Blog: Agronomy & Extension

When does spring wheat reach physiological maturity and when is the proper timing for pre-harvest glyphosate application?

Andrew Hector on August 5, 2026

By Andrew Hector, Agronomy Extension Specialist – Cereal Crops, Manitoba Crop Alliance

Properly identifying spring wheat growth stages is important throughout the season, but growth stage identification becomes essential as we near plant maturity and approach the window for pre-harvest activities such as swathing or applying pre-harvest glyphosate.

What is physiological maturity (PM)?

At PM, wheat plants have accumulated the maximum amount of kernel dry weight. Therefore, at this point, final maximum yield has been determined, and no more dry matter is being accumulated in the kernels.

How to identify PM

When assessing growth stage, check representative areas of the field. Special attention should be given to the least mature part of the field, especially if you are applying a pre-harvest weed control product, to avoid maximum residue limit (MRL) issues.

The first indication of PM is the loss of green colour from the kernels,= and the appearance of dark pigment along the kernel crease (Figure 1). It’s important to note that kernels on the same head don’t mature simultaneously, with the middle kernels maturing first.

Figure 1. Wheat kernels prior to (top) and at (bottom) physiological maturity (note the darkened pigment strand).

The second indication of PM is when the peduncle (i.e., stem below the wheat head) changes from dark green to light green or yellow. Once the peduncle turns yellow, the plant is getting close to PM. However, change in peduncle colour is just an indicator (Figure 2). A fingernail test is also required to confirm growth stage.

Figure 2. Peduncle colour change associated with physiological maturity.

Pre-harvest glyphosate application for perennial weed control

Glyphosate is registered for pre-harvest weed control only, it is not a desiccant. Proper application timing can be challenging, especially if crop maturity is uneven across the field. Ensure the least mature part of the field is assessed for appropriate crop staging, to reduce MRL issues.

If applying, application should be conducted when grain moisture content (MC) is below 30 per cent, AKA the hard dough stage. Application prior to 30 per cent MC can reduce grain yield and quality. Furthermore, early application can lead to elevated residues in grain.

Conduct a thumbnail test:

  • Shell out the wheat head. Press your thumbnail into the kernel. At < 30 per cent kernel MC, and under reasonable pressure, the thumbnail impression or dent will remain. This indicates that plant has reach hard dough (Figures 3 & 4).
  • If the imprint of dent does not remain in the kernel, then the plant is not at the appropriate stage for a pre-harvest glyphosate application.

Always read and follow label directions. Check with your grain buyer before applying a pre-harvest product to ensure grain acceptance.

Figure 3. Thumbnail test assessing kernel moisture. Source: Keep it Clean.

Figure 4. Kernels at various times during grain filling: a. watery ripe, b. late milk, c. soft dough, d. hard dough (loss of green colour) and e. ripe for harvest. Source: Dave Hansen, Growth and Development Guide for Spring Wheat.

Additional Resources

I’ve noticed a lot of wild oat escapes in some of my fields this year; what can I do to prevent it from getting worse next year?

Coles Ag on August 5, 2026

By Ashley Ammeter, Whole Farm Specialist, Manitoba Crop Alliance

Despite our best efforts, sometimes even the best laid weed control plans go wrong!

The first thing to remember is that not all weed escapes are created equal. In some cases, weeds can survive because of application timing issues, challenging weather conditions or late flushes that emerge after spraying. However, when weeds aren’t controlled by herbicide applications, herbicide resistance should also be on your radar.

A recent survey in Manitoba found that in fields with uncontrolled wild oats, 100 per cent of populations were resistant to Group 1 products, 82 per cent were resistant to Group 2 products, and 82 per cent were resistant to both Group 1 and 2 herbicides. Those numbers show how important it is to take a closer look at wild oat weed escapes.

Start with scouting

Examples of field-scale weed distribution patterns that may help diagnosing weed escapes. Image from: Dr. Charles Geddes and Alberta Grains.

