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Digital Corner

by Dale Cowan

Thermal time measurements .

There are two main ways we track crop growth and development. In corn and soybeans we use Crop Heat Units (CHU) and for grains and horticultural crops we use Growing Degree Days (GDD) .

These thermal time measurestrack both temperature and days and are usedto measure the intervening time between critical growth stages.In corn for example it takes 160 CHU for corn to emerge and approximately 80 to 90 CHU for each new leaf. By knowing the planting date and CHU accumulations it is possible to predict crop growth stages. This can be useful for planning and managing product applications.

There is a two part formula for calculating CHU. A daytime component that uses temperatures above 10 C andmaximum of 30 C and the night time temperature is above 4.4 C and no upper limit. The formula is quiteinvolved so Iwon’t display it here.

The maximum day time contribution to CHU is 16.3, to have a day of 30 CHU then the night time contribution is 13.7, the twoadded together is the daily total.Themaximum daily total possible is 35 CHU that would take a maximum day time temp of 30 C and a night time temperature of 28 C . We did not have many warm nights and not many days near 30Cin 2023. The year over year comparison of CHU accumulation is in the chart below.The slow accumulation started in May largely due to cool nights and we never really caught up. We are now at stagewhere we have accumulated sufficient CHU to attain maturity. Although growth has been slow we are approaching black layer( maturity)on corn in the next 10 days. CHU accumulatios begin on May 1stand conclude at the first day of -2 C .

Total CHU accumulation in 2023 as of end of September is 3194 compared to 3433 in 2022 at Ridgetown. If corn was planted on May 15 then the crop would need another 150 CHU. At present daily CHU of 15 that is10 more days. Depending on the Relative Maturity of your hybridI would think most corn willblack layer within next 10 days. Early maturing hybrids planted in first week of May are likely at black layer.


Growing Degrees (GDD)are calculated by averaging the high temperature of day and night and subtracting from a base temperature. For Winter Wheat it is a base 0 C crop. Anytime temperatures are above 0 C wheat will grow.It takes 80 GDD For wheat to germinate and another 50 GDD to emerge for each inch of planting depth. For wheatplanted on September15 in Ridgetownit emerged on September 22nd when the GDD reached 143.As planting gets delayed into fall the accumulation of GDD slows down due to cooler temperatures and emergence will take longer.

As we approach the harvest season there are plenty of things to observe in the corn fields. Cob uniformity is one of them which is often attributing to uniformity of emergence. The same CHU were available to all seeds. Uneven planting depth is likely the main reason for differences in cob size and differences in maturity and harvest moistures. As you look at yield maps this fall also take a look at the moisturemap. Yield and moisture are inversely related. High moisture usually means lower yields often associated with field conditions and planter performance. Good input for winter planning for next year.


Start Your Wheat Off Right

By Kent Wolfe

When it comes to wheat production there are many factors that need to be considered to grow a high yielding crop. In this article I am just going to focus on a couple of the most important early considerations. The first step is to make a plan that will identify key area’s that will get the wheat crop off to a great start, these would include seeding Date, Rate & Depth. 

Planting Date

Timely planting of winter wheat is the most important yield contributor, unfortunately this is not always in our control as we are seeing this fall in many areas. Ontario research has shown a decrease of 1.1 bu/ac in yield for each day past the optimum date which in our area is from September 25th to October 10th.



Figure 4-4 Optimum Date to Seed Winter Wheat across Ontario

Seeding Rate

One thing we can control to offset the planting date is rate. These are determined based on seeds per acre, which in turn will equate to pounds per acre. Varieties will differ in the number of seeds per pound, so adjustments will need to be made if switching varieties or sometimes even lot numbers. We should aim for 1.5 -1.6 million seeds per acre on most varieties if planting at the recommended planting dates. Rates should be adjusted by 100,000 seeds/ac either up or down for each five days before or after the optimum date in your area.  

Planting Depth

General rule of thumb is to always plant into moisture, in a perfect world 1” to 1 ¼” would be ideal for both germination and timely emergence. It takes approximately 80 GDD (growing degree days) for the seed to germinate and an additional 50 GGD for each 1” of planting depth. If the soil is extremely dry and there is no moisture in the top 3”, plant the seed at 1” depth and wait for a rain. The plants needs the 1” minimum depth to allow the nodal roots to develop properly and anchor the plant, this will help reduce heaving in the early spring.

Resources: pub 811 Ontario Agronomy guide

                   University of Guelph (Ridgetown Campus) Dr. Dave Hooker 


Successful Steps for a Great Winter Wheat Crop

By Cory Cowan

As one of the most widely cultivated grain crops globally, winter wheat plays a vital role in meeting the world's food demands. It also is a valuable crop to have in your rotation, not only for improving soil health but also for yield in the crops that follow in your rotation.

From selecting the ideal variety and preparing the soil, to understanding optimal planting dates and techniques, farmers must carefully plan their winter wheat planting strategies. By delving into key factors such as climate conditions, seed quality, and pest management.

Selecting The Right Variety of Winter Wheat

Choosing the appropriate variety of winter wheat is crucial for a successful planting season. With numerous options available from our seed partners at C&M seeds you can have peace of mind you are growing the correct variety for your farm. Based on soil type you can position the best variety. For heavier soil types Cruze or Blaze has been a solid option as well they’re newer variety to their line up Swoop. Both Cruze and Blaze have been great varieties across all soil types with Blaze doing exceptional on loams and sandy soils.

It has been shown that timely fungicide applications at critical growth stages not  only protects your yield it reduces incidence and severity of fungal pathogens that reduce grain quality.





Starting with a current soil test to adjust levels of essential nutrients and soil pH assures a good start and improves vigor and sets yield potential for next spring. Seeding rates need to be adjusted by seeding date with delays in seeding requiring higher rates. Often starting at 1.6 million seeds and increasing by 200,000 seeds per acre for each week past optimum seeding date to a maximum of 2.2 million seeds per acre. With adjustments made for poor seed bed conditions.

Winter wheat planting requires careful consideration of timing and specific conditions to ensure successful establishment. Ideally, planting should take place during the September to October time frame. This timing allows for sufficient root , crown and tiller development. The image below from OMAFRA shows the ideal planting dates across Ontario which is crucial for achieving the highest yields possible.


Finally, fall herbicide selection is a great way to start and stay clean from weed pressure throughout the year. This fall application is an effective way to get the upper hand on tough to control resistant weeds. Two programs that growers have a had great success with are 60 ml/ac of Eragon Liquid with 400 ml/ac merge ahead of planting or Infinity Fx at first true leaf after your wheat has emerged.

Your AGRIS trusted advisor stands ready to help establish a successful winter wheat crop. 

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