By the time this issue arrives in your hands, planting season will be but a recent memory, and the 2020 hemp growing season will be in full swing. This year is a significant one for hemp farmers and the industry as a whole.

The 2019 growing season—the first after the federal government legalized hemp farming in the U.S. under the 2018 Farm Bill—was rife with many challenges. Columnist Marguerite Bolt of Purdue University outlines five of the top challenges growers faced last year. Still, as Bolt wrote, “The more time we spend in the field looking for problems, the more likely we are to find them, but also to find solutions.” While she was referring to hemp pests and pathogens, this applies to many aspects of hemp growing.

As you’ll read in “The Test of Time”, in 2019, an acre of Sarah Kelley’s hemp crop tested hot—an estimated loss of $20,000 in biomass. In addition to other possible solutions, Kelley says, “We’re going to test a little bit earlier instead of trying to reach the full maturity level. That’s when you get a little bit leery of testing hot.”

This issue’s cover story, “The Future of Fiber,” shares similar stories with different solutions. “Like many other fiber farmers ..., the Bio-Regen Co-op is experimenting with genetics. After their seeds from China resulted in hot crops in 2018 and 2019, the farmers are now primarily testing out a Polish variety certified by the Association of Official Seed Certifying Agencies (AOSCA),” Hemp Grower Associate Editor Theresa Bennett writes.

As farmers learn with each acre planted, university research also grows by leaps and bounds. In June, HG premiered its first Hemp Virtual Event (as part of its Cannabis Conference virtual event series), featuring a session, “The Latest in Hemp Research,” where researchers detailed their current projects.

This growing season will not be perfect, as U.S. hemp growers continue to learn valuable lessons. The weight of upcoming legislative changes bears down on those in states not yet compliant with the U.S. Department of Agriculture’s interim final rule; for many of those states, current regulations have been comparatively a bit more lax. Testing challenges need to be worked out, as do end markets. (The cover story on fiber and the Hemp Watch department on animal feed highlight some promising end markets and the hurdles they face.)

Yet, despite the inevitable trials of this year’s growing season, with another year under its belt after the fall harvest, the federally legal hemp industry will grow better and stronger once again.

Illustrations by Britt Spencer

The Agriculture Improvement Act of 2018 (the 2018 Farm Bill) might have legalized hemp nationwide, but the law had an ulterior motive. One of Congress’ motivations was to help farmers across the United States cash in on the skyrocketing global demand for cannabidiol, or CBD—one of the naturally occurring chemical compounds that can be extracted from the tall, fibrous hemp crop.

Hemp is a variety of the Cannabis sativa L. plant that has been used for thousands of years to produce everything from clothing to building materials. While hemp can still be a viable cash crop for all these purposes, the real money-maker for many U.S. farmers today is CBD.

CBD is reported to offer many of the same natural health benefits as the tetrahydrocannabinol (THC) found in cannabis, just without the mind-altering effects. (In other words: THC gets you high; CBD doesn’t.) Because of this, products that contain CBD are popping up everywhere—in oils, lotions, bath salts, beverages, pet food and more. Restaurants are now even selling meals prepared with CBD.

But the law, while decidedly pro-CBD, does not make profiting from CBD an easy proposition. If the U.S. Department of Agriculture’s interim final rule implementing the 2018 Farm Bill goes into effect as drafted, farmers with hemp that contains more than 0.3% THC in state-administered tests must pay to destroy their crops in addition to losing the potential commercial value of the plants.

Unfortunately for the nascent U.S. hemp industry, failed tests are fast becoming the norm. From Florida to Washington state, farmers who had intended to grow hemp with high concentrations of CBD are actually inadvertently growing what the federal government classifies as illegal marijuana (plants containing more than 0.3% THC)—or, to the hemp industry, “hot hemp.”

In Hawaii, the Honolulu Star-Advertiser reported in August 2019 that 18 crops—more than half of the hemp crops cultivated for the state’s pilot program—were unusable due to high THC levels.

In the here and now, crops are testing hot—and the rush to grow CBD-rich hemp may be causing the problem.

Meanwhile, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) said about 12% of hemp field tests came back hot for the 2019 growing season. The percentage of hot hemp didn’t change from 2018 to 2019 even though the number of registered growers increased tenfold. The regional newspaper Isthmus also reported that two Wisconsin growers anticipated a complete loss of about $40,000 on a crop of 70 hemp plants that tested at 0.5% THC content.