Identifying why your herbicide failed to control wild oats is the first step toward finding a solution. Start by scouting the field to narrow down the cause. Consider factors such as application timing, weather conditions, late flushes after spraying and the size of the weeds when you sprayed. Look out for distribution patterns in the field that might suggest application issues, such as plugged nozzles, missed areas or poor coverage. If you’re able to rule out these causes, its time to consider herbicide resistance.

For more information on narrowing down potential causes of weed escapes, see our resource on scouting after herbicide applications.

Herbicide resistance testing

If you suspect herbicide resistance, the next step is to collect samples to send for testing. Currently, most herbicide resistance tests require samples of mature seeds from the suspected weed patch. While some species may not have mature seed until after harvest, wild oats will likely have mature seed before your crop is harvested. Keep a close eye on your wild oat patches so you can collect seeds before harvest.

The Resistant Wild Oat Action Committee has information on how to collect samples, where to send them for testing and how to interpret the results.

Managing weed escapes this season

Even if you’re waiting on herbicide resistance test results, there are still steps you can take this season to manage the long-term impacts of surviving wild oats.

Before seed set, consider mowing patches to prevent the seed maturing and returning to the soil seedbank. If you plan to submit a sample for resistance testing, leave a small patch so you can collect mature seed.

At harvest, combines can spread wild oat seeds up to 145 m. Rather than chopping and spreading straw and chaff in heavy wild oat patches, consider dropping and baling the straw. This can help contain the patch and minimize spread.

Build a long-term strategy

Whether or not you have herbicide-resistant wild oats, using an integrated weed management strategy gives you the best chance of success in your fight against weeds.

Integrated weed management incorporates cultural, mechanical and chemical control practices to manage weeds. These are just some of the possibilities!

Combining multiple strategies can significantly improve your success in managing wild oats:

  • Use herbicides with different modes of action such as pyroxasulfone, fall-applied granular herbicides or other effective modes of action.
  • Diversify crop rotations. Winter cereals can be more competitive, later-seeded spring crops allow more time for wild oat control prior to seeding, and forages are harvested before wild oat seeds shatter and return to the soil.
  • Consider targeted tillage in the fall to promote fatal fall germination of wild oats, or in the spring to stimulate early germination of wild oats that can be controlled prior to seeding.
  • Improve crop competitiveness through practices such as higher seeding rates, narrower row spacing, careful placement of fertilizers to feed the crop not the weeds or choosing taller varieties.

With weed escapes, its not only the surviving plants that matter; it’s also the thousands of seeds they contribute to next year’s weed problems! Taking the time to identify why those wild oats survived allows you to build a management plan that uses “many tiny hammers” to keep the weeds at a disadvantage and protect the effectiveness of herbicides into the future.

Is fungicide actually effective on Sclerotinia head rot in sunflower?

Morgan Cott on August 5, 2026

By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

This is one of the most difficult questions to answer because there are many things to consider. I also don’t want to be outright negative because we do still have options for sclerotinia management in sunflowers. However, management is the operative word.

First of all, sclerotinia head rot infections have an interesting pathway. Spores use dead sunflower florets, plus pollen, as the base to infect a sunflower plant. The spores grow into the receptacle, infecting and decaying the entire head after a period of time. Sclerotinia wilt (basal stalk rot) and mid-stalk rot are also infected by the same sclerotinia species, but it will be via the mycelia that grow from the sclerotia bodies in the soil for basal stalk rot. Mid-stalk rot is also infected by ascospores, but this can be earlier in the season than head rot or at the same time.

Sclerotinia sclerotiorum Diseases of Sunflower​ (White mold) – The American Phytopathology Society (APS)

So, management of sclerotinia does not start at flowering. Crop rotation is the most obvious management tool that we are familiar with in sunflowers, but it is not reliable. Yes, always put at least three years between sunflower crops and any other oilseed that is a host to sclerotinia, but sclerotia bodies have a long life in the soil and it feels impossible to get rid of them.

