Finding additives to supplement peat moss could make horticultural produce more sustainable and ensure that peat is available to use for many years, according to a professor and researcher at Assiniboine College.
“You don’t want to harvest it as a one-time media and throw it in the garbage,” said Poonam Singh of the Brandon college’s Russ Edwards School of Agriculture and Environment.
Singh noted that around 24,000 hectares of peatland has been drained for use in Canadian horticulture, with 14,000 under active extraction. Canada is now one of the largest global peat producers, sourcing the material from sphagnum moss.
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WHY IT MATTERS: Peat is one of the most established soil supplements and growth mediums that gardeners and horticultural operations use but peatland restoration can be difficult.
According to the Canadian Sphagnum Peat Moss Association, peat forms through the gradual accumulation of plant material that has undergone incomplete decomposition in waterlogged, oxygen-poor and acidic wetland environments.
It has a lot going for it as an agricultural product. Peat moss’s high water-holding capacity, natural structure and lack of pathogens make it popular as a growth medium for ornamental and food production in controlled environments.
—> READ MORE: Recovering Manitoba’s peat bogs
The material’s ability to absorb and hold 12-20 times its dry weight in water makes it valuable for managing moisture. Its capacity to enhance the soil’s ability to hold and gradually release nutrients while reducing fertilizer runoff is praised for nutrient management. Additionally, peat provides aeration through natural air spaces that encourage strong root growth and plant development. It doesn’t compact through the growing cycle, maintains low electrical conductivity and has a pH that supports plant health.
Peat’s sustainability problem
It doesn’t restore itself very quickly however, and the process of harvesting often turns odds against renewed sphagnum moss growth after the site is depleted.
“At one time, it used to take 40 years … to bring (peatland) back to its original biodiversity level,” Singh said.
Researchers like Singh are instead looking for things they can add to make harvested peat go further. That list includes compost, coconut coir or biochar, wool fibre, cattails, wood products and even insect frass and worm castings.
They’re testing how much of the peat they can substitute and which kinds of peat extenders they can blend in while maintaining peat’s effectiveness as a growth medium.
Replacing peat with even 10 to 20 per cent alternative growing media can positively impact the industry, Singh said.
“There are so many other materials that have potential.”
In particular, the research is looking at materials that are byproducts or would otherwise be wasted from other sectors.
“If there is a waste product of one industry that can be used as a growing media, what could be better than that?” Singh said.
Those substances have a high bar to clear though. Peat is a versatile, highly mixable substance due to its structure, predictable performance and low disease risk, researchers noted. This allows for specific mixes tailored to particular crops or growing conditions.
Peat additive performance
Singh’s research suggests that at least some substitution is possible without giving ground on plant health and growth. In one 2024 study using cattails, mixing the additive in low levels (between 10 and 20 per cent), supported comparable plant growth. Plant size, chlorophyll content, leaf development and root growth were all measured.
Much higher than that though, and plant growth started to slow. Singh believes that was caused by nitrogen immobilization due to microbial activity.
Currently, Singh and her team are looking at how composted cattail fibres affect the nitrogen immobilization that raw fibres caused in the first trial. She hopes that will let them increase the proportion of cattails in the mix.
