Early results from a multi-year University of Manitoba study suggest it might be possible to shave nitrogen fertilizer rates by 10 per cent or more when paired with the right products.

WHY IT MATTERS: Fertilizer costs are high, while fertilizer efficiency is continually being pushed thanks to federal emission reduction targets. Nitrification inhibitors, including best practices and their efficacy, are one feature of the conversation.

The research is led by Mario Tenuta, research chair in 4R nutrient management at the U of M, in collaboration with Manitoba Agriculture’s Manasah Mkhabela. There are four sites across different growing regions of the province, including the Prairie East Sustainable Agriculture Initiative (PESAI) in Arborg, Roblin, Melita and Carberry.

The study was launched in 2023 in response to Ottawa’s target to cut nitrous oxide emissions from fertilizer by 30 per cent by 2030.

Inhibitors and greenhouse gas emissions

The team’s goals were twofold: measure nitrous oxide emissions under different nitrogen rates and test whether nitrification inhibitors could curb losses without affecting yield. Plots were set up with zero, 70, 90 and 100 per cent of recommended N rates, both with and without nitrification inhibitors. The same treatments stay on the same ground each year to track the impact as soil reserves change over time.

Rotation on the plots began with canola in 2023, followed by wheat in 2024 — the only season from which full yield and emissions data are available so far. The study is ongoing.

Rebalancing the nitrogen equation

For farmers, the takeaway may be less about adding bushels through less nitrogen loss (and therefore more nitrogen availability) than about widening the profit margin by applying less fertilizer with the same yield.

The additional cost of inhibitors has been the complicating factor in that efficiency argument. Tenuta’s own earlier work suggests the products don’t reliably boost yield on their own.

“They reduce nitrogen losses, but farmers are already applying enough N that having more in the system usually doesn’t help them,” he said.

For farmers to see a robust economic argument for inhibitors, there must be enough room to strategically trim nitrogen rates, without yield impact, to offset the extra cost of adoption. The thought is less about cutting nitrogen application so much as rebalancing overall soil nitrogen.

Results and insights

A single year of data doesn’t offer much rigous data, but there have been some initial insights.

On the emissions side, apart from an anomaly at Roblin, inhibitors performed as expected.

“At the Arborg site, nitrous oxide dropped 23 per cent when we used a nitrification inhibitor,” said Mkhabela during a July field day at PESAI this summer.

There were comparable reductions recorded at Melita and Carberry.

Yield appeared to be unaffected by the inhibitor in 2024, but results suggest the soil at that time still held significant nitrogen reserves. Wheat grown with 100 per cent of recommended N averaged 64 bushels to the acre (bu./ac.). At a 10-per-cent reduction plus inhibitor, yield held at 63 bu./ac. Even at 30 per cent below the recommended rate, yield only dropped to 57 bu./ac. Unsurprisingly, the plots without extra nitrogen fell behind on yield, at 37 bu./ac.

Lags in plant impact to applied nitrogen, however, encourages researchers to be a little careful in speculating how deeply farmers can cut.

A 10 per cent rate reduction is low-risk, Tenuta noted, but much bigger cuts are more of a gamble.

Nitrogen stored in soil continues to feed the plants long after the last application of the nutrient. The more agressively nitrogen rates are reduced, the more quickly soil reserves will be depleted.

“If we drastically reduced nitrogen by 50 per cent, we probably wouldn’t see an effect in 2026,” he said. “But by 2028 we’d really see it.”

Similarly, the respectable yields Mkhabela observed with a 30 per cent nitrogen reduction will almost certainly diminish over time.

The long-term goal is to find that sweet spot: the lowest nitrogen rate that will consistently deliver good yields.

When asked where he thought that sweet spot would end up, Tenuta was conservative. Based on wider research, he guessed it would land in the neighbourhood of 10 to 15 per cent.

That might not be dramatic enough to get producers lining up to change long-held habits, he acknowledged.

“Nitrogen management is so ingrained in us,” he said. “We always think about going up, not down.”

Perception matters

Manitoba Agriculture farm management specialist Darren Bond broadly agreed, saying the decision isn’t only economic; perception matters, too.

Regardless of what the research says, producers will ultimately be the ones to pull the trigger on a management change.

“Is there benefit if you cut nitrogen 10 per cent and add an inhibitor? Maybe. Maybe not. Either way, we’re dealing with slivers,” said Bond.

He also noted environmental conditions can swing yield by 25 bu./ac. If farmers are asked to make decisions over pennies while weather can rewrite the whole outcome in a day, motivation tends to diminish.

“Mother Nature bats last when it comes to this type of stuff. That’s why producers are reluctant to cut nitrogen,” Bond said.

With a little more data, however, Bond noted the mental calculation on the issue could shift. That same nutrient-application-to-impact lag means that short trials tend to flatter aggressive rate reduction insights. For field studies like this, where changes unfold incrementally over years, longer trials are needed.

“Let’s go past three years to four, five, even 10, and start seeing what really changes,” Bond suggested.

The study’s long-term scope isn’t locked in yet, but Mkhabela told the PESAI tour crowd that the team is aiming for 10 years of funding.

Keeping it real

Current policies are adding another layer of consideration to the debate.

Government has launched a number of funding streams meant to bolster fertilizer efficiency in the wake of their 2030 emission goals. Those include subsidies and incentives through the Sustainable Canadian Agricultural Partnership (S-CAP) and other programs that may fund dual-inhibitor products, combining nitrification and urease inhibitors to offer additional benefits for growers.

“Urease inhibitors are like an insurance product to allow that nitrogen to get into the root zone and become more stable,” Bond explained. “The nitrification inhibitor is mainly impactful on greenhouse gases.”

Persistently tight margins could also change the outlook, he noted. When nitrogen was cheap, farmers just applied more urea to buffer against nitrogen losses. If prices rise and margins narrow further, the efficiency gains from nitrification inhibitors could start to look a lot more compelling.

Tenuta says it’s important not to over-promise with these products. Enhanced-efficiency fertilizers, including nitrification inhibitors, can play a role, but farmers need a clear-eyed view of what they can and can’t do.

“I don’t want good practices, and these products, to get a bad name,” he said. “If we can show farmers they can reduce losses and maintain profit, that keeps nutrient stewardship moving in the right direction. That’s the take-home message here.”

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Manitoba’s crop experts outlined one tactic to help farmers find out at the 2025 Crop Diagnostic School earlier this year at Carman.

Farmers using a ‘nitrogen ramp’ approach will increase nitrogen rates in increments, based on soil test recommendations.

It involves taking “whatever the nitrogen recommendation was from your field based in the soil test, and then comparing that to the nitrogen ramp to see, are you actually hitting (the target)?” said Anne Kirk, cereal crop specialist with Manitoba Agriculture.

“When is it the greenest? And then also, considering, if we’re applying more nitrogen, is that economical as well?” Kirk added.

If you’ve tested a nitrogen ramp in your cereal crop, there are a few ways to determine if your plants are taking up nitrogen as intended.

It can just be gauged by the amount of biomass in your crop and the colour of the leaf tissue to the naked eye, Kirk said — but there’s a catch to that strategy. Changing light conditions throughout the day can trick the eye and make it difficult to gauge differences in the shades of green in the leaves.

Farmers can take the guesswork out of the process with a nitrogen ramp calibration strip, she noted. Similar to a paint colour swatch you might see in the local hardware store’s paint department, the tool can help give more concrete insight.

“It’s not to identify which one is sufficient or deficient,” but rather is a comparative measure, she cautioned.

“If you have 80 pounds of nitrogen per acre compared to 100, is there actually a colour difference, or are they about the same?”

For the more tech-savvy, a device called a SPAD meter measures the amount of chlorophyll in a leaf. To take a reading, the user presses the flag leaf between the two paddles on the meter.

Kirk noted that while these readings don’t mean much on their own and do not replace soil nitrogen testing, they can be helpful when measuring against other parts of your field or where a different application rate was put down.

Nitrogen application strategies

When it comes to fall or spring nitrogen application in winter cereals, there are pros and cons to both.

“If you’re applying all of your nitrogen in the fall, the risk is that you can have excessive leaching if you have a wet fall,” Kirk said. “You can also have denitrification (gassing off of that nitrogen) and it wouldn’t be available to the plants.”

A full burst of nitrogen in the fall could also lead to excessive top growth in your plants, which could mean a less healthy crown going into winter and perhaps more winterkill, added Kirk.

“If you apply all of your nitrogen in the spring, the risk is that it could be dry … and if it doesn’t rain, that nitrogen isn’t actually getting down into the soil to your plant,” she added.

At the opposite end of the spectrum, field conditions in a wet spring could mean a grower may not get nitrogen on the field before it’s too late.

To avoid risk, Kirk suggests using a split N application — a portion applied in the fall and a portion in the spring to reduce the risks from both of these types of potential losses.

The key is making sure that nutrient is available to winter cereals when the crop is likely to need it the most.

“We know that winter wheat takes up about 30 to 40 per cent of its total nitrogen needs by stem elongation,” said Kirk. “So we really want to make sure that nitrogen is on and available for the plant by the time stem elongation happens.”

For more information on nitrogen ramp calibration strips, visit the Manitoba Agriculture website.

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“It was, you know, exciting,” Nykolaishen said, adding he “put a lot of work into this, and to get recognized like that was pretty fulfilling.”

Nytro and Green Lightning received the award for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form. It’s meant to help farmers reduce the cost of their nitrogen inputs.

“What you get is essentially water, but it has elevated levels of nitrate/nitrogen in the water,” he said. “It’s used as fertilizer, generally foliar application, so you spray it on, but it can be applied into the dirt at seeding time as well.”

—> WATCH: For more from Chris Nykolaishen, click here.

The 10-foot container model allows farmers to cheaply create their own nitrogen.

“The proposition of the Green Lightning Machine is to reduce your cost input year-in and year-out,” Nykolaishen said. “The cost-per-pound of nitrogen through the machine is approximately three and a half cents.”

The innovation award Nytro and Green Lightning took home was for sustainability. Nykolaishen explained the machine’s environmental benefits.

