CHARLESTON, S.C. – More South Carolina farmers are applying for permits to grow industrial hemp and Clemson University researchers believe applying best management practices can result in higher quality and increase profits.
Brian Ward, an organic vegetable specialist and assistant professor at the Coastal Research and Education Center (REC), gave an update on the South Carolina hemp crop during a recent field day. One variety discussed was Hurricane Hemp – Florence, developed after Hurricane Florence leveled much of the hemp crop in 2018 and farmers lost about 15% to 20% of their yields.
“Lines that were being planted weren’t bred for South Carolina blew down,” Ward said. “After this happened, researchers with Arrowhead Seed Company went to the drawing board with their breeders and came up with this cultivar.”
A massive stalk system and massive root system give Hurricane Hemp – Florence stability and make it suitable for growing in South Carolina.
“These systems allow the plants to stand up better in wind storms,” Ward said.
The Hurricane Hemp – Florence line has been tested for two years in South Carolina and now Clemson researchers are conducting tests to determine production requirements such as plant spacing, fertility and planting dates. Knowing this information is important “so that yields can be optimized, upfront costs can be reduced and profits can be greater,” Ward said.
Typically, when new cultivars are developed, research on cultural practices is conducted to optimize yields, traits and active phytocompounds such as the essential oil CBD, cannabidiol, in the case of industrial hemp. So far, research has found a majority of the cultivars perform best at the 60-inch spacing, but some cultivars perform better at lower plant densities. In addition, most cultivars are reaching peak biomass yields and CBD levels at nitrogen rates of 60 pounds to 120 pounds, with most preferring about 80 pounds of nitrogen per acre in split dry or precision fertigation strategies.
Ward’s fertility study involves plants that receive 225 pounds of nitrogen per acre, 150 pounds per acre and the commercial standard 75 pounds per acre. Researchers found plants grown in the 75 pounds to 95 pounds-per-acre area actually produced the most biomass.
“This is a lot cheaper on a per-acre basis,” Ward said. “So, with optimal spacing and optimal fertility, farmers are likely to get optimal yields.”
In addition to this research, Ward also discussed a study focused on CBD and THC (tetrahydrocannabinol) levels found in industrial hemp. CBD is an essential oil derived from hemp plants, which are cousins to marijuana plants. THC is a psychoactive ingredient that can alter a person’s mental state and cause that person to become intoxicated, or feel “high.”
Ward plans to study plant hormones to determine if THC production can be arrested as CBD production increases. Researchers believe this could help reduce the number of plants per acre, as well as control when CBD is produced. The study will include Hurricane Hemp – Florence and a hybrid variety.
“After this year, we’ll know more on a molecular level of what’s going on with the production levels of CBD and THC,” Ward said. “Once we know this, we can start writing a production guide for growing hemp in South Carolina.”
South Carolina hemp facts
Industrial hemp was first grown in South Carolina in 2018 when the South Carolina Department of Agriculture gave permits to 20 farmers to grow the crop as part of a pilot project. In 2021, 213 permits were issued in South Carolina. In 2020, the S.C. Department of Agriculture’s Hemp Farming State Plan received approval from the United States Department of Agriculture (USDA). The state Department of Agriculture works with the Clemson Cooperative Extension Service and Clemson Department of Pesticide Regulation to provide information for industrial hemp growers.
Hemp is used to make a variety of commercial and industrial products including rope, clothes, food, paper, textiles, plastics, insulation, supplements, oils, cosmetics and biofuel. There are three main types of industrial hemp: CBD; culinary grade for flour, cake and oils; and fiber. Ward said that fiber is gaining momentum and getting regional and national recognition as a staple fiber source when added to cotton.
Other Clemson teams also have received university funding to study different aspects of industrial hemp, including diseases as well as insect and weed pressures.
“A lot of people are helping fill a niche in the entire spectrum of research that needs to be conducted with a new industry,” Ward said.
In addition to hemp research, participants in the Coastal REC field day also learned about grafting research in vegetables, an anaerobic soil disinfestation using cover crops, a green bean variety trial being conducted under both ideal and heat-stressed conditions, herbicide issues in tomato and other vegetable crops, and downy mildew in cucumber, Fusarium wilt in seedless watermelons and how cultivars of beet greens differ in susceptibility to Phoma and Cercospora leaf spots.