Even as 36 states and four territories have legalized marijuana for medical use, this cannabis product is still listed as a Schedule 1 drug by the U.S. Department of Law Enforcement. That means, federally, the government’s position is that marijuana has no accepted medical use and a high potential for abuse.
It’s a conflicting and confusing technicality that only means one thing: Scientific studies to learn the best methodologies for advanced cannabis cultivation have lagged in the face of a rapidly growing demand for high-quality products. Without government funding for understanding the necessary agricultural improvements for enhancing the yields of different cannabis species, the wings and prayers continue.
Still, yield increase in plants has been the topic of study by many researchers. Work on cannabis (in particular hemp varieties that are not considered a Schedule 1 drug) and other types of crops is useful for growers looking to overcome their yield gap for all kinds of cannabis. Interestingly, new research into the benefits of focusing on the rhizosphere, or the root level of the soil, is proving especially powerful for improving crop yields.
When it comes to industrial-scale productivity for high-yield cannabis, growers are looking not just for the total dry weight to increase but also for consistent cannabinoid profiles dependent on the strains they grow. Canadian researchers Rachel Backer et al. identified the following factors that contribute to cannabis yields per plant, per square meter, and per watt of lighting electricity:
- Specific strain or genetics of the cannabis
- Density of plants grown together
- Pot size
- Intensity of light, both artificial and natural
- Use of fertilization
- Addition of rhizobacteria
In terms of commercial production, most growers have already done their own research in determining which strain will offer the highest market value. They are usually well aware of their space limitations and what lighting systems work best for their individual farms.
What many in the agricultural community might not incorporate, though, are biostimulants, or products that include the bacteria that can benefit the overall health of the soil-based ecosystem where roots grow. In this cannabis cultivation guide, we’ll look at what independent science says about how soil amendments influence yields for advanced cannabis cultivation as well as improve the cannabinoid content in your plants.
The Yield Gap Quandary - Harvesting Cannabis
Throughout history, cannabis growers simply haven’t maximized their yields. There continues to be a yield gap between the current yields in commercial production and the maximum flower yield possible within a plant’s genetics. Succinctly put, this is the yield gap quandary.
The problem, again, is the lack of scientific research. David J. Potter, in his scientific review on how to cultivate cannabis, admits from the start that the inhomogeneous plant and wide range of active ingredients make studies especially challenging. Add in the many different conditions and methods that go into agricultural production, and the quandary becomes even muddier.
For example, what is the best way to define and measure yields? For some studies and growers, the most important consideration is the yield of dry flowers, as they contain the highest concentration of medicinal compounds such as CBD and THC. However, some manufacturers utilize the whole plant, including the stems and leaves, for their products.
Studies using certain cannabis strains may not translate to growing marijuana with different genetic structures. Plant variety will always demand a level of experimentation in the real world by growers interested in increasing their yields. How each plant variety and genotype react to temperature and light intensity, for example, have yet to be documented by science.
Physiological stress is another variable that needs to be addressed. Yet, replicating the realities of poor soil quality, high salinity levels, and extreme weather due to climate change isn’t easy in the confines of a laboratory.
What Science Says About How to Cultivate Cannabis
Even with the significant questions still needing to be answered to reduce the yield gap, science does have much that can be gleaned to refine how to grow large marijuana plants. This includes methods that range from growing rooms with traditional bench set-ups, aeroponics, and hydroponics.
Cannabis farmers, regardless of their growing method, can maximize the strength, resilience, and productivity of their plants by first overcoming the presumptions that there is little that can be changed.
For example, research has shown that increasing plant density will reduce yield per square meter. However, another study concluded that adding a slightly stressful condition of increased plant density and maximum temperatures could contribute to increased THC within cannabinoid development. This correlates to research that shows that increasing pot size will reduce THC per square meter, especially with some strains such as White Widow.