Here are some additional management tools that, if layered, will definitely help manage the potential of sclerotinia infections of any kind, in any crop:

Nitrogen – avoid excess nitrogen rates, as this will encourage dense vegetative growth and prime conditions in the lower canopy for sclerotia development.

Weed control – many broadleaf weeds and volunteers can be host to sclerotinia, which can multiply sclerotia in the soil after a season of successful weed infections.

Tillage – tillage will move sclerotia bodies around in the soil, burying them and then also bringing them to the surface in a cycle. No-till simply leaves the sclerotia on the soil surface, ready for germination at any moment. The best practice may be to rotate multiple years of no-till with non-host crops so the sclerotia germinate but do not have a proper host to multiply, thereby decreasing in population.

Genetics – unfortunately, this still does not seem like it will be an option in sunflowers as it cannot be perfected or reliable enough to build resistance, or even tolerance, to sclerotinia. It has been found in the past that some hybrids did appear to have partial resistance, though that degree of resistance is easily exhausted in high sclerotinia incidence.

Fungicides – let’s get into this and I will summarize some recent work done in the Dakotas.

 

Sunflower susceptibility to head rot increases as bloom stage progresses and then decreases at R6 staging, where conditions have to be ideal for infection. At R7 and beyond, infection will not occur. Interestingly, at early bloom if temperatures are high, that is when risk is lowest during all susceptible stages.

In 2017-18, North Dakota State University (NDSU) researchers conducted fungicide efficacy trials using Proline and Endura (Lance WDG equivalent) and different application methods on head rot (boom-mounted nozzles and drop nozzles). Summarizing a large project, these are the key takeaways from NDSU plant pathologist Michael Wunsch:

  • Proline displayed moderate reductions in Sclerotinia head rot when disease pressure was low to moderate (<30 per cent incidence) with both standard boom-mounted nozzles and drop nozzles
  • Residual activity may be limited to the first 1 – 3 days after bloom
  • Coverage to the front of the head is optimized in the first half of bloom using standard boom-mounted nozzles
  • Endura (Lance WDG equivalent) showed little or no efficacy against head rot irrespective of application method
  • A significant part of the yield gain associated with fungicide applications targeting Sclerotinia head rot was presented by management of other diseases (rust, Phoma, Phomopsis, etc.)

See full presentation document on “Are fungicides useful for managing Sclerotinia head rot in sunflowers?” by Michael Wunsch. Or Michael Wunsch explains it in this YouTube video.

Essentially, if relying on fungicide, application has to hit the front of every sunflower head and within one day of infection, which is next to impossible to predict. The direct application to the front of the sunflower head may be improved with drone applications, but that is just speculation at this point.

MCA is in the third year of a field-scale trial in our Research on the Farm program, allowing sunflower farmers to test their product(s) of choice and method of choice for the control of Sclerotinia head rot. In 2026, we have two participants that conducted the trial using their spray drones, so we are looking forward to those results and subsequent data collection. See full results from 2024 and 2025 trial years here.

In conclusion, manage your sunflowers very well! Shift focus from sclerotinia control to managing other sunflower diseases, such as rust and Phomopsis, and keeping the full plant healthy to better fight infection. Other management practices to follow are appropriate nitrogen fertilization to prevent excessive vegetative growth, crop rotation of at least four years, control of broadleaf weeds that may also be a host and no-till management where sclerotia bodies on the soil surface form apothecia and then ascospores but have no host to reproduce.

Other resources

What exactly are corn, sunflowers and flax dealing with in this standing water and saturated soils?

Morgan Cott on July 2, 2026

By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

The crops we grow and work with in Manitoba do not generally do well in extended periods of flooding or saturated soils. Roots and growing points need oxygen to develop, so plant growth is delayed in these conditions. Disease development is also escalated in wet, hot, humid conditions, so that is another impending threat down the road.

