He tells them two things:

• don’t hold your breath and
• you’ll need to work with what you have.

WHY IT MATTERS: Wild oats is a tough weed to control, with no one herbicide capable of tackling the Prairie pest.

“Do not expect any quick help on that front with wild oats,” said Micklich, precision ag specialist and owner of Progrow Agriculture in Vegreville, Alta., in a presentation at Agronomy Update 2026.

“It is an extremely complicated plant,” he said.

“It’s actually hexaploid, so it has six different sets of chromosomes. What that means is it’s extremely unpredictable on … how each chemical interacts with each other in the target sites. So it’s just an extremely hard plant to map out.”

But don’t despair. Cultural control practices — such as increasing seeding rates and adding an early-maturing crop to rotation — can go a long way towards removing these pesky oats from your field, he said.

“There is no shortage of options to be used in the fight against wild oats.”

However, producers may need to reconsider any “this is what I’ve always done” attitudes they may be harbouring, advised Micklich.

“We need to move to ‘what do I need to do? And how can I manage this?’ We need to be more long-term focused.”

READ MORE: Farm gets aggressive on wall-to-wall resistant wild oats

Herbicide-resistant wild oat (HRWO) is of “special concern” according to Alberta Grains. And for good reason: according to the most recent herbicide resistance survey, resistance is building and building fast.

The survey results reveal that 69 per cent of Alberta fields sampled for resistance in wild oat contain HRWOs.

Of that percentage, 62 per cent of fields are resistant to Group 1 herbicides, 34 per cent to Group 2 herbicides and 27 per cent are resistant to both.

Those numbers are growing. The producer organization points to “drastic increases” in HWRO in Alberta since a Western Canada-wide survey in 2000.

Make the switch to TKW

There are several tasks producers should perform prior, during and after the crop season when dealing with HRWO. Micklich pointed to examples such as scouting for post-spray efficacy, identifying cross-resistance, seed sampling and reaching out to dealers for resistance testing if necessary.

One of the most important things producers can do to fight HRWO is increase seeding rates. However, some may have to make an adjustment in how they measure seed.

For producers who haven’t made the switch from bushels or pounds per acre to 1,000 kernel weight (TKW, sometimes known as total seed weight or TSW), or the weight of 1,000 seeds, this will be the time to do so.

In 2019, Harry Brook, agrologist with Alberta Agriculture, told Alberta Farmer Express why TKW is a more precise gauge of seed size measurement.

“Where there is significant variation in seed size between one variety and another, bushels per acre is a poor seeding tool to use,” he said.

“With peas, for example, there can be as much as 75 per cent seed size variation. That can have a big impact on plants per square foot.”

Added Micklich, “when you’re just doing a two bushel an acre measurement, that’s a volumetric measurement. It’s just not that accurate anymore.”

“What we want to do is use 1,000 kernel weight and calculate it off of what your target plant per square foot is, because if you just use bushels off of seed weight, your rate will sway. It can sway up to 20, 30 per cent just based off of seed weight if you’re just doing 120 pounds an acre and that’s it.”

Add early maturing crops to rotation

Adding early maturing crops such as peas and winter wheat to a rotation is likely the most important tool growers can use prevent reoccurring wild oat growth, said Micklich. The idea is to kick wild oats out of the seed bank before they’re physically mature, decreasing their survivability drastically.

“So if we can knock it off the plant in mid-August where it’s not quite mature … you reduce the survivability of that seed over winter.”

Taking preventative measures against wild oats early – particularly with late-harvested crops like wheat and canola — makes sense because there aren’t many control options once the oats establish.

“That (wild oat) seed will reach maturity before we get to it and (the seeds) will drop. So you’re just replenishing that seed bank. I wouldn’t say you’re starting from square one, but you’re just not eliminating that seed,” noted Miklich.

“A lot of times in east-central Alberta, by the time we harvest canola, it’s getting close to freezing. Most guys aren’t going to be doing a post-harvest spray. So you just get yourself in a weird spot where there’s nothing you can do to try and reduce that seed bank until the spring.”

Herbicide layering now a must-do

With so much herbicide resistance already a part of wild oats, producers don’t have much choice but to layer herbicides to control the weed, said Miklich.

“This is mandatory — you’re just getting ahead of it by initiating this.

“The concept of it is we’re trying to use different groups or modes of action sequentially throughout the growing season.

“The basis of it is you do a fall apply in say Group 15; a pre-burn, say, in a Group 2 or Group 15, and then an in-crop, say, in a Group 1 … Whatever group you would have the most efficacy with.”

Minimize tillage

There are several reasons to minimize tillage, but in the case of wild oats a big one is preventing the incorporation of wild oat seed underground where it can remain dormant for years, in the process increasing their life spans.

“When guys are high-speed discing their wild oat patches. that is one of the worst things we can do for it because you are burying that seed and it will sit in dormancy.”

What growers need to do, offered Micklich, is induce germination of the wild oats.

“So say, in a pea crop, if you’ve had that stubble sitting for a month in the sun, a lot of those wild oats will be germinated. Either the frost will get it or it will give us a point of attack to eliminate those seeds: a germinated seed that you can kill or do something with is one less seed in that seed bank.”

The post Think beyond the herbicide jug when dealing with wild oats appeared first on Grainews.

Lupins outpace field peas and faba beans in terms of protein and starch level ratios, with up to 40 per cent protein and six per cent starch, making the crop attractive for plant-based protein production.

“The interest in Canada, especially in Western Canada, was always trying to look for something potentially new and different to try to bring into into our cropping rotations,” Robyne Davidson, a pulse research scientist at Lakeland College, said during a field school tour at Farming Smarter near Lethbridge.

”Down here, you guys have way more options. I hail from central Alberta, where we basically have four, maybe five crops that we can rotate through,” says Davidson, who has been researching lupins for about 15 years.

Another draw that has piqued some Prairie interest has been lupins’ status as a pulse crop that stands up against aphanomyces root rot.

“We had a fantastic two million-acre industry in Alberta for field peas, and bam, we have aphanomyces that we have no (seed treatment) control for. We have this wonderful industry, that if we don’t figure it out, it’s going to take us down to nothing very quickly. I’ve watched it happen in France,” Davidson says.

“Lupins are absolutely resistant to aphanomyces. The difference is between ‘resistant’ and ‘tolerant.’ If you are a field pea or a lentil, aphanomyces is devastating to you; dry beans is a little bit variable. Same thing with chickpeas: you can grow chickpeas in a field with aphanomyces, and you will find lots of spores in the roots and the plant will seem fine. It may also be contributing to the population. When it comes to aphanomyces, we are looking at six to eight years before you can come back and kind of hope for the best.”

Potential markets

There also seems to be more of a thirst for a lupin market than seen during a failed push years ago. New research has shown it’s an excellent feed for livestock such as horses and dairy cattle, given its amino acid and fibre content.

According to Davidson, studies have shown a return on investment of five-to-one, with milk and butterfat production higher on a lupin feed diet than a soybean/corn diet.

“We talk about the feed industry, because we are not going to have a food industry until we have a well-established feed industry in this province for lupin,” she says, adding the feed to food industry use is about 80 to 20 per cent.

For all its positives in maintaining pulse crop diversity in rotation for soil health, fixing nitrogen, high protein levels and low disease pressure compared to other pulse crops, Davidson cautions lupins have very structured conditions to thrive, with careful site selection.

Lupins are sensitive to high-pH soils, performing poorly in alkaline soils with pH around 7.8. Lupins prefer acidic soils around 5-6.5, which in Alberta can be found more commonly the further north you go, into the Peace region. Lupins are better suited for areas with longer growing seasons, such as in southern Alberta with lower pH, and in Manitoba, with different varieties maturing in ranges of 95 to 125 days.

Odyssey or Basagran cannot be used for weed control for lupins. Edge can be used as a pre-emergent herbicide. Once you have weeds coming up in the crop, you are pretty much limited to Metribuzin.

Lupins are also a high-water crop, requiring 10-12 inches on a lighter soil, avoiding heavy clay. You can still get a decent crop with lower moisture, but a good crop of lupins will get you about 40-45 bushels per acre, Davidson says.

“If you have an area on your field that is maybe under seven (pH), then yes, maybe you can put it on there,” she says, adding economic factors also factor in with middling contracts currently of around $450 per tonne.

