Blog: Agronomy & Extension

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.

How much 10-34-0 can be applied with my corn seed?

Morgan Cott on May 5, 2026

Oddly, I have had this conversation more this winter/spring than ever before. On paper, there is a finite answer. Anecdotally, there are a few different options and it is all dependent on soil type and soil conditions, moisture, etc.

First of all, side-banding any type of fertilizer is much safer than placing it with the seed. Some fertilizers are safe in certain quantities with the seed, but very few. Side-banding is much safer and provides quick access to the roots. Midrow banding is the safest method, but roots take that much longer to access the fertilizer row, which negates the “starter” effect. The other factor that indicates the level of safety is soil moisture; the drier the soil, the more risky it is to place any fertilizer with or near the seed.

I’m guilty of thinking that fertilizer toxicity to the seed is mainly due to the nitrogen content and a result of ammonia burn. Salt injury is actually more common and affects germination and early season growth, so applying fertilizers that have a low salt index in closer proximity to the seed is best, if any has to be close to the seed at all. Bonus points if there is good soil moisture at the time of fertilization.

As I mentioned, on paper there are defined rates of 10-34-0 that can safely be applied in-furrow with corn on 30” rows. This table shows those rates and placement that will help to avoid salt injury to the corn crop.

Table: Amount of 10-34-0 (gal/acre) to help avoid salt injury to corn grown in 30” rows.

After having some discussions with Manitoba corn farmers on various soil types, I did get some reasonable responses explaining increasing rates in heavier, wetter soils. But more importantly, decreasing the above rates in dry and/or lighter soils. These were purely anecdotal and not research-based.

I recommend being very conservative in 10-34-0 rates if you are new to trying this method of application, and especially if you are planting in dry conditions and/or coarse soil textures. Start small and have many conversations with your peers on their experiences with various rates of 10-34-0 in-furrow. Use that information to make a conservative decision of your own.

Remember, start your season with success and make smart choices. Do not make decisions that could get your crop off to a bad start. We live in Manitoba – Mother Nature is hard enough on us in spring.

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