Journal of the NACAA
Volume 14, Issue 1 - June, 2021
Preliminary Evaluation of Two Industrial Hemp Cultivars: Suitability for Production, Agronomic Traits, and Performance
- Komar, S. J., Agricultural Agent, Rutgers University
William Bamka, Agricultural Agent, Rutgers University
A preliminary experiment was conducted to evaluate hemp Cannabis sativa cultivar’s suitability for production in New Jersey. Two cultivars were evaluated during the 2020 growing season. No differences were observed between cultivars in plant height, yield per plant or cannabinoid (CBD) concentration. Although not significant, a trend towards higher cannabinoid concentration in the upper portion of the plant was observed in the Suver Haze cultivar. Both cultivars tested above the 0.3% threshold for Tetrahydrocannabinol (THC) suggesting that harvest timing is a critical consideration for successful production. Both cultivars evaluated were susceptible to a variety of insect and disease pests which may reduce both yield and marketability if not properly managed. This preliminary study reveals the need for more research to determine the hemp cultivars best suited for New Jersey production.
Industrial hemp is a non-psychoactive variety of Cannabis sativa L. grown for multiple end-uses including oil, fiber, and grain products. Industrial hemp was once an important crop in the United States prior to being banned from production under The Marihuana Tax Act of 1937 (Williams & Mundel, 2018). During the second World War, industrial hemp was identified as a critical product needed by the government, due to difficulty in sourcing fiber for packaging, rope, and other key products and as such was commercially grown domestically by American farmers. The 2014 Farm Bill once again paved the way for domestic production of hemp (Johnson, 2018). The 2018 Farm Bill further directed the United States Department of Agriculture USDA to establish a national regulatory framework for hemp production in the United States. These rules were completed in early 2021 and took effect on March 22, 2021. Hemp production represents a new opportunity for New Jersey farmers with 2020 being the first season that production is legal in the state (New Jersey Department of Agriculture, 2019). There is interest from producers related to the feasibility of hemp production in New Jersey, as it is grown for a wide variety of consumer and industrial products (Cherney & Small, 2016). Industrial hemp may represent a new crop and market opportunity for New Jersey farmers. Additionally, industrial hemp may fit nicely with existing crop rotation practices of other field crops and has been reported to result in returns that are similar to other traditional field crops (Thompson et al., 1998). Since hemp is a relatively new potential crop, New Jersey producers have many questions related to production including cultivar selection, insect and disease management and many other agronomic considerations. In recent years, there have been several studies conducted to evaluate hemp as a potential crop (Darby et al., 2018; Walker, 2015), with a great deal of emphasis focused on the economic feasibility of hemp grown for various end-uses (Hanchar, 2019). Although there is interest and speculation related to hemp production, there has been limited research conducted in the northeastern United States and none in New Jersey to quantify the feasibility of hemp production. Agronomic research on hemp is a critical first step to develop appropriate extension recommendations, as well as, to gain an understanding of the suitability of this crop for New Jersey production, crop susceptibility to insect and disease pests, weed competition and other production concerns. This study evaluated two CBD cultivars that were being grown commercially in New Jersey during the 2020 growing season for suitability for field production, regulatory compliance, and marketability. This initial study was conducted to determine future research needs and to inform producers of potential production limitations.
