Tenuta is a tenured soil ecology professor at the University of Manitoba, currently serving as the senior industrial chair in 4R nutrient management. He’s a research scientist, the kind of academic you might expect to find working in a lab, dressed in a white coat. But Tenuta is out of the lab every chance he gets, making sure his research is focused on farmers’ real-world problems and making sure new research results are accessible to the industry.

This is not a typical career for someone who grew up in the Toronto suburb of Brampton. How did Tenuta get from a botany student in downtown Toronto to a Brandon crop show soil pit? And why does he care about western Canadian farmers?

It started at home

Tenuta’s parents immigrated to Canada from rural southern Italy in the 1950s. Growing their own vegetables and fruit and even slaughtering goats, chicken and rabbits was the normal way of life.

“Self-sufficiency was a big component of surviving, historically, for the people there. When they came to Canada,” he says, “they brought a bit of a time capsule with them.”

This included growing their own food.

“If we weren’t growing it, we were buying it directly from a farmer, like chickens or rabbits or goats.” The Tenuta family had a dedicated insulated cellar in the basement to store wine, cold cuts and other preserves — the cantina, in Italian. A fig tree grew outside in a greenhouse, and there were plants throughout the house.

Tenuta was taken with botany. “As soon as I learned about photosynthesis, I said ‘Oh, that’s the coolest!’ I was disappointed I wasn’t born a plant when I heard that they make their own energy.”

And then there was the grass.

“My dad would go every year and get poultry manure from a farmer, and spread it on the lawn,” Tenuta says. “My dad knew that chicken manure was the best fertilizer.”

Later, Tenuta would learn that this is because chicken manure contains nitrogen and phosphorus. At the time, he was more concerned about how the manure would smell after rain.

“I’d be pretty embarrassed walking home from school. I could smell the house from half a mile away.”

With this background, nutrient management is an obvious fit for Tenuta. Even if he did start his academic career in downtown Toronto.

Getting out of the city

As an undergraduate in Toronto, Tenuta spent a lot of time outside the city. “I loved plants, so every weekend I’d go off and take my guidebooks and identify plants.”

Soon, many of his university projects were focused on the ground the plants grow in. Like many students, Tenuta was influenced by a professor who saw his potential. For Tenuta, this was ecologist Dr. Tom Hutchinson. Hutchinson spotted Tenuta’s interest in plants and encouraged his soil-based projects. Tenuta showed more drive than many undergraduate students, driving from Toronto to Guelph to read the latest research journals. (Research relied much more on location in those pre-internet days of the early 1980s.)

As he was finishing his first degree, Tenuta got a summer research job in Churchill, Man., studying goose poop and nitrogen mineralization. The experience left him hooked on learning about soil health.

“I was in the middle of nowhere with test tubes, soil and goose poop samples. It was wonderful.”

It was when he began studying at the University of Guelph that he really had a chance to “dig in” to soil science. Guelph was also where he realized how much he had to learn. Not just the chemistry, biology and physics of soil science, but also Ontario agriculture.

“I would spend weekends at farm shows,” he says. Tenuta’s brother, Albert Tenuta, is a plant pathologist in Ontario. When Tenuta landed in Guelph, Albert was already working at the Ontario Ministry of Agriculture, Food and Rural Affairs. When Albert and his colleagues put on conferences or workshops, Tenuta says, “I would just show up and learn.”

This willingness to delve into a new environment, to listen, and to ask questions, is the trait that’s served Tenuta well throughout his career, and it’s what makes his work useful for farmers and the agriculture industry.

Becoming an agronomist

Instead of talking about the day he graduated with a masters’ degree from the University of Guelph, or the day he finished his PhD thesis at Western University, Tenuta is proud of the day he became an unofficial agronomist — a professional who could offer farmers practical, useful advice.

That day came when a professor he greatly admired, the late soil scientist Dr. Eric Beauchamp at the University of Guelph, was working on a problem for a local farmer. Beauchamp brought Tenuta in to help find a solution. “He said, ‘We’re agronomists. Let’s think about this.’”

This was the first time anyone referred to Tenuta as an agronomist, someone who could bring useful skills to a real-life farm problem.

“It was a little thing, but it was really massive in terms of helping me create some confidence.”

