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Overhead irrigation in a field

Researching BMPs for Hemp Production in Florida

Dr. Zachary BrymDr. Zachary Brym, an assistant professor of agroecology with the UF/IFAS Tropical Research and Education Center, provided an overview of the hemp industry in Florida and the research that is currently being done on the topic.

Hemp was first utilized by people 10,000 years ago, and since then its uses have included textiles, animal husbandry, and other uses to support industry. Popularity declined during the world wars because of the rise of competing textile and materials industries and the growing legal challenges with Cannabis. Now hemp has had a resurgence in popularity with recent federal and state laws and is being introduced as a crop and a topic of research in Florida.

The Florida Department of Agriculture and Consumer Services (FDACS) is currently accepting permit applications for commercial hemp growers . Hemp, or Cannabis sativa, is identical to marijuana aside from its low THC content (0.3%). Research is being conducted at UF/IFAS to understand the agronomy of hemp in Florida and to examine whether hemp poses a risk as an invasive species and other environmental impacts that may be caused by hemp cropping systems. More research needs to be done to determine the best management practices for hemp production – especially related to fertilizer application.

Research hemp grown at TRECHemp is grown for three main products: fiber, grain, and flower. Plants grown for fiber are slender and tall, and the fiber is used to make textiles, biocomposite (e.g. building materials), and animal bedding. Grain is primarily used to produce hemp seed, seed oil and microgreens. Hemp grown for grain must be pollinated, so both male and female plants must be present in the field in the proper ratio. Both fiber and grain varieties are direct seeded in mass numbers within an agronomic system and machines are used for harvest. For flower production to reach maximum potential, the plants should not be pollinated. They are grown using transplants or rooted cuttings in raised beds, although they are being increasingly growing in an agronomic system. The often hand-harvested plants are pushed  to produce the most flowers. Flowers are used for essential oils, which can be broken apart into different cannabinoids (including CBD).

There are still many unknowns associated with hemp production. Some of these unknowns are where the adapted varieties are coming from, how each variety performs, whether the genetics are stable, whether the plants are under the legal THC levels, and how to integrate hemp into current cropping systems. There are also potential environmental risks, such as whether hemp will become invasive, how it will affect natural areas, and the limited nature of nutrient management and biosecurity. Many of these questions are currently being researched via the UF/IFAS Hemp Pilot Project, now in its second year.

Although there are not official best management practices (BMPs) for hemp production yet, there are some general guidelines growers can follow commonly Research hemp at TRECused for other crops. Especially in the early stages of production, growers need to consider how their operation could affect nearby water bodies. The amount of nitrogen applied should be based on soil quality and the type of hemp being grown. Excess nitrogen can cause hemp grown for fiber to lose strength and hinder the drying process. The lowest amount needed for desirable economic production should be used. Similarly, excess potassium will be absorbed by hemp and could cause weakening of fiber plants.  For phosphorus, growers should test their soil and monitor fields to know whether one or more applications are needed. Lower applications are better for sustainability. Research needs to be done in Florida to understand the impacts of nutrient application practices.

UF/IFAS research has found that hemp can grow well in multiple locations in Florida, perhaps even some surprising locations When grown in 6-8 inches of gravelly soil with a pH of 8, outside the expected preference for hemp, the plants grew 15 feet tall with 4 inches of roots. The plants need a well-drained, moist environment, but will quickly die if they experience flooding. The plants are sensitive to light and have many problems with weeds. There are limited commercial herbicide options for hemp production, so the weeds must be controlled at planting and until the hemp plants are established. Some diseases hemp can suffer from include southern blight, bacterial leaf spot, and damping off.

As hemp becomes a more established crop in Florida, it is important to remember that there is a risk of it becoming invasive. Prices are also a concern because they depend heavily on supply and demand in addition to market competition. FDA rulings on the essential oil market are not fully developed yet. Although there are not yet definitive UF/IFAS recommendations for hemp cultivation given that research is ongoing, general BMPs and the 4Rs for fertilizer usage (right source, right rate, right time, and right place) can be applied.

Watch the recording of Dr. Brym’s presentation.

Written by Natasha Roberts, CLUE Communications Intern



Q: In the historical slide of the naturalization of hemp, can you explain what is meant by the term “naturalization” there?

A: You can think of them as feral (“wild”) populations

Q: How many applications per year (Nitrogen (N) and/or Phosphorus (P); nutrients in general)?

A: I don’t know is my most honest answer. If you are doing fertigation, it is likely you’re doing low dosing weekly. If you are doing granular you might do one at the beginning – maybe 50lbs of N/acre -and then sometime into the year you’re doing another 50-100lbs/acre. We got by with the slow release through the year, of course everybody knows what the rains do to the fertilizer that you put out early on in the year and how it moves through the system, so I’d say as we collect more information and get a solid idea on what the plant needs and when it needs it, we’ll start drawing down on those applications.