In terms of lights, cannabis-focused scientists discovered that artificial HPS lamps are superior to MH lamps for increasing crop yield per square meter. This is due to the fact that HPS lights emit higher levels of the yellow-red end of the light spectrum. Plants absorb this frequency within their chlorophyll and use it in the photosynthesis process.
Of course, environmental factors, including temperature and irradiance levels, also play a role in any natural marijuana plant growing kit and have yet to be fully understood.
Studies continue regarding plant growth in relation to individual plant nutrients, specifically in terms of how each nutrient reacts not only to the crop yield but also the levels of THC and CBD. Since this work cannot be done collectively on cannabis in general, research must take place on specific varieties, growing substrates, and within different phases of the growth cycle.
Still, science shows that increasing the duration of the flowering period — which can also be accomplished by reducing the vegetative period — can positively impact yields and THC levels. This is true for indica, sativa, and ruderalis cannabis plants.
What is Advancing Cannabis Cultivation Techniques?
Of course, an improved yield gap for a single season isn’t the only goal of modern farmers. They are also interested in their ability to have the highest number of growing cycles in a year — as well as support their soil for use in the following seasons.
That’s why scientists are focusing less on research with lighting, temperature, and plant density and more on biostimulants and crop responses.
Another study by Rachel Backer et al. hones in on rhizobacteria and the role of microbes for cannabis. Rhizobacteria are the beneficial bacteria that live within the soil molecules in the shallow depths of the land where roots push through in search of water and nutrients to provide for growing plants.
The microbiome of soil is the subject of a relatively new understanding, but the concept is based on both science and common sense. The greater the diversity of microorganisms within the soil structure, the healthier the environment in which cannabis plants grow. Soil that is properly moist and rich in reduced carbon can support an extensive community of microscopic critters, and those tiny bacteria (as well as viruses, fungi, bugs, and other creatures) in turn support the soil and the life it supports.
These bacteria contribute specifically to:
- Nutrient acquisition and assimilation by the root structure
- Improved soil texture
- Resilience to abiotic stress, such as drought, heat, and salinity
- Reduced need for synthetic fertilizers and other agrochemicals
As a result, rhizobacteria also work to increase crop yields for cannabis farmers no matter what substrate they use. An interesting result of this independent study is that beneficial bacteria are indeed helpful not just in soil but in all types of environments where roots grow. It is clear from the research that adding rhizobacteria, often abbreviated as PGPR for “plant-growth promoting rhizobacteria,” can make a measurable difference in stimulating crop growth.
Role of Biostimulants in Plants
The agricultural industry is as diverse as it is traditional and historic, so it is important that farmers look at research that isn’t just focused on their crop. This is especially true for cannabis, which has been the focus of limited studies due to unfounded political concerns. Thankfully, the role of biostimulants in plants has been of growing interest to many researchers.
For example, a study published in the Cambridge University Press by Mia et al. looked at the power of microbial inoculation on banana plants. This research came on the back of additional studies on biostimulant plant growth for marigolds and carnations. In these crops, the goal was to achieve flowering in a shorter time frame to reduce the time to harvest and increase the number of harvests each year. These are similar (and in some cases identical) to the goals of many professional cannabis farmers.
The most studied relationship between rhizobacteria and crops is with legumes. Scientists Oke and Long found a symbiotic connection: legumes provide the bacteria in the soils with a reduced-carbon environment while the microorganisms provide legumes with a biologically available amount of nitrogen necessary for its vitality. This give-and-take is invaluable to cannabis plants as well.
Still, as yield definitions vary among growing operations, it is also worth noting that studies regarding rhizobacteria exist specifically for cannabis as well. Looking again at Rachel Backer et al., we see that these biostimulants and plant growth regulators also show the potential of increasing cannabinoid yields.
But how do these bacteria help plants? Plant biostimulants support the environment of the root structure to give plants access to nutrients and water in novel ways. A study by Agler et al. shows that there are certain species living within the soil that are more important than others. These key players within the rhizomicrobiome help to regulate and balance the ecosystem around the roots.
