Seed switch timing factors in a wet spring

Yield potential still high for late-planted crops, so don’t panic yet

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Despite the wet and cool spring, Ontario field crop experts say there is still a lot of potential in late-planted corn and soybeans – that includes both long and short-season varieties.

Despite anxious feelings and generally unfavourable planting conditions, that is, things could still work out.

Why it matters: Shorter-season corn and soybeans bring tradeoffs between yield and costs. Despite planting delays, swapping for such varieties is not always necessary.

Yield potential still high

Ben Rosser, corn specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), says research comparing planting date and yield in corn – conducted under good conditions – does not show a clear linear decline.

Test trials conducted in Elora between 2006 and 2009, for example, showed corn maintains a 95 per cent yield potential as of May 20. This University of Guelph study, conducted by Dave Hooker and Greg Stewart, showed the same yield potential for corn planted by May 25 in Exeter, and May 30 in Ridgetown.

Data from a study from 10 years ago that shows the decline in corn yield compared to planting date at three sites in Ontario.
photo: Courtesy Ben Rosser, OMAFRA

While early May is the ideal time to plant soybeans, says Horst Bohner, soybean specialist for OMAFRA, it’s the weather of high summer (August and September) that most influences final yield. Indeed, in a 2017 article published for the ministry’s Field Crop News, Bohner says soybeans planted in early June still yield over 90 per cent, when compared to those planted a month prior.

“It has been a very difficult spring so far but it’s early enough things can still turn out well in the end,” said Horst in a more recent email exchange. “When you’re dealing with the weather patience becomes part of life.”

Weighing costs and returns necessary

However, short-season varieties might be appropriate for some producers. Rosser says giving up some yield for lower end-of-season corn moisture levels – and subsequent drying costs – might make sense in some cases. Those farming in areas with less than 2800 heat units, for example, should already be considering a switch.

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“If you’re in the 2800 to 3200 heat unit area, your window is probably May 20 to 25, and if you’re in the zone over 3200 you can probably hold into your hybrid selections until the end of May or early June,” he says.

“If you’re pushing maturity, though, switching before those dates might be necessary.”

As a guideline, Rosser says those who do switch should look for hybrids with 100 fewer heat units for each delayed week. He adds growers who have less expensive drying costs and more storage capacity, still might be able to maintain longer-season corn.

For soybeans, Bohner’s says swapping varieties is generally not necessary because changes in day length helps speed-up maturity in the fall (he calls this the photoperiod effect). Producers intending to plant winter wheat, though, might want to consider shorter-season varieties if planting is delayed past June 15.

Late planting reduces the period in which the plant itself can grow, however. This, says Bohner in his 2017 article, results in shorter plants with lower pods, a reduced number of pods per plant, and less time for those pods to fill. Selecting taller varieties can help offset lower vegetative growth. Increasing seeding rates by at least 10 per cent for a minimum of 200 000 seeds, as well as planting in narrow (7.5 inch) rows, will increase both the height of the lowest pods and the number of pods per acre.

About the author


Matt McIntosh

Matt is a freelance writer based between Essex County and Chatham-Kent. He is interested in all things scientific, as well as rock n' roll, hunting and history. He also works with his parents on their sixth-generation family farm.



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