Davidson hopes lupins can follow the same path as field peas 25 years ago: a new crop no one grew and knew little about, it came to more prominence as soon as best practices management was improved. Its agronomic characteristics include the woody stem preventing lodging, and a strong taproot, with similar seeding and nutrient requirements to field peas.

Davidson is continuing to study the potential of lupins and is working with six different seed companies worldwide.

“These companies want lupins in Canada and they are knocking down the door,” she says, adding Australia, Denmark and France, and the U.K. have approached her.

“Over the past 10 years since I’ve been looking for and testing varieties, we have come a long way. There’s no question we need to find some varieties that are slightly more drought-tolerant. But I don’t think that’s a huge stretch. I think they’re out there. I just got to find them.”

To learn more about the variables in growing lupins, contact Davidson by email.

The post European seed firms hope lupins catch on in Prairie pulse rotations appeared first on Grainews.

If it seems the rain we do receive these days doesn’t go as far as it did in the past, it’s more than a hunch.

We’ve all had the experience of drinking more on a hot day. As it turns out, the atmosphere reacts similarly under global warming.

In the study “Warming accelerates global drought severity” published in the journal Nature, the University of California’s Santa Barbara Climate Hazards Center director Chris Funk says global warming is causing the atmosphere to behave “like a sponge, soaking up moisture faster than it can be replaced.”

In other words, the air is getting thirstier — a phenomenon that researchers say has increased the intensity of global droughts by 40 per cent over the past four decades.

“Drought is based on the difference between water supply (from precipitation) and atmospheric water demand. Including the latter reveals substantial increases in drought as the atmosphere warms,” Funk says in a release.

Globally, the areas in drought expanded by 74 per cent between 2018 and 2022. Atmospheric evaporative demand (AED) was responsible for 58 per cent of that increase.

“Our findings indicate that AED has an increasingly important role in driving severe droughts and that this tendency will likely continue under future warming scenarios.”

Most now accept that the climate is heating up, although debate continues as to the cause. Less well understood is the connection between global warming and the “desiccating influence of the atmosphere,” Funk said.

The atmosphere’s growing thirst adds a third dimension to precipitation and soil moisture equation driving crop yields — one that could challenge the viability of contemporary crop rotations.

University of Manitoba researchers recently published a study on how different crop combinations perform under drought conditions.

“The main objective of this study was to compare cropping systems that incorporated … diversity, intercropping, cover cropping, and heat tolerance with a “business-as-usual” rotation,” the research team, consisting of Samantha Curtis, Martin Entz, Katherine Stanley, Doug Cattani and Kim Schneider, reports in the Canadian Journal of Plant Science.

Atmospheric dryness (measured as vapour pressure deficit) during the two-year study in 2020-2021 was well above the long-term average.

The business-as-usual rotation selected for this study was wheat-canola-wheat-soybean, grown over two years at the Ian N. Morrison Research Farm located at Carman, Man.

The study also included a warm-season combination (corn-sunflower-dry bean-canola), a biodiverse rotation containing nine crops (fall rye with a cover crop-intercropped corn and soybeans-intercropped peas and canola-green fallow mixture), a perennial grain (Kernza intermediate wheat grass) and an organic rotation (millet-green fallow mixture-wheat).

The business-as-usual rotation yielded only 71 per cent of the biodiverse rotation and 59 per cent of the warm-season rotation. It also had a lower net return than the warm season rotation and fewer “live root days,” which is a measure of soil health potential, than either the biodiverse or the warm-season rotation.

The biodiverse rotation resulted in a net return similar to the business-as-usual crop mix, but needed half as much the nitrogen fertilizer. “While the biodiverse rotation required more seeding passes and greater plant diversity knowledge, the benefits observed here suggest that incentives and educational programs to speed adoption of biodiverse systems should be a priority,” the research report says.

“If growing conditions in Manitoba continue to become hotter and drier as predicted, growing more water-use efficient crops such as fall rye, corn, sunflower, and corn-soybean intercrops would increase climate resilience.”

A drying atmosphere also sets stage for the devastating wildfires now sweeping through wide swaths of Western Canada’s boreal forests every spring and summer, creating the prolonged and hazardous smoke conditions cloaking the region.

One of the unanticipated outcomes from all that smoke is its counterbalancing effect cooling things down.

A recently released University of Washington paper says wildfires in Canada and Siberia may reduce the earth’s warming by up to 12 per cent globally and 38 per cent in the Arctic over the next 35 years.

“Because the aerosols in smoke brighten clouds and reflect sunlight, summer temperatures during fire season drop in northern regions, leading to reduced sea ice loss and cooler winter temperatures,” lead author Edward Blanchard-Wrigglesworth says in a release.

No one can say this is good news. The authors point out that wildfires are expected to intensify in coming years, which doesn’t bode well for human health or forest biodiversity. And their effects on the boreal forest may escalate the release of more carbon into the atmosphere.

What all this is telling us is that even with computer modeling, improved real-time monitoring and technologies such as the emerging AI, we don’t have a good handle on the cascading effects of a changing environment. The effects and counterbalances are constantly setting new changes in motion.

I am reminded of an expression I’ve heard now and again from some of the more seasoned farmers I know: “Nature always bats last.”

The post Western Canadian agriculture’s growing thirst appeared first on Grainews.

While imports of other companies’ off-patent brands of glyphosate may buffer the immediate shock, the long-term implications could reshape weed management across the Prairies.

Hugh Beckie, a former Agriculture and Agri-Food Canada weed scientist, explored this very scenario in 2019. At the time, he was based at the University of Western Australia, so his modelling focused on Australian farming systems. But while the crops may differ, both Australia and Canada depend heavily on glyphosate-based weed control, making many of his findings relevant here.

Beckie’s work laid out not just the impacts of losing glyphosate, but the sweeping, system-wide changes farmers would need to adopt in its absence.

To understand what that shift might look like on the ground, Glacier FarmMedia spoke with Kim Brown, provincial weed extension specialist with Manitoba Agriculture, about the tools, trade-offs and decisions farmers may face if glyphosate were to disappear from the weed control toolbox.

Brown says Canadian farmers have already been working to reduce their reliance on glyphosate due to the rise of herbicide-resistant weeds.

“We’ve already been going down that road where glyphosate for certain weeds just has not been working,” Brown says.

“We’ve had to find alternative methods for weed control.”

That said, a full loss of glyphosate would escalate the challenge considerably, especially given that weed pressure is a constant in Prairie fields.

“There are weed seeds in the soil. The weed seed bank is vast,” she says.

“Every single year there will be weeds.”

That tracks with what Troy LaForge, who farms in the brown soil zone near Cadillac, Sask., about 65 km south of Swift Current, predicted when we asked him to consider what his fields would look like if glyphosate were to someday disappear from the market.

“What we would probably see is a progression in winter annual and perennial weeds, and from that perspective, we may have to change up to some different oilseeds where we can use actives like clopyralid (the Group 4 active in products such as Lontrel and Curtail) and some of the graminicides (Groups 1 and 2) that are more effective on perennial grasses like quackgrass and foxtail barley,” he says.

“We’d have to change to some different crops, and I honestly don’t know what those would be at this moment, but we may have to change because we just don’t have means of keeping weeds under control otherwise.”

Southwestern Saskatchewan is not generous with the rainfall and not typically canola country, but if glyphosate were to go away, “it might mean that we’ve got to start growing canola more continuously to use a product like glufosinate (the Group 10 active in Liberty) for example.”

Brown concurs there are other herbicide options, even in glyphosate-tolerant systems, thanks to stacked traits — but those alternatives likely won’t cover the same broad weed spectrum that glyphosate does.

“We will have alternatives,” she said.

“But it’s going to get a lot more complicated, and it’s definitely going to get more expensive.”

READ ALSO: Glyphosate class action moves forward in Canada

Farmers may also need to revisit herbicide products they aren’t currently using and some they haven’t used in years. Brown said some older chemistries may play a bigger role again, particularly in rotation or in tank mixes.

However, product availability, crop safety and regional fit will be key considerations.

“To me, as a no-tiller, the No. 1 issue is going to be what we replace it with, and at this point, the actives that are registered are going to increase our costs significantly,” LaForge says.

“And it’s probably going to mean that we’ve got to bring back some active ingredients that we haven’t had for a while and just have higher levels of toxicity at the end of the day.”

Losing glyphosate would also push integrated weed management (IWM) to the forefront.

“Those tools have always been there,” Brown says.