Timing has not been ideal for corn. If you have puddling or any degree of flooding or standing water, corn at V5 or smaller is at vulnerable staging for survival. The growing point remains below ground until V6 and I think most corn crops were moving into the V6 at the time of the June 23 heavy rainfalls. It can be very stressful for a crop to have excessive moisture arrive as the growing point emerges from underground. No matter where the growing point is in the plant, if it is below the waterline, conditions become anaerobic and it cannot “breathe.” While photosynthesis can still be occurring in parts of the plant above the waterline, root growth is restricted below the waterline and all nutrient and water intake is hindered.

At this point in the season, I want any standing water to recede quickly and I also want the air temperature to stay mild during that period so there is no rapid growth or additional stress. Already, a week after the heavy rains, there is very visible rapid growth in corn fields across southern Manitoba.

Partially flooded corn field. Photo by Eric Tyschinski, MCA summer student.

Sunflowers are equally stressed in anaerobic conditions. Even though their water use is very high, if the plant cannot breathe, it cannot grow. In these times of excess moisture, we don’t want the crop to be in standing water for longer than three days, and cloudy, mild temperatures are best to keep other stresses to a minimum. Unfortunately, sclerotinia development is a significant threat in these conditions, and as the fields dry out, humidity will be high and conditions will be favourable to development, so basal and stalk infections could become severe this year. Keep an eye on stressed sunflower fields to ensure new growth is still coming and plants are still photosynthesizing. 

Effects of excess moisture in flax are exactly what we would guess: it has a low tolerance to severe stresses and will not survive long. The estimate for flax in standing water is about three days before the crop really starts to struggle and yield will be affected. Fortunately, stem root diseases are only a minor issue in flax crops and the wet soil conditions won’t affect this crop as much as it would others with regards to disease intolerance.

With all crops, check for new growth regularly to determine how efficiently the crop is still working and developing. Dig up a few plants to assess root growth. In saturated soils, roots don’t need to grow downward to find moisture, so the benefits of a strong root system later in the season might be diminished. Root health may suffer, which will be identifiable by the colour of the root. These are all good assessments to continue until the soil water subsides, the field starts to dry out and the crop can grow as intended.

Partially flooded flax field. Photo by Eric Tyschinski, MCA summer student.

Helpful Resources:

I’ve been hearing a lot about spray drones; can I spray pesticides by drone on my farm now?

Ashley Ammeter on July 2, 2026

By Ashley Ammeter, Whole Farm Specialist, Manitoba Crop Alliance

This topic has definitely been getting a lot of attention lately!

The short answer is yes, in some cases, agricultural pesticides can now be applied by drone in Canada. However, there are important rules and regulations to follow, drone spraying is not without risk and there are some unique considerations that are important to understand.

What changed?

On June 10, 2026, the Pesticides Regulatory Directorate (PRD) of Health Canada (formerly the Pesticide Management Regulatory Agency or PMRA) issued a Letter of No Objection, an interim measure which allowed the application of pesticides by drone in some circumstances, and was intended to apply until a final policy decision could be released.

On June 30, 2026, the PRD of Health Canada finalized their policy, allowing application of pesticides by drone for any product already registered for conventional aerial application. The full details of the new policy are available here.

Licenses and certification

If you’re considering drone spraying, there are several licenses and certifications you need to be aware of.

In Canada, drones weighing more than 250 g (including spray drones) must be registered, and the operator must have a drone pilot certificate from Transport Canada.

In Manitoba, commercial pesticide applicators must have a pesticide applicator license, but farmers applying pesticides on their own farms are exempt from licensing.

Always read and follow the product label

It is important to remember that pesticide labels are legal documents. Regardless of how you’re applying the pesticide, always read the label carefully.

If the product label allows aerial application to the crop you wish to spray, you may be eligible to spray by drone. You must follow all label directions for aerial application, including spray volume, application rate, droplet size, spray buffer zones or any other instructions. The only exception is that statements on nozzle distribution (ex. “Nozzle distribution along the spray boom length MUST NOT exceed 65% of the wing- or rotor-span”) are not applicable to drones.

