Making the corn switch decision

Those who switched hybrids during 2019’s late planting season generally had more success

Reading Time: 4 minutes

The 2019 planting season forced farmers to make more complex corn seed and planting timing decisions than they have in years.

A wet and cool spring kept many farmers in Ontario out of fields until June and in some cases, for risk takers, July.

Farmers who planted shorter-season corn hybrids generally made the right choice in 2019, said experts at the Southwest Ag Conference in Ridgetown recently. In the future they could be even more aggressive in making that switch.

Related Articles

Why it matters: After a year of making some tough choices, it’s a good time to question historical recommendations around hybrid switching.

Greg Stewart of Maizex and Ben Rosser, Ontario Ministry of Agriculture and Rural Affairs’ corn specialist have looked at Ontario corn committee data for several years. Stewart says the question is whether short-season hybrids have improved enough in yield, that there’s little penalty to switching.

“Would you choose them if you knew more about the hybrids?” he asks.

Switching to a shorter-season hybrid means more chance that the corn from that hybrid will reach maturity. Sticking with a longer-season hybrid may increase yield, but could also mean the corn doesn’t reach maturity or more drying costs could be incurred to get the corn to a marketable moisture level.

Stewart first looked at the Ontario Corn Committee data over three year groups starting in 1987 and at plots in Elora, Woodstock and Ridgetown.

The data showed that, over time, the average variation after adjusting hybrid yield impact based on 100 corn heat units was 7.2 bushels per acre from 1987 to 1989, 6.9 bushels per acre from 1997 to 1999, 7.3 bushels per acre from 2007 to 2009 and 4.4 per cent from 2017 to 2019.

That means that there’s no significant long-term trend toward shorter-season hybrids catching up to longer-season hybrids, says Stewart, although the average difference is smaller over the past three years.

If that’s the case, and there’s still incentive to stick to longer-season hybrids as long as possible, what do the economics look like?

Stewart looked at drying costs, based on a higher cost at seven cents per bushel and a lower cost of four cents per bushel.

Data from the OCC trials from 2017 to 2019 says there needs to be 4.2 bushels to pay for each extra point of moisture average. At those drying costs, that would mean 3.7 bushels more would be needed at the higher drying cost and two bushels would be needed at the lower drying cost to cover the increased drying needed for the increased moisture likely resulting from the higher-yielding, longer-season hybrids.

So if corn was harvested at 200 bushels per acre and 25 per cent moisture, the break-even yield at 28 per cent moisture at the higher drying charge would be 211 bushels per acre and at the lower drying cost, 206 bushels per acre.

Stewart admitted in response to questions that test weight is difficult to quantify in relation to the change in hybrids. Local farm realities also must be taken into consideration, such as if the farm has all of its corn to plant or 20 acres left.

Looking at dates to change hybrids

Farmers in 3,200 corn heat unit (CHU) areas have generally switched hybrids after May 30, in 2,800 to 3,200 CHU areas, from May 20 to 25 and in areas with less than 2,800 CHU, May 15 to 20.

They do that to avoid having immature corn, which was a challenge last year.

It’s not just the frost that’s the challenge. When the daily temperature reaches a high of 12 C, further grain fill is limited, says Rosser.

If, in Ridgetown, which can grow 3,450 heat unit corn, planting is delayed to June 1 instead of May 1, about 500 heat units of growing opportunity has been lost.

Rosser says farmers shouldn’t just jump to a shorter-season hybrid because they have some “flex” in them. So a hybrid normally planted May 1, could still be planted in June 1 and still reach maturity. However, if planting is delayed much later than that, getting to maturity could be a challenge.

“They have flex, but there are some limits to that,” he says.

Rosser says that for each week after the local deadline for switching hybrids, growers should move the corn heat units needed to mature the hybrid down by 100 points, for the first two weeks. After that, because weeks in the fall don’t equal the heat units of weeks in early summer, drop the corn heat units by 200 per week, says Rosser.

On the farm

Case studies from 2019 also showed there were advantages to dropping CHUs, but some farmers still didn’t get that corn to black layer, which is when it is considered mature.

One farm in North Kent collected the Unseeded Acreage Benefit through Agricorp because it hadn’t planted by June 21, but the operators weren’t excited by the economics around soybeans. The growers also had a livestock neighbour who would take immature corn or corn for silage, so they had a fallback if the corn didn’t mature.

They planted 2,950 heat unit corn on June 25, which Rosser says still might have been too high for that time of year. The corn only made it to half-milk line.

A hog farmer, who needed corn for feed, decided to plant corn instead of soybeans and that way avoid having to buy their feed corn.

Corn planted in June 9 was fine, corn planted June 19 almost got to black layer, but corn planted June 23 got to half-milk line.

In a third case, a farm southwest of London in a 3,300-3,400 CHU area, risked planting late, including on June 29 and July 4.

They cut back the hybrid to 2,300 CHU for the July 4, planting, but only were able to get it to half-milk line.

“There’s not a lot of data getting into late June or early July,” said Rosser. “We still have work to do on that.”

Chad Anderson, an agronomist who works in Lambton County, said making the choice whether to plant soybeans or corn often came down to whether or not growers had the unseeded acreage benefit claimed. If that was added into corn calculations, then corn, even at 100 bushels per acre, still made sense, especially to livestock farmers who needed it.

In his example, corn that was planted in June still came out more profitable than soybeans, but the reverse was true once the calendar turned to July.

About the author


John Greig

John Greig has spent his career in agriculture journalism and communications. He lives on a farm near Ailsa Craig, Ontario. Contact John at [email protected] or follow him on Twitter @jgreig

John Greig's recent articles



Stories from our other publications