“In the past, we haven’t used those tools as effectively as we could. But we’re going to have to now because we won’t have a choice.”

Brown stresses the value of crop competition: adjusting seeding dates, seeding rates, row spacing and cultivar selection all help. But the biggest lever, she says, is crop rotation.

“Crop diversity is probably the single biggest thing we need to do when it comes to weed control.”

Life cycle diversity — mixing annuals and perennials, or at least spring and fall crops — can help break weed cycles and reduce reliance on any single product or practice.

Beckie’s paper indicates how Canadian farmers may have a leg up over their Australian counterparts when it comes to managing glyphosate resistance.

In Western Canada, about 40 per cent of canola acres are planted to herbicide-resistant varieties, but resistance hasn’t taken off the way it has in Australia. That’s largely thanks to the widespread use of glufosinate-tolerant cultivars and more diverse crop rotations.

Still, Beckie warns, losing glyphosate as a pre-harvest option would hit hard in pulse crops, where there are few good alternatives for controlling tough perennial weeds.

Harvest weed seed control (HWSC) is another tool Brown mentioned, and it also played a central role in Beckie’s post-glyphosate scenario. Originally developed in Australia — where herbicide resistance evolved faster and hit harder — HWSC focuses on capturing or destroying weed seeds at harvest to prevent them from replenishing the seed bank.

Beckie’s modelling leaned heavily on this strategy, especially in the absence of effective pre-harvest herbicides.

HWSC has also been gaining traction in Canada and could become more relevant as farmers look for non-chemical ways to keep weed populations in check.

“You want to destroy the weed seeds, or you want to move them, or take them off the field and not let them add to the weed seed bank,” Brown says.

Tillage remains an option, and Brown notes it’s something most farms already have the equipment to do — but bringing tillage back as a primary weed control tool comes with consequences.

Brown points out that glyphosate was instrumental in the widespread adoption of minimum- or zero-till systems, and that if it’s no longer available, it could set things back significantly.

“There’s going to be many negative consequences with that,” she says, “including soil degradation, increased greenhouse gases and even just fuel consumption.”

Hence at LaForge’s farm, for example, tillage is just not an option.

“If we have to go back to tillage in this part of the world, we (would) probably decrease our yields instantly by 30 to 40 per cent,” given the amount of soil moisture that would be lost in the process, he says.

The availability of glyphosate has increased the diversity and productivity of the farm’s rotations and “created a whole new level of soil conservation in this area.”

There’s some hope on the horizon.

Brown points to emerging technologies such as laser weeding, electrocution, steam weeding and the potential for new herbicides or non-traditional weed control products. Much of this innovation, she said, is being driven by the urgency of the current situation.

“There’s a lot of research being done because of the very situation that we’re in right now,” she says.

Extension specialists such as Brown will play a key role in helping farmers adjust. She said the core message around integrated weed management isn’t changing, but the urgency and scope of that message are growing.

“We’re just going to have to get a lot more educated on some of these products that are out there that we need to be using,” she says.

“We have to raise that level of comfort, because that will be new territory for many farmers.”

The post What would happen if Roundup disappeared? appeared first on Grainews.

The two best defences are:

• Crop rotation with a break of at least two years between canola crops.
• Cultivars with effective resistance to the disease pathotypes in a field.

Seed treatment and early-season fungicides can also help, especially if the first two are compromised.

This article will explain blackleg disease and how it works, then provide management details to keep canola yield loss to a minimum.

What is blackleg?

Blackleg, also called phoma stem canker, causes necrosis of canola stems at ground level, restricting moisture and nutrient movement in the plant. In severe cases, the fungus can completely cut off this essential flow, killing the plant. In many cases, plants survive partial restriction but experience yield loss due to limited seed fill.

Two fungal pathogens cause blackleg — Leptosphaeria maculans and Leptosphaeria biglobosa. Both species are widespread throughout the Prairies. L. biglobosa is weakly virulent, and often associated with upper stem lesions. It rarely causes significant yield loss. L. maculans does more damage.

Canola plants are susceptible to blackleg infection at all growth stages. Infection at the seedling stage tends to cause more yield loss because the disease has time to develop through the growing season. That is why seed treatment and early-applied fungicide can help, especially if cultivars have limited genetic resistance. More on that later.

Blackleg pathogens overwinter on infected canola residue. In spring, fungus on old stem and root pieces produces fruiting bodies called pseudothecia and pycnidia. Pseudothecia release microscopic sexual spores, called ascospores, which become airborne and disperse to infect new canola plants. Ascospores are the primary agent of infection.

During the growing season, the pathogen also produces pycnidia, which appear as pepper-like spots within lesions on canola leaves and stems. Masses of tiny spores called pycnidiospores ooze from the pycnidia. These spores spread short distances by rain splash and wind, and cause secondary infection within a crop. Infected stubble can continue to produce ascospores and pycnidiospores for three to five years, although viability drops off considerably after two years. That is why crop rotation is an effective management practice. Again, more on that later.

From the original infection site, usually on leaves, the fungus grows down through the plant. As the season progresses, cankers form at the stem base. In severe cases, these cankers will completely fill the base of the stem, causing premature death.

The disease triangle

Diseases require a pathogen, a susceptible host and the right environment. Blackleg thrives in warm, humid conditions and with frequent rain showers.

Infection can occur in dry years, provided early-season showers produce the environment for spore germination, dispersal and infection. University of Manitoba research (Guo and Fernando, 2005) showed that pycnidiospore dispersal peaked during rainfall, and ascospore dispersal peaked several hours after rainfall of greater than two millimetres (or one-tenth of an inch). Ascospore dispersal persisted for approximately three days after such events. Wind increases pycnidiospore dispersal.

Yield loss

Agronomists can determine blackleg severity based on visual assessment of stem cross sections. With blackleg, discolouration often appears in a wedge pattern. If discolouration is more like a light-grey starburst pattern, it may be verticillium stripe.

The blackleg severity scale:

• 0 — No diseased tissue visible in the cross-section.
• 1 — Diseased tissue occupies up to 25 per cent of the cross-section.
• 2 — Diseased tissue occupies 26-50 per cent of the cross-section.
• 3 — Diseased tissue occupies 51-75 per cent of the cross-section.
• 4 — Diseased tissue occupies greater than 75 per cent of the cross-section with little or no constriction of affected tissues.
• 5 — Diseased tissue occupies 100 per cent of the cross-section with significant constriction of affected tissues; tissue dry and brittle; plant dead.

Research from Alberta (Hwang et al., 2016) found that each unit increase in disease severity reduced canola seed yield in the infected plant by 17.2 per cent. An updated yield loss model, also from Alberta researchers (Wang et al., 2020) showed the increase in yield loss as more quadratic than linear. Here is the conclusion, as written in the Wang et al. report from the Canadian Journal of Plant Science: “The results of the current study indicated that blackleg severity–yield loss relationships were explained by quadratic equations, in which slight L. maculans infection (disease severity of one) was associated with a small increase in yield relative to plants with no disease at all. When disease severity increased to ≥2, however, yields began to decrease dramatically.”

For these reasons, when disease levels approach a severity rating of two on a field (late in the season) Canola Council of Canada agronomy specialists recommend a change in blackleg management for that field in future years.

The Canola Council of Canada used these research results to build an online tool, the Blackleg Yield Loss Calculator, that calculates blackleg yield loss (and economic cost) based on field scouting results.

STEP 1: Scouting

Blackleg infection can occur at any time, and early infection tends to cause the greatest yield loss. Lesions may occur on cotyledons, leaves, stems and pods. These spots are dirty white, round to irregularly shaped, and usually dotted with numerous small, black pycnidia. Use a hand lens to help identify pycnidia specks. Under moist conditions, a viscous pink liquid carrying the pycnidiospores oozes from the pycnidia.

While very early-season scouting can indicate the need for a fungicide spray, canola growers and agronomists will use later-season scouting to assess disease severity, estimate yield loss and identify fields where increased future management is required.

Scouting at swathing or the week or two before straight combining requires cutting through the base of canola stems to assess stem canker. Look for dark necrotic discolouration in the interior of the stem base. This was described earlier, in the yield loss section.