“First and foremost, the product is salt-free, so you’re not adding any salt to the soil.”

“And then you’re making it on your farm,” he said. “Synthetic fertilizers generally come in (from) overseas and getting to port and then having to get out to your farm. This is made on your farm, you know, where you need it.”

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Idaho potato farmer Blake Matthews caught the attention of Nature United with his crop-nutrition-first approach to pest management.

Matthews grows 3,000 acres of irrigated annual crops, including 400 to 500 acres of potatoes, the same in sugar beets, and the rest split among corn, barley and wheat. Over the past five-plus years, the farm applied one in-season fungicide to potatoes and only last year applied localized spray for insects — specifically, grasshoppers.

This minimal pesticide requirement may sound unbelievable, especially to other potato growers. “We do make some big claims,” Matthews says.

In addition to lowering pesticide use and synthetic fertilizer use, Matthews also says soil organic matter across the farm is in the three to four per cent range, up from a range from 0.7 to two before he put the focus on soil health and plant nutrition.

These numbers, in turn, caught the attention of Brad Johnson, Idaho agriculture strategy manager for Nature United (called The Nature Conservancy in the U.S.). Johnson says the non-government organization’s goal is to help modern agriculture become more sustainable. “We want to keep all tools, but seek judicious respectful use of pesticide products,” Johnson says.

Matthews Land and Cattle is one of Johnson’s demonstration farms.

Potatoes are an input-intensive crop, Johnson says. Potato crops often get soil fumigation for nematodes, along with fungicides and insecticides throughout the growing season. Matthews has all but eliminated these applications, Johnson says.

What’s more, Johnson adds, Matthews has also reduced tillage from four or five passes down to two passes, and reduced overall water use by 18 to 20 per cent.

Matthews “lets biology run the system,” Johnson says.

The core of the system is a soil health plan from long-time local agronomist Jared Cook. “Diseases and insects attack weak plants,” says Cook, agronomic specialist and sales consultant with Rocky Mountain Agronomics in Idaho. “And weakness is often related to nutrition.”

Cook has been working with Matthews and his family business, Matthews Land and Cattle, for 14 years. A key part of the soil health plan is manure compost from dairies and cattle feedlots, which improves organic matter and reduces the need for other fertilizer sources. Cook also prescribes two broad-spectrum hormones, which he won’t share because they are, he says, part of his competitive advantage.

For nutrients, Cook wants balance. He doesn’t want nitrogen availability to get ahead of the other nutrients. “In that situation, nitrogen robs yield,” he says. (Later in this article, Western Canadian crop nutrition experts comment that this can be true for potatoes and wheat, but perhaps not canola.)

“My game is to prioritize mineral nutrition, then use hormones to drive greater response,” Cook says.

The author told Cook during their interview that he usually looks at hormones and biologicals with a degree of skepticism. Cook supports that skepticism. “My approach has changed,” he says. “Ten years ago we didn’t have as many players in this space and I had almost complete trust. Now growers need a trusted advisory team.”

Cook emphasizes his methodical approach to nutrient decisions for all crops, using weekly and biweekly plant sap analysis of new and old leaves in combination with rapid soil testing. For Matthews, his in-season top-ups run through the irrigation system while watering.

With traditional tissue tests taken from new growth only, “you actually never know where the nutrient is coming from,” Cook says. “It could and should be from roots like normal or it could be from old leaves, where mobile nutrients are leaving the old growth to support new growth. We know yield is optimized when you can hold the plants’ old growth and new growth leaf nutrient density to a tight tolerance between them.”

Without accurate diagnosis, input use is “a guessing game and we just don’t need to be guessing,” Cook says. “These new advances in plant testing methods give us the edge in making the right decisions.”

Of course the final question is: does this intense level of management pay?

“We haven’t seen anything really for a yield change. We have, however, seen our quality go up in many different aspects,” Matthews says. “As far as the spend goes, for the most part, we’ve just traded dollars. We’ve replaced fertility with the compost, and replaced fungicides, insecticides and fumigants with nutritionals and biologicals. Overall, though, we probably save about $100 per acre from what our old program used to be.”

Reaching out to Prairie expertise

For many farms, ideal fertilizer management is simple: use soil tests to identify the right rate based on the farm’s yield target. Then choose nutrient sources that meet crop needs at the lowest cost and the greatest logistical efficiency. Manure can be a great nutrient source and organic matter booster when available and when applied based on nutrient analysis.

With these basics established, farms could dig deeper — in the way Matthews has — and hire an experienced agronomist to develop a more comprehensive plan.

Jared Cook outlines the four practices at the heart of his program:

• Balanced nutrition can make plants more resilient to insects and disease, and reduce the need for fungicides and insecticides.
• If farms put the primary focus on higher nitrogen rates, that extra nitrogen — when other nutrients are out of balance — can actually rob yields.
• Plants with correct nutrition have higher sugars (brix) and more secondary metabolites – compounds plants use to defend themselves.
• There are 16 essential elements, each with a specific mode of action. We need to pay closer attention to micros.

Do those four practices work for the common crops and farm systems in Western Canada? We polled western Canadian specialists — crop nutrition researchers, experienced agronomists and plant physiologists — to see what they thought of Cook’s four practices.

Balanced nutrition can make plants more resilient to insects and disease, and reduce the need for fungicides and insecticides. Is this true?

“It’s true, a crop with balanced nutrients can better tackle diseases and insects,” says Raju Soolanayakanahally, a plant physiologist with Agriculture and Agri-Food Canada in Saskatoon. “Balanced nutrients permit vigorous growth, thus providing active immunity as a result of increase phytonutrient, protein and lipid synthesis. Apart, photosynthesis will operate at its peak under balanced nutrition and adequate soil moisture. So if pests attack the plant, the plant can divert resources to tackle biotic stress without compromising yields.”

In general, experts agree healthy plants will be hardier plants. However, that does not mean healthy plants are immune to disease.

“Higher fertility leads to more vegetative growth, and lush canopies create a microclimate conducive for higher disease severity,” says Mike Harding, crop assurance lead for Alberta Agriculture and Irrigation. “In many cases the conditions for maximum plant growth are also the conditions for maximum disease potential.”

Chris Manchur, agronomy specialist with the Canola Council of Canada, adds, “We all know sclerotinia risk is higher in high-fertility environments.”

Jason Voogt says crop resilience to disease or insect pressure has “more to do with genetics.” The owner and lead agronomist with Field 2 Field Agronomy at Miami, Man. gives an example: “We had 200-bu./ac. oat crops in 2024. I would say those oats didn’t lack anything, yet we would have had major losses to crown rust had we not sprayed a fungicide this year.”

Ross McKenzie, retired agronomy research scientist with Alberta Agriculture, agrees nutrition is one path but not the only path to hardier plants. “A number of good agronomic factors, including soil fertility and fertilizer management, increase crop health, improve yield potential and help to reduce the impacts of diseases and/or insect pressure,” he says. “Probably the most notable is earlier seeding and slightly higher seeding rates.”

Lyle Cowell, Nutrien senior agronomist based at Tisdale, Sask., can cite many studies showing how specific nutrient deficiencies can increase specific diseases in specific crops. For example, “early examples showed that phosphorus deficiency leads to increased seedling rot due to pythium,” he says, citing a 1935 journal article by T.C. Vanterpool in the Canadian Journal of Research.

However, adding a nutrient to a crop that is not deficient will not “cure” a disease, he says. “For example it has often been suggested that copper will reduce ergot in wheat, but this is only true if the wheat is deficient in copper.”

If farms put the primary focus on higher nitrogen rates, that extra nitrogen — when other nutrients are out of balance — can actually rob yields. Is this true?

“I do not believe this for canola,” says Mario Tenuta, research chair in 4R Nutrient Stewardship at the University of Manitoba. He does believe it for other crops, giving two examples: wheat can lodge with excess nitrogen, and potatoes can have excess vine growth — two things that could, in theory, increase disease.

“I don’t believe this, except in the extreme, like where nitrogen levels become so high that they are toxic,” says Harding. “Studies I’m familiar with show that excess nitrogen is not advantageous or detrimental to yield. I do believe that excess nitrogen is a waste of money, so it will rob profit, but not yield. It is also possible that the lack of other nutrients may rob yield, but excess nitrogen will not.”

Others, including Cindy Grant, were believers. A retired research scientist with Agriculture and Agri-Food Canada at Brandon, Man., Grant says yield can decrease if growers add excess nitrogen without a balanced supply of other nutrients.

“Years ago, when I was a student and before it was widely recognized that our soils would be deficient in sulphur for canola, my husband-to-be had severe sulphur deficiency on his canola field,” Grant says. “It ended up getting every disease you could think of because the deficiency weakened it. I had one trial where every treatment that I used to improve nitrogen efficiency decreased canola yield because of an nitrogen:sulphur imbalance.”

Plants with correct nutrition have higher sugars (brix) and more secondary metabolites — compounds plants use to defend themselves. Is this true?

This one left most of our experts scratching, especially with regard to brix — a measure of plant sugars often used to assess grape sugar content when making wine. Higher brix means potentially higher alcohol content in the wine.

Cowell says brix is becoming a bit of a hot topic. “I have oddly been asked about brix many times this winter,” he says, “and my reply has been the same. If you grow wine and want to harvest for best sugar content, then brix is a tool to use. Otherwise, where is the data?”

Tenuta has a similar thought: “If brix was so useful, we’d be all be using it like a soil test.” He did, however, agree that good plant nutrition can lead to secondary metabolites useful in plant defence.

Xiaopeng Gao, associate professor of soil fertility and agronomy at the University of Manitoba, says “proper nutrient supply can improve plants’ photosynthesis efficiency, producing more sugars and secondary metabolites such as flavonoids, alkaloids and phenols. These compounds can help plants against attacks from pathogens and pests. Additionally, some compounds such as flavonoids can improve plants’ antioxidant properties, and therefore increase tolerance to abiotic stresses such as heat and drought.”

Soolanayakanahally agrees. “Higher secondary metabolites can impart better defence against pest and disease.”