All told, Vote Hemp estimates that only about 50% to 60% of the hemp planted in 2019 will be harvested because of “crop failure, non-compliant crops and other factors.”

Why is this happening?

For one thing, scientific research methods, seed-certification processes and regional farming know-how are all still developing. In time, a hot crop will likely be a statistical outlier as the industry figures out how to perfect the low THC/high CBD balance, experts tell Hemp Grower. But in the here and now, crops are testing hot—and the rush to grow CBD-rich hemp may be causing the problem.

“The biggest factor contributing to the issue of hot hemp is probably the genetics that growers are sourcing,” says Bob Pearce, Ph.D., a professor of agronomy at the University of Kentucky who helps lead the school’s hemp research program. “Cultivars that produce predominantly CBD also produce small amounts of THC, typically in a pretty consistent ratio for that cultivar. So, as CBD increases, so does THC. Then you throw in environmental stress and management on top of a marginally compliant cultivar, and you start to see problems with hot hemp.”

Hemp experts have offered their top three recommendations for growers looking to seize the CBD future while preventing their crops from running hot.

“A lot of growers are going to struggle to reach 10% or higher CBD and 0.3% THC if they continue with current strains and practices.” — Jeanine Davis, professor, Department of Horticultural Science, North Carolina State University

1. Choose Known Cultivars.

Hemp growers should select known cultivars that have consistently tested well below 0.3% THC in their local areas, Pearce says. In most cases, the reason hemp tests hot is because of bad genetics. Farmers in Kentucky, for instance, might be using seeds bred for West Coast soil and climate when what they really need are cultivars developed specifically for Kentucky.

However, choosing a proven low-THC cultivar has its drawbacks. Pearce says some cultivars that have tested below 0.3% THC also produce less CBD—roughly 2% to 5% by his estimates. Most growers are aiming for 10% CBD. Pearce acknowledges the trade-off but says it’s better to have a legal plant with less CBD than a destroyed crop.

The most important thing, he stresses, is to obtain seeds and plants from reputable sources so growers have “some assurance they are getting what was advertised.” One problem, though, Pearce warns, is that seed and plant certification programs for hemp are currently in their “infancy at best and non-existent at worst.”

While many states have approved lists of hemp seeds, these are far from sure bets—at least not yet. Leeann Duwe, a spokeswoman for the Wisconsin DATCP, says the state of Wisconsin precertifies hemp seeds through a lab analysis of the variety. The DATCP looks for the total THC or the ability to calculate the total THC. If the THC is below 0.3%, then the variety is approved. However, the state’s approval of a seed variety does not guarantee a plant will pass a preharvest test for THC levels, Duwe tells Hemp Grower.

In Canada, where the industrial hemp market is more established (since legalization under the Cannabis Act in 1998), the Industrial Hemp Licensing Unit of Health Canada publishes a list of approved cultivars for each growing season. (At press time, the 2020 list was not available, but the 2019 list can be found here: http://bit.ly/Canada-approved-cultivars.)

Jeanine Davis, Ph.D., associate professor in the Department of Horticultural Science at North Carolina State University, says she expects to see more self-testing take place over the next year as a result of the Farm Bill and hot tests. Farmers want to do what they can to make sure they avoid a hot test.

“A lot of growers are going to struggle to reach 10% or higher CBD and 0.3% THC if they continue with current strains and practices,” she says. “What I saw in the western part of North Carolina in 2018 and 2019 is growers selecting strains that would produce the highest CBD possible and that would test at 0.3% total THC for the official test. If THC went above 0.3% at harvest, they weren’t too concerned because ... they had buyers.” Even though they had buyers, however, possession of hemp that exceeds the 0.3% threshold at any point is considered illegal. (For more on CBD to THC ratios, read "Cornell University Breaks Ground on Hemp Research.")

The new proposed federal rules push the time for official testing at a lab registered by the Drug Enforcement Administration (DEA) 15 days prior to anticipated harvest time, which makes a big difference in THC levels. “So same rules, just new time frame for when the official testing needs to take place,” Davis says.

“With the publishing of the interim federal hemp rule, we will see a big change in the strains growers choose to grow,” Davis says. “Many of the strains produced now will not test out at 0.3%15 days before harvest.”

The good news is that the hot hemp problem is spurring research and development in new cultivars. In one example, the Spanish company Hemp Trading and the Spanish university UPV claim they have developed the first entirely THC-free hemp variety with high cannabigerol (CBG), a cannabinoid that can be extracted from both cannabis and hemp plants for medical use. (CBG can be found early during a hemp plant’s growth and is later converted into different chemical structures. CBD and THC start as CBG.)