In particular, the strain of Bacillus has been shown to be one of these hub species. It is commercially available in a proprietary blend with the Tribus line of products by Impello. These plant biostimulants include the following active species:
- Bacillus subtilis
- Bacillus amyloliquefaciens
- Bacillus pumilus
Unlike deficiencies in nutrients or excessive moisture conditions, there aren’t simple tests that can be performed to determine if a rhizosphere is lacking a healthy diversity in microorganisms. Instead, commercial farmers can identify overall concerns present in the plants and soil texture to recognize benefits. Actually, the reality is that the vast majority of fertile soils throughout the globe are already under stress — and microbial inoculants can be a solution for dramatic improvements.
How Microbes for Cannabis Can Close the Yield Gap
Commercial cannabis farmers can think of rhizobacteria such as Bacillus as secondary staff, working under the soil to improve the overall health of their growing substrate. Throughout the day, growing season, and off-season, this colony of microorganisms completes a number of important tasks.
Let’s take a closer look at how microbes for cannabis and plant biostimulant products make a difference in terms of crop yields and other measurable factors.
Reduce cannabis plant pathogens
Pathogens degrade the health of plants by attacking a number of fronts, and studies show that biostimulants help to defend against many. Independent research by Impello found that consistent application of Tribus Original on plants increased the stem diameter by 16%. This robustness is correlated to the inhibition of pathogen growth within the plant.
However, a strong diversity within the soil microbiome also allows the plant to build a natural resistance to harmful pathogens. This is akin to humans eating probiotic-rich yogurt every morning to improve the health of their gut microbiome. Adding “good” bacteria to the digestive tract helps to reduce future problems when “bad” bacteria is introduced through foreign foods. The same can be said for plant pathogens.
Better nutrient uptake (with a lower level of chemical fertilizers)
In the last century of farming principles, those in the agricultural industry were led to presume that if you want more nutrients in the soil for plants then the answer was simply adding them through chemical fertilization methods. In truth, that’s a marketing ploy to pressure small farmers to avoid organic best practices.
Science now shows that another effective option is to support the health of the fertile soils to increase nutrient uptake in plants. Plants require six major nutrients for growth: nitrogen, phosphorus, potassium, magnesium, sulfur, and calcium. By providing microbial inoculants as a soil amendment, farmers improve the bioavailability of these and other minerals for a measurable increase in crop yield.
Less pesticide residue on cannabis flowers
Another common problem confronted by cannabis farmers who utilize chemical additives to treat their plants is the lag time between treatment and harvest. This decreases the number of growing cycles for a season and reduces total crop yield.
Plant biostimulant products can be applied up until the day of harvest, meaning less pesticide residue on flowers while enhancing the genetics of the seed stock.
Reduced time between growth cycles
Depleted and unhealthy soil can cause major problems for any farmer. This is why growing operations that focus on food production such as corn or soy, implement a crop rotation schedule throughout the years. A monoculture of nutritional requirements will cause an imbalance within the soil’s rhizosphere, leading to a risk of pathogen and pests.
Microbial inoculants can be used throughout the year and the growth cycle, limiting downtime. Impello’s Tribus line contains three different formulas designed for specific times. Tribus Grow is best for the vegetative phase of a plant’s life, while Tribus Bloom is better applied during the flowering phase. Tribus Original can be used throughout the growth cycle of the cannabis plant.
Improved cannabis resiliency during extreme weather events
Climate change has resulted in extreme weather conditions on every corner of the globe. In the United States alone, recent events have included severe wildfires caused by persistent droughts and a destructive hurricane bringing massive deluges of rain. Rising sea levels are connected to rising salinity levels in soil, which are also at risk of erosion brought on by increased wind conditions.
Challenging weather conditions has been a constant in agricultural life since humans began farming. Research shows that supporting soil texture and structure with rhizobacteria can help growers weather the inevitable storms better.