One opportunity led to another, and soon Tenuta found himself with a PhD learning how nitrogen and amendments can control potato pathogens. Then immediately afterwards he was off to the University of California, Davis for a post-doctoral fellowship. He was studying nematodes as indicators of soil health and learning about California agriculture.

Near the end of his contract, the University of Manitoba happened to have an opening in their soil science department, so he flew to Winnipeg for an interview.

“I had all intentions to go back to California. I was loving it there.” There was funding to extend his research contract, and the weather was definitely better just west of Sacramento.

But Tenuta liked his trip to Winnipeg. He liked the people he would be working with (“there didn’t seem to be any infighting”), and, given the importance of agriculture to Manitoba’s economy, he saw that research work on soil health in Manitoba had the potential to be especially useful.

Back to square one

When he moved to Winnipeg in 2002, Tenuta had strong academic and research credentials, but, once again, very little knowledge of the local agriculture industry. He needed to learn about prairie crop production, including the details of farm machinery and the business aspects of grain farming.

Tenuta was lucky to land in an office down the hall from well-known soil scientist Don Flaten. “He was my sounding board.”

Flaten was welcoming and encouraging; Tenuta was never afraid to go to Flaten’s office with questions like, “What’s a mid-row bander?”

As well as talking to Flaten, Tenuta also sought out the people he wanted to help: farmers.

Prairie farmers are lucky to have access to several academic research scientists who take time to understand how their research connects to real-world production practices. When researchers understand the pressures farmers face and how farmers balance multiple factors to make decisions, they are better equipped to design research projects that solve farmers’ problems and communicate solutions so they can be used in the field.

“Sometimes there’s an expectation that you’re a researcher, you’re a professor, you know it all already,” Tenuta says. We’ve all seen someone in a position of authority who’s afraid to admit they don’t know something. But Tenuta would never try that. “Especially not in a room full of farmers!”

Throughout his career Tenuta has made time to learn directly from farmers, as well as searching out information everywhere from podcasts to print magazines.

His form of learning is a two-way street. “I love it when people ask questions, because that challenges me, and it’s me scratching my head. And that also leads to new questions to ask. If somebody’s asking something, that means there’s a knowledge gap. And that means there’s a need.”

Tenuta tries to focus his research where it will be useful. Farmers coming forward with similar questions, or bringing requests through commodity associations, helps Tenuta identify research needs. When farmers push producer-run commodity groups to invest farmers’ money in specific areas, it’s easier for researchers like Tenuta to attract matching provincial and federal government funding to work on the problem.

When government staff realize “somebody cares about this research,” Tenuta says, “they’re willing to sponsor a portion of it.”

Dual roles

When they’re successful, scientists like Tenuta are balancing two extremely different roles: as communicators providing practical information to the agriculture industry, and as academics in the world of teaching, lab work and research publications.

“We’re servicing a sector, an economic sector — agriculture and industry. And at the same time, we’re in an institution of higher learning and we’re fostering knowledge creation and training students.”

Choosing the right research projects is key to making this work.

“We’re always trying to find something that’s fundamentally interesting and new in terms of knowledge.” That’s the academic side — university researchers are expected to break new ground.

But to also be a good communicator, and useful to the industry, the work must be relevant. “There’s the commodity and farmer route.

“It’s kind of like having feet in two different areas and bridging them.”

Tenuta believes the foundation for success in both these roles is to keep learning.

When Tenuta goes to his campus office he tells his kids and wife, “I’m going to school.” They make fun of him, he says. His 15- and 12-year-old children are still at the age when the idea of one day leaving school seems exciting.

But not for Tenuta.

“I’m still in school. I’ve never left school.”

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Glacier FarmMedia GrowPro and Grainews present a webinar on managing nitrogen rates for better efficiency, featuring speaker Dr. Mario Tenuta, host Laura Rance-Unger, vice president of content for Glacier FarmMedia and moderator Kari Belanger, editor of Grainews.

Many farmers are modifying nitrogen timing, placement and product. But if they are not varying their rate, they are not achieving the full economic efficiency and environmental sustainability potential of 4R nutrient management. Dr. Tenuta will discuss ways farmers and agronomists can take nutrient stewardship to the next level .