This is promising, to be sure, but there are multiple variables during the growing process that can impact THC levels—even if you choose the right seeds.

All told, Vote Hemp estimates that only about 50% to 60% of the hemp planted in 2019 will be harvested because of “crop failure, non-compliant crops and other factors.”

2. Pay Attention to the Soil.

Preventing hot hemp is not only about selecting the right plant and the botany of that plant; it’s also about the biology of the soil and the enzymes converting the CBG to CBD, says Michael Goodenough, a managing partner of D&G Agtek, the parent company of sweetheal.com, a hemp and CBD producer in Connecticut.

“When the cannabis plant has been grown naturally in healthy living soils without stress, the CBG converts to CBD,” Goodenough says. “Living soils...naturally convert the sand, silt, clay and organic matter into nutrients that the plant can control and uptake as it desires. By allowing the plant to control this process, we see increases in all the sought-after cannabinoids and terpenes, including the minor ones we have yet to fully understand. This also helps prevent the undesired production of THC, increases the plant’s own natural defenses, creates less work for the farmer and, in turn, makes it less risky to grow.”

Goodenough notes that hemp in the U.S. is often grown on land that used to grow other crops, and the soil may have been neglected for years, especially if the farm went bankrupt.

Through his work, Goodenough has helped develop remediation processes that he says could take hemp with high THC content and then convert it into other cannabinoids like CBD.

3. Harvest Early.

In addition to paying attention to the soil, Goodenough says growers should also rethink taking their plants to full term. Cannabinoids increase with time in the plant, which is why growers should consider employing an in-house testing protocol and be prepared to harvest before the THC levels exceed 0.3%, even though harvesting early results in lower CBD levels as well.

“One thing farmers need to start thinking about is the ideal harvest time to maximize what they’re growing for but also to minimize risk,” says Kyle Sosebee, J.D., a hemp and cannabis lawyer based in Massachusetts. “We know that THC spikes at the very end of the growing season along with a lot of the other cannabinoids. What we may end up seeing is farmers harvesting earlier than they otherwise would just so they have a bigger safety margin and avoid that end-of-the-season spike in THC.

"That may become part of the growing strategy for farmers: They’re going to short themselves on CBD, but it’s going to be better than a total crop loss if your entire crop goes hot.”

How many times have we heard that a balanced diet is essential to our health? Plant nutrition isn’t much different. Hemp plants can thrive or struggle depending on how you design your fertilization programs. Plants require 17 essential elements for growth. They obtain hydrogen (H), oxygen (O), and carbon (C) from irrigation water or as a gas via the atmosphere. Growers must provide the remaining 14 elements to help hemp plants thrive.

These include the macroelements:

• nitrogen (N)
• calcium (Ca)
• phosphorus (P)
• magnesium (Mg) and
• potassium (K)
• sulfur (S).

And they also include the microelements:

• boron (B)
• manganese (Mn)
• chlorine (Cl)
• molybdenum (Mo)
• copper (Cu)
• nickel (Ni) and
• iron (Fe)
• zinc (Zn).

The quantity of macroelements and microelements required varies by type of plant, but they are all required by the plant for growth.

Photo by Brian Whipker

Cobalt (Co), selenium (Se), silicon (Si) and sodium (Na) are four beneficial elements that promote plant growth but are not considered necessary to complete the plant life cycle. With hemp production, many growers are providing Si to promote overall plant health.

Providing a complete fertilizer package that contains all the essential elements is important to maximize plant growth. When designing a fertility program, it is also important to keep in mind some key principles that ensure there is a nutritional balance. Just like with human health, where we must balance our intake of sugar, protein, grains, fruits and vegetables, too much of one item can lead to imbalances in the plant due to antagonistic effects. For example, if too much P is provided, it can hinder the uptake of other elements and lead to Fe, Mn and Zn deficiencies.

Key Considerations

Nitrogen Form. Nitrogen in fertilizers primarily comes from three sources. Nitrate-nitrogen is the main form the commercial floriculture greenhouse industry uses for its plants. While the cost is higher, it’s the preferred form of N because it promotes compact plant growth. The same applies predominantly to hemp grown for cannabinoids; in the cannabis industry, the market currently lacks plant growth regulators registered for use on cannabis, so you can opt for nitrate as a source for N to help avoid excessive overgrowth, also known as plant stretch.