There are 16 essential elements, each with a specific mode of action. We need to pay closer attention to micros. Is this true?

The experts generally agreed with this.

“I believe there is a growing need to pay attention to micros across Prairies,” Gao says. His reasons: one, canola, soybeans and corn have high requirements for micros and their acres, in total, are increasing. Two, fewer mixed farms mean lower use of livestock manure. And three, we are paying more attention to the importance of micros (for examples, iron and zinc) for human health.

Cowell says pay closer attention to micronutrients only if you need them. “The idea that micronutrient deficiencies are ‘hidden’ is a fallacy — these deficiencies tend to lead to yields falling off a cliff,” he says. He sees zinc applied to soils with no need for extra zinc and while he has seen boron deficiencies, it was “only on terrible soils that no one should farm.” Cowell’s conclusion: “Beyond that, this becomes a wasteland of marketing and improper sales.”

MORE ON MICROS: Soil fertility, revisited

Harding says manganese and zinc are “often heralded as having disease-reducing properties.” He also says boron availability is connected with clubroot infection in canola, and chloride deficiency can “predispose some crops to certain infections or physiological issues” — but again, only if they’re short.

Harding puts this whole conversation in perspective: while macronutrient and micronutrient fertility is a “critical agronomic principle necessary to allow the crop to reach its genetic potential, it is probably only occasionally a significant modulator of disease,” he says. “It is never as impactful as primary disease management principles like genetic resistance, crop rotation, clean seed and fungicides.”

The take-away

How do farmers use this information?

We interviewed a venture capital investor recently who encourages Canadian agriculture to at least pay attention to those voices at the fringe of common practice. Those may be the people who bring forth revolutionary ideas to make farming more efficient, more productive and more profitable.

In many cases, though, farms can advance all three of these by exploring the practices we already know.

Whether leaning into what we know or exploring the new and untested, it helps to have help. Get sound advice from an experienced agronomist. And listen to that little voice in your ahead that wonders, ‘Can this be right?’

“As we’ve gone down this road, the No. 1 skeptic has been my dad,” Matthews says.

What the family discovered together is that “the old days of strictly managing nitrogen, phosphorus and potassium are gone,” Matthews says. And from that point, their work with Cook has shown “plants in balance will have lower pest management costs.”

While we do not have much crop data to support this claim on the Prairies, the logic in those two broad statements is sound — as our experts have shown. How farmers achieve that “balance” is still open to debate. But if we are to make the efficiency gains we need to make, these are discoveries worth making.

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Crops exhibit different water use efficiency in every part of the Prairies. Water use efficiency is also weather dependent and when combined with best management practices for fertilizers and desirable crop genetics it leads to maximum yields. The late Les Henry and I exerted significant effort to derive yield equations for the Prairies that are based on water-use efficiency. The “available growth water” for any crop is based on “available” soil water plus growing season (May, June, July) precipitation, plus irrigation, where applicable.  

We can obtain information such as average values from Environment Canada or provincial data. We can also gather actual values from farmer precipitation records, Brown moisture probe and soil texture to convert moist soil depth to available water. Finally, we need to determine which fertility products work and which do not, and, of course, choose the former. 

Advanced nitrogen management 

Nitrogen (N) fertilizer management is receiving considerable attention these days due to fluctuating prices of nitrogen fertilizers and crops and the realization that maximum yield does not always result in maximum profit. The amount that a producer spends on additional fertilizer to achieve maximum yield may not result in higher profit, or at times, a profit at all. It is important to remember that:  

(crop price x yield inc.) – (N price x N rate) = Net Return  

Hence the 4R (right source at the right rate, right place and right time) principle leads to selecting the right fertilizer product and using it at the right rate to achieve maximum economic return. The key is to manage N availability for plants by reducing losses, especially when there is a long period from application to crop demand. During this period, N is susceptible to loss as a result of primarily three loss pathways — volatilization, denitrification and leaching. 

Enhanced efficiency fertilizers can play a role by offering protection against these loss mechanisms. 

Enhanced efficiency fertilizer 

Based on the definition provided by the Association of American Plant Food Control Officials (AAPFCO 2008), enhanced efficiency describes fertilizer products with characteristics that allow increased plant uptake and reduce the potential of nutrient losses to the environment, such as gaseous losses, leaching or runoff, as compared to an appropriate reference product. Urea has been our common reference product. 

Why the interest in enhanced efficiency fertilizers now? Enhanced efficiency fertilizers are part of a good 4R nutrient stewardship plan. Relative research on 4R nutrient stewardship has shown that enhanced efficiency fertilizers optimize soil and nutrient management, improve crop yields, lower environmental losses without sacrificing yield potential and, based on their definition, grow more on less land.  

However, producers rarely have the means nor the luxury of time to strictly adhere to these principles. Therefore, it appears that one of the main reasons that producers move to using enhanced efficiency fertilizers is for operational efficiencies versus agronomic efficiencies, due to increasing farm size. Based on Statistics Canada data, the average size of farms has doubled in the last 50 years, whereas the number of farms decreased by the same proportion.  

Let us examine some examples starting with broadcasting urea in the fall, which is not an efficient means of applying N. However, dual inhibitor stabilized fertilizer allows for that inefficient practice to become efficient by suppressing all three N loss mechanisms, as it contains both a urease and a nitrification inhibitor. This maintains a higher level of ammonium nitrogen for a longer period.  

The choice of the right product, especially at the right rate, becomes essential in this practice, since some inhibitors, such as dicyandiamide, have a bacteriostatic rather than a bactericidal mode of action. In other words, they inhibit but don’t kill microorganisms. Further, dicyandiamide is 67 per cent N and serves a dual role as a controlled-release fertilizer. Research in Eastern Canada raised concern as it revealed that shallow banding (<two inches) results in greater losses than broadcasting of urea. Shallow banding is inadvertently carried out in many one-pass systems (side-banding or mid-row-banding). Research in Western Canada verified this observation. 

In light of the above observations, it becomes apparent that enhanced efficiency fertilizers can simplify fertilizer application. For example, fall application of urea becomes more effective in Prairie environments. Further, single applications can replace split applications in humid environments. In the end, enhanced efficiency fertilizers, when used properly, can contribute to improved regional economic development and net farm income. 

4R nutrient stewardship  

The first step in managing your soil is knowing what’s in it. Therefore, soil testing is of high importance. We have already covered the basics of soil testing in a previous article. Then you need to decide what you are going to fertilize for — in other words, crop choice and potential yield. And finally, what you are going to fertilize with, which brings us to the choice of product. 

The major factors that make a product’s effect different or the same include product chemical makeup, soil chemistry, plants and of course a combination of all of the above. The comparison of all the above factors will have to be based on the same placement, the same rate and the same time of application, which again brings us to the 4R principle. 

Several different enhanced efficiency fertilizer products have been in existence for many years and a number have been recently introduced in the market. The enhanced efficiency fertilizer products can be divided into three major categories: 

1. Uncoated slowly available fertilizers containing N, such as urea-aldehyde, condensation products (e.g., urea-formaldehyde reaction products, sobutylidenediurea or IBDU), triazines, etc. 

2. Physical coating or barrier around soluble N fertilizer, such as sulphur-coated urea, polymer-coated/controlled-release urea, and combination products. 

3. Stabilized materials that include urease inhibitors, nitrification inhibitors, or dual inhibitors. 

When it comes to major crops in Western Canada, only the first two categories are in use.  

Let us examine these types of enhanced efficiency fertilizers starting with urease inhibitors. 

When to consider urease inhibitors 

The use of urease inhibitors is warranted and recommended when there’s a high risk of volatilization. Factors that will affect ammonia volatilization include:  

• Soil moisture as it affects the dissolution of urea which is the first step in hydrolysis. 

• High soil pH as it shifts pH equilibrium toward ammonia. 

• Warm temperatures as the enzymatic rate is faster at higher temperatures. 

• Low buffer capacity as soil is less able to resist localized pH increase. 

• High crop residues as there is greater urease activity in plant residue, less soil contact and higher moisture content. 

• And, finally, wind as it leads to evaporation and physical removal of ammonia. 

In general, ammonia volatilization occurs due to a rapid rise in pH around an unprotected urea granule. When urea is applied to the soil, the enzyme urease mediates a reaction that causes it to hydrolyze. This reaction converts urea to ammonium (NH₄+), which is great, as ammonium is a cation and can be adsorbed onto clay colloids.  

The problem is that the reaction also creates bicarbonate that elevates the soil pH in the vicinity of the fertilizer granule. Increases of up to three to four pH units have been shown to occur in many studies. If the pH of the soil solution is less than 7.2-7.5, ammonium will be the dominant ion present. However, as the pH increases, ammonium is converted to ammonia and, of course, ammonia, being a gas, will result in loss.  

Surface broadcast urea, spray-applied urea-ammonium nitrate or prolonged exposure of urea with no rain will worsen this loss. So will conditions such as heavy dew, followed by warm wind, especially under heavy plant residue.  

As a result, many people use volatilization inhibitors for peace of mind or as insurance. But is this wise? 

Recommendations to lower volatilization 

Several practices have been recommended to reduce volatilization. They include:  

• Use of urease inhibitors (Watson et al.1990), who demonstrated the benefit of using a urease inhibitor (NBPT). 

• Slow-release forms (Rao, 1987), which demonstrated the benefits from the broadcast application of two slow-release sources, sulphur-coated urea and lac-coated urea. 

• Irrigation shortly after application (Holcomb et al., 2011). The researchers plotted the amount of irrigation versus total ammonia N loss and demonstrated that when water is applied, there is an immediate reduction in ammonia volatilization with increasing irrigation rate. They found that irrigation with 30 mm (1.2″) of water resulted in approximately 0.5 per cent loss, whereas irrigation with two mm (0.08″) of water resulted in approximately 60 per cent loss. 

All the above practices have been researched several times over the years. However, the most common practice in Western Canada has been deep banding the fertilizer into the soil, as in most cases the ammonia produced due to volatilization is absorbed by the soil above the deep band. 