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Tillage causes physical disruption to soil organisms, especially larger ones like earthworms, and those that have large networks like fungi. “Tillage can physically destroy the networks of hyphae (long, thread like filaments) that fungi create, and for the larger bodied organisms like earthworms tillage could cause death due to crushing, removal of their tunnels and burrows, and so on,” says Dr. Mario Tenuta, professor of applied ecology at the University of Manitoba. “The other thing that tillage does is redistribute materials, and that’s one of the reasons why farmers do till, to mix in surface crop residue below the surface. Once residue is in contact with the soil, it’s also in contact with active soil organisms, which can speed up decomposition of the material.”

Disrupting fungal networks limits P

But the most critical issue from a plant productivity and crop production standpoint is the effect of tillage on the networks of mycorrhizae fungi, which relay nutrients and compounds to plants. “Primarily for crop plants, the network transfers phosphorus to plants, which allows them to photosynthesize for better yields and feed the fungi to keep that network surviving and active,” says Tenuta.

“Tillage breaks the network, which has to be completely re-synthesized and that requires a re-deployment of the whole network,” says Tenuta. “The reconstruction process will take energy from the fungus, and that takes energy away from the process of acquiring phosphorus and translocating it to the plant, because the fungi are trying to repair itself instead. It’s a loss of efficiency for the fungus and the plant.”

Because commonly, farmers till in the fall after harvest and/or the spring before the crop is planted, there is a delay in re-establishing the fungal network. “The early season uptake of nutrients for a crop can be compromised because of that,” says Tenuta. “In that period of time where it’s getting rebuilt, it’s not as efficient in transferring the phosphorus and that can be a big thing for a plant or a crop because it’s often the early season uptake of phosphorus that is really critical for plant establishment and growth.”

Farmers can’t compensate by simply putting on more phosphorus fertilizer. “Farmers can do a couple of things, they can increase soil test phosphorus, or the background level of phosphorus that’s available for plants, but researchers have found that even if they do that, some crops highly dependent on mycorrhizal fungi such as flax, are still compromised for early treatment P uptake,” says Tenuta.

“To get over that negative hit on the mycorrhizal fungus, and its inability to help with phosphorus acquisition, it’s necessary to add phosphorus in and/or near the seed row in a band, not just broadcasting it, so that the phosphorus is more available to the emerging seedling in the early spring. It makes things more complicated, and more input intensive and expensive in management of the phosphorus.”

As well, there is a limit to the amount of phosphorus that can safely be placed with the seed in the furrow without causing seedling injury. The safe amount of in-row phosphorus is well documented and available on provincial websites. Safe levels depend on the soil type, the crop, the source of phosphorus and moisture. Tenuta recommends farmers band phosphorus to the side of the seed-row if unsure of safe in-row limits.

Wet soils tempt tillage

The good news is that the fungal networks do rebuild themselves within a year, but not necessarily fast enough to make a different to the new crop. “If a farmer has done a fall and spring tillage, then plants a crop like wheat or corn, if we compared it to a no-till crop, early on in the season there would be more presence of fungi in the roots of the plants in the no-till situation,” says Tenuta.

“If we went back later in the growing season, colonization of the roots by the fungi would be about the same. They will rebuild the network but it’s delayed, and eventually it’ll catch up and establish with the crop. However, it may not be as efficient later in the season. A lot of our crops need phosphorus earlier on in the season so that’s the problem. If it catches up later on it might be too late.”

Rarely do no-till farmers use tillage unless they have a major issue that is hampering their ability to achieve their yield potential. But do the costs in terms of losing the benefits provided by soil organisms outweigh the benefit of a tillage operation in these cases?

“Often there is a problem related to establishing the crop, in getting a stand emergence that’s decent to get good yields, so if there is something that is near catastrophic happening in their situation, that’s compromising their yield, they are playing a balancing act,” says Tenuta. “That balancing act is, they may compromise their early phosphorus acquisition by doing tillage, but they may not get a decent crop unless they do till. They may be able to compensate with good phosphorus management but it becomes a pragmatic decision for the grower in terms of doing tillage.”

If producers really want to try and get moisture levels down in their soil and decide to till, they need to think carefully about their phosphorus needs, says Tenuta, especially in crops that are very sensitive to early-season phosphorus that require mycorrhizae. “If they have a crop like flax, corn or sunflower that requires early-season phos­phorus and are very mycorrhizal dependent, I would really recommend them to think about making sure they have good phosphorus as a band when they plant,” he adds.

