Date of Award

12-11-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Agricultural and Environmental Sciences

First Advisor

Emmanuel Omondi

Abstract

The farm bill of 2014 and 2018 legalized hemp (Cannabis sativa L.) production for cannabidiol (CBD), grain, and fiber uses in the U.S. Agronomic management practices for floral hemp for CBD production were not well studied. To optimize the agronomic management practices for high CBD content and THC concentration below the compliance level of 0.3% on a dry weight basis requires specific management and adaptability. A two-year field study was conducted at the Tennessee State University Agricultural Research and Education Center (TSU AREC) in Nashville, Tennessee, to evaluate two production systems, the Non-Chemical System (NCS) and the Chemical-Based System (CBS), under a uniform nitrogen rate of 100 kg ha⁻¹ using four feminized floral hemp cultivars. The study also compared two mulch types (plastic and straw) and two propagation methods (seed and clone) for their effects on biomass yield, CBD concentration, and tetrahydrocannabinol (THC) compliance. CBS and NCS did not differ significantly in biomass production; however, disease severity was higher in the NCS system. Plant height and biomass were both enhanced under plastic and straw mulches. ‘Fukuoka’ cultivar, grown under straw mulch within the NCS production system, recorded the highest CBD across production years. A three-year field trial of six fiber hemp cultivars planted at three different dates at the TSU AREC showed that Futura-83, Fibor-79, and Muka-76 had significantly greater plant establishment density, producing approximately 15–20 t ha⁻¹ of biomass. Our results showed that optimal planting window for fiber hemp was between 18 May to 10 June.

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