When it comes to deep banding, research in the ’70s with anhydrous ammonia showed higher yields than broadcasting other N sources, making people believe that it was a better N form. However, John Harapiak with Western Co-op Fertilizers (Westco) at that time suggested that urea should be placed in the same depth as anhydrous ammonia. In 1985 Harapiak published the average ratings from 28 trials carried out between 1977 and 1980, illustrating the benefits of deep banding. It turned out that it was banding, rather than the form, that was providing the advantage, since urea produced the same results. 

In conclusion, deep banding remains the standard placement method of urea-based fertilizers in Western Canada. However, as the farm size increases, farm operators are seeking operational efficiencies and are switching to broadcasting. Research results in Western Canada support the use of urease inhibitors to minimize the risk of nitrogen losses when deep banding placement is replaced with either shallow banding or broadcast. 

Volatilization stabilizers  

North Dakota State University’s soil science department has extensively examined several volatilization inhibitors. In nine studies that were reported at the North Central Extension-Industry Soil Fertility Conference in 2011, several products demonstrated little value as fertilizer additives to inhibit urea hydrolysis, nitrification or ammonia loss from soil.  

On the other hand, many studies have demonstrated the value of N-(n-butyl) thiophosphoric triamide (NBPT) as a volatilization inhibitor. For more information, I would strongly recommend that one should read the Nitrogen Extenders and Additives publication by NDSU.  

Further research by North Dakota State University showed that NBPT-treated urea had the potential to increase grain yield and protein content of hard red spring wheat compared with a homogenous blend of urea and ammonium sulphate product, urea plus ammonium sulphate, and urea alone. Adding sulphur sources did not result in a yield advantage over urea alone. Urea treated with NBPT may optimize hard red spring wheat yields even at rates lower than the optimum fertilizer recommendation. 

When to consider nitrification inhibitors 

With nitrification and volatilization inhibitors, we are addressing three types of nitrogen losses: volatilization, denitrification and leaching. One important component to remember is that both nitrification and volatilization reactions are mediated by enzymes. Therefore, our aim is to minimize their action. Both leaching and denitrification losses occur due to nitrate. 

The factors that affect nitrification are moisture (moist, not saturated), temperature (maximum approximately 27 C and minimum zero C) and pH (favoured by pH below seven and slowed by pH greater than six). 

When we apply urea or ammonium fertilizers (e.g., ammonium sulphate), enzymes such as ammonia monooxygenase convert ammonium to nitrite (nitrification). These enzymes are found in soil bacteria and microorganisms. Nitrification inhibitors act to reduce the enzyme’s oxidation action and prolong the presence of ammonium in the soil. Limiting the nitrification of ammonium will also minimize the emissions of nitrous oxide. 

A very interesting project was carried out back in the ’80s at the University of Saskatchewan examining leaching and denitrification losses of fall- versus spring-applied nitrogen. Up to approximately 35 per cent of autumn-applied 15N-labelled fertilizer N was lost via denitrification and seven to 20 per cent became immobilized by the following spring. Leaching was not responsible for the lower efficiency of fertilizer N. The potential denitrification rates were markedly higher in zero tillage and the population of denitrifying microorganisms was up to six times higher than in the conventional tillage fields. Further, crop residues doubled the gaseous N losses. Temperature above 5 C did not alter denitrification rates nor did a wide range of mineral N. 

Are all nitrification inhibitors the same? 

Again, the principle of the right source and rate has to be adhered to. Research at North Dakota State University showed that, for example, SuperU and Instinct maintain urea in the form of urea and/or NH4+ for an extended period whereas other products behaved as non-treated urea. The reason for this benefit is based on the fact that these products protect nitrogen from loss, since nitrogen in the ammonium form is not at risk of leaching and denitrification losses. 

Check the active ingredient concentration 

The concentration of the active ingredient delivered by a product has a direct effect on how well a product will inhibit loss of nitrogen through nitrification as well as ammonia volatilization. For example, research dated back to the ’60s demonstrated that higher concentrations of dicyandiamide (DCD) equate to a higher percentage of nitrification inhibition. Furthermore, a concentration of approximately one per cent of the active ingredient is required to obtain maximum protection from denitrification.  

However, it is impossible to coat urea, for example, with that level of DCD. Hence the inhibitor is added to the product when it is in the liquid form, (i.e., before granulation). I reported on some research back in 2019 with three products — one containing 8,500 ppm of DCD and 600 ppm of NBPT, the second 870 ppm DCD and 600 ppm of NBPT and the third 665 NBPT. I demonstrated that the second and third products performed equally in inhibiting volatilization. However, the second did not perform equally with the first in inhibiting denitrification as a result of the lower concentration of DCD. 

Dual inhibitors 

Dual inhibitors provide both a urease inhibitor and a nitrification inhibitor with one coating. The advantage of using dual inhibitors lies in the fact that the urease inhibitor will prevent volatilization. Meanwhile, the nitrification inhibitor will prevent leaching and denitrification — in other words, integrated active ingredients.  

This results in both immediate and extended N availability, while extending the safety to soil biology. The only possible disadvantage would be that dual inhibitors do not offer time delay or a controlled-release mechanism. Fertilizer placement will affect the effectiveness of the dual inhibitors. Deep banding of urea treated with dual inhibitors has shown no benefit over untreated urea in many studies whereas when broadcasting or shallow banding they showed tremendous benefits.  

Polymer-coated/controlled-release ureas 

Now we turn to enhanced efficiency fertilizers with a physical coating or barrier around the soluble N. The products in this category that are used in Western Canada are known as polymer-coated urea or controlled-release urea. It is important to understand nitrogen demand for various crops and nutrient application timing to make proper use of these products. 

Polymer-coated urea can improve plant uptake of the nutrient when properly applied — in terms of timing and placement — and reduce losses of nitrogen to the environment. Also, depending on climate conditions, it can alter nutrient availability timing so nutrient is available when crops need it. 

Adherence to the 4R nutrient stewardship principle is of utmost importance, as some components differ from other enhanced efficiency fertilizers. Right time is still important with polymer-coated or controlled-release urea. In order to be successful in using a polymer-coated product, one must understand when peak N demand is for their crop. For example, if the “delayed-release fertilizer” delays the nitrogen availability past when the crop needs the N the most, the producer will suffer yield loss. 

It is extremely important to remember that moisture is needed for polymer-coated ureas to work. This is because the polymer coating protects the urea. The polymer coating helps prevent volatilization losses, but moisture needs to enter the granule and dissolve the urea so the urea can diffuse through the coating. The nitrogen then moves into the soil.  

However, if there is no moisture, urea can be stranded inside the coating. If one broadcasts the polymer-coated urea instead of placing it in the soil, especially in drier environments, the lack of moisture means fertilizer granules sit on the soil surface. While stranded on the surface, they won’t become hydrated. Therefore, broadcasting polymer-coated urea without incorporating it in Western Canada is not usually advisable because lack of moisture means fertilizer granules sit on the soil surface and volatilize.

The photo in Figure 1 was taken seven weeks after the broadcast application of polymer-coated urea. One can observe here that the broadcast polymer-coated urea was stranded by lack of moisture, which can occur in prairie environments. This can lead to increased volatilization which means your crop won’t get to use it, which is like letting your profits evaporate. Therefore, incorporating polymer-coated urea will decrease volatilization and increase plant uptake.

Back in my Westco days, we carried out 18 experiments to determine the suitable conditions for controlled-release urea application in Western Canada. Figure 2 was taken during a three-year experiment with forages in the Peace River region and illustrates why controlled-release urea should be incorporated into the soil. Delay in release of N from controlled-release urea meant the crop was unable to take advantage of the N during the best growing conditions. 

Polymer-coated ureas and seed placement 

Seed-placed polymer-coated urea provides an effective means of reducing seedling injury from seed-placed nitrogen. From a 4R point of view, this consistently provides the best placement for polymer-coated urea products. Research in Western Canada has shown that polymer coating dissolves to sync well with canola’s maximum N uptake. And although wheat and barley demand is less well-timed to polymer coating dissolution, it still constitutes an effective method of placing polymer-coated ureas, especially since when untreated urea is seed placed, it is where the plant needs it, but can burn the seedling. Polymer-coated urea is recommended with winter wheat only when all N is intended to be placed with the seed and rates of N are more than 55 lb. N/acre. Based on the time of application and placement, the economic response of polymer-coated urea use is as follows: fall-banded polymer-coated urea < spring-banded polymer-coated urea < seed-placed polymer-coated urea < seed-placed polymer-coated urea/urea blend. The greatest opportunity for economic benefits with polymer-coated urea was for canola followed by wheat and barley. 

Both soil temperature and soil moisture govern polymer-coated urea N release. Cool conditions at seeding will slow the release of N from polymer-coated urea. Lack of contact with soil moisture may also affect the release rate; therefore, polymer-coated urea should be applied such that it has soil contact. It is recommended that a blend of polymer-coated urea and readily available N (e.g., urea or ammonium sulphate), be used to supply immediate early-season crop N needs, and polymer-coated urea-N for season-long feeding of a crop. The economic benefit of a 25 per cent urea-75 per cent polymer-coated urea blend was shown by Alberta Agriculture. 

Polymer-coated urea is a technology that “works,” i.e., provides protection of urea under conditions of high volatilization. High volatilization conditions are not predominant in many parts of Western Canada unless the 4R principle is not adhered to. Simply replacing your standard urea usage with polymer-coated urea can result in poor economics, especially in drier environments. It is important to understand where in your cropping system polymer-coated urea can bring value. 

Right place and time 

To summarize, there are many instances when nitrification inhibitors can be effective in Western Canada. These include: 

• any conditions that will lead to losses from nitrates due to denitrification. 

• fall application or early spring applications. 

• slow spring melts. 

• irrigation. 

• wet, light soils, or wet, heavy textured soils, or continually wet soils.  

Further, one has to consider the conditions, such as seasons and soil types, under which nitrogen losses will be minimal. Those include seasons and soil types where nitrogen-loss conditions occur after the nitrification inhibitor has become ineffective or when soil-plus-fertilizer nitrogen far exceeds crop nitrogen requirement, whether this is intentional or a result of weather conditions.  