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It was about -20 C in Weyburn the day of the IHARF seminar. “A day like today, you actually wouldn’t mind if it was a few degrees warmer,” Tenuta said. Whether or not we would like a little more heat in Saskatchewan in February, Canada has made some international commitments to reduce our greenhouse gas (GHG) emissions. Our federal government has committed to lowering emissions to 30 per cent below 2005 levels by 2030.

Canada has set and missed targets like this before. However, with a new Liberal government that’s already announced a carbon tax, this time may be different.

Tenuta came to explain to the IHARF audience how environmental policy changes might impact Prairie agriculture.

Agriculture and GHG

“Agriculture makes up about eight per cent of the GHG emissions in Canada,” Tenuta said. This doesn’t include carbon dioxide emissions from our use of fuel (diesel, gasoline or natural gas). It also doesn’t include any carbon sequestered in the soil. This is based on definitions set out by the Intergovernmental Panel on Climate Change.

The federal government also calculates emissions by “economic sector” based on some different definitions. When economists adjust the numbers this way, “if we include emissions from transportation, from your tractor, pesticides, and so forth, it now jumps up to 10 per cent, in terms of all agricultural activity,” Tenuta said.

For policy-makers looking for ways to reduce Canadian emissions, a sector contributing 10 per cent of the total makes a nice target.

Information about agriculture’s GHG emissions is available on the Agriculture and Agri-Food Canada website. AAFC lists out the three main gases emitted by agriculture:

• Carbon dioxide (CO2), which is released during soil cultivation;
• Methane (CH4), which is associated with cattle and livestock manure; and,
• Nitrous oxide (N2O), which comes from using fertilizer and manure.

According to the AAFC website, to add up emissions of the three gasses, you need to convert everything to CO2 equivalents. A tonne of N2O is equivalent to 298 tonnes of CO2. This is because N2O is a lot more effective at trapping heat.

Carbon dioxide released during cultivation, Tenuta explained, hasn’t changed much since 2005. The other two components make up a much larger component of our emissions. “When you hear about imposing potential changes in agriculture, they’re actually focused on methane and nitrous oxide emissions.”

Tenuta said government policy will likely focus on two areas: reducing methane in cattle and dairy production, and the use of nitrogen in food production.

Tenuta focused his talk on how nitrogen use might be impacted by future policy rather than the methane aspect — presumably because he is a soil scientist, and most of the IHARF participants were grain and oilseed farmers.

What about carbon credits?

Before he moved on to talk about nitrogen use, Tenuta paused to talk about carbon credits.

He pointed out that if you’ve been zero tilling since 2005, you haven’t changed your emissions. Your carbon was captured before the benchmark year, so you have minimal arguments for getting a credit.

Some participants asked about getting credit for increasing yields, or sequestering carbon in straw. Tenuta said, “the wheat or the canola eventually gets decomposed back to CO2. It never gets sequestered.”

Right now, he said, no international agreement includes carbon sequestration. While Canada might push to include it, Tenuta described the situation as a “hot potato.” Canadian carbon emissions from the forestry sector fluctuate widely from year to year — driven by forest fires. Including forest fire emissions in our GHG commitment would make it difficult for Canada to meet targets.

“At a political level, Canada probably will give you carbon credits, to make sure you’re happy,” Tenuta speculated, “but that doesn’t have a bearing on international obligations.”

Tenuta is not a fan of carbon credits for sequestration. If you come out of zero till, “you quickly will lose your carbon as you disrupt the soil.” If you make a management decision to till to control weeds or deal with moisture, “does that mean somebody has to give back that carbon credit?”

Tenuta believes grain farmers can make the most progress toward lowering GHG emissions by lowering emissions from nitrous oxide.

Nitrous oxide emissions

We’re emitting nitrous oxide when we use nitrogen as fertilizer.

At a long-term farm site south of Winnipeg, the University of Manitoba monitors GHG emissions. (Tenuta says very few places in the world do this.) Every time they apply fertilizer to grow crops on the site, they can measure N2O emissions from the land. When they grow crops that biologically fix nitrogen (like soybeans), they can’t measure any N2O emissions.

“This is our conundrum: we need nitrogen fertilizer to produce most of our crops,” Tenuta said.

What could this cost?

The Trudeau government has announced a tax on carbon of $30 per tonne by 2018 and $50 per tonne by 2022.

Tenuta has estimated the potential costs of various levels of a carbon tax on fertilizer use. He’s considered two components: first, a charge to farmers for the emissions caused by using nitrogen fertilizer; also, a charge to fertilizer manufacturers for emissions from making the product.