If the label states “DO NOT apply by air” or “DO NOT apply by Remotely Piloted Aircraft Systems (RPAS)”, you may not use a drone to apply that pesticide. If the label requires a closed cab for ground application, you cannot apply that product by drone unless a similar “closed cab” system is used for the pilot.

In addition, the person who mixes and loads the pesticide must be different from the drone pilot. Mixers and loaders must wear the personal protective equipment (PPE) required for mixer/loaders by the pesticide label, and the drone pilot, visual observers, or anyone handling the drone must wear the PPE required for ground application. 

How well does drone spraying work?

This is where things get complicated. Drone spraying can be a useful and effective application method, but achieving consistent efficacy requires an understanding of some of the factors that make drone applications unique.

Sprayers 101, a non-profit website providing information on agricultural spraying, has several excellent articles focused on pesticide application using drones. I highly recommend their resources! Their article Safe and Effective Pesticide Application using Drones provides an excellent overview of factors to consider before jumping into drone spraying.  

One of the biggest challenges is determining a drone’s effective swath width. A drone’s swath width can vary significantly depending on the drone design, the height and speed of travel, spray droplet size, and weather conditions. The result is that the swath width that gives you adequate pesticide coverage and efficacy may differ from the values reported by manufacturers or determined by spray droplet deposition testing. Calibrating your equipment and measuring swath width under your conditions and spray settings is critical to preventing uneven pesticide coverage.  

Drift is another important consideration. Like with other aerial application methods, drone sprayers can be particularly susceptible to drift if conditions are not suitable. In addition, most spray drones use rotary atomizers, which differ from conventional nozzles. Most conventional nozzles follow an international standard, producing known droplet sizes at given flow rates and pressures. Rotary atomizers, however, are not standardized and may produce larger or smaller droplets than an operator expects. Understanding your equipment and application settings is critical to minimizing the risk of drift.

The bottom line

If you’re thinking of using a spray drone, whether you plan to operate it yourself or hire a custom applicator, make sure you understand the regulatory requirements and application best management practices. Like any spray operation, success with drone spraying depends on taking the time to do it right.  

For anyone interested in learning more, Sprayers 101 has many excellent resources. The articles linked below are a great starting point to learn about pesticide application with drones:

I think I have hard water, should I be adding AMS to my herbicide spray mix?

Coles Ag on June 2, 2026

By Ashley Ammeter, Whole Farm Specialist, Manitoba Crop Alliance

Water quality can play a significant role in pesticide performance, but it’s a consideration that often flies under our radar until a herbicide application doesn’t work as well as we hoped. If you suspect hard water, adding ammonium sulphate (AMS) could the right call, but first it’s important to know what’s actually in your water. 

Start by testing your water

The first step in managing potential spray water issues is to test your water. While it’s generally good practice to test your water quality, it’s even more important if you suspect that poor water quality is affecting the performance of your herbicides. Agricultural spray water analyses are offered by many accredited agricultural laboratories, such as AGVISE Laboratories, A&L Canada Laboratories, Central Testing Laboratory and Horizon Lab.

Once you have a water quality test, Sprayers 101 has a helpful article on how to make sense of your water quality test results.

Why is hard water a problem?

Hard water contains high levels of positively charged minerals such as calcium (Ca2+), magnesium (Mg2+) and others. These minerals bind to herbicide molecules, preventing them from being absorbed by the plant and reducing efficacy.

Glyphosate (e.g., Roundup) is commonly associated with hard water antagonism, but hard water can reduce the efficacy of all weak acid herbicides (found in Groups 1, 2, 4, 6, 9, 10, 14, 19 and 27).

How much hardness is too much depends on the herbicide, rate and water volume you’re using. For glyphosate, Bayer suggests a hardness limit of up to 700 ppm, when using higher rates or lower water volumes.

Should you add AMS?

If you have hard water but don’t have access to an alternate water source, adding AMS is an effective strategy.

