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Corn planting dates and yields

The spring of 2011 was a tough, tough spring to get seeds in the ground,” says Mike Cowbrough

February 9, 2012  By Carolyn King

The spring of 2011 was a tough, tough spring to get seeds in the ground,” says Mike Cowbrough, weed management program lead with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). “As the days progressed, growers started to get anxious. To get a bit of perspective, we wanted to look at how important planting date has been to final corn yields over the past decade.”

Planting date, although very important, is just one factor in the success of a corn crop.


So Cowbrough and Greg Stewart, OMAFRA’s corn industry program lead, put together the table shown below of corn planting dates and average yields in Ontario from 2001 to 2010. This table and the better-than-expected yields in 2011 are good reminders that planting date is just one factor in the success of a corn crop.


“It’s well established that, if the soil conditions are fit, the earlier you plant the better. What I take away from the table is that planting date, although very important, doesn’t trump everything,” says Cowbrough. “If you get good heat and adequate moisture in July and into August, and you don’t get a frost in September and the good weather lags into October, yields can be pretty good. And I think a lot of people saw that in 2011.”

Stewart agrees
“There is pretty solid, scientifically validated data that planting date does impact yield, but crop performance hinges on the rest of the season. The table shows there’s no sense in panicking too much about late planting. If we use 2011 as the classic example, moving planting dates into June wasn’t nearly as negative as you might have expected because of the growing conditions in the rest of the season.”

chart single  
 This table shows the differences between corn planting dates and overall yields in Ontario from 2001 to 2010.


However, he notes, “It was an interesting situation in 2011. By the first of June, a number of growers were asking themselves whether to plant corn. Looking at that table, you could say there is certainly a precedent that end yields in our province are not absolutely controlled by planting dates. Another consideration in spring 2011 was that Environment Canada – which has been uncannily correct with its forecast in the last little while – was predicting a warm summer and an open fall. As well, corn prices were as high as they’ve been in a long time. And of course we have hybrids that are much better at handling stresses, including later planting.”

Therefore, Stewart decided to tell growers at the beginning of June, that if they wanted to plant early, now was the time. If not, he added, “then it ain’t ever going to happen because the stars probably aren’t going to align for you as well as they did this year.”

As it turned out, he was right and the conditions were perfect for late-planted corn in 2011.

“July and August had pretty darn good growing conditions, even though we got a little scared about the lack of rainfall in July. Then it was essentially frost free in many parts of the province right through to the end of October. We also ended up with good prices. And we have hybrids that seem to be able to perform under a whole range of conditions,” says Stewart.

Dr. Mark Lawton, technology development lead for Eastern Canada with Monsanto Canada Inc., says that while planting early is always better, what occurred in 2011 could change views on the impact of late planting.

“What is different now, from a DEKALB perspective, is that when you have to change the maturity, you’re not giving up the yield potential that you would have 5, 10 or 15 years ago,” says Lawton. “In 2011, a lot of our customers changed their hybrid because they had to plant in June instead of April. Often they were moving to hybrids that are three to six days earlier. We had a lot of feedback through harvest where growers were shocked at how well their corn crops were yielding despite the late planting.”

The table also shows the overall upward trend in corn yields over the past decade. A big part of the reason for the upward trend is improved genetics for both earlier maturity and full-season hybrids. The improvements are significant enough that they tend to muffle the relationship between planting dates and yield.

Along with much better genetics, other factors contributing to the overall upward yield trend include environmental effects and better agronomics.

“When you look over even the last half-decade, we have had some particularly warm growing seasons that have given us an advantage,” explains Stewart. “In terms of agronomics, one change is that our producers are doing an increasingly better job at planting. Many producers are taking advantage of planter improvements, tillage improvements, and so on, to do a more uniform job of planting, compared to 10 or 20 years ago. Beyond that, it’s hard to pick other agronomic factors. Our OCC [Ontario Corn Committee] trials have been pretty much the same in terms of the agronomics behind them, other than perhaps seed treatments.”

Cowbrough hasn’t seen any major changes in weed management practices. “Generally speaking, in the last 20 years, Ontario producers have understood the importance of early season weed control, and I think for the most part they execute that better than most in North America.”

Looking back at 2011, Lawton summarizes the reasons for good yields despite late planting: “We have Mother Nature to thank for that, and also the genetics and the seed treatments, the equipment that gives good seed-soil contact, precision planting and all the tools that farmers use on a daily basis to get the most from their land in any year.”


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