Materials and Methods
Field experiments were conducted during the 2020 growing season at the Clifford and Melda Snyder Research and Extension Farm, Pittstown, New Jersey to evaluate two hemp Cannabis sativa L. cultivars. Two cultivars, Suver Haze (High Point Hemp LLC) and Elektra (Black Dirt Canna LLC) were selected for evaluation since they were the most grown and readily available cultivars in the region during the 2020 growing season. Plants were grown from feminized seeds and purchased as transplants from local producers. The test field consisted of a Quakertown silt loam, 2-6% slope (Fine-loamy, mixed, active, mesic Typic Hapludults). The crop rotation included spring barley in 2018, followed by fallow in the 2019 growing season. The test field was fertilized with 250 pounds/A broadcast of 20-10-10 prior to raised bed formation. Two-millimeter black plastic mulch (Filmtech, Allentown, PA) was placed on 6’ centers and equipped with drip irrigation at .22 GPM/100ft (Rivulis, Gvat, Israel) and fertigation. Due to a lack of registered herbicides, no herbicides were used during this study. Weed control consisted of approximately 6” of rye straw mulched in row middles. The two cultivars were hand transplanted on June 23, 2019. Treatments were planted in a randomized complete block design with four replications. Plots consisted of ten plants per replication planted on a 6’ spacing between plants (6’ X 6’ grid). Plots received an additional 5 pounds/A of nitrogen as ammonium sulfate via fertigation on August 1, 2019 and again on August 7, 2019. Plant heights were measured weekly during the growing season from ground level to terminal inflorescence. To evaluate susceptibility to disease and insect pressure, plants were monitored weekly. Selected plants were hand harvested on September 29, 2019. Plants were cut using loppers and individual branches removed. Individual branches were further thinned, and fan leaves removed. Flower buds were hand trimmed using hand shears (Felco, Seattle, WA). Wet harvested bud weight was recorded. Flower buds were dried at 800F for 36 hours and dry yield calculated as pounds per plant. Random samples of each cultivar were collected and submitted for regulatory THC compliance to the New Jersey Department of Agriculture Hemp program. In addition, flower buds from selected plants were collected from the lower third of the plant, the middle of the plant and the upper third of the plant, and analyzed separately for cannabinoids to determine if plant location of buds impacted cannabinoid concentration. Additional samples were collected on September 16, 2019 and October 6, 2019 to evaluate cultivars for cannabinoid analysis to determine if harvest date impacted cannabinoid concentration (Rutgers New-Use Agricultural Products Laboratory, New Brunswick, NJ).
Data were analyzed for variance and means separated using Welch’s t test (R: R Core Team -2020).
Results and Discussion
Despite the late transplanting date, both cultivars responded well to growing conditions and demonstrated rapid growth often seen from hemp grown under plastic culture. Early season storms resulted in severe lodging, toppling nearly one hundred percent of the plants in this study. As a result, individual plants were staked and tied. The plants responded well to being staked and resumed the rapid growth rate observed throughout the study. Plant standability has been anecdotally reported as a concern for hemp grown outdoors for CBD production, particularly when grown on plastic mulch. A similar observation was noted by colleagues conducting hemp research in southern New Jersey suggesting that standability may be a concern regardless of cultivar when using plastic mulch. Although not statistically significant, Suver Haze plants tended to be taller and with more upright growth habit than Elektra plants which tended to be slightly shorter (Figure 1). Plant growth habits may have a significant impact on many production factors including plant spacing, row spacing and susceptibility to plant lodging.
Figure 1. Mean plant height (inches) to terminal inflorescence of hemp cultivars evaluated during the 2020 growing season, Pittstown New Jersey. Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020).
Yields were similar across cultivars with Elektra plots recording a slight numerical advantage in both wet yield and dry yield (Figure 2). No differences were observed across cultivars in CBD percentages with a numerical advantage being observed in the Suver Haze treatment on September 16, 2020. Total CBD percentage improved in the Elektra plots with a slight numerical advantage observed on October 16, 2020 (Figure 3). Although total CBD percentage increased in the Suver Haze plots over time, the rate of increase was numerically less when compared to Elektra plots suggesting that harvest timing is crucial to maximize CBD percentage and ultimately marketability of floral material. No differences were observed in THC concentration across either cultivar or sampling date.
Figure 2. Mean yield (lbs/plant) of harvested female flower buds collected during the 2020 hemp cultivar study, Pittstown, NJ. Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020).
Although not significant, a trend towards higher THC accumulation was observed in the Elektra plots with a dramatic increase in THC concentration being observed across sampling dates (Figure 4). The relationship between CBD and THC accumulation is an important consideration when selecting hemp cultivars for CBD production.
Figure 3. Effect of sampling date on total CBD percentage of hemp, Pittstown, NJ Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020).
Figure 4. Impact of sampling date on total THC percentage across two CBD cultivars Pittstown, NJ 2020Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020).
