Corn Planting 2019: When the Going Gets Tough… By Greg Stewart, Maizex Agronomist


Although we are in just the first few days of May, persistent rainfall and cooler temperatures are delaying corn planting across much of eastern Canada and already the questions are coming about switching to less than full season hybrids.  The main message is that it is certainly too early to panic.  Most data sources suggest that the appropriate switch date from full season to shorter season hybrids is in the May 21 to May 27 window.

The most recent planting date work done in Ontario (U. of Guelph and OMAFRA) demonstrates that a May 25 planting date essentially indicates  a 5% yield lose compared to the same adapted hybrids planted before May 10.  Although this represents an unwanted loss it does mark a threshold where switching to shorter hybrids before that date will in most years cause you to give up more than 5% yield.

Joe Lauer a Wisconsin based agronomist has also done some analysis of planting date studies and found that drying cost was an important factor in determining switch dates between full-season and shorter-season hybrids.  If your corn drying costs are relatively expensive then switch dates should move to the earlier part of the window.

Corn Plays Catch Up – Corn Belt research has indicated that later planted hybrids actually require fewer CHUs to reach maturity than those same hybrids planted earlier in May.  The numbers essentially suggest that a 3000 CHU hybrid planted on May 5 would require 3000 CHU to reach black layer.  That same hybrid planted on May 25 (20 days later) reaches black layer in about 2875 CHUs. Most of the CHUs that you give up because of a May 25 planting date are made up by the later planted corn developing with relatively fewer CHUs.

2019 – In shorter season (< 2850 CHU), snow friendly areas it is still the right call to plant full season hybrids right up to the holiday Monday, May 20.  In these shorter season areas the holiday Monday marks a day that you may reconsider hybrid changes, especially if the forecast is not favourable. As you move south towards 3200 CHU areas there is another week to stick to adapted full season hybrids. Beyond 3200 CHU areas full season hybrids work right into the first days of June.

Notes – The thoughts on this page are sound as long as you have not already picked hybrids that are 150 CHU longer than your normal full season options.  Although this is a nice strategy to push yields you may need to forego it in 2019.  Similarly, growers who have already selected a nice range in hybrid maturities are under less pressure to switch any hybrids compared to those who are already weighted heavily to full season selections.

If you can’t fight Mother Nature and need to switch to shorter season hybrids be sure to discuss the possibilities with your Maizex representative.

Here are a few additional ideas to consider to maximize planting efficiencies when we finally get a break in the weather.

1)  Have a Plan, Print it Off, Make Copies.  Be sure your cropping plans are ready to go and that copies exist everywhere, cabs, trucks, one to your mother-in-law, just in case.

2Brainstorm.  Most of you farm with a team, even if it is just one or two other people, buy a box of doughnuts the next rainy day and brainstorm with everyone how to keep things moving smoothly once things get busy.

3.  Don’t Scrimp on Starters.  When the season is delayed there is a tendency to want to eliminate fertilizer from the planter to speed up the process. This can work against you. In a backwards spring corn plants need every possible advantage to make yield and maturity; stick with at least some starter fertilizer, especially on lower testing fields and when planting late.

4.  Leave Nitrogen until Later.  It is difficult to ignore the need for at least 30 lbs N/acre applied at or near planting; but for the rest of the N there are 45 days and about 45 ways to get it applied after planting, so leave it until then.  30 lbs of N will carry the corn crop until it has 4-5 leaves.

5.  No Time for Recreational Tillage.  If a single pass of a cultivator gets the job done then start planting.  Focus on the quality of the seedbed, if it is fit then leave it and plant. The second or third passes that perhaps do a nice job of levelling the field can wait for another time.

6. Be Safe…..Body and MindNo backwards spring or delayed planting is worth risking injury.  Be careful, and keep yourself and those around you safe.  If the stress of the season is weighing on you, talk to someone.  There isn’t anyone on the Maizex team that wouldn’t love to talk things over.