To scout:

• Pull up 50 to 100 plants in a “W” pattern through the field, cutting 10 to 20 random stems at each of the five points in the “W.” Random selection is key to an accurate assessment. Do not seek out diseased stems. Start at a field edge, choosing the edge closest to a previous canola field.
• Clip at the base of the stem/top of the root and look for blackened tissue inside the crown of the stem. Start around one inch below ground level and take various cuts up through the stem base. The amount of infection present will help identify the level of risk and the best management practices for that field in the following years.
• Use the zero to five blackleg disease rating system to identify severity. Also, tabulate what percentage of the sampled plants have a blackleg infection. This is the “incidence” of disease.

Then, enter results in the blackleg yield loss calculator.

STEP 2: Test for blackleg races

If blackleg seems to be getting worse, agronomists and growers can test stubble to identify the dominant blackleg races present in a field. The population of blackleg races can shift in a field, and cultivars are not resistant to all races.

Canola activates a resistant response to blackleg when the plant “recognizes” the corresponding L. maculans avirulence genes (Avr) in the pathogen. This is called gene-for-gene (also called qualitative or major gene or race-specific) resistance. If a pathogen has an Avr gene that matches the plant’s resistance “R” gene, the R gene recognizes the pathogen and causes the plant to initiate a defence or immune system response. Resistance only results if both the Avr gene in the pathogen and the corresponding R gene in the host are present.

If the plant does not have an R gene that matches the pathogen’s Avr gene, the plant does not put up an immune response, and blackleg infection can occur. Stubble tests can identify the common Avr genes in blackleg-infected stubble, and growers can then choose canola cultivars with R genes that correspond with those Avr genes.

Various labs will test stem pieces for blackleg and can provide analysis of blackleg races present.

The first step is to gather samples. Collect fresh stem pieces around the time of swathing or in the weeks before straight combining. Cut just below the crown of the plant into the root material, to look for black discolouration in the cross-section. Collect 10 to 12 infected stems from each field, providing 10-inch (25-cm) stem lengths starting from around one inch below ground level. Some labs will use smaller pieces. Check with each lab for their protocols. See sidebar for labs.

Labs can also test old canola stem pieces collected from fields that will be in canola next year.

Next is the lab analysis. Labs determine the blackleg species present — L. biglobosa or L. maculans — and run DNA tests to determine the races.

Then it’s time to interpret the results. Lab results show the predominant race of blackleg or give a frequency breakdown of blackleg races found within the samples provided. Results also list the Avr genes found in each race. As noted earlier, major R genes in canola cultivars need to match up to Avr genes in the pathogen to be effective.

Lab results may look something like this:

• Race 1 — AvrLm2-Lm4-Lm5-Lm6-Lm7-Lm11 (25 per cent)
• Race 2 — AvrLm4-Lm5-Lm6-Lm7-Lm11 (50 per cent)
• Race 3 — AvrLm1-Lm4-Lm5-Lm6-Lm7 (25 per cent)

Growers will want to select a canola cultivar with a major gene that corresponds with an Avr gene found in all three races. Avirulence gene 4 (AvrLm4) is one example of a gene found in all three common blackleg races in that field. Using a cultivar deploying a major gene of Rlm4 (or Group E1) would be a suitable match. The next section describes this in more detail.

WATCH MORE: This video explains how to use a Leptosphaeria maculans race test to choose the right blackleg resistance for your canola field.

STEP 3: Choose resistant cultivars

Agronomists and canola growers can use results from step two to choose a cultivar with qualitative resistance to the predominant blackleg races in a field.

Cultivars often also have some degree of quantitative resistance (also referred to as minor gene or adult plant resistance), believed to come through the function of many genes each with a relatively small effect. Canola cultivars express quantitative resistance at the adult plant stage. The result is reduced development of necrotic tissue at the stem base compared to that found in susceptible cultivars. Canola breeders likely use both quantitative and qualitative resistance to develop blackleg-resistant canola cultivars.

Qualitative resistance, described earlier as gene-for-gene resistance, is a major-gene trait. Serious infection is more likely when the dominant blackleg race in a field does not match the cultivar’s qualitative R gene.

Using the same resistance genes repeatedly in the field over time can select for blackleg races virulent against that resistance.

The mix of blackleg races will be different in every field, and the mix changes over time. That is how a cultivar that earns an “R” rating at the time of registration may not actually perform like an R cultivar in every field.

The Western Canada Canola/Rapeseed Recommending Committee has established blackleg testing protocols and ratings to assess resistance. The resistance ratings currently available for commercial cultivars indicate disease incidence and severity relative to check cultivars in disease testing sites.

The committee uses the following to describe the level of resistance compared to the highly susceptible cultivar Westar:

• R (Resistant) = up to 30 per cent of the severity of Westar
• MR (Moderately Resistant) = 30-49 per cent of the severity of Westar
• MS (Moderately Susceptible) = 50-69 per cent of the severity of Westar
• S (Susceptible) = 70-100 per cent of the severity of Westar

Blackleg R-gene labels are voluntary for seed companies. Not all companies participate. Seed companies that participate in the blackleg R-gene labelling program use the following letter system to identify major resistance genes present in each resistance group (RG):

• RG A = Rlm1 or LepR3
• RG B = Rlm2
• RG C = Rlm3
• RG D = LepR1
• RG E1 = Rlm4
• RG E2= Rlm7
• RG F = Rlm9
• RG G = RlmS or LepR2
• RG X = unknown

Here are three example blackleg labels you could find on a bag of canola seed:

R (BC): The traditional R rating means the average field performance of blackleg resistance was below 30 per cent of Westar, the susceptible check. The additional “(BC)” designation means the cultivar contains the resistance genes Rlm2 and Rlm3.

MR (A): The traditional MR rating means the average field performance of blackleg resistance was 30-49.9 per cent of Westar check. The additional “(A)” means it contains the resistance gene LepR3 or Rlm1.

R (CX): As an R-rated cultivar, the average field performance of blackleg resistance was below 30 per cent of Westar check. (CX) means it contains the resistance gene Rlm3 and an unidentified major resistance gene.

The Canola Encyclopedia has a table of current canola cultivars and their traits. It identifies the blackleg R gene label for participating cultivars.

Genetic resistance is a key part of blackleg risk management. When growers use other management practices — especially longer breaks between canola crops and R-gene rotation — they protect genetic resistance and minimize the effect of these new strains.

STEP 4: Extend the break

Crop rotation allows for infected canola residue to decompose, reducing the spores available to infect the next canola crop.

A break of two or more years between canola crops on the same field will give most blackleg resting spores time to degrade, greatly reducing the risk. In tight rotations, scouting is essential and it becomes more important to use cultivars with genetic resistance to the most common blackleg races in a field.

Years ago Randy Kutcher, at the time a research scientist with Agriculture and Agri-Food Canada in Saskatchewan, led a rotation study to test the necessity of the recommended one-in-four rotation when growing blackleg-resistant cultivars. The four-year rotation was a key management step in the years before resistant cultivars. Kutcher published the results in the article, published in the Canadian Journal of Plant Pathology in 2013. Access it online here.

Kutcher and his co-investigators compared the following rotations:

• continuous canola (C)
• continuous pea (P)
• wheat-pea (W-P)
• wheat-canola (W-C)
• wheat-pea-canola (W-P-C)
• wheat-pea-wheat-canola (W-P-W-C)
• wheat-flax-wheat-canola (W-F-W-C)

Location one was on dark brown soil at Scott, Sask., from 1998 to 2007. Location two was on black silty clay soil at Melfort, Sask., from 1999 to 2006. Kutcher and his colleagues ran four replicates of the seven rotations with all phases of each rotation present every year. They also repeated every phase with two different canola cultivars — a blackleg-resistant hybrid typical of the most advanced cultivars available at the time, and a blackleg-susceptible open-pollinated (OP) cultivar “typical of those in use when the four-year rotation recommendation for canola was developed,” the journal article reported.

Here is an excerpt from the article abstract:

“The results suggest that canola cultivars with strong blackleg resistance can be grown more intensively than once every four years with limited yield reduction. However, the increased severity of infection and amount of infested residue produced as canola rotations are intensified, which occurs even with resistant cultivars, increases the risk of inoculum carryover, resistance breakdown and yield loss. Therefore, it would be prudent for western Canadian canola growers to adhere to less intensive inclusion of canola in rotations, such as one canola crop in four years, as an effective blackleg management strategy.”

While tighter rotations can maintain low blackleg levels, scouting is essential. Blackleg severity scores of two or more in an R-rated hybrid is a sign of race shift. On that field, canola may need a three-year break between canola crops and a shift to hybrids proven to have different blackleg R genes.

