Stretch Your Peat Supply
Caught short in the peat panic? Experts share tips on incorporating alternative components into your growing media to make it through the spring season.
October 15, 2011
Faced with the most dramatic peat shortage in decades, growers have been scrambling to secure their growing media supplies for the coming spring season. Despite paying higher prices, they’ve had to get their orders locked in or risk being locked out.
On Sept. 23, the Canadian Sphagnum Peat Moss Association, whose members represent 95 percent of North American peat production, announced harvests in the East were projected to be 70 to 85 percent short due to prolonged heavy rains making the bogs unharvestable. The hardest hit areas were New Brunswick and Quebec, which account for two thirds of all of Canada’s peat production. While Western Canadian provinces fared better, the West only accounts for a third of the total supply.
As we went to press, North America’s leading peat suppliers were working with customers to make sure they get their orders in. Customers who buy prepared mixes were given priority over those who buy raw peat to mix their own. When asked if alternative components would be blended into mixes to help stretch the peat supply, Chuck Buffington, who directs sales for the Flowers Pro division of Syngenta, which owns Fafard, says the mixes will stay true to what growers expect.
“We’re not going to play with formulas to save peat. We want growers to get the same formula they are used to receiving,” he says. “We do have alternative mixes with less peat and good performance on the growing end. We’ll offer alternatives to growers to help reduce peat requirements they might have. Any time you change growing media components, you get different results. We don’t take it lightly. Before we offer a new formulation, it’s tested.”
Growers can expect to pay more for media with a higher peat content, Buffington adds. “It will depend on the product. The more peat that’s used, the greater the increase will be,” Buffington says. “If you do the math, if our harvest is significantly less, we’ve got a lot of fixed costs to spread over a smaller volume, which increases our costs of production significantly.”
What if you are a grower who mixes your media and can’t place an order for straight peat moss? Substrates expert Bill Fonteno of North Carolina State University says growers are best off purchasing a mix that’s close to what they used before. “If you work with the large growing media companies and describe what you put in your mix, you can get a mix that performs in a similar fashion,” he says. “You’re better off partnering with a company on a prepared mix than trying substitutions on your own.”
Fonteno also cautions that professional grower grade and retail grade peat is not the same. “There are differences in water uptake, air, pH and nutrition,” he says. “It may look the same but it’s not the same and the results can be very different.”
Working With Wood
Wood has been getting a lot of attention as a growing media component. The nursery side of the industry is more accustomed to using bark as a growing medium than greenhouse growers. “With bark, you have to be careful because nursery and greenhouse production requirements just aren’t the same,” Fonteno says. “The particle sizes are bigger for nursery production – ¾ inch to ½ inch. Greenhouse production needs finer bark for more moisture.”
Bark also is more widely used in the South than the North because Northern growers have greater access to peat. While the classic greenhouse mix is 60 percent peat, 20 percent perlite and 20 percent vermiculite, a bark-based mix could be 35 to 40 percent bark and only 20 percent peat. “Getting growers in the North to use 40 percent bark is a big switch,” he says.
Growers who are storing bark supplies need to monitor it. “Any pile of bark can develop pH and EC issues while being stored,” Fonteno says. “The pH can drop and soluble salts increase, which can be problematic. It can become more variable. Growers should check piles at least two weeks prior to using them to be safe.”
The latest trend has been grinding and milling whole trees as a substrate. “The good news is the wood is not sawdust and doesn’t break down quickly,” Fonteno says. “If you use it as 25 to 40 percent of the total, you generally do not have problems with pH and nitrogen draw down.”
Glenn Fain at Auburn University in Alabama has been working with growers on using whole pine trees ground at the thinning stage, when the trees are 12 to 14 years old. “We use the entire tree, needles, cones, squirrel’s nest and use a hammer mill to grind it into a finer product,” Fain says. “Our focus, when we were approached by the industry, was to find a product that’s locally available. The majority of the cost is freight, getting it to the grower. But on the down side, if you choose a substance that is widely available, commercial companies are less interested in investing in production.”
The growers have found they can use the ground wood as 20 to 30 percent of their growing medium and not see a difference in the plants they are producing, but if at least half the media was wood, they would have to adjust their practices and manage nutrition differently, Fain says.
Additional experiments have been with the byproduct of cedar, which is processed into a fine material to extract oil for the fragrance industry. “The cedar company could produce 500 to 600 cubic yards a week, but once you move it a long ways, the freight becomes expensive,” Fain says. “The limiting factor is access.”
