[deck]At the base of sustainability discussions lies the soil—the last frontier of agricultural environmental stewardship. Canadian researchers and industry members are tackling soil health in a variety of creative ways.[/deck]
In November of 2012, the government of Prince Edward Island, the P.E.I. Federation of Agriculture, the P.E.I. Potato Board and the Kensington North Watersheds Association all signed a memorandum of understanding with the Canadian Fertilizer Institute to further the industry’s goal of increasing environmental sustainability in the province through improved fertilizer use.
The agreement is entitled the 4R Nutrient Stewardship Memorandum of Understanding, the four R’s referring to “right source, right rate, right time, right place.” According to Gary Linkletter, chair of the P.E.I. Potato Board, CFI will supply $150,000 of funding to support education and demonstration projects largely in the Kensington North Watershed area of the province. A board will be appointed to help oversee the project during its three-year tenure. Prince Edward Island is the first province to get on board, but CFI’s 4R system is designed to be adaptable across the country.
When it comes to fertilizer, whether you put on more or less, it’s about what’s left after the crop has used what it needs. If you put on too much, the excess goes into the environment.
– Gary Linkletter
“When it comes to fertilizer, whether you put on more or less, it’s about what’s left after the crop has used what it needs. If you put on too much, the excess goes into the environment,” says Linkletter. “It’s always about tuning the fertilizer to the crop … That’s the big issue we’re trying to target.”
Linkletter believes growers have long been conscious of the need for improved fertilizer use, but there’s always room for more education. “What is required to keep the environment in a sustainable condition?” he asks. “We’re always trying to keep the environmental factor as part of our operations. I think this project will give growers a sense of the best way to do that. There are some growers who are really progressive but all of us can benefit from extra knowledge.”
The initiative is an encouraging signal that the industry is pitching together to analyze and mitigate the impact of chemical inputs on the environment over the long-term. But it’s only the tip of the iceberg. Across the industry, researchers and industry members are employing creative thinking in tackling sustainability matters.
Decreasing Phosphorous
It goes without saying that a major part of managing soil health involves the management of inputs.
Last May, the Department of Agriculture, Aquaculture and Fisheries in New Brunswick reduced its recommended phosphorous input levels as a means of reducing the risk of phosphorous runoff and leaching to tile that could negatively affect bodies of water.
“Phosphorous in acid soils as we have in eastern Canada is immobilized in a chemical complex with aluminum,” reads the department’s report. “As more and more phosphorous is added to the soil via fertilizer, manure, etc., over time phosphorous levels become excessive. Excess phosphorous in the soil may then move below plant roots to the subsoil tile water and/or as erosive runoff to surface water that may result in environmental degradation.”
Prior to changing the recommendations, different groups of researchers conducted several years of Small Replicated Plots Trials followed by On Farm Field Demonstration Trials in Quebec and New Brunswick, in which they experimented with different levels of phosphorous. Following the On Farm Field Demonstration Trials in New Brunswick, the researchers met with a group of industry representatives to get feedback on the new numbers. What came out of those meetings was a sliding scale, with maximum and minimum recommended levels of phosphorous that worked for everyone. As well, recommendations would now be based on percentage ratios of phosphorus to aluminum instead of simply parts per million of phosphorous in the soil. For example, under the old recommendations soil tests greater than 78 ppm or H+ would call for 114 kg/ha of P2O5 fertilizer, whereas a P/Al ratio of greater than 22 per cent would now call for a range from 60-80 kg/ha of P2O5.
Pat Toner, a soil management specialist with the department who worked with Crop Development Officer Daniel Savoie on the On Farm Field Demonstration-Implementation Project, says the ultimate intent of the recommendations, at least for East Coast growers, is to encourage a “build and maintain” approach to phosphorous application. “If you have a really low phosphorous-aluminum ratio, for example, you’re going to put on a higher amount of phosphorous fertilizer. That’s to meet the needs of the crop that year and build up the phosphorous in the soil for future years,” Toner explains. “When the prices of fertilizers increase, you could apply at the lower range of the recommendation to ride the year out. It saves you money and shouldn’t reduce your yield.”
Toner explains that the plant can only access phosphorous the roots can reach—in other words, the plant will never use up everything that is added to the soil. “You could put a lot of phosphorous on, but a lot of it can get lost or locked up, and [the plant is] only going to get as much phosphorous as the root can reach. The excess phosphorous does not help the plants, and could create excessive phosphorous loading’ in the soil.”
What’s at stake for the environment if too much phosphorous is added that is lost from the crop? “In P.E.I., you’ve got more intense farming, and your soils there run into sandy loam, whereas New Brunswick soils are running loams, silt loam—usually a sand erodes a lot worse,” Toner explains. “If the sand moves down and goes into a shallow water body like an estuary, and it has light penetration coming in and the tide is in, water becomes slack and stationary. The phosphorous fertilizes the algae, and you get a big flush of algae which clogs up the area. That aquatic plant growth in the water demands more oxygen leaving less for the fish life which may also lead to suffocation.”
