Response of Trachyspermum ammi L. plants to organic and chemical fertilizations and drying methods

This study was carried out to determine the vegetative growth, chemical compositions, and essential oil content of Trachyspermum ammi L. in response to different fertilizer types. The results obtained in a 2-year study (2022/2023–2023/2024) with five separate, different fertilization treatments, i.e., control (without fertilization), compost (5 tons per acre), compost (10 tons per acre), compost (15 tons per acre) and chemical fertilizer N, P and K. However, chemical fertilization yielded the highest values for the vegetative growth parameters and seed yield. Moreover, it improved leaf mineral contents (N%, P% and K%) total carbohydrates. Moreover, the chemical fertilization resulted in the highest oil yield (29.59 kg/acre and 30.87 kg/acre) in the 1st and 2nd seasons, respectively. oven-dried seeds yielded the highest oil content under the chemical or 15 tons/acre without significant difference between them compared to shade as well as sun-dried methods. Similarly, thirteen components were identified in the essential oil of ajwain. However, the compost (15 tons per acre) produced the highest yield of thymol (53.35%), while the greatest values of γ-terpinene (40.90%), were scored by the control treatment. Thereupon, it is preferable to organic compost (15 tons/acre) treatment supplemented by NPK, which may fully substitute for chemical fertilizers without reducing the growth and seed yield, chemical constituents, and oil productivity of ajwain. It is clear that chemical fertilization resulted in the highest growth and seed yield, chemical constituents, and oil productivity, but the difference between chemical fertilization and 15 tons/acre organic fertilizer treatment was statistically insignificant.