STEP 5: Use enhanced seed treatment

Gary Peng, a research scientist with Agriculture and Agri-Food Canada in Saskatoon, recently completed studies on early blackleg infection and seed treatment. Peng showed that early blackleg infection at the cotyledon stage leads to higher disease incidence and severity at canola maturity.

The Canola Research Hub has a summary of the study, called Exploring novel seed treatment options to mitigate the impact of blackleg on canola. The summary says L. maculans inoculum of over 10,000 spores per gram of soil can result in severe blackleg via root infection, especially if roots are wounded (by root maggots, for example). Of the seed treatments Peng tvested, fluopyram, Saltro (active ingredient pydiflumetofen) and Bion (acibenzolar-s-methyl) showed promise to protect susceptible cultivars against the early blackleg infection, either through roots or from cotyledon and leaf wounds. Saltro is currently available for canola in Canada. Another option, not tested in this project, is Lumiscend with the active ingredient inpyrfluxam.

Peng also co-investigated another study, along with Dilantha Fernando and Shuanglong Huang from the University of Manitoba, looking at fungicide seed treatment to protect those cotyledons. When researchers applied L. maculans ascospores and pycnidiospores directly into canola plants through fresh wounds, fluopyram seed treatment reduced blackleg relative to non-treated control. The treatment did not show a benefit on resistant cultivars. Researchers showed that seed treatment could protect canola plants from blackleg spores that enter early through wounds on cotyledons. Insect feeding and hail can cause these wounds.

Again, the critical note here is this: Is the chosen canola cultivar actually resistant to the blackleg races in a field? If resistance is compromised, seed treatment known to be effective on blackleg may be a good tool to protect against critical early-season blackleg infection.

STEP 6: Apply foliar fungicide

Early-season fungicide can benefit partially resistant or susceptible cultivars, especially if environmental conditions are moist enough to support early infection. Use Group 11 products with high water volume for coverage, and ideally apply before infection.

Gary Peng, continuing his blackleg fungicide work, also looked into foliar application on very small canola plants. In his paper, Early fungicide treatment reduces blackleg on canola but yield benefit is realized only on susceptible cultivars under high disease pressure, published in 2021 in the Canadian Journal of Plant Pathology, Peng concluded that Group 11 fungicide applied to a blackleg-susceptible cultivar at the two- to four-leaf stage could reduce disease severity enough to provide benefit. Read the paper online here.

Early-season fungicide to prevent blackleg can provide a return on investment in a field with all of the following:

• Canola is in a tight rotation.
• The canola seed lot does not have enhanced seed treatment.
• Blackleg was present in the previous canola crop and infected stubble is found in the same field or in a neighbouring field. If the field was not scouted but the area has a history of blackleg, you could assume blackleg is present. This covers the pathogen part of the disease triangle.
• The cultivar is susceptible to blackleg races in the field. Wounds from hail or insect feeding can increase the risk of infection. This covers the host part of the disease triangle.
• Moist weather with wind, mist and rain splash (early in the season, during the critical infection window) can increase the spread of blackleg spores from stubble to living tissue. Fungal growth also tends to be more active in moist conditions. This covers the environment part of the disease triangle. 

Fungicides can go in a tank mix with herbicides — both of which tend to provide greater economic benefit when applied early. Fungicides for blackleg have protectant activity and little or no eradicant activity, so growers will want to apply them before blackleg symptoms appear. Consult the label or a current guide to crop protection for application details on all fungicides registered for blackleg.

Noteworthy extras

Verticillium stripe and blackleg. Researchers have shown a connection between blackleg and verticillium stripe infection. Often both diseases are found together in a plant. One way to reduce verticillium risk may be with a strong blackleg-resistant cultivar, but this hypothesis has not yet been tested.

Weeds as blackleg hosts. Canola volunteers and related weed species stinkweed, shepherd’s purse, wild mustard and flixweed are all blackleg hosts. If not controlled, these volunteers and weeds act as a disease bridge, reducing the effectiveness of rotation and cultivar resistance for disease management.

Tillage and burning to manage blackleg. Randy Kutcher, while with AAFC at Melfort, looked at tillage and burning to manage crop diseases. He published in the journal in 2010. He wrote the paper based on Saskatchewan field studies from 2000 to 2004, which included some very dry years. The paper has this statement: “Leaf spot severity of barley was usually slightly reduced under conventional tillage (CT) compared with zero tillage (ZT), but regardless of severity, barley yields were either similar or more often higher under ZT than CT. There were occasional effects of burning on barley yield, but results were inconsistent and sometimes depended on the tillage system. Canola yield tended to be greater under ZT than CT, but the effect of burning was inconsistent.… We conclude that use of fire to manage diseases of barley and canola is ineffective.”

ALSO: Labs that test canola stubble for blackleg races

Check sampling protocols for each lab.

Manitoba’s Pest Surveillance Initiative (PSI) Lab

Winnipeg, Manitoba

Discovery Seed Labs

Saskatoon, Saskatchewan

20/20 Seed Labs

Nisku, Alberta

Winnipeg, Manitoba

SGS Canada Labs

Sherwood Park, Alberta

Grande Prairie, Alberta

To take the CEU quiz for this article, CLICK HERE.

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Eric McLean, who farms near Oak River, Man., thinks farmers should avoid the “easy button” approach to crop production.

Adding another crop to the canola-cereal rotation may not make buckets of money this year, but it offers benefits down the road.

“With canola, we’ve seen the increases of verticillium (stripe) that’s been taking off the top end (yield) potential in canola,” said McLean, who was part of a panel discussion on pulse crops at Manitoba Ag Days in Brandon in January.

“We have to keep trying different things. Honestly, that is the solution, to have that diversification in the crop rotation.”

McLean shared the stage with growers who have tried alternative pulse crops such as faba beans, lupins, non-genetically modified soybeans and black beans.

READ MORE: Faba beans for Prairie gardens — and fields

McLean, who runs JS Henry Seeds, is convinced growing a pulse crop this year will pay off in coming years. It can reduce canola disease pathogens and improve the soil.

That sounds great, but there are practical realities: for instance, if producers aren’t seeding canola, what are they planting?

Jeff Kostuik, general manager of Verve Seeds and a former crop diversification expert in Manitoba, says that’s not the right question. Many farmers would add peas to their crop rotation, but they can’t because of issues with aphanomyces, a serious soil disease.

So, farmers need an alternative to peas. One option could be faba beans.

The crop hit a high of 120,000 acres on the Prairies in 2021. Since then, acres have dipped to around 80,000.

That’s partly explained by export demand. Canada exported 38,000 and 28,000 tonnes of faba beans, respectively, in 2019 and 2020.

Those sales have declined, and domestic feed use is now more important.

“Canadian export performance over the past six years shows that fababean usage is increasingly a domestic affair, with only two major destinations: Egypt and the United States,” Marlene Boersch of Mercantile Consulting wrote recently.

“Most Canadian-grown fababeans are primarily used domestically for pet food and livestock feed.”

Faba bean acres and production may have dropped in Canada, but there’s a mood of optimism right now.

A seed dealer at Ag Days said more growers are inquiring about faba beans, and acres will likely jump in 2025.

Part of that optimism is coming from the food industry.

There is growing interest from food manufacturers who want to use faba beans as a source of protein.

To tap into that opportunity, Canadian plant breeders have developed varieties that are low in vicine and convicine, a pair of compounds that can cause severe health problems in a small percentage of people.

For that population, consuming faba beans with vicine/convicine can damage red blood cells and trigger a serious disease called favism.

Canada’s faba bean industry is transitioning to low vicine/convicine varieties, which could make a world of difference.

“That barricade of the anti-nutritional, the vicine/convicine, was so important in the breeding efforts to eliminate that (issue),” Kostuik says.

“It has certainly opened things up.”

Faba bean prices are decent this winter, around $10 to $11 per bushel.

Top-end yields of 100 bu. per acre are possible in Western Canada, but 60-70 bu. are more reasonable targets, Kostuik says.

One of the keys for higher yields is early seeding. It’s important to get them in the ground as soon as possible to avoid hot weather during the flowering period.

“It’s a big bean. You want to get it in early. It takes in a lot of moisture at the beginning of the season,” Kostuik says.

“The past research (shows) seeding date is one of the biggest things for yield.”

It’s likely that a farmer, growing faba beans for the first time, won’t hit a home run on yield.

However, that’s acceptable because a diverse rotation has other benefits, McLean says.