Also, for the inhibitors to be effective, they have to be in proximity with the NH₄ in the soil. Therefore, any separation between a nitrification inhibitor and NH₄ — or where the positional availability of NH₄ is a factor especially under dry soil conditions — could reduce any benefit from an inhibitor. We should also keep in mind that there is no single “best” fertilization system since every farm, field and year has unique demands, resources and conditions. 

Conclusions 

Several take-away messages can be derived from this article: 

1. Know your fertilizer placement depth. If it’s not deep enough, stabilize. 

2. Efficiency is about potential loss versus the value of time. Understand how valuable time can be, since completing operations in a timely manner can contribute to increased profitability. 

3. Rate matters. Know the science behind the products you are using and recommending. Ask questions. Make sure there are third-party data. Again, remember the definition of enhanced efficiency products. They allow increased plant uptake, therefore, should be used at lower rates than non-stabilized products. 

4. Find the balance between agronomics and economics. The highest possible yield does not usually mean the most profitable crop. Nitrogen management tools can help you and your client determine the maximum economic yield.  

5. Focus on the fundamentals of crop nutrition first. Know when the crop needs nitrogen, then apply it when the crop can use it.  

6. If the conditions do not warrant the use of inhibitors, your client doesn’t need them. 

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

References 

Karamanos, R.E. and Henry, J.L. 2007. A Water-Based System for Deriving Nitrogen Recommendations in the Canadian Prairies. Chapter 11, in.  

Bruuslema, T. (ed.). Managing Crop Nitrogen for Weather. Proceedings of the Symposium “Integrating Water Variability into Nitrogen Recommendations.” International Plant Nutrient Institute, Norcross, Georgia. 

J. Environ. Qual. 38:1383–1390 (2009) and 42:1635–1642 (2013). 

Watson et al. 1990. Effectiveness of the urease inhibitor NBPT (N-(n-butyl) thiophosphoric triamide) for improving the efficiency of urea for ryegrass production. Fert. Res. 24:11-15. 

Rao, D.L.N. 1987. Slow-release urea fertilizers — effect on floodwater chemistry, ammonia volatilization and rice growth in an alkali soil. Fert. Res. 13:209-221. 

Holcomb, J.C. et al. 2011. Effect of irrigation rate on ammonia volatilization. Soil Sci. Soc. Am. J. 75:2341-47. 

Thapa, R., Chatterjee, A., and Cattanach, N.R. 2015. Managing nitrogen loss for hard red spring wheat, Crops & Soils: Volume 48, Issue 5, p. 22-24.  

Aulakh, M.S and Rennie, D.A. 1986. Soil and Tillage Research 7:157-171 

Goos, J.R. and Guertal, E. 2019, Evaluation of Commercial Additives Used with Granular Urea for Nitrogen Conservation. Agronomy Journal 111:1-7. 

Karamanos, R. 2019, The Impact of DCD and NBPT Concentration on Nitrification and Volatilization, Soils and Crops 2019, 5 March, Saskatoon. 

Tiessen K.H.D., Flaten D.N., Grant C.A., Karamanos R.E. and Entz M.H. 2005. Efficiency of fall-banded urea for spring wheat production in Manitoba: Influence of application date, landscape position and fertilizer additives. Canadian Journal of Soil Science 85:649-66. 

Tiessen, K.H.D., Flaten, D.N., Bullock, P.R., Burton, D.L., Grant, C.A. and Karamanos, R.E. 2006. Transformation of Fall-Banded Urea: Application Date, Landscape Position, and Fertilizer Additive Effects. Agronomy Journal 98:1460-70. 

Karamanos, R.E. 2017. Fall and Spring Placement of Nitrogen Fertilizers. Where do Enhanced Efficiency Fertilizers Fit.  in Proceedings 2017 Manitoba Agronomist Conference, December 13-14, Winnipeg, Faculty of Agricultural and Food Sciences, University of Manitoba, Winnipeg, Manitoba. 

Karamanos, R. 2013. Nutrient Uptake and Metabolism in Crops. Understanding the Basics of Crop Growth and Development, Prairie Soils and Crops 6:52-63. 

Kryzanowski, L., Akbar, A., McKenzie, R.H., Middleton, A.B., Sprout, C., Henriquez, B. and O’Donovan, J. 2010. Enabling Adoption of Environmentally Smart Nitrogen (ESN) Technology to Maximize Economic Returns and Environmental Benefits in Alberta. Alberta Agriculture and Rural Development and Agriculture and Agri-Food Canada. Edmonton, Alberta 103 pp. 

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Farmers invest heavily in nitrogen fertilizer, but not all of it makes it into the crop. Some is lost to the environment, tied up in the soil, or simply underutilized. Understanding how much nitrogen actually gets taken up by plants is key to improving efficiency — both for profitability and sustainability.

Measuring efficiencies

The most common method for measuring nitrogen efficiency is the “difference method,” in which researchers compare two plots — one fertilized, one not — and calculate the difference in nitrogen uptake. This approach is simple, inexpensive and practical.

However, it assumes fertilizer doesn’t change soil nitrogen dynamics — an assumption which isn’t entirely accurate. Since soil nitrogen interacts with applied fertilizer in complex ways, this method can give a rough estimate, but lacks precision.

A far more accurate method involves tracking nitrogen itself. Using a stable isotope of nitrogen called N-15, researchers enrich fertilizer and trace its exact movement in the soil and plants. This “isotopic method” provides a direct measurement of how much applied nitrogen reaches the crop, rather than relying on assumptions.

To that, though, there’s also a downside: it’s incredibly expensive. A single acre’s worth of isotope-labelled fertilizer can cost over $170,000, limiting these studies to small research plots.

Despite the cost, isotopic research is uncovering valuable insights into nitrogen efficiency. At the CropConnect Conference in Winnipeg in February, Kelsey Griesheim, a North Dakota State University (NDSU) assistant professor of soil fertility, shared what her isotopic studies have revealed about nitrogen uptake and efficiency in cropping systems.

The bulk of Griesheim’s presentation centred on several studies that she conducted in central Illinois, prior to her tenure at NDSU.

Subsurface versus surface dribble

In one of those studies, Griesheim looked at nitrogen placement during sidedressing, comparing a traditional subsurface knife application to a Y-Drop surface dribble system.

The study tested four treatments. The first was broadcasting all nitrogen up front; the second was a 50/50 split with subsurface sidedressing; the third was a 50/50 split using Y-Drop; and the last treatment was a repeat of the third treatment.

“That’s not a typo,” Griesheim says, referring to that repeated treatment. “We wanted to know whether that first application more efficient than the second. By taking the difference between those two treatments, you can prise that apart and look into it.”

The results showed more nitrogen was taken up by the crop at the sidedress stage, meaning late-season applications were generally more efficient. However, under certain conditions, the subsurface application was more efficient than Y-Drop.

“If you have conditions conducive to ammonium volatilization, the subsurface application will be higher in efficiency than the Y-drop application,” she says.

Banded placement outperforms broadcasting

Griesheim also tested nitrogen placement at planting using Precision Planting’s Conceal system. The study compared four treatments: a single-band and a dual-band UAN application straddling the seed row, a surface dribble with a drag chain, and a broadcast application. All treatments applied 80 lbs. of N per acre.

“What we saw was that overwhelmingly, a banded placement was consistently more efficient than broadcasting,” Griesheim said. This result wasn’t surprising, since the banded application places the fertilizer closer to the roots.

However, neither the Conceal system, nor the drag chain application, nor the number of bands appeared to have any impact.

“There was really no difference there,” she says.

Nitrogen form matters

Griesheim’s final project examined different nitrogen fertilizer forms, all applied using Y-Drop placement. The study compared potassium nitrate, UAN and liquid urea, along with an untreated check. To ensure accurate results, potassium levels were balanced across treatments to prevent any yield response from added potassium.

“What we found for this project was that potassium nitrate was highest in efficiency, followed by UAN and then by urea,” Griesheim says, adding the trend showed fertilizers with more ammonium had lower efficiency.

Overall findings and future research

Her research in Illinois revealed interesting findings about nitrogen efficiency that could impact future research.

First, in a large number of the studies, Griesheim notes, treatment differences weren’t detectable by yield, but they were detectable by efficiency.

That’s encouraging, she says. “It means that we can have differences in our management practices that aren’t reducing yield but are increasing efficiency, which is where we want to be.”

Second, nitrogen loss was a major factor influencing efficiency. Whether through immobilization (where nitrogen gets tied up in organic matter and becomes unavailable) or losses such as through volatilization, her research shows more research is needed to understand how nitrogen moves in the system.

Another big takeaway was timing. Fall-applied anhydrous ammonia led to significant nitrogen loss before crops could use it. She noted, however, this is likely a factor of the warmer ground temperatures in central Illinois, and farmers in Canada probably wouldn’t see the same kind of losses. Nevertheless, it does indicate synchronizing fertilizer application with crop uptake has the potential to improve efficiency.

Finally, her results showed the soil — not the inputs — was providing the bulk of the nutrients for the crops.

“There was not a single time where the fertilizer was the major source of nitrogen for the crop,” Griesheim says. “It was always the soil. I find that really interesting.”

What that suggests is that nitrogen movement isn’t only driven by the placement of the fertilizer. It also suggests more attention should be paid to management techniques that look beyond 4R practices that focus on placement, to practices that influence how nitrogen is stored, released and lost in the soil.

That insight led Griesheim to her latest ongoing study at NDSU that is looking at the isotopic efficiency of nitrogen applications for conventional till and no-till cropping systems.

“We know from very extensive literature that tillage will impact carbon quality and quantity, as well as soil moisture and temperature,” she says. “Those are things that would definitely impact nitrogen.”

One year of that multi-year study has been completed.

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In a recent presentation he made at Manitoba Ag Days in Brandon, Bryce Geisel, a senior agronomist with Koch Agronomic Services, tackled the issue, digging down into these loss pathways and how applying the right practices can keep nitrogen where it belongs.

