Kiki Fontenot and Kaylee Deynzer

Until 2020, research on outdoor hemp (Cannabis sativa L.) production was nonexistent in Louisiana. In different regions, many components of hemp production vary, such as optimum planting dates, plant density and regionally adapted cultivars. These are critical components to an effective hemp management program that the LSU AgCenter sought to identify to accurately advise commercial hemp producers in Louisiana. This article discusses the production practices and lessons learned from cultivating hemp throughout a two-year research study.

Hemp contains many cannabinoids, such as CBD, but its notable trait is that it contains less than 0.3% delta-9 tetrahydrocannabinol (THC), which is the psychoactive compound found in cannabis. When producing commercial hemp, only female plants are cultivated because the flowers contain the essential oils that are extracted for products such as salves, tinctures and more.

Nine cultivars of essential oil-type hemp were grown using organic practices, including organic weed and pest control, at the Central Research Station in Baton Rouge during 2020 and 2021. The cultivars were planted on April 15, May 15, June 15 and July 15. Cultivars were planted at 3-, 4- and 5-foot in-row center plant spacings.

A pre-plant application of Nature Safe organic feather meal (13-0-0) was applied at a rate of 100 pounds nitrogen per acre. After transplanting into the field, each plant received 5 ounces of fish emulsion solution (5-1-1) using a backpack sprayer. Hemp plants were fertilized weekly with a water-soluble nitrogen amendment at a rate of 10 pounds nitrogen per acre. Fixed dual head halogen lights were installed to extend the photoperiod and provide 18 hours of light to the field. Plants grew vegetatively for two to three months before entering the reproductive stages of flower development for two months until harvest.

The rows were covered with 48-inch white on black (white side up), nondegradable, embossed plastic mulch for weed control. Row middles were routinely managed for weeds using string trimmers and lawn mowers. Grasses and weeds, predominately purple nutsedge, grew near the plastic mulch and were controlled by applying the nonselective, organic herbicide Scythe. Neem oil was applied upon increasing insect counts in the field. The insect pests of concern were the bertha armyworm and the spotted cucumber beetle. Following the initial application, insect counts never grew above a concerning threshold for repeated applications. Southern blight, a disease caused by a soil-borne pathogen, resulted in high counts of plant mortality during both years. To mitigate its impact, the fungicide Blocker 4f with the active ingredient pentachloronitrobenzene (PCNB) was used.

Plant measurements were taken and recorded throughout the growing season. Once the buds reached maturity, the entire plant was harvested by cutting the stem 2 inches above the soil. Individual plants were labeled, separated and immediately transferred to the drying facility. Plants were hung upside down to dry in a walk-in cooler and stored at 72 F with a dehumidifier to maintain 35% relative humidity. Once dried to a moisture content below 12%, the flowers were trimmed by hand using pruning shears. The fresh weight, dried weight and total bud yield of the plants were recorded. Dried bud tissue was extracted according to the Louisiana Department of Agriculture and Forestry hemp extraction protocol. Analysis of the cannabinoids CBD, CBDV, CBDa, D 9-THC, THCa and THCV was performed with Dionex ICS-3000 system.

Lessons Learned

With the environmental challenges that were faced, 3-foot in-row spacing was adequate for plants, yet we cannot recommend an optimum planting date at this time. The supplemental lighting achieved the goal of encouraging vegetative growth yet was difficult to maintain due to installation challenges and power requirements. Of the nine cultivars grown in the trial, Oregon White was the sole cultivar to remain compliant by not exceeding the 0.3% THC threshold for commercial hemp production.

In the 2020 trial, southern blight was reported in all major growing areas in Louisiana. Hemp was not immune to this disease and plant fatality rates ranging from 11%-77% were found in all cultivars in the LSU trial. Moreover, 2021 ranked as the third wettest year for Baton Rouge with monthly rainfall ranging from 8-12 inches during the growing months of April through September. Total crop failure was recorded for all April and May plantings due to root rot from standing water in the fields, while the June and July plantings that were grown under the cover of a hoop house grew successfully until Hurricane Ida in September, resulting in 100% mortality.

Results from this study indicate prospective farmers may need to grow hemp for CBD production in greenhouse structures to protect the plants from Louisiana’s unpredictable spring and summer weather. Future trials will be conducted in field conditions using high tunnel structures in the fall and winter seasons to offset storms, heat, rain and disease damage.

Kiki Fontenot is an associate professor in the LSU AgCenter School of Plant, Environmental and Soil Sciences and is an extension horticulture specialist. In January, Fontenot will become the director of the AgCenter Southwest Region. Kaylee Deynzer was a graduate student studying horticulture.

This article appears in the fall 2023 edition of Louisiana Agriculture magazine.

Hemp cuttings ready to be transplanted into the field. Photo by Kaylee Deynzer

Mature hemp plant growing in Baton Rouge. Photo by Kaylee Deynzer

Newly planted hemp transplants grown under a high tunnel. Photo by Kaylee Deynzer