When added to spray water before your herbicide, the negatively charged sulphate ions in AMS tie up the hard water cations before they can antagonize the herbicide. To calculate how much AMS to use, Sprayers 101 has a helpful calculator, but many agriculture labs that offer spray water tests will include AMS recommendations in your test results, and herbicide labels or the Manitoba Agriculture Guide to Field Crop Protection often include water quality recommendations.

In some cases, reducing water volumes and/or increasing your herbicide rate can help counteract the effects of hard water, but always make sure to stay within label guidelines. 

Other water quality issues to be aware of

Along with hardness, there are a few other water quality factors to keep on your radar:

  • Dirty water (turbidity): Particles of soil and organic matter can bind herbicides and reduce performance. Clean water is particularly important for herbicides that are known to strongly bind to soil, such as glyphosate and diquat (e.g., Reglone).
  • Bicarbonates: Bicarbonate ions can inhibit herbicides, particularly the Group 1 “dims,” including clethodim (e.g., Select, Centurion) and tralkoxydim (e.g., Achieve) and the Group 4 herbicides MCPA amine and 2,4-D amine.
  • pH (acidity or alkalinity): The pH of your spray water can impact pesticide solubility and breakdown. Unless recommended on the product label, it is generally not advised to adjust the pH of your spray solution. For those interested in learning more, Sprayers 101 has a helpful article.

My last piece of advice: always read and follow the directions on your pesticide label. While they can be long and unwieldy, the pesticide label includes key details on how to use your herbicide safely and effectively.

Learn more

Does applying a fungicide at herbicide timing to control cereal leaf spot diseases in wheat and barley provide a yield boost?

Coles Ag on June 2, 2026

By Andrew Hector, Agronomy Extension Specialist – Cereal Crops, Manitoba Crop Alliance

This question comes up regularly which makes sense. Early season outbreaks of fungal leaf spot diseases like Tan Spot do occur in Manitoba, such as in 2024. To answer this question, we need to dig into the research.

There have been a few studies done in Western Canada over the last 15 years investigating this very practice in both wheat and barley.

  1. The impact of fungicide and herbicide timing on foliar disease severity, and barley productivity and quality
  2. Evaluation of disease, yield and economics associated with fungicide timing in Canadian Western Red Spring wheat

In both these studies fungicide application timings were evaluated on their impact on leaf spot disease severity, overall crop yield, and economic returns of the practice. In both studies, it was found that a foliar fungicide application at herbicide timing (2-3 leaf) did not lower upper canopy disease incidence and severity compared to the check (no treatment or herbicide only).

For barley, the western Canadian study found that the half rate foliar fungicide treatment at herbicide timing provided only a small increase in crop yield compared to the herbicide only check. The study examining spring wheat’s response to early season fungicide found that fungicide application at herbicide did not significantly improve crop yield compared to the untreated check. Across both studies, researchers concluded that fungicide timing for leaf diseases should focus on protecting the upper canopy, particularly the leaves that contribute most to yield.

There has also been some research on this topic out of North Dakota. Andrew Friskop from North Dakota State University recently compiled replicated foliar fungicide timing trial data from 2008-2024. He evaluated the yield response based on “disease risk” scenarios determined by previous crop, variety resistance, tillage, environmental conditions and disease onset.

Figure 1. NDSU disease risk categories for development of residue-borne foliar diseases.

His finding suggests that under moderate and high-risk scenarios, (where wheat was grown on wheat stubble, a susceptible variety was planted and the disease [tan spot] was established early and firmly in the crop), a fungicide application at tillering could provide a small benefit of 2.2 – 3.7 bu/ac. In basically all other production scenarios he found that a foliar fungicide application at tillering would provide very little yield response.

Figure 2. Summary of yield response by disease risk level for early season fungicide application.

What is the difference between GDD, CHU and RM? Why and when are they each important?