“When you put it out on your field, nitrogen is eventually going to make its way into the soil. That’s where we want it to be,” Geisel says, adding that from that point, the nitrogen would either be taken up by the plant or it would be lost to various mechanisms at play. Those loss mechanisms include volatilization, denitrification and leaching.

Volatilization

Volatilization occurs when urea, an inaccessible form of nitrogen for plants, is converted into ammonia and evaporates into the atmosphere. For this conversion to happen, Geisel explains, three factors are needed: urea application, water for hydrolysis, and the urease enzyme, which breaks down urea.

“The urease enzyme is broken down from residues in the crop or microbes in the soil,” he explains. “It’s pretty much everywhere, so we know we are going to have urease enzyme in your soil.”

Ammonia volatilization is most common at the soil surface and can be reduced by incorporating urea into the soil or relying on rainfall to wash it down. Factors such as soil moisture, pH, temperature, soil type and the presence of crop residue influence the extent of volatilization. For instance, high pH and lighter soils increase volatilization risk, while warmer temperatures speed up the conversion.

Leaching

Leaching happens when nitrate moves down through the soil with water, beyond the root zone. Sandy soils are especially prone to leaching after heavy rain or irrigation. This can cause nitrogen loss, particularly in fields with tile drainage. To reduce leaching, it’s important to delay the conversion of ammonium to nitrate, which allows more nitrogen to remain in forms accessible to plants before water carries it away.

“Leaching is just kind of that movement of nitrate down through the soil and out of the growing zone, the root zone of your crop,” Geisel explains. “And denitrification is going the other way.”

Denitrification

When soils are waterlogged, and oxygen becomes scarce, denitrification occurs. In these conditions, certain bacteria begin using nitrate — the nitrogen from fertilizers — instead of oxygen. As a result, some of the nitrate is broken down and lost to the atmosphere, meaning it’s no longer available for crops. This process is most likely to happen when the soil is about 60 per cent saturated, which is wet enough to limit oxygen. For farmers, this means if fields remain too wet for too long, nitrogen losses can occur, reducing the effectiveness of fertilizer and potentially affecting crop yields.

“We want to delay that nitrogen becoming nitrate as long as possible,” Geisel says. “The longer we can delay, the more likely nitrate will get to the crop.”

READ MORE: Nitrogen, nitrates and nitrites

Limit losses with 4Rs

Geisel emphasizes that the 4Rs — right rate, right time, right place and right source — are key to reducing nitrogen losses. By focusing on these strategies, farmers can boost nitrogen efficiency, minimize waste and improve their bottom line.

Experiment with rate

Every field has a point where adding more nitrogen stops increasing yield and starts to waste resources. Finding the right rate can be a challenge. It involves balancing the crop’s needs with the risk of over-application. Geisel advises farmers to review and adjust nitrogen rates frequently.

“Everyone has a number for their fields they like to use,” Geisel notes. “It’s good to have that, but it’s also good to do a little check on how they’re doing every year.”

By testing variations, such as slightly higher or lower rates, farmers can determine if they’re using too much nitrogen or if they could push the rate for better efficiency. But Geisel advises farmers to make sure the changes implemented would be noticeable.

“I’d recommend at least a 20 per cent differential from what you were doing,” he says. “If you get into that five to 10 per cent difference on your nitrogen rate, there’s a good chance you aren’t going to pick that up within the field.”

Experiment with timing

Finding the optimal timing for nitrogen application is a complex task, largely due to the unpredictable nature of weather and varying crop needs.

Geisel points out that grass crops such as wheat, barley, corn and oats require a steady supply of nitrogen throughout their growth stages. He also lumped potatoes in with that group, because they tend to need nitrogen later in the season.

Canola, though, requires nitrogen much earlier in its life cycle, which adds another layer of complexity and makes it trickier to experiment with, he says.

“But one thing that is consistent with all the crops was that the small seedlings were not taking up a lot of nitrogen.”

This creates a risk for nitrogen to be sitting unused on the soil, where it becomes vulnerable to losses — but it also creates an opportunity, allowing for adjustments so the crop can access the nitrogen once the plants begin their rapid growing phase, and nitrogen losses are less of a concern.

Geisel stresses the importance of carefully managing application timing, suggesting farmers experiment with different strategies, such as split applications, to better align nitrogen availability with crop needs. However, he acknowledges, the daily grind of the growing season also poses challenges.

“The efficiency of your operation is going to come into play, as well,” he says. “Once the field season gets going, trying to do multiple applications across the field becomes very difficult, logistically.”

Experiment with placement

Nitrogen placement offers more control than either timing or rate, with various application methods available to optimize efficiency and minimize losses.

One of the most commonly used placements is spring broadcast urea, which allows farmers to cover large areas quickly. However, Geisel points out, this placement comes with a significant risk of volatilization, especially if the nitrogen was not incorporated into the soil soon after application. The risk is particularly high when rainfall was insufficient. Ideally, a half inch or more of rain is needed to push the nitrogen into the soil and reduce volatilization losses. Without enough rain, volatilization can significantly reduce the effectiveness of the applied nitrogen, Geisel notes.

Shallow banding, a technique where nitrogen is placed just below the soil surface — typically up to two inches deep — offers a more controlled approach. This method has become popular for urea because many seeders were designed to handle side- or mid-row banding. While shallow banding reduces volatilization compared to surface broadcasting, it still carries risks, such as losses from denitrification and, to a lesser degree, volatilization, depending on soil conditions and weather.

Deep banding, where nitrogen is placed three inches into the soil, is considered the best method for minimizing nitrogen loss. This method substantially reduces volatilization and denitrification risks by keeping nitrogen at a depth where it’s less vulnerable to environmental factors.

“When we got that nitrogen down three inches into the soil, there is very little that’s going to be lost from denitrification or volatilization, but leaching is still a risk,” Geisel says.

However, deep banding can be costly and often slower, which can make it less attractive for some farmers.

Geisel also touched on the role of soil pH in nitrogen placement. Higher pH levels reduce the risk of ammonium volatilization, which occurs when nitrogen is left exposed at the soil surface.

He cautioned that pH typically increases when urea is placed in the soil, so farmers have to be aware of that dynamic as well. If the nitrogen is placed too shallowly or is not properly incorporated, the pH spike could lead to higher volatilization rates, undermining the effectiveness of the fertilizer.

Experiment with source

Geisel underscores the importance of choosing the right nitrogen source in minimizing nitrogen losses.

“Source is definitely something that gets a lot of focus in terms of nitrogen management,” he says. “We can start to play around with it and start making them more effective just by choosing a different source.”

But rather than focus on all of the different fertilizer sources, Geisel zeroes in on the nitrogen sources that have been developed specifically to reduce nitrogen losses.

Polymer-coated urea falls into that category. It consists of urea granules coated in a polymer that delays the release of nitrogen, ensuring it’s available during critical growth stages.

“It is activated by moisture, temperature, and time,” Geisel explains.

While this product reduces volatilization risk, crops still face the risk of loss from denitrification and leaching, especially if it’s applied near the surface. Geisel advises moving it deeper into the soil to mitigate these risks.

Geisel also discussed enhanced-efficiency nitrogen (EEN) products, which include both single and dual inhibitors. Single inhibitors include urease and nitrification inhibitors.

Urease inhibitors block the enzyme responsible for converting urea into ammonia.

“We want to make sure we put enough of that product down, or it’s not going to have an impact on that bacteria,” he said.

Urease inhibitors, such as NBPT, help keep urea stable longer, reducing nitrogen losses. Higher concentrations of the inhibitor lead to more effective protection and give crops more time to access the nitrogen.

Nitrification inhibitors, such as DCD (dicyandiamide), delay the conversion of ammonium into nitrate, keeping more nitrogen in its stable, ammonium form.

“What we were trying to do here is basically just run interference,” Geisel says.

These inhibitors help ensure nitrogen remains available for crops by delaying nitrification until the plants can use it.

Dual inhibitors combine the benefits of both urease and nitrification inhibitors, offering more protection against all loss mechanisms, especially in high-risk scenarios like fall applications.

“A lot of this has to be a balance between the economics, the efficiencies, and the losses that you are looking at,” Geisel says.

To a great extent, using 4R techniques to make nitrogen efficiency adjustments require an element of trial and error. Geisel stresses that the 4Rs don’t have to be treated in isolation.

“We can incorporate a source with a timing, with a rate; they’re all tied together,” he says. “That is the big takeaway.”

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Nitrogen is one of the most abundant and important of all elements but misunderstood by the general public. Nitrogen exists in three oxide and gaseous forms: nitrogen dioxide (NO₂), nitrous oxide (N₂O) and nitric oxide (NO). These three gaseous forms often confused me, despite my chemistry background, so do not blame crop production specialists for getting them cross-wired.

Nitrogen dioxide

NO₂ is a reddish-brown gas that is poisonous and highly reactive. It’s a contributor to the haze often seen in cities with high traffic densities. In the presence of water, it quickly forms nitrous or nitric acid, which in contact with the soil rapidly becomes calcium or magnesium nitrate or other stable nitrate compounds. In nature it’s the usual gas that’s formed from lightning strikes, up to a few pounds per acre, when it’s washed into the soil by the accompanying rain or hail.

Nitrous oxide

N₂O, well known to us as laughing gas, is a gas used in dentistry or medical surgery but its use is becoming restricted since it has become a drug now frequently used recreationally.

Its agricultural story is much more sinister, as the dreaded gas produced by cropland is some 300 times more potent than carbon dioxide as a contributor to global warming. It’s a very stable gas that takes more than 100 years to break down in the atmosphere. Up to seven per cent of global warming is attributed to this gas, whose significant source of origin is agricultural cropland.

Nitric oxide

Here I could say that NO means “yes.” This is a very important gas in human, animal and plant health. Nitric oxide is the molecule (gas) that regulates many systems in both animals and plants. It not only plays a number of key roles in your body but also in all plant growth. NO regulates such processes as seed germination, root development, grain and fruit production. Both plants and animals are able to synthesize NO from nitrogen compounds. Next time you go to the drugstore you will see very many nutrient supplements that claim to boost the NO level in your body to improve your health. You may expect lots of exciting research in future on the role and use of NO in plants and crop production systems and hence animal health.

