more attractive commodity in the market.
El-Nagar emphasized, “Our findings suggest that Azospirillum lipoferum soil inoculation combined with seaweed extract foliar application is a promising strategy to enhance ajwain production, both in terms of fruit yield and oil quality.”
This research paves the way for future developments in sustainable agriculture, particularly in the cultivation of medicinal and aromatic plants. By leveraging the power of biostimulants, farmers can achieve higher yields and better-quality products, ultimately contributing to a more sustainable and profitable agricultural sector. As the demand for natural and organic products continues to grow, the insights from this study could play a crucial role in shaping the future of the industry.