Fertilizers and supplements used in cannabis cultivation
What you need to know
Fertilizers and supplements are essential in any cannabis cultivation system but need to be properly managed in order to garner their full benefits while ensuring production of a safe crop.
Fertilizers and supplements can represent a risk pathway for the introduction of chemical and microbial contamination in the consumable portions of the cannabis plant and particular care should be taken to follow directions for use prescribed on the label and to use products that are compliant with the Fertilizers Act and Regulations in order to reduce potential for contamination.
Additional requirements for any additives used in the production of cannabis (including fertilizers and supplements) may be applicable under the Access to Cannabis for Medical Purposes Regulations (ACMPR), which are administered by the Office of Medical Cannabis, Health Canada. For further information please contact ACMPR-RACFM@hc-sc.gc.ca.
Fertilizers and supplements
Fertilizers refer to products that are manufactured, sold or represented for use as plant nutrients. They include:
- macronutrients: nitrogen (N), phosphorous (P), and potassium (K)
- secondary nutrients: Calcium (Ca), Sulphur (S) and Magnesium (Mg)
- micronutrients: Boron (B), Chlorine (Cl), Manganese (Mn), Iron (Fe), Zinc (Zn), Copper (Cu), and Molybdenum (Mo), which are required in smaller amounts mostly to treat a nutrient deficiency
Supplements are substances other than fertilizers that are manufactured, sold, or represented to improve the physical condition of the soil or to aid plant growth or crop yield. They include (but are not limited to) products such as microbial inoculants, signalling compounds, wetting agents and surfactants, humic and fulvic acids and composts.
Plant growth regulators
Plant growth regulators are a subset of supplements that trigger specific growth responses in plants (for example, an increase in root growth, shoot development, initiating flowering, etc.). Plant growth regulators are regulated either by the Canadian Food Inspection Agency (CFIA) or by Health Canada's Pest Management Regulatory Agency (PMRA), depending on the mode of action, use pattern and performance claims.
In general terms, products that are intended to promote growth are regulated by the CFIA and products that inhibit growth (for example delay ripening) are regulated by the PMRA. Some plant growth regulators can do both – for example auxins (a naturally occurring plant growth regulator) can kill a plant if applied in high amounts (herbicide) or promote plant growth at lower concentrations (supplement).
Specialty fertilizers are a class of fertilizers that are exempt from registration if they are recommended for use only on household plants, urban gardens, lawns or golf courses or in nurseries or greenhouses.
Fertilizer-pesticides and how they are regulated
Fertilizer-pesticides are combination products that are regulated jointly by the CFIA and the PMRA. The pesticide component is registered by the PMRA first, for use with a fertilizer, and the combination product is then registered by the CFIA under the Fertilizers Act.
Currently two fertilizer-pesticides are approved for specialty uses (including home and garden and greenhouse applications): corn gluten meal and ferrous sulphate. All other "speciality use" fertilizer-pesticides are no longer permitted for use or sale in Canada by the PMRA. Farm fertilizer-pesticides are still allowed, but are typically customer-formula products, which are exempt from registration.
Registration vs. regulation
Some fertilizers and most supplements require registration and pre-market assessment by the CFIA before being imported and sold in Canada. Section 3.1 of the Fertilizer Regulations specifically exempts certain products from registration. For additional guidance on which products require registration and which are exempt please consult: Registration Triggers for Fertilizers and Supplements.
All products that are registered under the Fertilizers Act appear on a list of registered products on the CFIA's website. The labels of registered products bear a Fertilizers Act registration number. Unlike the PMRA, the CFIA does not maintain a list of products approved for use in cannabis cultivation.
The CFIA's pre-market assessment and registration process consists of a detailed, science-based evaluation of product safety information and labelling. These assessments focus on the evaluation of hazards towards human, plant, animal health and the environment. To assess a product, the CFIA evaluates the product label (including directions for use and precautionary statements), the manufacturing method, a complete list of ingredients and source materials and results of analyses for contaminants. However, the complete list of ingredients is not mandatory in fertilizer and supplement labels.
Many products regulated under the Fertilizers Act are exempt from registration and may be imported into or sold in Canada without prior CFIA approval. However, all regulated products must still meet all the prescribed safety and labelling requirements. The CFIA conducts routine marketplace monitoring of all regulated products. This includes product inspections at the manufacturing or retail site, verification of the product's registration status, review of the label and sampling and testing for pathogens, pesticide residues and heavy metals.
Fertilizer and supplements used in the cultivation of cannabis
Cannabis, as any other crop, requires the addition of essential nutrients (fertilization) to the nutrient solution (hydroponic system) or to soil throughout the lifecycle of the plant to aid plant growth and proper development. Both deficiencies and excess nutrients can have negative impacts on crop production. Furthermore, appropriate addition of plant growth supplements (for example plant growth regulators) can also modulate the production of metabolites such as the Tetrahydrocannabinol (THC).
Health risks associated with using fertilizers
Some fertilizers and supplements may present physical hazards (such as combustible dusts) and health hazards (such as toxicity, corrosiveness or irritation) to the handler/applicator or by-stander. This information, as well as the proper Personal Protective Equipment required for manipulation of the product, will be shown on product labels.
In addition to worker/by-stander hazards of exposure, fertilizers contaminated with pathogens, heavy metals, dioxins and furans or pesticides may pose risks of contamination of the final product (cannabis plant) irrespective of the mode of application (foliar versus growing media solution).
Cannabis plants are hyper-accumulators of metals and will take up heavy metal contaminants present in the nutrients solution either via the root system or foliage above the level they need to grow. For this reason, it is especially important that cannabis growers ensure that any products they use meet the CFIA standards for heavy metals and other contaminants.
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