Tips for Incorporating Rhizobacteria in Cannabis Cultivation
What is advancing cannabis cultivation techniques? The latest agricultural best practices used for the production of marijuana and hemp plants for a growing commercial recreational and medicinal market include supporting a healthy diversity of microorganisms within the soil.
However, published scientific studies on particular levels, timetables, and specific amendment protocols are lacking. Not only has funding and politics been a consistent challenge for research, but it is also difficult to replicate the ever-changing in-field conditions within a laboratory environment. The variations of growth media for cannabis, in particular, can confound many independent scientists without experience with the crop.
That’s why Impello has an internal research and development team to determine the best formulas and methods for the integration of rhizobacteria. This team includes some of the front trailblazers within the cannabis industry, including Tim Gordan, who oversaw the first hemp farm in the United States to receive USDA organic certification. These dedicated scientists work on behalf of current cannabis cultivators to create tips for how to grow large marijuana plants.
They recommend not waiting until there is an obvious issue with your soil. Preventative measures will reduce costs while maximizing crop yields for current and future productivity. That said, if you recognize tell-tale conditions such as yellowing leaves, premature bloom drop, or stunted growth, start the use of a microbial inoculant right away.
Other tips for integrating microbes for cannabis include:
Rhizobacteria tend to settle at the bottom of containers, so shake the bottle if you plan to use only a small amount on a test area. If you are adding Tribus to a large irrigation tank (100 milliliters treats 200 gallons), try to use bacteria-rich water within 24 hours.
Independent tests found that it’s almost impossible to use too much, much in the way it’s almost impossible to eat too much yogurt. Cannabis experts recommend using the product at least once a week or with every watering, especially when the plant is in the active growth phase.
Healthy, loamy soil will aerate naturally with the help of strong root systems. Mechanical tilling will not only rip small roots, but will also negatively impact the colonies of bacteria forming under the soil crust. Excessive tilling and compaction will decrease crop yields, no matter the soil amendment protocols.
While there is a growing list of benefits that researchers have discovered for adding microbial inoculants to soil, these rhizobacteria can benefit from additional soil amendments. Consider incorporating plant-based fertilizers, such as Impello’s Lumina with amino acids and polypeptides.
Science Shows Good Bacteria Increases Cannabis Crop Yields
Cannabis farmers must consider a wide range of agricultural practices when refining a growing operation. Fertilization, seeding rate, harvest time, and amendment protocols create a seasonal timeline that can cause the yield gap to either to grow or shrink.
Yet, the goal isn’t just to increase crop yields year after year. Modern farmers also want to support the Earth while producing high-quality cannabis with an effective entourage effect. Czech researcher Ethan B. Russo published research on the biochemical processes of the plant — which demand much more than what industrial hemp cultivation required years ago.
Today, advanced cannabis cultivation is all about refining and improving the growing environment for plants while maximizing the use of natural sunlight and minimizing the need for any manmade chemicals. Through modern scientific review, the use of rhizobacteria to improve the overall health and structure of soil has shown to be one of the most effective means for improving crop yields in both weight and quality.
As soil fertility declines worldwide, cannabis farmers have a unique opportunity with integrating microbial inoculants into their soil’s microbiome. They can protect and enhance their land while producing crops that offer the best presentation of each strain’s genes.
What are advanced cannabis growing techniques?
Advanced cannabis growing techniques may include but not be limited to anything that takes your grow to the next level. Techniques to boost your cannabis yields, biostimulants, topping, trimming, lollipopping, fimming, and more.
What are Biostimulants?
Biostimulants are a new type of agricultural additive product that many European experts have observed to improve plant growth and crop yields. Experts claim that biostimulants reduce the need for plant inputs, like fertilizers and pesticides, while maintaining an ideal quality and quantity of crop output. Read more about what are biostimulants.
What is the best soil for cannabis?
Any natural soil is great for growing cannabis including a mixture of loamy, clay, and more. What really matters for advanced cannabis cultivation is adding the right amendments to your natural soils to provide the proper drainage, texture, nutrient uptakes, and more. Learn more about what are soil amendments.
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