Improving Resistance
At the Potato Research Centre in New Brunswick, Benoit Bizimungu is tackling soil health from a different angle—through breeding potato selections with improved resistance to diseases and pests. The overall reduction in the use of chemical inputs, says Bizimungu, is a major goal of the project “because we are developing eco-friendly potatoes for industry. We require a variety that relies on fewer inputs and with improved water use efficiency.”
As an example, he says, late blight is a major focus of the project due to its destructive effects, as well as the fact that the pathogen keeps changing to resist chemical protection and to overcome genetic resistance. “Our goal is to keep looking for improved disease resistance so we can help the industry offer better protection with less use of pesticides.”
In addition to attempting to breed potatoes with broad-based resistance to late blight, Bizimungu and his colleagues are looking to breed varieties with cold-induced sweetening resistance. “If you can store varieties at low temperatures, you actually provide a way to reduce storage disease incidence and reduce the use of sprout inhibitors. The problem is that most of the varieties, when stored at temperatures of less than approximately 10oC, produce sugars, which is not good when they are processed into fries or chips. We are aiming at transferring genes from wild species that confer cold-induced sweetening resistance into improved varieties, which means they will produce lower sugar levels under long-term cold storage.”
Selections are currently on trial that already exhibit such resistance. They potentially will be released through Agriculture and Agri-Food Canada’s accelerated release program this spring.
Bizimungu believes that breeding new varieties with increased resistance is a means of stewardship—both of the potatoes and the environment—in a long-term sense. “Breeding as a mission is a long-term process where we build on what has been done, to bring new traits that industry is looking at. It’s a long-term endeavour. For late blight disease resistance, for example, you’re looking at a system that is always changing, so you need to keep track of the changes in pathogen population.”
In his view, an integrated approach to sustainability, which considers all aspects of production and management systems, is the best approach. “As breeders we are glad to hear that variety choice is taken into consideration. If you are talking about trying to use less fertilizer, we know that most varieties, including Russet Burbank, are very demanding in terms of fertilizer needs. To move into using less chemical nutrients, we’d require varieties that require fewer fertilizers, have improved resistance to disease and pests, and have cold-induced sweetening resistance,” says Bizimungu.
“There are differences in terms of chemical inputs requirements,” he emphasizes.
Bio-Control
Total soil health is no longer possible, if it ever was, within any field in Canada. If potatoes are the crop of choice, they could be afflicted by a wide variety of problems that return ever year. What is possible, as Bizimungu argues, is an integrated approach to management. And a little creative thinking.
Among the many problems that cause headaches for potato growers across Canada is common scab, which renders potatoes unmarketable and causes significant crop losses each year. Common scab is caused by a naturally-occurring bacterium in the soil, Streptomyces scabies. “There are no real means to control common scab in Canada,” says Claudia Goyer, a molecular bacteriologist at the Potato Research Centre in Fredericton. “Sometimes people use fumigants, but [those are] very harsh. What we’re looking at are solutions to control it using naturally occurring soil bacteria.”
This is where the creative thinking comes in. Goyer and her team selected soil samples from both healthy and afflicted fields, selecting bacteria in the soil that were effective in controlling common scab. They screened about 40 different bacteria, selecting the best possible isolates. “Then we looked at efficiency in the greenhouse and found that they could decrease 50 per cent of common scab in the greenhouse,” she says.
More creative thinking will be needed as the team decides how to best deliver the helpful bacteria for application in the soil. They have considered a variety of options, including powder or hard-shelled beads which would release the bacteria slowly over the season. Trials will be performed next year, after which the common scab bio-control will begin the approval and registration process.
Goyer sees soil health as essential, but a difficult task facing growers, who must overcome plenty of hurdles to producing a successful crop. “The way I see that is that it’s difficult. I think the growers already do a good job, but it’s important to use simple things like longer crop rotations and being careful about how clean your potato seeds are–all the basic things are good insurance that your crop will be healthy. When you cut corners, especially for soil-borne diseases, this could increase the number of pathogens [in the soil].”
All things considered, in the effort to improve soil health for potato growers—through reduction and management of inputs, breeding resistant varieties and introducing bio-control measures—Canada is ahead of the game.
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Resistant Varieties
Common scab gives growers across the country a major headache each growing season. According to Claudia Goyer, molecular bacteriologist at the Potato Research Centre in Fredericton, there are no varieties that are completely resistant to common scab although some varieties show some tolerance to the disease. The level of tolerance also depends on the environmental conditions (dry summers are conducive to common scab) and the aggressiveness of the pathogen. “One of the easiest ways to ensure that you are having fewer problems with common scab is to ensure that you’re using a tolerant variety whenever possible,” says Goyer.
Common tolerant varieties include the following:
- Superior (table market)
- Satina (table market)
- Russet Burbanks (french fry)
- Gold Rush (french fry)
- Marcy (chipping)
- Dakota Pearl (chipping)
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