It’s confusing, but you must distinguish between N₂ (nitrogen), NO₂ (nitrogen dioxide), N₂O (nitrous oxide) and NO (nitric oxide) — in summary, a group of gases that can so easily be confusing even to specialists.

Nitrogen salts, such as nitrates and nitrites, are the foundations of the whole world’s biological system. Nitrogen is the key element in all foods and food production and as salts they can be totally essential or destructive, both as nitrites and nitrites.

All nitrogen compounds, whether organic or chemical, are basically very unstable. To fix nitrogen either in the form of nitrate, nitrite or ammonia takes a great deal of energy. For this reason, fixed nitrogen is the key element of almost all explosions. Semtex, TNT, dynamite, picric acid and countless other explosives in bombs, guns and rockets are nitrogen-based. The triple bond that holds N2 together is very strong, but the bond between nitrogen and other atoms is very weak and highly unstable, as in explosives.

Nitrates in food and crops

Nitrates are present in very many of the foods that we eat, such as bacon and cured meats where they function as preservatives. Such meats are usually salted with common salt and saltpeter, which is either sodium or potassium nitrate. I remember, as a youth, when a pig was killed on the farm, we had to rapidly cover the hams and sides with common salt and then rub in saltpeter to initiate the curing process. (Remember here that clostridium botulinum bacteria (botulin) produce a toxin that is millions of times more toxic than snake venom.)

In the actual process of curing the meats, the salt draws out the water and surface bacteria on the meat can convert the sodium or potassium nitrates to nitrites. It is these nitrites that are then converted to nitrosamines which are implicated as cancer-causing. Recent research, though, has shown that adding vitamin C (ascorbate) to the meat curing process promotes the conversion of nitrite to nitric oxide. As a consequence, nitrite levels in food have been significantly reduced to less than 100 parts per million (p.p.m.), resulting in much-reduced nitrosamines — the problem compound within the food.

Processed meats are not our only processed source of nitrates in food. Vegetables, such as beets, celery and broccoli, for example, may contain significant nitrate levels. It so happens that toxic nitrosamines can be formed in the human body if we ingest both nitrates and amines in our food, even if you are a vegetarian.

Nitrates, nitrites and livestock problems

Nitrates are present in all horticultural and field crop plants. Normally nitrates are taken up by plants and are primarily converted to plant protein. However, under unusual growing conditions such as a sudden severe frost on a rapidly growing forage crop or crops intended for hay or silage or a severe drought on well fertilized pasture, feeding problems can occur.

Cattle are much more likely than horses to experience nitrate or nitrite poisoning. When consumed by cattle, the nitrate levels, if high enough, cannot all be converted to protein and the excess nitrates or nitrites may enter the bloodstream, where they combine with the blood hemoglobin to produce methemoglobin, a form that cannot transport oxygen. Death can occur from asphyxiation. If you suspect nitrate poisoning, consult a veterinarian immediately for help.

If you suspect high nitrates in hay or forage, the nitrate levels will not dissipate over time but you may ration the amount fed to your cattle. Sheep and goats are also sensitive to high nitrate levels, but seem to be more tolerant than cattle. Horses are much more tolerant than ruminants such as cows, sheep and goats — but there are recorded cases of significant nitrate poisoning in horses. In the spring of 2001 in Kentucky, thousands of mares aborted their foals — and the cause was finally resolved to be the well fertilized pasture grasses in that state. The grass pastures were hit by unusually cold and even freezing weather that stopped grass growth but did not stop the accumulation of nitrates. The pasture grasses became unusually high in nitrates and nitrites that were taken up by the mares. The nitrate damages the hemoglobin in the red blood cells, preventing oxygen circulation, resulting in fetal death.

If harvested hay or forage is suspected to be high in nitrates, have them tested by any of several Prairie laboratories. It is generally accepted that the total dietary nitrate in dry matter should be no more than 5,000 p.p.m. or 0.5 per cent by weight. Over this level, high-nitrate hay or forage should be diluted by 50 per cent with other feed. Levels of 10,000 p.p.m. (one per cent) can cause death in cattle and should not be fed.

Cattle should not be allowed to graze on drought-stricken cropland high in nitrogen, nor on well fertilized pasture or late-seeded well fertilized crops heavily damaged by frost. Both instances can result in nitrite accumulation.

In this discussion on N and its oxides and chemical compounds I hope I have enlightened rather than confused you. Nitrogen, on the other hand, in its biological forms, is so incredibly diverse and complex that it would take textbooks to explain.

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But like most things in farming, a lot depends on the weather. Less nitrogen equalled more profits in trials done in 2023 because it was a dry growing season.

“When you are reducing your nitrogen rates… by 15 per cent, we did find it was economical to have those reductions,” said Jessica Enns, research manager with the Western Applied Research Corporation, which is part of the Saskatchewan Agri-ARM network.

The network has a mandate to transfer technology from research to farmers and evaluate the economics of technology.

In 2023, researchers from the East Central Research Foundation at Yorkton led a project looking at oat profitability at four locations in Saskatchewan: Outlook, Melfort, Prince Albert and Yorkton. The trial at Outlook was irrigated, while the others were not.

The research project was supported by SaskOats, which wanted trial data on reducing rates of nitrogen fertilizer by 15 and 30 per cent and what that means for profitability.

Most oat growers apply about 90 pounds per acre of nitrogen fertilizer to the crop annually, Enns said.

That delivers about 120 lbs. to the crop, assuming the soil contains 30 lb. of residual nitrogen.

Over the last few years, there’s been more discussion about cutting the amount of nitrogen per acre because the federal government has set a target of reducing greenhouse gas emissions from fertilizer by 30 per cent by 2030.

That target was one reason for the SaskOats project: to understand the implications of reducing nitrogen rates on oats.

Unfortunately, 2023 was an abnormal growing season in Saskatchewan, so the results were a bit wonky. One of the trial sites, in Melfort, normally receives 228 millimetres of moisture from May to the end of August.

In 2023, 124 mm of precipitation was recorded.

“It was a very dry year … so we didn’t see a huge response to nitrogen,” Enns said.

The economic analysis was based on a price of oats of $5.25 per bushel and a fertilizer cost of 82 cents per pound of nitrogen.

Using those numbers, the researchers found:

• Cutting nitrogen by 15 per cent at the dryland sites increased net revenue by $17-$28 per acre, depending on the evaluation method.
• At Outlook, revenue jumped by $4-$9 per acre.

“In conclusion, reducing 125 lbs. (soil + fertilizer N) by 15 per cent was economical at all sites under the conditions of this study,” the research report says.

However, the results also showed cutting nitrogen rates by 30 per cent was not beneficial at Outlook.

“(It) reduced net returns by about $20 per acre at the high-yielding Outlook site.”

The results suggest growers could cut fertilizer rates and possibly increase profits if they know the growing season will be drier than normal.

However, it’s difficult to predict the growing conditions for a particular year.

“There isn’t a farmer out there that wouldn’t want to reduce their costs and make more money,” Enns said.

“There is a lot of research going into… where can we find those cost savings. Is it varietal-specific? Is it region-specific?”

Decisions around rates of fertilizer often boil down to risk management.

If prices for a particular crop are high, a grower might be reluctant to cut rates. No one wants to compromise yield and profits because the crop ran out of nitrogen.

“If you receive quite a bit of moisture, then you’re missing out on $20-$30 per acre (or more).”

Enns will present the full results of the Oats N Response study at the Prairie Oat Growers Association annual general meeting and conference, scheduled for Dec. 4 in Banff.

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Let us first examine what dry and drought mean.

A dry year means reduced crop growth and reduced nutrient uptake, since biological, chemical and physical processes are altered, resulting in a reduced soil nutrient availability to crops. Further, depending on management, dry and drought mean altered residual fertilizer nutrients.

Let us use nitrogen as an example by examining the plant nitrogen-use efficiency. This is the total dry matter or grain yield produced per unit of N absorbed. This physiological parameter, also called physiological efficiency (PEN), is defined as kilograms (or pounds) of grain/kg (or lb.) of fertilizer N used by a plant and is calculated by subtracting the yield of the control treatment from the fertilized treatment and dividing it by the difference between the uptake of N by the fertilized treatment minus that of the control one:

PEN = Y_N – Y₀ / U_N – U₀

The PEN represents the ability of a plant to transform a given amount of acquired fertilizer N into grain yield and thus depends on genotype characteristics (e.g. harvest index) and environmental and management factors, particularly during reproductive growth.

Low PEN usually suggests suboptimal growth conditions, often caused by nutrient deficiencies other than N and/or by drought stress, insect predation and disease.

As a result, the soil nitrogen status is greatly affected and variability within a field is increased. Obviously, fertilizer does not move very far from where it was placed when it is dry. Also, poor crops do not use nitrogen and lack of moisture means no nitrogen movement.

But as has happened in many parts of the Prairies, late rains and subsequent regrowth of crops change the nutrient status. Also, you may notice a decrease in soil pH, which can be followed by an increase in EC (salts) and available P. These will correct themselves in time.

See examples below from my time as director of the Saskatchewan Soil Testing Laboratory following the dry years of the late 1980s and early ’90s and then wet mid-’90s:

This type of variability will also occur during wet and dry periods within the same growing season.

Other factors influencing crop response to fertilizer application

Applied fertilizer use depends on corresponding soil nutrient availability and potential losses of applied fertilizer. However, several other agronomic factors can cause a poor response to applied nutrients.

Crop cultivars often have varying nutrient requirements depending on yield potential and agroecological conditions.

Available soil nutrient supply at planting will influence crop response to fertilizer. Fertilizer management requires proper assessment of both the soil’s nutrient status and the crop’s nutrient requirements. It is widely accepted today that soil testing allows producers to make more qualified fertility management decisions based on soil nutrient inventory and interpretive criteria of this inventory.

