A Scientific Approach Comparing Growing Substrates for Cannabis

A Scientific Approach Comparing Growing Substrates for Cannabis
Professor DeBacco
Research Article
Nemati, R., Fortin, J. P., Craig, J., & Donald, S. (2021). Growing mediums for medical cannabis production in North America. Agronomy, 11(7), 1366.
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What Growers Typically Look For..
High porosity
Fast draining
Maintains moderate water content between irrigations
Quick dry downs to reduce the risk of root pathogens
Well-balanced physical and chemical properties
High consistency
Free of weeds and pathogens
Main Categories
Rockwool
Phenolic Foam
Peat Based
Coir Based
Living Soils
Rockwool Overview
Rockwool is made from basalt rocks or other minerals which are liquefied at high temperature and then spun into fibers that can then be made into different sizes and shapes such as : blocks, cubes and slabs.
It can hold more nutrient solution and air than any other growing medium.
Rockwool…
Lightweight inert soilless substrate
Provides moderate to good aeration
Excellent water holding capacity
Low CEC (Nutrient retention)
Easy to handle and use
Homogeneous
Durable
Pathogen free
*However, microbial life does develop in rockwool during the growth cycle of plants.
Phenolic Foam
Relatively new sterile soilless substrate that comes in a range of sizes
Phenolic Foam has…
Consistent texture
Excellent aeration
Moderate to low water holding capacity
Superior drainage
Helps keep the top surface drier, limiting algae growth
Peat Moss
Peat moss has a high buffering capacity for water, pH and nutrients.
It is acidic, hydrophobic and low in nutrients.
Additives are incorporated to make it suitable for growing plants.
Peat has a spongy structure without lignified fiber.
Lignified fibrous material may originate from other species growing on the peat bog if any.
Coir Properties
Various particle sizes from fine dust to large chunks
Hold high volumes of water
Hydrophilic properties
Tough structure
Excellent wettability and can rewet easily
*Reducing the need for wetting agents.
Slow breakdown rate and therefore
does not shrink during production cycle
High aeration and drainage
*Can depends on particle size distribution.
Living Soils
The living soil category has no defined standards.
It can be as simple as incorporating a microbial inoculant into a growing media but it can be much more complex
The living soil matrix must support microbial populations
Biodiversity is important to maintain a balance between mineralization, plant protection and biostimulation.
The basic components of living soils are peat moss, coir pith, coir chunks, naturally aged bark, wood fiber, composts and natural additives.
A variety of inoculants can also be used in living soils: compost, bacterial inoculants, mycorrhizae and actinomyces to name a few.
“Best” Growing Substrate
It is not easy to suggest what is the best growing medium for cannabis production.
Each category of growing medium has its strengths and weaknesses and choosing any of these categories depends a lot on the growing technique and production system.
Many factors have to be taken into account when selecting a growing substrate.
Overall, coir-based products are the intermediate substrates showing more advantages and less weakness
Expandable coir bags allow for minimal storage space, sterile starting conditions and a supportive growing substrate.
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