Most cannabis information available today is based on observations made by underground growers during repeated production cycles over the course of the past several decades. Indeed, prohibition has stifled cannabis research for most of the 20th century. In the near future, however, there will be many legitimate cultivation studies as legalization and legitimacy often come with the ability to scientifically research and examine all aspects of cannabis cultivation practices.
Until those studies are published and shared across academic and cultivation channels, cannabis cultivators are left with dozens of questions, including: Are there other, more productive growing methodologies than what I am currently using? Are there cultivation methods that enhance production of certain cannabinoids or terpenes? Which input has the biggest positive impact on yields and cannabinoid production?
Given the many variables under a cultivator’s influence, it’s good to question your practices today so that you remain ahead of the technology curve tomorrow. Here are six areas in which more information will spur further questions and better solutions.
1. Lighting:
Do we know exactly what light level and spectrum each cultivar prefers in each stage of production?
Is it a fixed spectrum, such as a blue-dominant spectrum in vegetative growth and a red-dominant spectrum in flowering stages, as is commonly believed and accepted as fact by some? Or is it possible the plant prefers a roving spectrum throughout a daylight period so that all spectrums are available throughout the day? Or is it best to mimic nature and utilize blue and red spectrums as many currently do? Conversely, is there a preferred targeted application that yields superior results? Is there a perfect spectrum for every stage of growth? These are the types of questions academic studies and white papers can and should answer.
2. Precise nutrient application and utilization:
I have witnessed clones taken from the same mother plants inexplicably outperform all others clones around it under similar environmental conditions and lighting, and in the same growing media and amendments. The only hypothesis I could drum up was that the plant received exactly what it wanted exactly when it wanted it, whatever “it” is.
Today, reports on nutrient applications are starting to hit the mainstream cannabis market (including in Cannabis Business Times’ “Nutrient Matters” series by researchers at North Carolina State University (NCSU)). These first studies are looking at the low-hanging fruit of cannabis nutrition, namely: What are the specific nutritional requirements of a cannabis plant in each growth stage? Many growers might intuitively know this, but it does not take away from the importance of such studies leading us to a deeper understanding of how this plant works.
Indeed, projects like the NCSU research could help growers determine if we sometimes apply fertilizers or amendments that are not utilized by the plant during specific stages. If it can be shown that cannabis plants only use/absorb/feed on certain elements at certain life stages and completely ignore anything that is not needed, growers can develop more efficient and precise nutrient application systems and methods, which is both environmentally and financially responsible. Deeper analysis into nutrient needs of cannabis plants also might reveal systems, nutrient formulations or amendments that accentuate or accelerate the production of biomass or desirable compounds.
3. pH fluctuation:
Traditionally, cannabis growers prefer a pH range of 5.8 to 6.8. Many choose 6.2 to 6.4, as within this range, they are likely to get most, if not all, of the desired nitrogen, potassium and phosphorus (NPK) minerals, as well as many other essential elements required for healthy plant growth. By raising or lowering the pH of a nutrient solution, it raises or lowers the availability of the required elements.
Is a plant receiving the desired amounts of elements at proper levels when employing this method? Or would it be best to fluctuate the pH? Put differently, would a slight variation in pH from one watering cycle to another improve health, growth and cannabinoid production? If you had a watering cycle that watered plants two to four times a day depending on methods and media, the first application of the day could have a pH of 5.8. The second application could be 6.2, the third could be 6.4 and the fourth could be set at 6.8. Would fluctuating the pH during watering ensure that all NPK elements are fully available throughout the watering cycle? Or would that be ineffective?
4. Temperature fluctuation:
Traditionally, indoor cannabis is produced in a very controlled environment where high and low temperatures are set and closely monitored. Outdoor plants, for their part, are subject to the whims of nature, resulting in wide-ranging daily and seasonal swings in environmental conditions, especially temperature. Outdoor cannabis plants typically flower in late fall, when temperatures are cooler. (Daily light interval (DLI) determines when a cannabis plant will flower, not temperature, but that is not the focus here.)
But what temperature range is best? Should you maintain constant set point temperatures? Or maybe allow for outside temperature fluctuation influences to dictate temperatures to some degree? Not too extreme, but perhaps you should set cooler temperatures in flowering stages and night cycles to mimic daily and seasonal temperature shifts.
Which temperatures are best for cannabinoid production and terpene preservation while maintaining proper humidity and vapor pressure deficit parameters? Cooler temperatures lend themselves to terpene preservation as terpenes evaporate at higher temperatures, yet most cannabis cultivars’ yields suffer if cultivated in cooler environments. There is an obvious balance between healthy and vigorous plants that yield well, produced in warm environments, and plants produced in cold/cooler environments with a primarily focus on terpene production and/or terpene preservation. What temperature is best for compound production and preservation? And what are the parameters?
5. Ethylene Gas:
Besides the factors listed above, there are many influences to investigate that have been utilized for decades by modern agriculture in a multitude of applications. For instance, ethylene gas is utilized to accelerate the maturation of fruits and flowers in some cases. I have seen a grower who used an ethylene gas buildup during the last days of flowering to cause a majority of a plant’s large fan leaves to dry up and fall off, without compromising the product’s quality. Would it be possible to mature cannabis early without compromise of yield, desirable compounds, or quality at scale by elevating ethylene levels?
6. UVB light spectrum levels for THC production:
Millions of dollars already have been spent investigating this one influence. Yet, even when compiled, the resulting studies and research are conflicting. Most published papers indicate there is a significant benefit to using UVB lighting to increase THC production, while investigations by others indicate very little impact.
Other questions remain: How much UVB light spectrum does a cannabis plant prefer? How much is too much? Can UVB have a positive influence on yield? Does UVB aid in control of contaminants such as powdery mildew?
But Wait, There’s More
Many other areas of cannabis production need further investigation. The cannabis plant is responsive to many influences, such as organic natural enzymes like seaweed and other organic inputs.
Plant hormones are another potential production influence that merits further research. Gibberellins are a group of plant hormones that stimulate stem elongation, germination and flowering. Auxin is another plant hormone that is produced in the stem tip and promotes cell elongation and inhibits growth of lateral buds.
All of this is to point out that we don’t know what we don’t know, and I believe a lot of facts about cannabis cultivation and commercial production have yet to be truly established. So, avoid sticking to your guns unless you have research as ammo.