Because fertilizer prices fluctuate so much, Tenuta expects a potential tax on fertilizer manufacturer (which would likely be passed on to farmers), to be the less distressing component.

“Don’t so much worry about the carbon tax on the manufacturer’s end, what you need to worry about is, eventually, a potential carbon tax on using the fertilizer on your soil.”

It’s not impossible to imagine a tax on GHGs emitted through nitrogen use. Tenuta has estimated the potential costs.

To do this math, Tenuta assumed:

• Two per cent of applied nitrogen is emitted as N2O;
• Application rates of 100 kg of N/hectare, (about 89 pounds per acre).

After calculating estimated emissions and converting the carbon tax to N2O equivalents, he’s calculated that a tax could reach $57.39 per hectare ($19.08 per acre) with a $50 carbon tax. (If you’re trying to do the math at home, Tenuta assumes we’re emitting 0.002 tonnes of N per hectare. He converts that to the N2O equivalent, then to the CO2 equivalent. Then he multiplies that by the per tonne price of the tax. I’ve converted his results to dollars per acre.)

Tenuta estimates that a $30 per tonne level of carbon tax is equivalent to a tax of $11.45 per acre on fertilizer use, and $2.49* per acre on fertilizer manufacture.

“My objective as a researcher/professor is to help you adjust so we never have to get to this point of being charged for emissions. That’s my goal, is to help you avoid that.”

If the government sees the agriculture sector reducing emissions, Tenuta speculated, a tax like this may never be implemented — the government wouldn’t see a need to use a tax to influence our behavior. “Voluntarily, let’s use the 4Rs: right rate, source, placement and timing.”

As well as general stewardship, Tenuta recommended using stabilized nitrogen and controlled release nitrogen products to reduce emissions. “In general we find the nitrification inhibitors and ESN reduce emissions by about a third,” he said.

“We have new technology. And 20 years from now you’re going to have even fancier fertilizer.”

Didn’t go over well

Of course there were a lot of comments, most of them not too happy.

One farmer asked how we can possibly pass these taxes on to consumers. Tenuta said farmers will find a way to stay profitable, and once there’s an opportunity in the form a carbon tax, companies will invest to develop new products along the lines of stabilized nitrogen to help farmers reduce emissions.

“I don’t think there’s doom and gloom,” he said.

“You’re not farming the way you did 25 years ago. It’s going to change.”

It already has. Tenuta has done the math. “Every year we use more fertilizer.” Over the last two decades, fertilizer use has increased by about one to 1.5 pounds per year acre for major field crops.

We can’t keep increasing our nitrogen use and also lower emissions. “Our immediate challenge as farmers and an industry is to produce more food with the same amount of nitrogen or less. Nitrogen use efficiency in our system has to improve.”

Nobody likes a tax, especially not a tax that could damage our ability to compete internationally, and can’t be passed on to our buyers.

Tenuta didn’t expect the crowd to like his talk. When he put up his final slide, the audience started to laugh, and Tenuta laughed too. The slide title? “What pisses you off the most?”

These were our options, laid out on Tenuta’s slide:

• “no-till doesn’t count much for credits;
• increased yields don’t count for credits;
• possibly paying more for fuel;
• possibly paying for N2O emissions from soil;
• possible restrictions on N fertilizer use;
• not gonna be easy to reduce N2O emissions; and,
• university researchers doing GHG research.”

If we’re going to remain profitable and adapt to the changes coming in the future, we’re all going to need to keep that sense of humour intact.

*This number was changed on April 9, 2017, to reflect errors that were included in previous versions. 

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“Soybean cyst nematode moves with soil, any method by which you can move soil, you can move it,” says Tenuta. From equipment moving to migratory birds to wind erosion, if the soil moves, the cyst nematode moves.

Soybean cyst nematode, says Tenuta, can be managed, but growers need to be on the lookout for unexplained significant yield losses “that can’t be blamed on any one thing” prior to it being detected in the soil, as the pathogen can be present for many years prior to detection.

If you fear cyst nematode could be an issue, look at your fields: is there waviness, a lack of levelness across the field? This could be caused by a number of other issues, like nutrient deficiency, unbalanced PH levels, and more, so it is important, says Tenuta, to determine the cause. “One of the most important things is to dig up those plants and examine the roots. Look for the cysts on the roots, they can be seen easily with your eyes.”

