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In cannabis cultivation, the concept of crop steering has gone from agronomic obscurity to widespread adoption in a short period of time. Biological crop steering is a hot topic among indoor growers and one that is constantly evolving with continued experimentation and advances in grow room data collection.
Generally speaking, crop steering is about precision control of fertigation and environmental conditions to elicit predictable responses from the cannabis plant. But, this approach ignores the biological environment.
Microorganisms, including bacteria and fungi, play a significant role in nutrient absorption, stress response, etc. The Future of Cannabis Project tackled this concept in a recent live conversation led by Brandon Rust of Dagga Garden and Bokashi Earthworks.
Rust discussed his approach of probiotic biological crop steering to drive better outcomes. It’s a fascinating approach and well worth a deep dive.
What Is Biological Crop Steering?
Biological crop steering, according to Rust, takes the “methodology of ‘regular’ crop steering and introduces deliberate microorganisms to trigger targeted outcomes.”
Microbes encourage nutrient cycling, pathogen suppression, and exudate secretion and can improve resistance to biotic and abiotic stress factors. Often, the benefits of microbes come from their secondary metabolites, which are the products of normal bacterial or fungal biological functions.
For example, Rust has eliminated the need to fertigate with phosphorus (following initial soil formulation) because of a weekly inoculation with a probiotic mix. This routine inoculation, filled with a complex blend of microscopic lifeforms, releases sequestered phosphorus from the soil. He also uses this approach to release iron in a biologically available form.
Building a formulaic ecosystem for the microorganisms ensures less competition for the beneficial components while reducing space and nutrients for the more problematic ones.
He describes this as a “biological reactor,” which needs the right fuel for the best outputs. If you create a biological reactor within a sterile indoor system, you have the tools to produce a near-genetically perfect plant.
The Indoor Environment Conducive to Biological Crop Steering
Within an enclosed system, inputs are largely controllable, whereas the outdoor environment guarantees fluctuations thanks to the weather, seasonality, and biological pathogens. Therefore, because of this level of control, crop steering is almost exclusively a method used for indoor growers.
Rust explained how biological crop steering requires even more control over the indoor environment. It requires a sterile system. A sterile blank canvas means the cultivator can introduce precisely the elements they want, including building a perfect microbiome in the living soil or supplying specific inoculants throughout the grow.
Rust’s work may be new to cannabis, but research has begun exploring how inoculation within a sterile environment can improve other crops. In 2020, “Steering root microbiomes of a commercial horticultural crop with plant-soil feedbacks” tested soil inoculation for chrysanthemum.
While this was a less-targeted approach than Rust has developed, this research offers some insight. The study determined three outcomes:
Firstly, and unsurprisingly, the researchers discovered that inoculation altered the root microbiome composition. Secondly, it correlated to improved bacteria diversity within the root system thanks to “complex and connected microbial networks.” Finally, it also increased plant biomass.
Biological crop steering could quickly become a well-established practice for commercial cannabis cultivation with further refinement and continued experimentation.
Biological Crop Steering Still Driven by Data
Biological crop steering still relies on a comprehensive data set, as with any crop steering methodology. Traditional crop steering constantly measures electrical conductivity, pH levels, humidity, temperature, and other common environmental indicators.
For Rust, he relies on continuous soil testing. Unlike extensive post-harvest phytocannabinoid and contaminant testing, soil testing doesn’t break the bank.
Through soil testing, he can determine what macro and micronutrients are available. Then, he uses this to correlate with the inoculants he’s applied. Using this data, alongside intel gathered from crop monitoring, he can push or pull the plant’s development toward his chosen goal.
As his probiotic biological crop steering experiments continue, Rust plans to add leaf and sap testing.
Is Biological Crop Steering Possible at Scale?
Despite the perceived complexities, Rust suggests that this is the most cost-effective and straightforward cultivation method, especially for use at scale. Following soil testing, he can determine what application and inoculations are required.
Once the top dressing is prepared, it’s easy to delegate the application to employees. Even with hundreds or thousands of plants, it’s possible to use biological crop steering to guide individual cultivars toward their full genetic potential.
Taking Precision Cannabis Cultivation into the Future
The basic crop steering methodology has already dramatically improved outcomes within cannabis cultivation—better yields, better phytocannabinoid and terpenoid profiles, and ultimately just a more predictable final product.
Is the incorporation of the microbiome the next logical step? Considering the direct and measurable impacts that different bacteria, yeast, and fungi have on plant development, there is no reason why it shouldn’t be rolled into steering, alongside electrical conductivity, drybacks, and pH.
Right now, few cultivators are doing what Rust is, using biological inputs to steer plants toward their full genetic potential. His current work is paving the way for additional refinements in the commercial cultivation environment to further perfect the crop steering practice.