Michael Esposito with MCR Labs
In commercial cannabis, most successful operators try to carefully balance yield, quality, and expenses. One common mistake growers make is assuming they will perform optimally by placing as many plants as possible in a given space and feeding them the strongest nutrient blends they can manage without causing toxicity in their plants. They may also provide additional CO2 within their grow rooms with the understanding that available carbon fixed via photosynthesis directly translates to an improved yield. While it is true that optimizing bench spacing, feeding, and auxiliary CO2 within a grow can generate the best quality and yield, there are diminishing returns to all of these factors which can end up reducing a grow’s profitability over time if careful consideration is not taken into account.
While there is not a large body of literature on optimized cannabis production currently, studies carried out on other similar crops over the years can be used to help us elucidate the best practices for maximizing profitability in a cannabis cultivation operation. ICP-MS analysis of plant tissues can guide us towards ideal fertilization practices, studies of impacts of CO2 on model plants as well as general microscopy can guide our usage of supplemental CO2, and large scale studies on impacts of spacing and light can work in conjunction with basic understandings of plant physiology to allow us to determine the correct amount of plants per bench for optimal yield and quality.
Studies carried out on cannabis, hemp, and crops similar to cannabis and hemp allow us to elucidate best practices for use in large scale cultivation operations.
While most agricultural testing labs are unable to test cannabis material, some licensed laboratories within certain states can now provide accurate nutritional analysis results via ICP-MS. This allows cultivators to customize feed programs to both optimize plant health and maximize profit by cutting expenditures on excess fertilizers that plants otherwise would not fully utilize. Nutrient analysis also provides opportunities for growers to implement their own trend analysis, allowing them to catch problems in their plants before symptoms arise.
With regards to CO2 stress at both excessively high and inhibitory low levels of ambient CO2, there is a clear response in leaf physiology across most plants. Studies of excessive CO2 exposure in plants are carried out with increasing frequency as environmental CO2 levels continue to rise, allowing for more data on plant responses to elevated atmospheric carbon to be generated at an increasing rate as researchers and the broader agrisphere express concern over rapid climate change. At the moment, growers can look at the utilization of their supplemental CO2 by monitoring ppm within their grow room to see if plants reduce the excess down to ambient levels. Additionally, growers can use simple microscopes to quantify the amount of stomata present on the leaf surface of their crops to identify if stomatal density may be negatively affected by their supplemental CO2 levels.
Lastly, impacts of shading – both positive and negative – have been studied across a wide range of ornamental and agricultural crop commodities for decades. Some basic concepts of botany allow us to understand how the majority of plants respond to light stimuli. While there is no known “optimal spacing” across the broad range of varying cannabis cultivars, through experimentation and trial-and-error cultivators can begin to better understand their crops and each individual cultivar’s spacing requirements for optimal flower and secondary metabolite yields. With the knowledge of shading impacts on plant yield and secondary metabolite production, cultivators may find they actually increase their yield and potencies by placing less plants on each bench, allowing light to penetrate deeper into the canopy with each harvest.
- Imo, Moses. (2011). Analysis of nutrient interactions in cropping systems.
- Landis, Hunter & Hicks, Kristin & Cockson, Paul & Henry, Josh & Smith, James & Whipker, Brian. (2019). Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol-Hemp. cftm. 5. 10.2134/cftm2018.09.0081.
- Li, Yuanyuan & Xu, Jiajia & Haq, Noor Ul & Zhang, Hui & Zhu, Xin-Guang. (2014). Was low CO2 a driving force of C4 evolution: Arabidopsis responses to long-term low CO2 stress. Journal of experimental botany. 65. 10.1093/jxb/eru193.
- Thakur, Meenakshi & Bhatt, Vinod & Kumar, Rakesh. (2019). Effect of shade level and mulch type on growth, yield and essential oil composition of damask rose (Rosa damascena Mill.) under mid hill conditions of Western Himalayas. PLOS ONE. 14. e0214672. 10.1371/journal.pone.0214672.