The other two forms of N contained in most fertilizers are ammoniacal nitrogen and urea. Many organic fertilizers have N in these forms. Farmers growing hemp for fiber and grain would use ammoniacal N because much more of it is used per acre and it is cheaper. In commercial floriculture greenhouse production, these two forms of nitrogen are strategically deployed but are only used to a limited extent. Many growers will use ammoniacal nitrogen and urea-based fertilizers during the first two weeks after plants have been transplanted into the final container to help establish the plants and encourage a flush of new growth. After that point, most growers rely upon a nitrate-nitrogen based fertilizer.

The key takeaway here is to supply most of your N from nitrate-nitrogen. Evaluate your fertilizer type by reading the fertilizer label to ensure the N form you are providing is on target.

Moderating P Applications. Phosphorous fertilization strategies have been studied extensively over the past five years. One of our graduate students, Josh Henry, worked on optimizing P fertilization rates for his master’s degree thesis. In essence, plants require a baseline level of P to grow adequately (Fig. 1). For a continuous fertilization program for plants grown in a soilless substrate, the target concentration is between 8 parts per million (ppm) and 15 ppm of P. Providing levels below that will result in less plant growth, while concentrations above that level provide little benefit while costing more money. Phosphorus is also the primary contributor to plant stretch. Too much P will lead to excessive internode elongation and tall plants. That’s why it’s important to limit excessive P applications.

Whipker headshot by Jake Gravbrot; All other headshots courtesy of respective subjects.

Plant nutrition experts are currently debating whether the P rate needs to be amplified just before flowering in hemp grown for cannabinoids to improve quality. Research led by Manitoba crop nutrition specialist John Heard on a dual-purpose hemp crop grown for seed and fiber suggests that extra P is not required by flowering hemp (Fig. 2).

The researchers found that hemp plants front-end load P during the first half of the growing season as seen with the plant’s upward accumulation of P. At midseason, the total accumulation in the plant plateaus. This indicates that the plant uptakes limited additional P. Hemp relies upon those internal P reserves and translocates (moves) P if it is required in other parts of the plant. This suggests that adequate P levels should be provided to hemp grown for flower during the first half of the production cycle for the plant to accumulate an adequate reserve that can be translocated if needed later. Providing a P boost late in the growing season appears to not be needed. A scientifically based trial is needed to clear up this uncertainty with greenhouse-grown hemp.

While the target P level for greenhouse-grown hemp is not currently known, we would speculate based on the scientific data from other species that levels of 15 ppm to 20 ppm P supplied on a constant basis should be all that is required. At North Carolina State University, we have begun an experiment looking into optimal P rates supplied at a constant level throughout the hemp crop cycle and will be able to further refine those recommendations in the near future.

Ratio of K to Ca to Mg. Providing a proper K to Ca to Mg balance is important for hemp production. Too much of one element does not in itself result in toxicity symptoms. Instead, excessive levels of one element has an antagonism against the others. For instance, excessive K will result in either a Ca deficiency or an Mg deficiency being observed in a plant. Many instances of Mg deficiency observed in hemp may be due to excessive K being supplied and not due to the lack of available Mg to the plant. Figure 3 illustrates the trend that is observed in the leaf tissue concentration of a plant when K is excessive.

For hemp, K, Ca and Mg all appear to be needed in larger quantities compared to other greenhouse floriculture species. In general, the rule is to provide K, Ca and Mg in a 4:2:1 ratio to avoid antagonisms. For commercial poinsettia production, we recommend a similar ratio around 200 ppm K to 100 ppm Ca to 50 ppm Mg; this would be a good starting point for hemp (which, like poinsettias, is a short-day plant) until scientifically based research can determine optimal rates. Also, keep in mind that excessive sodium (Na), which can come from your fertilizer source or irrigation water, can also interfere in K, Ca and Mg uptake.

Dialing in the Micros. Managing microelements can be a challenge in most fertilizer programs. The concentration difference from deficient to adequate to excessive rates is very narrow. Until you become comfortable mixing your own micronutrient fertilizer salts, it’s safer to rely upon premixed micronutrient packages or the micros provided in commercial fertilizer blends.

All in Balance. Providing all the essential elements is the key to optimizing plant growth. Equally important is balancing the proportion of elements provided to hemp so plants remain healthy.

Editor’s Note: A version of this article was originally published in the September 2019 edition of Cannabis Business Times (Hemp Grower’s sister publication) and has been reprinted with permission.