ASHS 2024 Conference

Successful field cultivation of hemp (Cannabis sativa L.) in Florida is restricted to summer months when rainfall is highest, as hemp is exceptionally sensitive to daylength. Given the prevalence of soils in Florida with poor nutrient and water holding capacities, controlled release fertilizer (CRF) could be ideally suited for outdoor cultivation due to its slow-release profile. To assess the effectiveness of CRF to support plant growth while minimizing water quality risks, the plant growth and biomass production of four hemp cultivars (‘Wife’, ‘Sunset Improved’, ‘FunDip’, and ‘Belle’) were evaluated in response to nitrogen and phosphorous availability from ten CRF formulations in Apopka, Florida during the summer of 2023. Plant growth was assessed post-transplant and monthly thereafter until harvest by measuring the height, widest width, and width perpendicular to the widest width of each hemp plant. At harvest, plants were severed at the soil surface and dried at 70 degrees Celsius for three days. For each plant, the total plant biomass and total flower biomass was measured. Significant differences in plant growth and biomass production were found among varieties; however, minimal differences were found in plant growth and biomass production within variety in response to varying CRF formulations. These results suggest that CRF can provide adequate levels of fertility for the growth and development of hemp cultivated outdoors in Florida, and that selection of hemp cultivar affects plant growth and yield.