It still pays to plant full-season corn hybrids


Spring 2019 was certainly a challenge for Ontario corn growers. With more than double the annual spring rainfall, many growers kept hoping the rain would stop and a planting window would emerge, but in many cases that opportunity didn’t arrive until June.

For Maizex agronomist Greg Stewart, it was the most delayed planting season he’s ever seen. One of the biggest management challenges, he says, was helping growers switch hybrids — deciding when to do it and how many corn heat units (CHU) to drop.

Speaking with farmers at the SouthWest Agricultural Conference (SWAC) last week at Ridgetown, Ont., Stewart reflected on the spring and noted how often he heard growers share the perception that shorter-season hybrids are now producing stronger yields, and they stand to lose little when switching to earlier-maturing hybrids. “The feeling in the countryside was… when thinking about switch date you could pull back on the CHU rating of your hybrid and have less risk than you would have had 10 or 20 years ago.”

With all the chatter, Stewart decided to test the hypothesis. In this interview with RealAgriculture’s Bernard Tobin, Stewart describes how he and OMAFRA corn lead Ben Rosser took a deep dive into Ontario Corn Committee (OCC) trial data to look for a trend. (Story continues after the video.)

The bottom line, according to OCC data, is there is still a significant yield advantage for planting full-season hybrids, says Stewart.

“The story really hasn’t changed in the last three years compared to 10 or 20 years ago… There’s still some yield to be had by pushing our CHUs.” What’s more, he notes that the extra yield trumps the drying costs associated with the higher harvest moisture associated with these hybrids, in a more average season. Of course, in a delayed and drawn out planting window, there’s still value in swapping out hybrids at some point.

Stewart says 2019 has influenced how he’ll be advising growers going forward. In the first week or two after your switch date, pulling back 100 CHU seems to do the job, he says. But when planting is further delayed he believes growers have to be more radical in their maturity shift.

Stewart uses a grower in a 3000 CHU area to demonstrate this approach. After a one-week delay, hybrid maturity should be reduced by 100 to 2900 CHU; after two weeks it should be cut by 200 (2800 CHU); and by 400 (2600) after a three-week delay.

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