Hence, soil testing has to be an integral part of an attempt to obtain optimum yields. However, like any other assessment tool, soil testing is subject to the laws of statistics and has many limitations. Understanding those allows an understanding of its usefulness.

Choose laboratories based on knowledge of how its staff assesses the soil nutrient inventory (from chemistry to quality of analyses) and how they interpret the results.

The steps in soil testing also come into play. An examination of the four steps involved in the traditional soil testing process suggests current techniques would:

• result in a statistical error of ±22 per cent due to the common sampling schemes (20 samples per field/unit);
• result in varying errors due to analysis (for example on a soil N content of 50 kg N ha^-1 in the 0-30 cm depth the maximum analytical error is approximately 12-15 per cent and this would increase as the soil test value decreases and vice versa);
• calibration techniques based on yield curves can commonly result in our ability to describe approximately 50 per cent of changes in the yield by the changes in soil test levels; and,
• fertilizer recommendation models can add wide variation in recommended nutrient levels.

Therefore, it is obvious that conventional soil testing databases have been developed to address “fields” as whole units, or better yet, “large geographic areas” from which deductions can be made for individual fields. This is important when databases thus derived are used for variable rate fertilization in precision farming.

It is remarkable that calibrations of soil tests took place in the 1980s and early ‘90s and a limited number in the early 2000s. Take phosphorus (P), for example. The most recent calibration and response experiment was conducted in Alberta from 1991 to 1993 with wheat, barley and canola.

It was very thorough research carried out on a wide range of soil types across Alberta to determine the frequency at which each crop will respond to phosphate fertilizer. Another thing to remember is that soil testing criteria developed in one region of North America (e.g., southern U.S. or Ontario) are often not relevant to western Canadian farms.

Finally, the quality of sampling can play an important role in deriving proper recommendations. Therefore, make sure a sample is taken from the depth you are sampling. Special care must be given in dry and wet soils. Why? Often samples are taken with probes attached to a truck with the sampler sitting at the front. Soil can fall off the probe in a dry soil situation or become compressed in a wet soil situation, resulting in false readings in both cases.

The nutrient status, especially that of N, of a field, can also be estimated from the previous cropping history, but is more accurately determined by a soil test.

It is generally accepted that improvement in the accuracy of N recommendations requires a reliable estimate of soil N-supplying capability. Mineralization of N is a function of environmental conditions; it can vary from as low as nil under drought conditions to as high as one-third greater than average under favourable conditions.

Late seeding usually results in lower yield potential and reduced response from N fertilizer due to moisture/heat relationships. Also, there is a greater risk of crop loss from increased disease pressure, insects, frost and poor harvest conditions.

Weeds compete with plants for moisture, nutrients and light. Applied fertilizers may stimulate the growth of weed seedlings almost to the same extent as a crop. It is important to control weeds to minimize the competition between weeds and crop plants.

Banding fertilizers or placing fertilizers with the seed makes them less accessible to weeds during the early growing season. However, if too much fertilizer is seed-placed, injury to the seedling will reduce emergence, resulting in higher weed competition.

Another issue is that seedling damage can lead to delayed maturity and increase the risk of damage from fall frosts in northern areas where the growing season is short. In canola, increased seed chlorophyll content indicates delayed maturity and influences crop quality.

Disease infestation also comes into play. Well-nourished, healthy plants have some resistance to many disease organisms. Inadequately nurtured wheat plants seem predisposed to certain diseases such as common root rot. Take-all root rot, for example, is reduced when wheat plants absorb ammonium N and is increased when the plants take up excessive amounts of nitrate-N.

Soil moisture can’t be ignored. Water-holding capacity/movement through the soil profile will depend on the soil’s physical properties. Once water enters the soil, it will move under the effect of gravity or capillary suction. In lower rainfall environments, soil moisture reserves must be considered when choosing fertilizer rates.

The risk of crop damage or failure is higher on poorly drained or flood-prone fields. Lower N fertilizer applications are advised on these fields if adequate drainage cannot be provided. Although well-fertilized crops usually withstand more water, if water stands for more than two or three days, causing saturated conditions, considerable crop damage or complete failure may result.

Coarse textured soils with water tables deeper than 1.2 to 1.8 metres below the surface are often droughty. Yield potential, to a large extent, is restricted by lack of moisture. High rates of N fertilizers are generally not recommended in these soils.

Other parameters influenced by changes in water regime

In addition to target yields, many other parameters vary with water regime, including mineralization, immobilization, leaching, denitrification as well as soil residual, mineralizable, and fertilizer N use efficiency and N content in plants.

Mineralization of N is also a function of environmental conditions (water) and can be effectively reduced to zero under drought conditions or become as much as one-third higher under favourable (moist) conditions compared to “normal” conditions.

Karamanos and Cannon (2002) used a limited amount of data from the work by others to derive a relationship between the mineralization rate constant (k_35C) and organic carbon content that allowed the estimation of mineralizable N. For organic matter levels less than eight per cent, an average estimate can be made by multiplying the percentage of organic matter from the soil test by 14. In general, under “normal” conditions, 80 per cent of mineralizable nitrogen is available to the crops.

Immobilization: We all understand that decomposition of plant residues requires extra N. How much N is required to fuel the decomposition process? It depends on how much crop residue is incorporated into the soil.

There is information to suggest that in high-residue situations, as much as 20-40 lbs. of broadcast-applied N can be immobilized during straw decomposition. The obvious way to prevent significant immobilization losses is to place the N fertilizer in compact bands. Broadcast-applied N is extremely vulnerable to immobilization losses when it is incorporated into the same soil layer as the straw.

Once the grain is harvested, incorporating the remaining crop residue will immobilize a significant amount of N from the soil in the following year. In these situations, loss of N fertilizer can be greatly reduced by concentrating the fertilizer in bands rather than broadcasting and incorporating it so that it is in intimate contact with the decomposing residue.

Leaching is not a major issue or an issue at all in most of the Prairies, with the possible exception of the Red River Valley and sandy soils. For example, nitrate leaching occurs when nitrate is carried below the crop root zone by water draining through the soil.

Unlike ammonium (NH₄+), nitrate (NO₃-) is a negatively charged ion and is not held onto soil particles. Further, unlike the other processes, nitrate leaching is not driven by microbes and is not as temperature dependent.

Nitrate leaching is most likely to occur under these conditions: sandy textured soils, high rainfall (or excessive irrigation), summerfallow (no crop present for uptake, therefore, significant amounts of surplus water drain through the soil profile), and high levels of soil nitrate.

Interestingly, periods of the highest water drainage correspond closely to periods of highest nitrate N content. Because subsoils are still frozen during the early part of the spring thaw, leaching is usually not of major concern.

In continuously cropped situations, nitrate leaching can be minimized because crop uptake prevents the accumulation of surplus soil nitrate in soils. Fall fertilizers should be banded after soils are cool, and nitrate-containing fertilizers should be avoided except on vigorously growing crops.

Denitrification is the anaerobic microbial process that converts nitrate (NO3-) into nitrogen gases including N2 and N2O.

Denitrification rates increase under anaerobic conditions when the soil is warm (at least 5 C, optimum above 20 C) and pH between six and eight and, of course, when high levels of nitrate are present in the soil. Losses from denitrification are most likely in poorly drained soils with high nitrate levels.

Although denitrification losses occur slowly on cold soils, cumulative losses in cold, wet soils can be significant during early spring thaw conditions. As I mentioned in my 2022 article on fall fertilization, research conducted at the University of Saskatchewan in the 1980s showed about 35 per cent of autumn-applied fertilizer nitrogen was lost via denitrification during snowmelt the following spring.

During the growing season, denitrification losses are much more rapid if soils are subject to flooding during summer months when soil temperatures are much higher. It can also happen later in the growing season after ammonium fertilizer has converted to nitrate, but before it has been used by the growing crop, especially on clay-textured soils in the black or gray soil zones.

Banding provides drought protection

Extensive research conducted on the Prairies, originally by the University of Alberta, led researchers to conclude that banding provides a form of drought-proofing. The research results indicated clearly that the advantage of banding over broadcasting became more significant as growing season moisture supply became less favourable.

The researchers suggested deep banding’s “drought buffering” should be regarded as a management tool to lessen drought’s adverse effects. Yields fluctuated much more dramatically with broadcast treatments than band treatments as the amount of water available to the crop was varied.

Since no region of the Prairies is immune to drought, band application of fertilizer would be beneficial in all regions. However, the greatest benefits would accrue in the brown, dark brown and thin black soil zones.

But this research does not suggest that banding is a substitute for moisture. Banding is only beneficial when there’s sufficient moisture to produce a crop. It’s of no benefit in the case of a total crop failure. Banding also slows the conversion of urea to ammonium and ammonium to nitrate, which can reduce losses by denitrification and leaching.

Good soil moisture opens new opportunities

Recent precipitation may ease drought in many Prairie regions. Remember that soil moisture is an important component of the crop yield equation and it is an invaluable tool for the producer for targeting crop yield for the upcoming growing season.

Targeting for low yields when yield potential is great will result in under-fertilizing crops, reducing crop yields and protein content.

Although precipitation is hard to predict, soil moisture is easy to estimate with a soil moisture probe. A soil moisture probe is simply a half-inch rod that is 3.5 to four feet long and has a 5/8-inch ball bearing at one end and a T-handle at the other. Soil moisture is measured by pushing the probe into the ground. When the soil runs out of moisture, you will not be able to push the probe any further. However, make sure you haven’t hit a stone or ice in the spring.

Here is the available water based on the texture and depth:

What are the opportunities?

Knowing soil-available moisture allows you to fertilize accordingly, resulting in target yields that are average, below or above average. Choose the right target and fertilize accordingly.

With improved moisture conditions, fertilization of crops that are to be grown on drought-stricken fields with moderate nitrogen rates will undoubtedly result in higher yield and/or protein content.

Make sure you have a soil test and probe several fields or management zones with different textures to establish the moisture status in your area and obtain a good estimate of potential yield. Supply the crop with adequate phosphorus and any other nutrients required.

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