Sowing smart: ajwain (trachyspermum ammi sprague) germination under the lens of depth and soil variability

Seed germination and seedling establishment are critical phases in the life cycle of Trachyspermum ammi (Ajwain), a medicinally and economically important plant. While sowing depth and soil type are known to influence these stages, their combined effects on Ajwain remain understudied, particularly in diverse agroecosystems. This study investigated the impact of four sowing depths (0, 1, 2, and 3 cm) and four soil types (red, black, sandy, and alluvial) on germination indices and seedling growth parameters. The experiment was conducted in controlled conditions using plastic bags, with germination percentage (GP), mean germination time (MGT), germination speed (GS), and seedling morphological traits monitored over six weeks. Data were analyzed using non-parametric tests and multivariate techniques, including Principal Component Analysis (PCA). Results revealed that shallow sowing (0 cm) in alluvial soil yielded the highest GP (60%), GS (3.00), and GI (5.00), while deeper sowing (2–3 cm) significantly reduced germination performance, particularly in sandy soil. Seedling growth was optimal at 1 cm depth, with sandy and alluvial soils promoting superior stem diameter and leaf development. PCA highlighted a trade-off between germination vigor (PC1) and seedling establishment (PC2), with 0 cm favouring germination and 1–2 cm enhancing later growth. Soil type played a secondary but notable role, with alluvial soil exhibiting resilience across depths. These findings emphasize the importance of shallow to moderate sowing depths (0–1 cm) for Ajwain cultivation, especially in well-drained soils like alluvial or sandy types. Farmers can leverage these insights to improve crop establishment and uniformity. Limitations include the study’s-controlled environment and focus on early growth stages. Future research should explore field-scale trials, long-term yield effects, and interactions with abiotic stresses to refine agronomic practices for T. ammi and similar small-seeded medicinal plants. This study contributes to optimizing cultivation strategies while highlighting the need for further ecophysiological investigations.