Horticulture

Aquaponics Could Lead to Higher Cannabinoid Levels

Across the Earth, we are still only at the beginning of cannabis’s resurgence as a medicinal wellspring of valuable secondary metabolites. Some markets have had more longevity, such as California, where a medical industry has existed for 25 years, and black-market cannabis provided a staple, hallmark cash crop for decades. From a recreational perspective, we’re just reaching our tin anniversary.

As more states and countries abolish regulations that have hurt humankind far more than they ever could have helped, opportunities increasingly exist for people wanting to get into cannabis. More opportunities mean more resources needed to cultivate one’s dreams into reality, and there’s no time like right now to evaluate how we can grow more cannabis than ever imagined on our Earth while constantly staying focused on sustainability.

Now that academia can research cannabis without being ostracized or defunded, scientists can help determine potential paths forward, and astute cannabis businesses should pay mind to this research to spark creativity that ensures that we leave our land as good as or better than we found it. For example, once cannabis was nationally legalized in Canada, land being used for cannabis cultivation quickly tripled. Traditional cannabis cultivation has been branded as untenable, requiring high energy requirements, fertilizer, and other resources. One method that has garnished interest specifically because of its sustainable nature is aquaponics.

In aquaponics, the effluent from aquafarming, defined by the National Oceanic and Atmospheric Association as “breeding, rearing, and harvesting of animals and plants in all types of water environments,” is utilized as fertilizer. This valorizes a waste product while simultaneously increasing water use efficiency by filtering the water for recycling. A 2020 study sought to optimize aquaponics for commercial cannabis cultivation during the flowering stage. [1]

The study compared three cultivation methods including aquaponics (11-cm portion of roots submerged in an aquaponics deep-water culture system), hydroponics (plants top-fertigated manually using a commercial fertilizer), and aquaculture (plants manually top-fertigated with the aquaponic solution).

Aquaponically grown plants were shorter with less branches whereas hydroponically grown plants had augmented canopy growth. Flower production was also greater with hydroponics, with one cultivar demonstrating “116% and 42% higher inflorescence biomass than aquaponic and aquaculture plants, respectively.” Interestingly, however, aquaponically grown plants produced 14% more total tetrahydrocannabinol (THC) equivalents and 11% more total cannabidiol (CBD) equivalents. Equivalents mean acidic and neutral forms. Aquaponic plants also produced more beta-pinene and limonene than the aquaculture or hydroponic cultivations. It’s worth noting, however, that when the cannabinoid content was multiplied by flower dry weight, hydroponics led to the most THC and CBD equivalents.

The researchers postulated several rationales for the higher cannabinoid content from aquaponic cultivation, including the potential for rhizobacteria in the aquaponic solution to have catalyzed secondary metabolite production. Another possibility was a flower dilution effect, where larger flowers contain lower levels of cannabinoids as has been seen with increasing nitrogen in fertilizer. [2] This was demonstrated in this study as well where higher nitrogen levels in hydroponics led to lower THC content compared to lower inflorescence biomass (aquaponics) containing more THC. This ultimately leads to the yield versus potency conundrum.

As the cannabis industry continues its global renaissance, cultivation options that respect the land and the wider ecosystem should be explored at all costs. To quote Chief Seattle, “Humankind has not woven the web of life. We are but one thread within it. Whatever we do to the web, we do to ourselves. All things are bound together. All things connect.”

 

References

[1] Yep B, Gale NV, & Zheng Y. Comparing hydroponic and aquaponic rootzones on the growth of two drug-type Cannabis sativa L. cultivars during the flowering stage. Industrial Crops and Products. 2020;157:112881. [journal impact factor = 5.645; times cited = 4] [2] Caplan D, Dixon MA, & Zheng Y. Optimal rate of organic fertilizer during the vegetative-stage for Cannabis grown in two coir-based substrates. Hortscience. 2017;52:1307-1312. [journal impact factor = 1.455; times cited = 27]

 

Image Credit: Psychonaught, Public domain, via Wikimedia Commons

About the author

Jason S. Lupoi, Ph.D.

Jason S. Lupoi, Ph.D.

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