“If we can elevate the two following crops (after) these pulse crop options, we can recoup any marginal losses … in the pulse crop,” he says.

“If you get an extra five or 10 bu. of canola … that will easily offset (the pulse crop).”

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To review, soil organic matter (SOM) is the small fraction of the soil that is mostly derived from plants and microbes. Most of Western Canada’s agricultural soils have between two and 12 per cent organic matter (OM). The table here shows typical organic matter levels for the various soil zones in Western Canada.

The amount of organic matter that accumulated in native soils prior to breaking was result of several thousand years of plant, microbial and animal residue additions to the soil. At the same time, soil organic residues were constantly breaking down and in various stages of decomposition.

The amounts and types of SOM were strongly influenced by climatic factors, which in turn, dictated the types of native vegetation and growth that contributed to soil formation and OM additions to soil. For example, in the Brown soil zone, the warmer, drier climate meant short prairie grasses dominated the landscape and added relatively lower amounts of OM to soil — versus the Black soil zone, where a cooler, wetter climate meant fescue grasses dominated the landscape and added relatively higher amounts of OM to soil. Landscape and geographic location also played an important role in soil formation and OM additions and decomposition in soil on upper-, mid- and lower-slope positions.

After many years of soil formation and development, the amount of OM in soil reached a steady state or equilibrium. As a result, soils in drier regions of the Prairies in the Brown soil zone typically have two to three per cent organic matter, versus those in the moister regions of the Black soil zone with seven to 12 per cent OM.

Parton et al. (1983) suggested soil organic matter is made up of different components or fractions that can be grouped into four types:

• Plant residues: Typically break down in one to five years.

• Active: Organic matter that breaks down over five to 10 years.

• Slow: Organic matter that breaks down more slowly, over 10 to 100 years.

• Passive or stable: Organic matter that takes more that 100 years to break down and is commonly referred to as humus.

Soil microorganisms break down plant residues, active and slow fractions of soil organic matter. Humus is the passive or stable fraction of the soil organic matter that results from decomposed plant and microbial matter. Humus is dark and gives soil its brown to black colour; typically, the darker the soil colour, the higher the level of humus. Organic matter plays many important roles in soil and has many positive effects on soil properties.

Chemical benefits

• Soil organic matter is a storehouse for various plant nutrients.

• As soil microbes decompose organic matter, nutrients are released for plant uptake.

• Increases the soil’s ability to hold positively charged cations, which is referred to as cation exchange capacity (CEC).

• Increases the soil’s ability to resist pH change and increased soil buffer capacity.

Physical benefits

• Acts like a glue to bind soil inorganic particles together to improve soil structure.

• Improved soil structure, which reduces surface soil crusting issues.

• Improved soil structure also reduces wind and water erosion potential.

• Iimproved soil structure also aids in water infiltration and water penetration in soil.

• Acts as a sponge to increase soil water storage and helps to reduce water runoff.

Biological benefits

• Increased organic matter increases soil microbial biodiversity and activity.

• Humus gives soil a darker colour, which helps enhance absorption of the sun’s energy. Darker soils warm up more quickly in spring, which stimulate more rapid crop germination and emergence.

• Increased nutrient cycling in soil provides nutrients to other soil microbes and plants.

• In healthy topsoil, organic matter stores significant amounts of N, about half of all the phosphorus and much of the sulphur.

The graph you see here shows how cultivation affected the various SOM fractions after 100 years of cropping. The amounts of plant residue, active and slow fractions of OM significantly declined over 100 years of cultivation using the wheat-fallow system. Summerfallow, which left the soil idle for a growing season, resulted in increased stored soil moisture. Tillage aerated the summerfallowed soil, which stimulated microbial activity, resulting in accelerated SOM breakdown and nutrient release. In the fallow year, there are no plants growing to contribute to the SOM pool. As a result, many years of summerfallow had very negative effects on SOM, soil quality and soil fertility.

The graph shows how using a crop-fallow rotation resulted in the decline of soil carbon by up to 50 per cent in Prairie soils over 50 to 100 years. The plant residue, active and slow carbon fractions were most affected, but the passive fraction (more stable organic matter) was relatively unaffected by cultivation.

Over the past 30 to 40 years, many Prairie farmers have shifted to continuous cropping, more diverse crop rotations and direct seeding of crops and have used adequate rates of fertilization to achieve optimum crop production and increased SOM additions to soil. The interaction of these practices has been very positive to improve crop production. Also important, significant progress has been made to increase SOM, which in turn, has improved soil quality.

Direct seeding and continuous cropping have meant plant residues are returned to the soil every year and the rate of decay of organic matter is much slower with the elimination of summerfallow. By cropping the land every year, organic residues are produced every year to maintain and increase soil OM levels compared to the old wheat-fallow system.

Applying optimum rates of fertilizers ensures optimum crop yields and provides increased crop residue return to soil. Returning more residues to the soil can increase SOM content. Farmers who have been direct seeding and continuous cropping for over 30 years are likely reaching a new SOM equilibrium or steady state level.

Can we expect to see SOM levels increase to original native prairie levels? Not much, when only growing only annual crops. Native prairie grasses pumped considerably more carbon back into soil versus our annual crops. For most Prairie farmers who have been direct seeding, continuous cropping and fertilizing to optimum for that past 30 or more years, odds are most fields are now near a new steady state level of SOM. This means less opportunity to sequester and hold additional carbon in soils. Odds are the amount of carbon added to your soils each year will be similar to amounts mineralized from annual breakdown of SOM. There will be some fluctuation in SOM over years due to effects of droughts or wetter growing seasons.

Can additional soil organic carbon be sequestered when switching from annual crops to forage crops? The short answer: “Yes.” Forage crops pump more carbon into soil versus annual crops. When putting land back into a forage crop for a number of years, a significant increase can be expected. For example, our long-term crop rotation study at Bow Island, Alta. found a significant change in soil organic carbon over 24 years. The adequately-fertilized forage treatment had 61.8 Mg carbon/ha versus the adequately-fertilized continuously-cropped treatments at 45.5 Mg carbon/ha in the top 30 cm of soil after 24 years of cropping. Plots seeded to permanent grass had by far the greatest increase in soil organic carbon capture versus all other crop rotations after 24 years.

In summary, Prairie farmers have done an excellent job shifting to direct seeding, continuous cropping, using much more diverse crop rotations and fertilizing crops adequately, along with various other good agronomy practices. This has very positively improved soil organic matter levels and improved soil health across all the soil zones of the Prairies.

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Prairie farmers use about one million metric tonnes of phosphate fertilizer annually, which has a value of over $1 billion. It is important that farmers and agronomists have a very good understanding of soil phosphorus and phosphate fertilizer management to help ensure fertilizer is carefully used and money is wisely spent.

In this article, I will focus on understanding soil phosphorus and, in my next two articles, will discuss soil P testing methods and developing wise phosphate fertilizer recommendations.

The soil P cycle

To understand soil P, it’s important to understand how P cycles in soil. The major processes of the P cycle include:

• adsorption of P onto surfaces of inorganic constituents;
• uptake of P by plants;
• cycling through plant residues; and
• microbial influences through immobilization and mineralization.

Both inorganic phosphorus (Pi) and organic phosphorus (Po) occur in soil. Both are important sources for crop nutrition. A great deal of research has been conducted in Western Canada in the past 40 years to understand the soil P cycle. Figure 1 shows a simple illustration of the P cycle.

The left side of Figure 1 shows the various forms of Pi which come from the parent materials on which soils have formed. During soil development, primary P minerals very slowly dissolve to provide P ions to the soil solution. The solution P can be taken up by plant roots; adsorbed to mineral surfaces; precipitate with various cations to form secondary P minerals; or incorporated into the biomass and soil organic matter. The fate of soluble Pi depends on the physical and chemical conditions in the soil environment.

Depletion of solution P by plant roots can cause a rapid replenishment by exchangeable and labile P forms. “Labile P” refers to a pool of soil P that is less available to plants but can undergo rapid chemical or biological changes to recharge or replenish the soil solution P. As the labile P forms become depleted, nonlabile secondary P minerals slowly solubilize to maintain the labile Pi pool. Concurrent to the dynamic interchange between Pi fractions, the cycling of Po also contributes to the maintenance of P in the soil solution.

Microbial P is the active hub of the Po cycle. Organic P can be taken up by soil organisms or can be mineralized to enter the soil solution as Pi. Po can also be stabilized as part of the soil organic matter or interact with soil minerals.