Early detection is key because “the lower the population, the easier it is to manage.” Untreated, the cyst nematode will gain traction. Prairie growers are in a good position, says Tenuta, because while it is a “matter of when not if” the disease will spread to soybean producing provinces, it hasn’t yet been found yet in the West.

Coming to your field soon

Albert’s brother, Mario Tenuta, is a Professor of Applied Soil Ecology at the University of Manitoba. He says, “soybean cyst nematode is present in several counties across the Manitoba/North Dakota Border. It is very clear that soybean cyst nematode will eventually be found in Manitoba. The pest will be introduced to Manitoba by floodwater, wind, birds and/or soil on machinery and vehicles. With a longer history of soybean cultivation in Manitoba, the pest will then build to levels detectable in surveys and/or causing visible disease symptoms.”

Being proactive is important, says Albert Tenuta. When it is found in the Prairies, growers will have the advantage of cyst nematode resistant varieties of seed, which Ontario growers didn’t have 25 years ago. “The cornerstone of effective cyst nematode management begins with resistant varieties,” says Albert Tenuta. “Those will help limit the amount of reproduction on the roots.”

You can’t overuse a particular variety, though, because no variety is 100 per cent effective against the disease. Rotation is also key. Prairie producers have the advantage here, says Albert Tenuta, because they have many different crops in their rotations than Ontario growers. (Some pulses can be hosts for cyst nematode, so be careful with those.) There are also some new seed treatment nematicides coming out which will “help suppress the reproduction on the roots on our resistant varieties.”

The first fields to see soybean cyst nematode will likely have lower populations and won’t see a significant yield hit, says Albert Tenuta.

Interestingly, the most common symptom of the disease is no aboveground symptoms at all, says Albert Tenuta, so growers along the North Dakota border and the Red River Valley — places more susceptible due to proximity to the disease — need “to be digging plants up every year and examining the roots. By the time you start seeing the visual symptoms — stunted plants, yellowing of those plants, a lot of weed escapees — in many cases growers are looking at a 20 to 30 per cent yield reduction.” Fungicides won’t do anything for cyst nematodes, says Albert Tenuta, but there will likely be more nematicides coming out down the line. One of the most important things to know is that “once cyst nematode is present, you’re not going to eliminate it, it’s a matter of managing it and managing it well.”

Albert Tenuta says he wishes Ontario had the management tools available today 25 years ago when cyst nematode was making inroads in that province’s soybean crops. If Prairie productions are vigilant, they can avoid the 50 to 70 per cent crop reduction that Ontario crops suffered from in the early days.

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The relationship between fungi in your soil and plant roots has a big impact on your crop health. This relationship can cause flax to be stunted when it’s grown in rotation after canola. Corn and sunflowers can also suffer when they’re planted on canola stubble.

“Following canola, we often see some interesting, funky growth responses,” said Dr. Mario Tenuta, soil science professor at the University of Manitoba. Tenuta was oan hand to talk about fungi at CanolaPALOOZA, a canola-based learning day hosted by the Manitoba Canola Growers and the Canola Council of Canada at Portage la Prairie, Manitoba, in June.

Arbuscular mycorrhizal fungi

“It’s a story of the soil, and fungi,” Tenuta said.

The word “mycorrhiza” comes from the Greek words for fungus and root. Mycorrhiza is the symbiotic relationship between fungi in healthy soil and the roots of a plant. The fungi help the plants take up minerals and water; the plants provide the fungi with carbohydrates.

“Fungi have these hyphae,” Tenuta said, describing their branching structures. When the fungi are living near a plant, their hyphae penetrate into the plant root structures. The fine surface areas of the hyphae help the plants absorb nutrients.

“What they’re doing,” said Tenuta, “is they’re helping the plant by taking phosphorus from the soil, and transferring it through these hyphae, into the root system. They don’t kill the root. They’re not a parasite, and they’re not a pathogen.”

“Most plants, most of our crops will have this relationship with this fungi, and they will take phosphorus from the fungus,” Tenuta said. “But there are some crops, canola being one of them, which do not do this.” Canola doesn’t have this ability to colonize with the fungi, and gets its phosphorus in different ways.

Because they are not fed by a growing canola crop, the arbuscular mycorrhizal fungi (AMF) in the soil are starved for the season when canola dominates in the field. The following spring, the AMF population are reduced, so the next crop will not have as many fungi to work with in gathering phosphorus.