Q: Why is growing hemp for fiber lower in value than growing it for CBD?

A: It just comes down to markets. So, the bast fibers, the outside fibers, you’d be using for textiles. You are competing with the cotton industry and the Chinese hemp industry. So, we’re talking about 60-70 cents/lb of fiber at maybe 8000 lbs/acre of the dry straw, which is what you would be bailing and selling to a processer. Of course, there have to be some fiber processors out there; we’re seeing some companies come out and give it a try, and then who is buying that product; that’s kind what’s going on for the fiber markets. The oil markets are still being established. We’re not sure how the FDA rules on it as far as long-term market. We saw some relaxation from the USDA and the federal government incorporating it. Again, I mentioned that price decline – how it levels out, how it sticks around, how the supply/demand works out, that’s a whole other thing. If it’s the next aspirin and it takes off or if it ends up just being a little flash – it’s kind of uncertain on how that’s going to work out.

Q: Is there any literature that hemp survives on well-drained soils?

A: … as opposed to flooded soils, which is what I would expect the question to be. If the concern is that the field floods and then we lose the crop because of the flooding. If the question is, “is it drought tolerant?”, then probably after establishment, or it has the best chance after establishment several weeks after the seed germinates or once the transplants go. The question poses interesting commentary into the type of conversation that I’m having, which is the various different “what if” scenarios. So, on one side, as an agronomist, we’re thinking about how to maximize production and how to make sure our farmers are making good on their crops. On the other side, thinking as an ecologist, we’re thinking about what is the least amount of environmental conditions that it needs to survive? So, we know that Cannabis has naturalized across the world. We do not necessarily see it in places that have been dry for long periods of time. Can hemp survive without irrigation? It’s something we have not yet seen information on in the industry, and it’s certainly something that would be sparse in the scientific literature.

Q: Are you considering split Nitrogen applications?

A: For an upcoming study we’ll probably do it as a split application just to confirm the crop gets established at, let’s say a 50lb rate, and then we’ll add our additional rates afterwards. I still do not have a good sense of where in the crop development the N is most important. I think split application is probably a better idea if we’re trying to prioritize the impacts to water quality. So, if you can, limit the amount of nitrogen in each application. We just have to do a better job with monitoring the water and monitoring the soil to see how all this lines up. Just to be clear, the UF/IFAS hemp program does not yet have a recommendation for hemp nutrient management. We’re trying to provide the information we have that comes out of the research program. We’re happy to do that, and have that conversation. We do not have those sorts of answers that say “what you should be doing in this case.” Be thoughtful, be mindful, and commit yourself to the general BMPs for the 4R’s.

Q: Can it legally be grown for CBD in Florida?

A: Yes… with a cultivation permit from FDACS. As far as legal help production in Florida, per the FDACS guidelines, if your hemp tests below 0.3% total THC 15 days before harvest, then any of the products are essentially legal for sale. I would caution the folks interested in flower for CBD, those tend to be the genetics that are really floating right around .3%, if not going hot, so be sure that you’re doing the THC testing or cannabinoid profile testing along the way. If the crop goes above that 0.3%, it does not matter whether it’s grain, fiber, or flower, you’re going to be working on destroying your crop, if not working through a mitigation strategy if one becomes available.

Q: Do we have any idea how far pollen will drift?

A: Another answer that we do not have good science to provide guidance. The options really are the information that we have from the isolation that would be required for breeding by the association for seed certification, which is about 1 mile. States across the country have been looking at a 10-mile radius as far as pollen drift concern in policy. How far that pollen drifts and is viable is probably somewhere in between. I have at least one research report that says that pollen went from northern Africa to southern Spain, so that’s a little bit farther than 1 mile or 10. I don’t think that pollen is still viable, but this just adds another wrinkle to this. You are going to want to know who your neighbors are and what they’re growing, as far as a hemp community.

Q: If there’s already literature that hemp does not survive on wet soils, why were soils with poor drainage selected?

A: There were a number of questions or things that we had to line up as a University hemp pilot project, and in order to do that, that piece of information – that hemp can’t flood – we heard anecdotally. Across the country there are several things about hemp cultivation that were heard anecdotally that did not turn out to be true. Some would say the basic soils – the limestone gravelly soil in Homestead – weren’t going to be able to cultivate plants, and so we selected some sites to represent Florida. The site in central Florida that we had a challenge moving water out of was one of those sites that we had access and authority to, and all the other pieces of the puzzle. We certainly learned something from it. Despite the late rains in the season, we did have some rains earlier in the season that we were able to push past. Now we have it well documented; I get to show you that picture that says, “don’t do it in flooded soils”. Doing it in a small research scale sometimes has the opportunity to learn from those sorts of experiences. Just as a last comment on the question, we’re not sticking with that site this year. So, we learned something from our first year, and we’re moving that site in central Florida away from that area to a better drained soil, something that we can work a little better with and something that we can be more confident that the hemp will grow to full term.