The Effect of Harvest Date on Temporal Cannabinoid and Biomass Production in the Floral Hemp (Cannabis sativa L.) Cultivars BaOx and Cherry Wine

Abstract

The objectives of this study were to model the temporal accumulation of cannabidiol (CBD) and tetrahydrocannabinol (THC) in field-grown floral hemp in North Carolina and establish harvest timing recommendations to minimize non-compliant crop production. Field trials were conducted in 2020 and 2021 with BaOx and Cherry Wine cultivars. Harvest events started two weeks after floral initiation and occurred every two weeks for 12 weeks. Per-plant threshed biomass accumulation exhibited a linear plateau trend. The best fit model for temporal accumulation of THC was a beta growth curve. As harvest date was delayed, total THC concentrations increased until concentrations reached their maximum, then decreased as plants approached senescence. Logistic regression was the best fit model for temporal accumulation of CBD. CBD concentrations increased with later harvest dates. Unlike THC concentrations, there was no decline in total CBD concentrations. To minimize risk, growers should test their crop as early as possible within the USDA’s 30-day compliance window. We observed ‘BaOx’ and ‘Cherry Wine’ exceeding the compliance threshold 50 and 41 days after flower initiation, respectively.

Cannabidiol industrial hemp growth, biomass, and temporal cannabinoids accumulation under different planting dates in southern Florida

“…Similar results have also been documented in other studies where both CBD and THC concentrations increased gradually and then started declining at the end of the growing season (Latta & Eaton, 1975;Pacifico et al, 2008). Linder et al (2022a) also reported THC concentration increased gradually and then slightly decreased when the plant approached maturity. However, no such decrease in CBD concentration was observed in their study.…”

“…Linder et al. (2022a) also reported THC concentration increased gradually and then slightly decreased when the plant approached maturity. However, no such decrease in CBD concentration was observed in their study.…”

“…As a result, THC concentration often exceeds the legal limit, which remains a bottleneck for hemp cultivation in Florida. Studies have demonstrated that CBDA synthase (CBDAS) enzyme also produces small quantities of THC as a side product during CBD synthesis (∼26 CBD:1 THC ratio) (Linder et al., 2022a; Zirpel et al., 2018), which could explain more THC concentration in high CBD yielding cultivars. Furthermore, most hemp cultivars are photoperiod sensitive short‐day plants, and flowering begins when day length (photoperiod) decreases to a certain threshold.…”

Hemp yield and cannabinoid concentrations under variable nitrogen and potassium fertilizer rates

“…As mentioned above, CBD concentration is primarily influenced by genetics and very little by environment (Burgel et al., 2020; Campbell et al., 2019; Toth et al., 2021). Other research further supports variation in CBD concentration due to cultivar (Linder et al., 2022a; Stack et al., 2021), as well as harvest timing (Burgel et al., 2020; Linder et al., 2022a; Yang et al., 2020).…”

“…Because CBD yield is a product of the biomass yield and CBD concentration, any factor affecting either or both of these parameters will affect CBD yield (Stack et al., 2021). Previous literature reports that the biomass yield of hemp is affected by plant maturity (Linder et al., 2022a), cultivar (Stack et al., 2021), transplanting date, and plant spacing (Linder et al., 2022b). As mentioned above, CBD concentration is primarily influenced by genetics and very little by environment (Burgel et al., 2020; Campbell et al., 2019; Toth et al., 2021).…”