As we saw with the 2019 winter wheat crop, if winter wheat is planted late and if conditions are not fit, there is a greater risk of winter survival issues.
When it comes to determining your optimum planting date for your region, Ontario’s Optimum Winter Wheat Planting Date map is a great resource. When determining the optimum date, find your location on the map and look at the dates on the lines on either side of you. The planting date range for that region falls between those two dates. If for example you live in the London area, the optimum planting date for your region falls between Sept. 25 and Sept. 30.
Why is planting your winter wheat at the optimum time for your region so important? It takes approximately 80 Growing Degree Days (GDDs) for winter wheat seed to germinate and another 50 GDDs for wheat to emerge for every inch of seeding depth. If you are seeding your wheat at a depth of one inch, it will take a total of 130 GDDs for the seed to germinate and emerge. If you plant deeper, it will take more GDDs for those plants to emerge. The later we plant wheat, the less GDDs we get resulting in less root growth and tillering before winter.
While this map can be helpful when determining the ideal time to get your winter wheat planted, it is a guideline and you should also make sure conditions are fit for planting when you are ready to go. If the conditions aren’t right and waiting a day or two beyond the optimum date means better planting conditions, then wait for the better planting conditions.
While it may come as a surprise, you can plant winter wheat too early due to the increased risk of snow mould, lodging and barley yellow dwarf virus (BYDV). It is generally not recommended to seed more than 10-14 days before the optimum date for your region.
If you are seeding more than 10 days before your optimum date, reduce seeding rates by 25 per cent to help manage these risks. If you are planting later than the optimum date, the seeding rate should be increased by 200,000 seeds per acre per week to a maximum of 2.2 million seeds per acre to compensate for the delayed planting.
Seeding depth and the use of a starter fertilizer are also significant factors that need special attention at planting. Winter wheat should be seeded at a depth of one inch; however, this can often be difficult due to the poor accuracy of drills. Therefore, target 1.25 to 1.5 inches to ensure you are seeding your wheat deep enough. Shallow seeding can result in plants being more prone to winterkill and heaving.
A seed-placed starter fertilizer should also be used because it provides nutrients for early growth and promotes root development. As a result, we see an improvement in winter survival and crop uniformity which helps with disease management the following spring.
The planting date map can be found under the downloads section at gocereals.ca.
– Joanna Follings is an OMAFRA cereal crops specialist