In early season growth crops, phosphorus is very important. Corn is highly dependent on phosphorus, so when corn follows canola in a rotation, yields can suffer. Wheat has a slightly lower dependency on phosphorus in the early season, but, the impact of following canola with wheat can still be seen in lab tests, and there may be a difference in yield.

“What we want growers to understand is this effect that, when they have canola in the rotation, following the canola some plants may be struggling to get phosphorus,” said Tenuta.

What can be done?

No-till farming practices can help to nurture the AMF in the soil. When there is tillage, the fungi can be damaged, and forced to re-grow again. “If you chop them up, and then you plant canola there, they’ll really get hammered,” Tenuta said.

Also, you can add phosphorus to the soil, to compensate for the lack of AMF.

Growing canola is hard on AMF populations, but thoughtful rotations can help them re-build. After canola, Tenuta suggested, grow something that’s not so dependent on phosphorus, something like rye, or buckwheat. “Buckwheat is fantastic,” he says. “Buckwheat doesn’t really need the mycorrhiza.”

Then, Tenuta said, “work your way up” in the rotation, giving the AMF time to recover before you seed flax.

In his extensive work involving soil and agriculture, Tenuta often finds canola standing out from the crowd. “Whenever we do studies with canola in rotations, and look at almost anything, we find that canola behaves differently.”

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“I talk to a lot of growers growing oilseeds and cereals, and they would take liquid hog manure any day if they had access to it,” says Mario Tenuta, Canada research chair in applied soil ecology and professor at the University of Manitoba. “To move it costs a lot of money, so unless you have a hog producer next to you, or you have pigs yourself, it’s too expensive to move or transport.”

Tenuta has just wrapped up a five-year research project looking at options for separating solids and liquids in hog manure, composting separated solids to concentrate phosphorus (P) at smaller volumes, while also stabilizing nitrogen (N) losses.

“We’ve found that it composts very well. We need to add bulking agents to it, like straw. It can compost very readily and produces a decent compost final product, and when we add that to soil, it’s a very good source of P and can also provide some N,” he says.

Once the liquid is separated into N and P “streams” using a commercial centrifuge, explains Tenuta, the researchers take the P from the liquid manure and concentrate it. “This increases its value and gives it potential to be shipped farther,” he says. “One of our approaches was to compost the material, produce a fertilizer that’s beneficial for soil and has other benefits.”

The University of Manitoba, along with the Manitoba Livestock Manure Management Initiative (MLMMI) and Manitoba pork industry representatives, has investigated several technologies for mechanical manure separation.

“I think it’s important to recognize that most soils in the province are deficient in nitrogen and phosphorus — we need nutrients,” says John Carney, executive director of MLMMI. “Manitoba is in a P deficit but there are a few areas that have a surplus because of livestock density. We have a P distribution problem. MLMMI is looking at various alternatives for relocating that phosphorus from a surplus region to a deficit region.”

Carney says Manitoba producers are showing more and more interest in optimizing manures. “They are motivated to try to get the most value from the nutrients in liquid manure. They want to get the nutrients into their crops and are motivated to do that both environmentally and economically.” he says.

Application options

Most producers hire professional applicators to get the job done, due to the high cost of customized application equipment and the difficulty of transporting manure.

According to Don Flaten, a soil science professor at the University of Manitoba, custom applicators must meet a rigorous set of standards. They must be licensed, and they must justify the cost of highly specialized and sophisticated equipment.

A large-scale intensive focus on manure management has improved the accuracy and efficacy of liquid manure application, says Flaten. “For larger livestock operations, it’s more effective to rent the services of manure management planners and custom applicators.”

Industry has sprung up around manure management; custom applicators sometimes work with nutrient management consulting companies. Scott Dick is part-owner of one such company, the Landmark-based Agra-Gold Consulting.

“We write nutrient management plans for submission to Manitoba Conservation, we work with producers in coming up with agronomic solutions using manure as a nutrient source, and we coordinate and schedule application for producers,” explains Dick.

Any livestock facility in the province with more than 300 animal units must file a manure management plan with Manitoba Conservation each year by July 10.

Agra-Gold’s consultants file plans indicating the amount of manure to be spread in the coming year, then does a series of soil tests and collects yield goals on a field-by-field basis. The company submits this information to Manitoba Conservation.