Morgan Cott on June 1, 2026

By Morgan Cott, Agronomy Extension Specialist – Special Crops, Manitoba Crop Alliance

This is such a great question and I understand the reasons for asking. First of all, I think it is understood that GDD & CHU both basically measure how efficiently a day’s heat will benefit a growing or developing crop. One main difference between the two measurements is that CHU does account for extremely high temperatures (>30oC) that negatively affect crop development. CHU also looks at both the nighttime low temperatures (4.4oC as the base) and daytime temperatures between only 10oC (base) and 30oC (optimum ceiling).

GDD has historically been used to help estimate certain agronomic events like insect emergence, weed emergence, frost-free days and specific crop staging. My understanding is that CHU is used more for maturity than for the ability to accurately predict these different timelines throughout the season. This might be why certain seed companies use CHU and RM for maturity ranking and GDD for staging references.

Pride Seeds is an example of this, because they break down maturity with both CHU and RM, in addition to two key reproductive stages in GDD accumulation.

When calculating GDD or CHU, you will start from the day after corn was planted. It takes from 100 – 120 GDD for corn to emerge following planting, which is in ideal conditions, including soil moisture and soil temperature, which were variable this spring (and every spring). Start your calculations from day 1 until the day of emergence and see if that fits the above. Now that corn has emerged and is actively growing in your current conditions, continue to monitor accumulating GDD with the following formula. This will give you a head start on expectations during the growing season. When to expect pollination, for example. Note that this GDD accumulation in relation to corn staging is all in relation to each individual hybrid. A shorter season hybrid will need fewer GDD or CHU to reach black layer than a longer season hybrid, of course.

 

Helpful Resources:

I’m switching my wheat variety; do I need to change my seeding rate?

Andrew Hector on May 5, 2026

The short answer is yes; you will most likely need to change your seeding rate, but this is not just because you are planting a different wheat variety. Rather, seeding rates should be adjusted annually to reflect seed source characteristics (germination, thousand kernel weight [TKW]) and the environment the seed is being planted into, to ensure you can achieve your target plant population.  

Let’s dig into why this is. For spring wheat, provincial target plant population recommendations are between 23-28 pl/ft2, with many producers targeting the upper end of this recommendation. Achieving your target plant stands sets your crops up for success, as crop uniformity is improved, weed pressure is combatted and resources are optimized.  Seeding rates should be calculated to achieve your target plant stand, which means accounting for germination percentage, expected mortality and, importantly, your TKW. TKW changes year-to-year and from variety to variety.

Let’s consider an example to illustrate the relationship between kernel weight and seeding rate. For this example, let’s call our two varieties variety one and variety two. When comparing these two varieties we need to consider:

  • TKW: The weight (g) of 1,000 kernels of wheat from a specific seed lot.
  • Germination: If using bin-run seed, a seed test is needed to determine germination percentage. If purchasing certified seed, then your seed provider will be able to provide you with this information.
  • Expected mortality: The percent of seed/seedlings that won’t produce a plant due to unfavourable conditions or biotic stress.
  • Expected seed survival: Germination – Expected Mortality.

Example #1:

Variety

TKW

Germ (%)

Expected mortality (%)

Expected seed survival

Target plant density (pl/ft2)

1

42

97

6

91

27

2

33

97

6

91

27

Using the formula provided by Manitoba Agriculture (below) we can see the difference in seeding rates and therefore seed costs.

Seeding by plant population formula:

Seeding rate (lb/ac) = Target Plant Population (pl/ft2) x TKW (g)

                                              Expected Seed Survival (decimal) x 10

 Variety 1:

Seeding rate (lb/ac) = Target Plant Population (pl/ft2) x TKW (g)

                                              Expected Seed Survival (decimal) x 10                                          

                                                         = 27 (pl/ft2) x 42 (g)

                                                                     0.91 x 10

                                                         = 125 lb/ac

Variety 2:

Seeding rate (lb/ac) = Target Plant Population (pl/ft2) x TKW (g)

                                              Expected Seed Survival (decimal)

                                                         = 27 (pl/ft2) x 34 (g)

                                                                     0.91 x 10

                                                          = 101 lb/ac

This example shows that there is roughly a 24 lb/ac difference between the two seeding rates to achieve the same desired plant population. If you seeded variety 2 at the same rate as variety 1, then you would have over seeded, which could result in a thicker canopy, bringing challenges like an increased lodging and disease development risk.

