March: Spring will be here before we know it.
Early-April: Spring must be nearly here.
Late-April: Spring is still a thing … RIGHT?
With the sun shining here in SouthWestern Ontario, a solid 11°C (52°F) reading on the thermometer, and a promising two week forecast of above freezing temperatures, things are finally looking up.
BUT, with this good news comes a reminder that even though spring has decided to make an appearance, producers may be better off in the long run if they can continue to exercise patience and wait for proper soil conditions.
In most of SouthWestern Ontario, corn should be planted on or before May 7th for maximum yield potential (May 10th for areas receiving <3,000 CHU-M1). After these optimal dates, planting delays reduce yield potential by approximately 1% per day throughout the month of May.
However, with the wet and cold spring we’ve had, optimal planting dates and associated yield losses may be less of a concern than soil moisture and soil temperatures. In areas receiving 3,000 CHU-M1 and more, planting should become priority – focusing more on soil moisture conditions than soil temperature – after April 26th (May 1st in areas <3,000 CHU-M1).
In terms of high moisture, fields that are entered too early will cause ongoing yield loss due to compaction. When it comes to soil temperature, germination and emergence cannot occur with corn if soil temperatures are below 10°C (50°F).
Being a warm season crop, corn thrives in optimal soil temperatures of 27-32°C (81-90°F). With long and cold winters here in Canada, growers are left with no choice but to plant long before soil temperatures reach that optimal level. So, what is a reasonable soil temperature for planting corn?
Growers around here are advised to start putting seed down when soil reaches temperatures within the 10-13°C (50-55°F) threshold. When soil temperatures reach the 11°C (52°F) mark, a 50% emergence could take upwards of 30 days. If the season allows, waiting until soil temperatures reach 14°C (57°F) will allow growers to reach the same level of emergence, but lessen that wait time from approximately 30 days to approximately 7 days.
Looking at the calendar right now is likely to cause growers some anxiety. Everyone is itching to get in the fields after a nasty winter. But, if you can hold off until conditions are more favourable, you’ll be thanking yourself come harvest.
Before you start putting corn seed in the ground this season, ask yourself:
· Are field conditions dry enough to enter without causing compaction?
· Is your soil temperature at or above the 10-13°C (50-55°F) threshold at 2-4 inches deep?
· Is there a consistent warming trend in the forecast?
· Are the next 24-48 hours forecasted to be precipitation free?
If you can answer yes to all of the above questions, you might be ready to start planting. Otherwise, try to hold off as best you can. We’re almost there.
- Herbicide Application: If necessary (and possible in terms of equipment), it may be advisable to change the plan from a pre-plant/pre-emergent herbicide to a side dress/post-emergent application. This change in plan may allow you to get seed in the ground within the optimal window, while still being able to provide your soil and your crop the nutrients they need.
- Plant Population: In colder than ideal soil conditions, it is recommended to adjust seeding rates to approximately 10% higher than in optimal conditions, in order to achieve desired stand population.
- Hybrid Selection: There is no need to change hybrid selections just yet, but as optimal planting dates approach and pass, speak with your seed sales rep as to whether you may wish to consider switching to a mid or short season hybrid.
- Planting Order: Should you have a mix of hybrids in your lineup for this year, remember to plant your full season hybrids first (late flowering followed by early flowering), followed by mid and short seasons respectively.
Here’s to a safe and bountiful season.
Additional reading: OMAFRA Agronomy Guide for Field Crops