Anthony Witcher of USDA’s Agricultural Research Service’s Southern Horticultural Laboratory in Poplarville, Miss., has been evaluating wood substrates to see if they cause phytotoxicity in plants. “Initial results indicate that substrate physical properties, not phytotoxic compounds, contribute to reduced seedling development in whole pine tree substrates compared with a peat substrate,” he says. “In previous research, it has been shown that reduced nitrogen availability has led to reduced plant growth during production in wood-based substrates compared with peat-based substrates.”
But growers can use 25 to 30 percent wood fiber with minimal adjustments to current production practices, such as irrigation and fertilizer input, he says. “This is assuming the wood fiber is processed through a hammer mill to an adequate particle size and will depend on the hammer mill being used,” Witcher says. “It would be up to the individual grower to try higher proportions of wood fiber, but we have obtained acceptable plant growth in substrates composed of up to 100 percent whole pine tree.”
The ideal nitrogen form ratio to use will depend on factors such as irrigation water quality, substrate amendments and the crop being grown. “Analyze pH before and during production on a small batch prior to committing an entire crop to the new mix,” Witcher says. “Wood has an inherently greater pH than peat moss and may not require lime to increase the pH depending on the ratio of peat to wood in the mix. A starter fertilizer or slightly higher fertilizer concentration should be used to minimize nitrogen immobilization, especially in short-term crops. Incorporating wood fiber may eliminate the need for perlite in the mix, because air space usually increases with the proportion of wood fiber.”
Growing Interest & Demand
Brian Jackson of North Carolina State University, who has been researching wood substrates since 2005 at Virginia Tech, says grower interest is high in response to the peat shortage. “The number of phone calls I have received from growers, mix manufacturers and other individuals who have access to wood resources, wastes and trees has more than doubled in the past month [September] compared to average months,” he says.
They want to know:
• Who is making it?
• Can they make their own?
• What are the main problems?
• What are the costs and equipment associated with these new mixes?
• What percentage wood can be used as a supplement in mixes?
“I think as a result of the recent interest in wood-based mixes for greenhouse crops, it will be one of the main materials investigated for use to stretch peat and provide growers with the mixes they need for next spring,” Jackson says. “Addressing this problem this fall is going to be critical for our industry. If all peat companies are facing the decreased supplies like has been reported, we will need to react quickly to work on solutions before the growing season begins.”
Just as there has been a shortage of peat, wood supplies have been under pressure in some markets, too, because the federal government has been providing incentives for using wood wastes as energy sources. “The horticulture industry was unintentionally affected, since much of the bark and mulch traditionally used for horticulture is now being diverted as a source of biomass for energy purposes,” Witcher says.
Comfortable With Coir
Coir (coconut fiber or coco peat) is a media component growers have been gaining more experience with. Although it doesn’t cost less than peat, it can supplement the supply. Fonteno says growers could substitute up to half the peat component with coir to make up the soil volume.
“If the mix is 60 percent peat and you substitute up to half the peat with coir, there isn’t so much of a problem,” he explains. “If you use all coir instead of peat, the media will dry out and wet up differently. Twenty-five percent coir is a nice addition, but coir is more expensive and has handling issues in the brick form.”
Coir is a byproduct of manufacturing coconut oil. Coco fiber also is used to make rugs, doormats and ropes. Growers who use coir need to monitor salt levels because the husks are soaked in saltwater. Not all suppliers process coir the same way.
Based in Canada, with production in South America, Densu Coir soaks and washes the fiber many times to squeeze most of the salt out. “Ours arrives ready to use instead of a brick form,” Densu Coir’s Jake Kabutey says. “The cost of shipment is higher but growers can use it immediately when it arrives.”
Growers should note coir products have increased potassium, reducing that need in fertilizer. The physical properties and structure also influence porosity and water retention. Mixing 10 to 15 percent coir into a growing mix enhances wettability while a mix of 25 to 30 percent coir offers good porosity, Kabutey says. “If the mix is too dusty, it will be too wet. We develop our mix particles for 20 to 28 percent porosity, which is ideal for plants.”
Hap Hollibaugh, a specialty grower who owns Cactus Jungle in Berkely, Calif., uses coir and composted rice hulls for the organics in his mix. “To buffer, we add humic acid and grape seed pomice as needed,” he says. “Coir is a great long-lasting replacement and the rice hulls are local.”
Richard Salas of New Summerfield, Texas, says he conducted extensive trials with a Mexican coir source. “Trials were done using 100 percent coir. Callas and garden mums were done on a very large scale and I was very impressed with the outcome,” he says. “Erwinia was virtually nonexistent in the callas. Mums needed some pH adjusting (coir is 7.0) through the crop cycle, but overall, things went smoothly. I know another grower who blended coir and peat (40/60) for a geranium trial and results were very good.”