Also, over seeding would have cost you money. Using a standard seed cost of 0.27 ¢/lb of seed (Manitoba Cost of Production Guide), then variety 2 at your normal rate would cost an additional $6.5/ac of seed that is probably not needed to reach your desired plant population.

Now, if the weather, disease, insects and equipment co-operate, you’ll achieve your target plant population. But it’s always best practice to do plant counts to get an understanding of the crop establishment and uniformity of emergence. More information on plant stand counts can be found here: Plant Stand Counts in Spring Cereals | Manitoba Crop Alliance.

Should I be looking at biologicals to offset high fertilizer costs?

Ashley Ammeter on May 5, 2026

First, let’s clarify what we mean when we’re talking about biological products. This is a broad group that includes both naturally occurring substances (such as humic or fulvic acids, seaweed extracts and enzymes) as well as beneficial microbes (such as nitrogen-fixing bacteria, phosphorus-solubilizing microbes, plant growth promoting rhizobacteria and mycorrhizal fungi). These products aren’t fertilizers themselves, but often claim to increase nutrient availability, improve nutrient uptake, improve stress tolerance or support plant growth.

Since high fertilizer prices have prompted some renewed interest in these products, I’ll focus mainly on nitrogen-fixing biologicals.

A quick note on regulation (and why it matters)

In Canada, most of these products are regulated under the Fertilizers Act. That means they must be properly labelled and prove that they are safe, but they do not need to prove efficacy before being sold. This makes replicated, independent research particularly important to test whether a product increases yield or can replace fertilizer under Manitoba conditions.

What has local research found?

Through our Research on the Farm program, MCA has tested a nitrogen-fixing biological product (Envita®) in several replicated, field-scale strip trials. In the eight corn and two spring wheat trials, we did not find a statistically significant yield increase when the nitrogen-fixing biological product was used.

Through their On-Farm Network, our colleagues with Manitoba Pulse and Soybean Growers (MPSG) have also tested many biological products. In 46 trials evaluating a range of microbial and non-microbial products, no statistically significant yield increases have been observed.

That doesn’t mean these products can never work. It does mean that predictable ROI has been hard to find under Manitoba conditions.

Does small‑plot research tell a different story?

Not really.

University and independent research in Western Canada and the North Central United States to date has largely lined up with what MCA and MPSG have found in on-farm trials. There are occasional positive responses, but they’re sporadic and can be hard to predict. For example:

Why are results so inconsistent? Formulation challenges, competition with the native microbial population and environmental differences all influence whether a product will find success. For those interested in learning more on this topic, Andrew McGuire with Washington State University has an interesting article.

So, should you use biologicals to offset high fertilizer costs?

Biologicals are an active area of research, and some products may eventually find a fit in our cropping systems. But based on local on‑farm and small-plot research to date, they are unfortunately not a silver bullet for high fertilizer prices.

If you do want to try a biological product, think about what problem you’re trying to solve. Is it a nutrient deficiency? Are you hoping to mitigate environmental stress? Are you trying to improve your long-term soil health? Consider the product claims, what the active ingredient is and how the product claims to work. Finally, if you do decide to try a product on your farm, I encourage you to consider conducting a replicated strip trial. Replicated strip trials let you test a product on your own farm, with your own management, and give statistically valid results. If you want to learn more about conducting on-farm trials, reach out to us for more information on the MCA Research on the Farm program.

The bottom line: For now, I recommend approaching biologicals with curiosity, caution and solid, on‑farm testing. To ensure you’re making efficient use of your fertilizers, use the 4Rs of nutrient stewardship (the Right Source @ the Right Rate, Right Time, and Right Place®) to guide your decision making, and check out this helpful factsheet on stretching fertilizer dollars and supplies from Manitoba Agriculture.

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