What’s your farm’s unique canola seedling survival?

Written by Walter Ens on Aug 12 2016

Category: Grow Grain

If you’re very precise at seeding, you’ll be rewarded with optimum plant stands and bigger yields. Start with precise seedling survival.

How do you calculate your seeding rates in the spring? If you’re like many canola growers, your seeding rate calculation looks like this: assume a thousand kernel weight (TKW) of 3 grams, knock off 50% for seed mortality and set the seeder at 5 lbs/ac. 

If you want to target big canola yields, it’s time to get a lot more precise in your calculations.

Seeding rate calculation

When I work with growers to calculate their seeding rates, I used the following equation set out by the Canola Council

Seeding Rate (lb./ac.) = [9.6 x desired plant density (plants/ft2) x TSW (grams)] ÷ estimated seed survival (%, expressed as a whole #) 

I’ve used this equation to calculate the scenarios described in this blog.

Myth: large seed gives me fewer plants/sq. ft.

Over the years, I’ve seen countless bags of canola seed returned because it’s “too big.” Some growers believe that large seed means fewer plants per square foot. Here’s why: 

Imagine a scenario where you had 100% seedling survival. Field A is seeded with 6-gram seed and Field B is seeded with 3-gram seed. Your plant stands would look something like this:

 

Seeding rate

Multiplier

Density

Seed TKW

Survival %

Field A

5 lbs/ac

9.6

18 plants/sq. ft.

3 grams

100%

Field B

5 lbs/ac

9.6

9 plants/sq. ft.

6 grams

100%

 

Research says that under average conditions, canola seedling survival is 50-60%. Let’s look at the same scenario using an average of 55% seedling survival:

 

Seeding rate

Multiplier

Density

Seed TKW

Survival %

Field A

5 lbs/ac

9.6

10 plants/sq. ft.

3 grams

55%

Field B

5 lbs/ac

9.6

5 plants/sq. ft.

6 grams

55%

In my region of Manitoba, an ideal canola plant stand is 7-10 plants/sq. ft. So when growers run the numbers on 6-gram seed with an assumed 50% survival, they return it. They know they’ll miss out on yield with a thin stand of 5 plants/sq. ft., or they think they’ll have to increase their seeding rate to 8 lbs/ac and buy more seed. 

The reality is that your farm’s seed survival rate is going to be different from anyone else’s, and that rate is affected by seed size.

For me, bigger seed size means more vigour

When the Canola Council calculated Canada’s seedling survival of 40-50%, they blended large seed and small seed in their sample. 

In my own personal experience, large seed gives you better vigour, lower mortality and more uniform plant stands than small seed. Over the past 12 years I’ve spent with Cargill, I’ve found these survival rates: 

  • Seed with a TKW of 6 grams generally has seedling survival of about 80%
  • Seed with a TKW of 3 grams has a seedling survival of about 50% 

If we put my numbers into our scenarios, our plant stands look something like this: 

 

Seeding rate

Multiplier

Density

Seed TKW

Survival %

Field A

5 lbs/ac

9.6

9 plants/sq. ft.

3 grams

50%

Field B

5 lbs/ac

9.6

7 plants/sq. ft.

6 grams

80%

We’re using the same seeding rates and still achieving our desired population of 7-10 plants/sq. ft. But don’t take my word for it – calculate the survival rates for your farm.

Calculating your farm’s unique seedling survival rate

Reputable seed companies do a good job testing their varieties to make sure their canola germination is 90% or better. Everything that happens after you open that bag of seed affects its survivability.

Dr. Neil Harker of Agriculture and Agri-Food Canada found nearly a dozen factors that impact canola establishment. It includes things like seed bed preparation, crop rotation, seed selection, weed management, fertilizer placement, insect pressure, seeding equipment, soil moisture, seeding rates, trash from previous crops and seeding depth – with the most important ones being the last four. 

  1. 1.In the spring, record the TKW of your canola at seeding. If this information is not stamped on the seed bag, the staff at your local Cargill can easily phone up the seed company and get the TKW for you.
    • You can also figure out TKW by counting 250 canola seeds, weighing them in grams and then multiplying that weight by four.
  1. 2. In June, when your canola is between the 3- and 5-leaf stages, go out into the field and count the number of plants you actually have in a square foot.
  2. 3. Compare your actual plant population to the density you targeted at seeding to determine your own seedling survival percentage.
  3. 4. Start using those percentages on your farm.

An ideal plant stand is essential for capturing your canola’s full yield potential

When you start out with the right rates, it makes it that much easier to achieve the right plant population and your desired yield. Corn growers understand this perfectly. They tweak their seeding rates until they have plants spaced precisely 8 inches apart, and then they know that their crop is exactly set up to reach its genetic potential. 

We can get there with canola. The effort we put into perfecting our seeding rates will pay off at harvest. Your Cargill agronomist can help you find that rate. Give us a call and we can help you set up your canola crop to achieve its full potential.

Tags: Canola, Seeding, Crop Establishment

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