The effect of organic amendments on cannabidiol yield and topsoil health (0–10 cm) in floral hemp (Cannabis sativa L.) production system

Abstract

Abstract Background Compost and cover crops enhance soil health and crop productivity in agricultural systems, yet their integration as soil management strategies in floral hemp ( Cannabis sativa L.) production remains underexplored. Understanding these effects is critical for optimizing cannabidiol yield while building soil health. Methods In a two-year field study in north-central North Carolina, USA, we evaluated the effects of compost, cover crops, and their combination, and a non-fertilized control on soil health and cannabidiol yield in two floral hemp cultivars, Spectrum and Therapy. The experiment utilized a randomized complete block split-plot design with soil health indicators and agronomic parameters measured across multiple growth stages. Results Treatment effects varied substantially by year and cultivar. In 2021, compost produced the highest cannabidiol yields for both cultivars–1.1 to 2.6 times greater than control and cover crop treatments. By 2022, compost-cover crop treatment had the highest yields for Spectrum, while Therapy responded minimally to amendments. Organic amendments increased soil organic carbon by 15%, total nitrogen by 20%, and microbial activity by 25%, particularly in year two. Mid-vegetative leaf nitrogen concentration emerged as a strong predictor of yield, explaining 52% of dry inflorescence and 40% of cannabidiol yield variation. Principal component analysis revealed that compost and compost-cover crop treatments clustered with enhanced soil biological indicators (soil organic carbon, total nitrogen, soil test biological activity, and permanganate oxidizable carbon) and higher yields, though year-specific environmental conditions resulted in distinct response patterns. Conclusions Compost and combined compost-cover crop amendments improved soil health metrics, with benefits accumulating by year two. Cover crops alone provided minimal advantage. The effectiveness of organic amendments depends on cultivar selection and environmental conditions, necessitating multi-year evaluations to develop reliable management recommendations for CBD hemp production systems.