Floral material was sampled and segregated by plant location to determine if sampling location influenced CBD and THC concentrations. In this study, no significant relationship was observed in either cultivar related to CBD concentration and sampling location on the plant (Figure 5). However, a trend was observed in Suver Haze plots with a small numerical increase being recorded in the top third of the plant. The impact of plant sampling location on THC concentration was variable with the highest concentration of THC being observed in the top third of the plant in Suver Haze, while the highest THC concentration being observed on the lower third of the plant in the Elektra plots (Figure 6). Although no statistical differences were observed in THC concentrations in total THC or across plant location, it is important to note that both cultivars tested, measured above the 0.3% regulatory threshold for THC and were noncompliant by New Jersey regulations and were subject to crop destruction. Unlike other crops grown in New Jersey, hemp production is subject to strict regulatory compliance measures. It is crucial that growers understand the relationship between CBD and THC concentrations and select cultivars that are suitable for production in New Jersey.
Figure 5. Impact of plant sampling location on total percent CBD concentration of two hemp cultivars Pittstown, NJ. Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020).
Figure 6. Impact of plant sampling location on total percent THC concentration Pittstown, NJ 2020. Any column with an * is different according to Welch’s t test. Analysis conducted in R: R Core Team (2020)
Hemp, like other crops is susceptible to myriad insect and disease pests which can result in significant yield, quality, and economic losses. Although some variability in disease severity was observed across cultivars (data not shown), diseases were found in both cultivars evaluated in this study. Diseases included hemp leafspots, caused by a variety of soilborne fungi including Bipolaris spp., Cercospora spp., were observed in the plots. Similar plant diseases have been observed in other studies (Darby, 2018). Due to limited fungicides currently labeled for use in hemp, producers should select cultivars carefully and follow integrated disease management practices to minimize the impact that diseases have on yield and quality. Several insects were identified in the hemp plots. Perhaps the most detrimental pest found in his study was corn earworm (Helicoverpa zea). Damage from this pest mostly impacted floral buds, resulting in buds that were not harvestable or severely damaged. Other insect pests included cannabis aphids (Phorodon cannabis), spotted lanternfly (Lycorma delicatula) and brown marmorated stink bug (Halyomorpha halys). The impact that these pests have on yield is yet to be quantified, but new reports of cannabis aphids have been documented as potential concerns in other studies (Cranshaw et al., 2018). Several other incidental insects were observed, suggesting that hemp is a suitable host crop for a wide array of insects.
Although there is significant interest in hemp production in the northeastern United States, and New Jersey, it is important to keep in mind that there have been very few U.S.-based agronomic research studies on hemp since the early 20th century. Particularly regarding production for CBD. Information from previous research is important and useful but may not always be completely applicable for modern production systems. Industrial hemp is an untested crop in New Jersey. As such, research is needed to provide data on planting, management, fertility, harvesting, and processing specific to New Jersey conditions.
While hemp production may provide an opportunity for New Jersey, it is crucial that producers carefully examine the market and accessibility of market channels as part of their overall operation. As is the case with any emerging agricultural product, limited data exists to quantify the economic feasibility of industrial hemp production in New Jersey. This study demonstrated that differences exist between cultivars relative to CBD:THC ratio, susceptibility to disease and insect pests, and marketability. Significant research gaps must be addressed before Extension recommendations can be developed.
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Hanchar, J. (2019). Economics of Producing Hemp for CBD in NY: Costs of Production, Land Based, Raised Bed, Plastic Mulch, Drip Tape Irrigation Production System, Initial Estimates, 2019. https://hemp.cals.cornell.edu/resource/economics-producing-hemp-cbd-ny-costs-production-land-based-raised-bed-plastic-mulch-drip-tape-irrigation-production-system-2019/ Accessed, 5 May 2021.
Thompson, E.C., Berger, M.C., Allen, S. (1998). Economic Impact of Industrial Hemp in Kentucky. University of Kentucky, Center for Business and Economic Research, Lexington, KY.
Walker, E. (2015). Status of Industrial Hemp in Tennessee. https://extension.tennessee.edu/publications/Documents/W777.pdf . Accessed, 1 May 2021.
Williams, D.W. & R. Mundel. (2018). An Introduction to Industrial Hemp and Hemp Agronomy. Cooperative Extension Service Publication ID-250. College of Agriculture, Food and Environment, University of Kentucky. http://www2.ca.uky.edu/agcomm/pubs/ID/ID250/ID250.pdf