Carbon (C) inputs, derived from litter and plant residues, provide the energy to drive the system by stimulating microbial activity. When C inputs are lacking, the turnover of labile Po slows down, and maintenance of solution P is limited to the quantity of labile Pi. Conversely, larger C inputs may result in the immobilization of solution P in labile and stable Po forms. Figure 1 shows a simplification of the P cycle but tries to portray the dynamic nature of soil P.

Crop rotation effects on soil P

In the 1980s, the University of Saskatchewan developed a sequential extraction technique to characterize the various Pi and Po forms and amounts (Figure 1). We used the technique to look at soil P changes in long-term cropping studies at Agriculture and Agri-Food Canada’s Lethbridge Research Centre on Dark Brown soil (Rotation A-B-C) and the University of Alberta’s Breton Plots on a Gray soil. We found that crop rotations and fertilizer management had dramatic effects on most Pi and Po pools. Among the observations:

• Not adding P fertilizer resulted in a continuous drain on almost all inorganic and organic P pools.
• Leaving the soil in fallow every second year accentuated the drain on Po pools.
• The addition of fertilizer inputs at both Lethbridge and Breton resulted in more dynamic P cycling. Phosphate fertilizer addition increased the size of all Pi and Po pools at both sites.
• The continuously cropped treatments that received both N and P fertilizer inputs had the highest total soil P levels of all cropping treatments.
• Continuous cropping and additional P fertilizer inputs had the most positive effects on soil P cycling at both sites.
• Continuous cropping, and the addition of both N and P fertilizers, resulted in benefits to the health and quality of soil P cycling at both long-term research sites.

Plant uptake of soil P

Many physical, chemical and biological factors affect plant uptake of soil P. In the top 20 cm (eight inches) of surface soil, plant roots occupy and contact less than one per cent of the soil volume. As a result, only an exceedingly small amount of P at the root surface is intercepted and absorbed by roots.

Most of the P taken uptake by roots is by mass flow and diffusion. As roots absorb water from the soil solution, a convective flow of water moves toward roots carrying P by mass flow. However, mass flow toward plant roots is often not sufficient to supply plant P requirements. As P is taken up by root hairs, the P concentration in solution near the root surface is reduced. This creates a P concentration gradient radiating from around the root. This causes P to diffuse toward the root along this gradient from an area of higher concentration toward the root surface where the P concentration is lower.

The proportion of P supplied by interception, mass flow and diffusion mechanisms depends on root characteristics, rate of water absorption and the levels of solution Pi and adsorbed P on the soil surface.

The soil-plant root interface is referred to as the rhizosphere. The rhizosphere zone is very dynamic in which living roots release exudates into the soil. These organic compounds stimulate microbial activity. As a result, the population of microorganisms in the rhizosphere zone can be up to 10 times higher than in the bulk soil. In P-deficient soils, microbes in the rhizosphere can intercept P before it can be taken up by roots. The release of organic C by roots into the rhizosphere affects the solubility and uptake of P and other nutrients.

The conditions in the rhizosphere differ from bulk soil, in that the preferential uptake of ions and water results in depletion or accumulation of ions in the rhizosphere. Prominent pH change in the rhizosphere is caused by differences in the cation/anion uptake, especially with nitrate-N (NO3- -N) and ammonium-N (NH4+-N) supply. Nitrate is negatively charged, and ammonium is positively charged. Preferential uptake of cations such as NH4+ result in higher net excretion of rates of hydrogen (H+) causing a pH decline in the rhizosphere. Preferential nitrate-N uptake results in higher net excretion of rates of hydroxyl ions (OH-) causing an increase of rhizosphere pH. The portion of P in soil solution can be influenced by changes in the rhizosphere pH. The ability of plants to preferentially change the pH at the soil-root surface can be a significant factor in influencing soil P availability and uptake.

Fine root hairs, which are tubular extensions of root cells, are a result of lateral cell growth and can increase the surface area of the outer roots by two to 10 times. Root hair length varies from 0.1 to 1.5 mm. Root hair density varieties from 50 to 500 million per square metre of root surface. Most plants have root hairs; however, some crops, such as canola, only have an extremely small amount of root hairs or none at all. Root hairs can aid in ion uptake by plants and are most important in the uptake of immobile nutrients such as P.

Vesicular arbuscular mycorrhizae (VAM), which are soil fungi, can form a symbiotic relationship with plant roots of some crops. The mycorrhizae use plant carbohydrates for their growth and in return supply nutrients for plant growth. The primary benefit of VAM is to form hyphae that extend from the plant roots to increase P uptake, water and other nutrients such as copper and zinc. VAM is particularly beneficial in soils with low plant available P. However, not all crops can be infected or benefit from VAM, such as canola.

Labile organic P compounds can be mineralized rapidly in soils by an enzyme produced and released by roots called acid phosphatase. Some research has shown that plant-produced phosphatase can hydrolyze Po for improved plant nutrition. More research is needed to better understand which plants can produce and release acid phosphatase and the benefit to P crop nutrition.

The interaction between soil and plant roots is highly complex and is influenced by soil types, crop species, root characteristics, forms of root exudates, pH changes in the rhizosphere, microbial activity, types of enzymes produced, and influence of VA mycorrhizae.

Summary

This is a brief explanation of the soil P cycle, effects of cropping and fertilizing on soil P, and soil-plant root factors that affect plant uptake of soil P. Research here in Western Canada has clearly shown that continuous-cropped soils, with the addition N, P and other needed fertilizers, have resulted in the greatest benefits to the health and quality of soils and to good P cycling in soils.

In my next two articles, I’ll discuss testing methods for plant available soil P and how to develop wise fertilizer P recommendations.

The post Understanding soil phosphorus, part 1 appeared first on Grainews.

The two primary weapons against fusarium — fungicides and resistant varieties — don’t offer the same measure of control as they do for some other important cereal diseases. That’s why Kelly Turkington recommends an integrated approach incorporating best practices that can be used from seeding to post harvest to help farmers get a better grip on fusarium head blight.

Turkington, an Agriculture and Agri-Food Canada plant pathology researcher at Lacombe, Alta., discussed fusarium head blight management with Grainews about after delivering a presentation on the topic at the Manitoba Agronomists’ Conference in December.

Resistant varieties

Turkington notes resistance to Fusarium graminearium, the main species found on Prairie farms, is generally improving, with breeders continuing to make incremental advances in reducing the incidence and severity of fusarium damaged kernels (FDK) and deoxynivalenol (DON) mycotoxins in infected crops.

However, he says growers still need to have realistic expectations around resistant varieties. Wheat rated MR for F. graminearum, for example, won’t provide the same level of control as a variety with an MR rating for stripe rust would, for example.

“Under favourable conditions, like we had in the eastern Prairie region this year, that MR rating reduces the amount of disease,” Turkington says. “You might have five parts per million of DON where you have a susceptible variety, but with your MR variety, you’re still looking at probably two to three parts per million of DON. It doesn’t eliminate it completely, so that’s something to keep in mind.”

Crop rotation

Fusarium can survive on the residue of infected plants, and in very short or continuous rotations of cereal crops, the pathogen can build up and cause serious infestations. Longer rotations of least two years between host crops allows more time for crop stubble to break down and therefore reduces the risk of fusarium infection.

Turkington notes many Prairie producers opt to grow a two-crop rotation, alternating between a cereal crop and canola, which is a non-host crop for fusarium. He says that isn’t ideal for limiting fusarium risk, but he recognizes disease control isn’t the only concern for farmers who have other important rotation considerations, such as commodity prices, reliable markets and management issues for non-host crops such as field peas.

“I always emphasize that I’m recommending a rotation based on my knowledge as a plant pathologist. But at the same time, I understand there are many factors that will influence what crops you decide to plant,” Turkington says.

“Long term, if we can get some better cropping options for growers, we may have a better suite of crops that growers can look at, providing that opportunity to extend the rotational interval between susceptible or host species.”

Turkington says in areas with farmland where F. graminearum is well established, longer rotations may not be enough to prevent a fusarium head blight outbreak in a field if the pathogen is a problem in another one close by.

He notes wind-blown fusarium spores can easily travel from one field to the next, which is why it’s recommended farmers to try to avoid planting small grain cereals right beside cereal or corn fields where F. graminearum levels are known or suspected to be high.