“Once the application is done we create an application map using GPS data, and the manure applicator takes samples that we send to the lab to get an accurate number on the amount of nutrients in that manure,” Dick explains. “Post-addition, we take the data and create a map, take the samples and soil tests and put together an agronomic report and economic summary of what happened on each field. We’ll then visit the producers and give them reports.”

With precision and specialized equipment farmers are getting much more out of liquid manure. “If you viewed it as a nutrient source rather than a waste product, by applying the science and following through with analysis and implementation, every step increases the value of that product,” he says.

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“What the heck is soil health?” asked Tenuta. “You hear a lot about it these days, especially this year, the 2015 International Year of Soils. A few years ago everyone was talking about soil quality, but that’s been exchanged for ‘health.’ But these two concepts are different. Soil quality is about the ability to produce food, whereas soil health has a different definition more akin to our own personal health — the continued capacity of soil to function.”

Soil management is an important research priority in Canada, and most farmers have implemented conservation practices such as zero-tillage in an effort to get the most out of their fields.

But Tenuta said we are only scratching the surface when it comes to understanding the role of the soil microbiome in promoting plant health.

What researchers do know is that “soil critters” like bacteria and fungi improve plant health by decomposing organic matter, cycling and redistributing minerals, maintaining reservoirs of nutrients, degrading pollutants, and naturally regulating pest species.

Plants and soil bacteria and fungi have a symbiotic relationship; plants also contribute to soil health. Tenuta said researchers are discovering that the roots of plants leak carbon that is utilized by soil bacteria and fungi. “Plants are actually farming soil organisms for their benefit around the root system,” he said.

It seems plants naturally cultivate beneficial bacteria and fungi near the surface of the root by sending out materials that promote their development. In turn, these micro-organisms have co-evolved to be able to utilize material emitted by plants.

“We’re learning that it’s the bacteria in people that determines our auto-immune responses. I think we’ll learn that it’s the organisms in the soil that determine soil health.”

Respecting soil complexity

Tenuta said increasing soil organic matter does not immediately lead to improved soil health if nutrients are “tied up” in forms that can’t be utilized by the plant.

The “soil food web” comprises many complex, layered relationships between soil organisms, and each layer is essential to ensuring nutrients cycle through the soil.

There are a variety of ways of accessing those nutrients — some organisms can draw nutrients directly from plant roots, while others get nutrients through decomposition and others through feeding on soil organisms. In healthy, biodiverse soils, lower-level trophic organisms are consumed by higher-level trophic organisms. The process gradually “unties” soil nutrients like nitrogen, phosphorus and sulfur so they can be utilized by plants.

“If you’re bad to your soil you truncate a lot of that diversity — the larger trophic organisms are the canary in the coal mine and you get rid of them in unhealthy soils,” said Tenuta.

A worst-case scenario is one in which producers get rid of higher-trophic organisms, which means lower-trophic organisms like bacteria and fungi increase to unhealthy levels. The release of some nutrients is dependent on bacteria and fungi dying. “Massive amounts of tillage will destroy earthworm burrows; pollutants could kill higher trophic organisms,” said Tenuta. “We’re getting better and better with agrochemicals, whereas a lot of them in the past were indiscriminate.”

Microbial nitrogen is released from bacteria and fungi to plants, Tenuta explained. “What we don’t want is for the nitrogen to stay in the organisms. We want this feeding to happen so nitrogen can be released.”

Tenuta also pointed to a particular group of fungi — mycorrhizal fungi — as playing an essential role in soil health. “Without these fungi most plants wouldn’t grow in natural soil because of lack of phosphorus. More than 80 per cent of plants are dependent on mycorrhizal fungi,” he said.

What can producers do to promote soil health? Tenuta says rotation is key, and producers should intentionally increase soil organic matter. But a greater respect for the importance of the soil microbiome is fundamental. “Have a mindset that you’re ‘growing soil,’ not just plants. Make it part of annual farm plans to think about feeding soil.”

Time is another key ingredient in understanding soil health. “Using soil tests, track soil organic matter, inorganic nutrients, yield and protein over many years,” he says. “Observe improvements in structure.”

Soil tests Tenuta noted include the Solvita Soil Health Test, Cornell Soil Health Test, Visual State Assessment Test, and the Soil Food Web Inc. Test.

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