Tis the Season for Sunn Hemp
“What are all those pretty yellow flowers growing in the farm fields”?
That would be Sunn Hemp – a leguminous cover crop that adds organic matter and nutrients to the soil during the fallow times of the year. Annual cover crops are used on our farmlands during the summer months to rejuvenate the soil with much needed nutrients, control weeds, prevent soil erosion during our active thunderstorm and hurricane seasons, and add herbage back into the soil before the next planting season. Sunn Hemp (Crotalaria junicea L.) is a legume, which means it contains nitrogen-fixing nodules in the root zone that actually capture nitrogen from the atmosphere and add it to the soil. The nodules are visible to the naked eye and they appear as the small yellowish-brown sacks in the photograph.
Since this plant can capture nitrogen from the atmosphere (which consists of 78% nitrogen), Sunn Hemp serves as a natural fertilizer for the soil. It can provide approximately 200 lbs/A of nitrogen to the soil, but it does vary depending on the cutting height Abdul-Baki_2001_Effect of cutting height on sunn hemp. Sunn Hemp is also is known to suppress plant parasitic nematodes that are present throughout the soils in Northeast Florida.
L&M Farms has approximately 2000 planted acres throughout the TCAA (Putnam, Flagler and St. Johns), and they have embraced Sunn Hemp as their sole cover crop this year. Yellow flowers will greet you as you drive along SR 207, Molasses Junction, Putnam County Boulevard, Cracker Swamp Road and beyond. They have been increasing their acreage over the last four years but, according to Farm Manager Larry Corn, they planted Sunn Hemp on all their farmland this year. Larry has seen the evidence from significant reductions in commercial fertilizers, and he believes this crop is a beneficial step towards sustainable agriculture. Other common cover crops in the TCAA include grain crops such as field corn, sorghum sudan and pearl millet. Although these options provide much less nitrogen, they do produce a comparable amount of biomass (i.e. 6000 to 9000 lb/A) that is tilled back into the soil.
“Can I get CBD oil from Sunn Hemp”?
No…Sunn Hemp should not be confused with Industrial Hemp. Industrial Hemp is a Cannabis sativa plant that has many industrial uses including fiber and textiles, food (seed oil, greens), forage for animals, building materials and medical benefits through cannabidiol (CBD) oil. UF has partnered with one local farm in the TCAA to investigate the production strategies associated with CBD varieties of industrial hemp. These trials are in the initial stages and plantings occurred during the summer of 2020. For more information, you can read the article published on May 19, 2020 (https://www.morningagclips.com/industrial-hemp-pilot-project-research-expands-to-on-farm-trials/). Results from these trials will be made available sometime in the next year. The latest updates on the UF Industrial Hemp research can be found at https://programs.ifas.ufl.edu/hemp/.
The author is employed by UF/IFAS Extension – An Equal Opportunity Institution.