Seeding

Using good-quality certified seed, and seed that has been tested for the fusarium pathogen, is thought to be helpful in fighting fusarium head blight in cereals.

Turkington says for farmers in those parts of the Prairies where fusarium is already well established, the primary concern is how much F. graminearum is present in a seed lot and its likely effect on seed performance.

“It’s very important in that situation to have a seed test done to look at germination and perhaps vigour, and then, of course, the disease load on the seed. That will give you some clues as to whether there are some issues with that seed lot,” he says.

“You have to have pretty high levels of seed infection to start to see a significant drop in germination and ultimately field performance. Typically, once you start getting above about 10 per cent seed infection rate, that’s where a lot of these seed performance issues start to show up.”

Turkington said research has shown fungicidal seed treatments don’t provide complete control of seed to seedling transmission of F. graminearum, but they can give crops a better chance of withstanding the disease and establishing a more uniform stand.

READ MORE: Fungicide timing for wheat leaf disease and FHB

If pathogen levels aren’t too high in seed, he says, good-quality seed treatment that’s applied using good application technology can help ensure rapid uniform seed germination, resulting in uniform seedling emergence and growth and a uniform plant stand.

This in turn will lead to uniform head emergence within the crop and a more uniform target for fusarium fungicide applications during the growing season.

Turkington says farmers wishing to protect cereal crops from fusarium should be mindful of seeding rates as well.

“Seeding rates relate to the uniformity of the target you’re trying to hit with fungicide, which is the head tissue. Lower seeding rates will result in more secondary tiller development and a potentially wider window for potential infection to occur,” Turkington says, acknowledging that challenging weather or soil conditions at seeding may also result in variable emergence and non-uniform crop development.

“It makes it much more difficult to get good coverage of all the head tissue in that field (and) that may increase your risk in in terms of having some issues with fusarium head blight,” he says.

According to Turkington, limiting irrigation at certain times on irrigated fields can also help. Since fusarium head blight thrives in moist conditions he says, reducing or withholding irrigation water for as long as possible after head emergence can help reduce the risk of disease development.

Limiting residue

Because F. graminearum can overwinter in crop stubble, practices that facilitate decomposition of this residue will help remove a potential source of inoculum. This can include using combine straw choppers/spreaders or other implements after harvest to chop up crop residue and distribute it widely over the field.

Turkington notes the smaller residue pieces are, the faster they will decompose. He adds making sure there’s a good spread of material across a field will help prevent those thick swaths of chaff and straw that may contribute to fusarium buildup in subsequent years.

According to Turkington, adjusting equipment so that disease damaged kernels are blown out the back of combines during harvesting can be another effective control measure.

READ MORE: Maps now mark the spots for fusarium risk

U.S. research shows that by removing smaller, lighter weight fusarium-damaged kernels this way, it can lead to grade improvements and also reduce DON levels in infected grain, he says. The practice typically works better for wheat and durum than for barley and oats, because of the type and extent of kernel shrivelling that occurs in these crops.

A potential drawback of this approach is it may increase the fusarium risk to subsequent crops, since it means highly infected material is going back in the field.

Turkington says the decision then for farmers is whether the benefit they hope to gain by having a more marketable grain crop outweighs the disease risk from FDKs, which are very prolific producers of the wind-borne spore stage of F. graminearum.

Turkington notes weed seed destroyers mounted on the back of combines could be another useful tool for limiting the spread of fusarium inoculum since in addition to weed seeds they can crush FDKs.

“I look at the research my colleague Breanne Tidemann had done with harvest weed seed destruction technology and feel it has a potential role to play. Here, you’re basically pulverizing that FDK tissue and facilitating its more rapid decomposition in the field. So there’s a much more rapid disappearance of that as a source of the disease,” he says.

The post More than one way to fight fusarium head blight appeared first on Grainews.

Although malting barley once yielded significantly less than higher-yielding feed types, this has now changed. 

“There’s been a pretty large increase in yield,” says Andrew Hector, cereal crop extension specialist with the Manitoba Crop Alliance. Newer varieties now produce yields close to CDC Austin, the top feed variety, he added. 

As a result farmers growing barley for feed are increasingly opting to grow a malting variety, even if it’s just to keep the door open to getting that malting barley premium, which can be as high as $3 per bushel, Hector says. 

But he says one of the biggest advantages of growing barley is that it gives farmers more control come harvest time. 

“It helps you space out your harvest if equipment or personnel constraints limit your options, offering more time management flexibility,” he says. 

Speaking to attendees at the Canadian Malting Barley Technical Centre’s CMBTC Producer Malt Academy course in Winnipeg last fall, Hector notes malting barley fits roughly into the same slot as wheat in a rotation. 

“Barley planted after cereal saw relatively low yield compared to something like canola,” he says, adding that in Manitoba over half of barley acres were planted into canola stubble.

Variety selection 

A good starting place for variety selection is the CMBTC’s annual Malting Barley Recommended Varieties list. 

Established varieties like AAC Synergy and CDC Copeland remain farmer favourites, while newer varieties such as AAC Connect, CDC Fraser, and CDC Churchill are quickly gaining in popularity. As mentioned, these new varieties are high-yielding, but also have better disease resistance and straw strength.

READ ALSO: New cereals on deck for 2025

“Some of the older varieties have poor lodging (resistance), and they didn’t stand as well, but lodging has vastly improved with these new varieties,” Hector says. 

The CMBTC recommends growers talk to their malting, grain, or seed company representatives to discuss options for growing malting barley. Farmers should also consult their provincial seed guide.

READ ALSO: New malting barley variety acceptance an uphill battle

Varietal purity 

Brewers demand variety purity in order to ensure consistency for their products. Shawn Pasieczka, a food safety grain specialist with Richardson International, said Richardson requests a minimum of 95 per cent purity and tests for it. To meet those standards, he recommends using certified seed.  

While Pasieczka says it’s possible to replant seed saved from previous crops, he warned that some buyers require certified seed. Even if the grower works with a company that doesn’t require certified seed, he recommended retesting the seed to ensure purity, and not to plant seed more than two years beyond certification. 

Seeding dates 

Generally, the recommended dates for planting barley depend on the region and variety, but generally they fall between late April and the end of May. 

READ ALSO: Critical factors in growing malting barley

“Seeding early is important if you want to maximize yield,” Hector says, but adds that the timing of seeding also impacts qualities such as protein levels and kernel uniformity and plumpness, which are important to malting companies. 

According to the CMBTC, North American brewers prefer protein levels between 10 and 11.5 per cent, while Chinese brewers accept slightly higher levels, up to 13 per cent. 

Seeding rates 

Hector says the recommended target plant population for malting barley is 22 to 25 plants per square foot. He points to research done by now-retired AAFC crop scientist John O’Donovan that showed that as seeding rate increased, kernel plumpness and protein concentration decreased. 

“They found that 300 seeds per metre squared was the optimum seeding rate for yield and malt quality,” Hector says. 

Nutrient levels 

A 2022 fertilizer use survey showed that nearly all malt barley growers applied nitrogen, typically as urea or anhydrous ammonia. 

When making nitrogen rate decisions for malt barley, growers should consult with their agronomists to ensure they’re getting the levels right. The CMBTC recommends soil testing to check nutrient levels. 

“There is a balancing act to determining how much nitrogen you should apply,” Hector says. “You need it to reach optimum yield, but excessive nitrogen risks higher than optimum protein levels.” 

Diseases 

The main diseases barley growers must contend with are scald, fusarium head blight and spot blotch. Disease levels depend on geography. Variety disease packages and cultural control methods can help, but at one point or another, a fungicide application could be necessary, and the proper timing of that application is critical. 

“Barley is a little different than wheat in terms of flower timing,” Hector explains. “The label recommendation is typically between 70 and 100 per cent of heads fully emerged on the main stem to three days post head emergence.” 

But Hector warns that heads that haven’t emerged will not have made contact with the fungicide and won’t have the coverage. So, he recommended trying to get as close to 100 per cent of heads emerged as possible. 

Crop protection products 

Malting barley has very strict standards when it comes to residue from crop protection products. Growers should check with the KeepItClean.ca campaign’s annual Product Advisory to ensure they don’t encounter market access issues when selling their grain. 

Products restricted for malt barley include the fungicides fluopyram and tetraconazole, the plant growth regulator chlormequat, and the herbicides glyphosate and saflufenacil. 

The post Fitting malting barley in your rotation appeared first on Grainews.