Vermicompost versus chicken manure: Comparative effects on hemp growth, heavy metal sequestration, and root microbial communities in Rosella, Superwoman S1, and Red Robin cultivars

With growing interest in hemp and sustainable agriculture, understanding the impact of organic amendments on hemp cultivation is essential. This study evaluated the effects of vermicompost and chicken manure on growth, soil nutrients, heavy metal accumulation, and root microbial communities in three hemp cultivars (Cannabis sativa L. subsp. sativa): Rosella, Superwoman S1, and Red Robin over a 120 day-period. Vermicompost improved growth (1.0–3.1 folds, dry wt.) and maintained higher soil nitrogen (1.1–2.5 folds), phosphate (1.2–1.3 folds), and potassium levels (1.8–3.5 folds) compared with a control. However, chicken manure enhanced only phosphorus (1.1–1.3 folds) and inhibited the growth of all cultivars. Hemp sequestered heavy metals in the roots, reducing contamination in shoots and leaves. Both amendments significantly influenced root microbiomes, promoting beneficial bacteria, such as Bacillus and Mycobacterium (vermicompost) and Shinella (chicken manure), which contributed to organic degradation and heavy metal transformation, thereby enhancing soil health.