The plants produce a group of chemicals called cannabinoids. There are more than 100 different cannabinoids isolated from cannabis, exhibiting varied effects.
Tetrahydrocannabinol (THC) is the primary and main psychoactive compound. Cannabidiol (CBD) is also one of the major active cannabinoids and is considered to have a wider scope of medical applications than THC.
The production, processing and use of marijuana have been regulated in Canada by Health Canada to assure high quality and safe products for consumers.
Since the introduction of Marihuana for Medical Purposes Regulations (MMPR) in April 2014, many growers have applied but so far only one in Alberta has been issued a licence for production. Lack of good practices and lack of sanitation program have limited the application’s success.
To help Alberta greenhouse growers gain more knowledge on the production of the medicinal plant, we conducted a study, with the financial support from Alberta Crop Industry Development Fund, Alberta Innovates – Technology Futures and Alberta Greenhouse Growers Association, to develop a Best Management Practices (BMP) guide for medicinal marijuana in Alberta as a greenhouse crop using industrial hemp as a model.
STUDY LOOKED AT THREE COMMERCIAL HEMP VARIETIES
Three commercial industrial hemp varieties were grown under controlled conditions and evaluated for their morphological characteristics and CBD content (used as a quality measure of the product in this study).
Variety ‘X-59,’ having a dwarf and compact growth habit, was selected and used to evaluate the impacts of plant density, fertilizer, growth media, temperature and photoperiod on the plant growth and CBD content.
Results demonstrated that industrial hemp can be grown in the growth chamber/greenhouse as a greenhouse crop and the dwarf type hemp variety is more preferable.
Plants should be managed properly, and special requirements on the nutrients, light intensity, temperature and photoperiod should be fulfilled to gain higher yield and high quality products, along with a high content of medical components, such as CBD. Plants grown at lower density (five plants/m2) had better growth, higher yield and higher CBD than the plants grown at high density (10 plants/m2).
A supply of higher K+ in the nutrient solution at the generative growth stage can increase the bud yield and CBD content.
TWO COMMERCIAL MEDIA WERE COMPARED
Two commercial grow media, Promix and coconut coir, were compared and there were no significant differences on plant growth, yield and CBD content between treatments.
However, we found that the coconut coir needs to be pre-treated very well to adjust pH and EC levels suitable for the plant growth.
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TIMELY PHOTOPERIOD ADJUSTMENTS
Photoperiod of 18 hours light and six hours of dark per day was used in vegetative growth stage and switched to 12 hours light and12 hours dark at the five-leaf stage.
Plants had good growth at both vegetative and generative stages.
Changing the light setting too early or too late was not suitable for plant growth – the former had less vegetative growth and plants were skinning and had less vigour the rest of the time, while the latter had too much vegetative growth and didn’t set enough flower buds. It also had small, immature flower buds.
CBD content greatly varies in a hemp population. In the current study, dried materials of one plant (‘X59’) had as high as 3.94 per cent CBD. This is very encouraging because there is a high potential to successfully develop a high CBD strain through continuous selection process and vegetative propagation techniques.
Good sanitation practice throughout the entire plant growth, harvest, drying and storage phases is very important to eliminate possible mould contamination. We have tested UV light treatment to reduce mould populations of harvested products during the drying process. It was effective.
USING UV LIGHT TREATMENTS TO CONTROL MOULD AND PLANT DISEASES
In our future study, we will evaluate the UV light treatment during the growth stage to control the mould and plant diseases.
It is essential that pH and electrical conductivity (EC) levels be closely monitored during the entire growth stage. We believe that the same management techniques can be applied to the greenhouse production of medicinal marijuana.
More research is needed to develop clonal materials with high CBD contents along with genetic fingerprinting. Clonal material available in the marketplace may not have information available on the purity of strains.
It is worthwhile to mention that more research funding is required and traditional funding agencies are still reluctant to invest in this area.
Financial support: Alberta Crop Industry Development Fund, Alberta Innovates – Technology Futures and Alberta Greenhouse Growers Association
Technical assistance: Julie Bernier, Sharla Eldridge
Authors: Yang Jian, Jan Slaski, Xiujie (Susie) Li, Limin Wu – Alberta Innovates – Technology Futures, Vegreville, Alta, and Mohyuddin Mirza of the Alberta Greenhouse Growers Association, Edmonton.