Factors Influencing Biomass, Cannabinoid Profiles, and Regulatory Compliance in Floral Hemp: Multi-Factorial Study of Production Systems, Cultivars, Mulching, and Propagation

Floral hemp production requires agronomic practices that maximize biomass and cannabidiol (CBD) yield while maintaining legal tetrahydrocannabinol (THC) limits. A two-year field study was conducted at the Tennessee State University Agricultural Research and Education Center to evaluate floral hemp (Cannabis sativa L.) production under a Non-Chemical System (NCS) and Chemical System (CS) at a uniform nitrogen (N) rate of 100 kg ha−1. Four cultivars (‘Fukuoka’, ‘Rushmore’, ‘Cherry’, and ‘Virginia’), two mulch types (plastic and straw), and two propagation methods (seed and clone) were evaluated for effects on biomass yield, plant height, CBD and THC concentrations, and the Compliance Regulatory Index (CRI). The production system did not significantly affect biomass; however, plant height and CBD and THC concentrations were significantly influenced. Across cultivars, mulched plants under CS were taller than those under NCS. Seed-propagated ‘Fukuoka’ under NCS and ‘Virginia’ under CS produced the highest THC concentration. ‘Rushmore’ exhibited greater consistency across production systems and propagation methods. In 2023, plastic mulch increased biomass by 38% compared with no mulch, while in 2024, straw mulch increased biomass by 154%. CRI varied significantly among cultivars and was influenced by year and propagation method. ‘Cherry’ clones and seed-propagated ‘Fukuoka’ showed greater CBD potential at the 0.3% THC threshold in 2023. Although CS with seed propagation showed a slight agronomic advantage, NCS demonstrated comparable performance. Significant performance declines in the second year suggest that continuous monocropping of floral hemp may compromise long-term productivity. A supplementary 2022 harvest-timing study demonstrated cultivar-dependent differences in cannabinoid accumulation and THC compliance during floral maturation.