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Pros, Cons Of Cutting Corn Seeding Rate

“The longer the seed takes to get out of the ground the more time there is for things to go wrong.”


With corn farmers facing ever-higher seed costs, does it make sense to cut the seeding rate to save money?

It depends, says Pam de Rocquigny, Mani toba Agriculture, Food and Rural Initiatives’ (MAFRI) business development manager for feed grains.

“If you’re willing to implement a higher level of management and hope that Mother Nature co-operates with you (it might work),” she told the Manitoba Special Crops Symposium in Winnipeg Feb. 11.

It’s something to consider if seeding is delayed past May 15 since a reduced plant population results in earlier crop maturity – always an important factor when growing corn in Manitoba. But generally, de Rocquigny said, reducing seeding rates costs more than it saves.

“The (Manitoba) corn growers (association) have done studies that show increasing the (plant) population is one of the easiest ways to increase yield and planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates,” she said.


Corn yields have been increasing, but so has the cost of seed. Thirty years ago (1979) seed cost just $12 an acre, de Rocquigny said. MAFRI says this year hybrid seed will cost $62.40 an acre based on a plant population of 26,000 an acre. That’s a fivefold increase, although the seeding rate is much higher now than in 1979.

In 1979, when corn sold for about $2 a bushel, the break-even yield was 78 bushels an acre, she said. Now, based on $4.50-a-bushel corn and a production cost of $386.65 an acre, the break-even is 86 bushels an acre. The 10-year average yield for corn in Manitoba is 88.2 bushels an acre, according to crop insurance data.

How much a grain crop yields depends on three factors: the number of plants growing in the field, the number of kernels of grain each plant produces and the size of those kernels, she said. Cutting the seeding rate means fewer plants per acre and potentially less yield. The ideal plant population for Manitoba grain corn is 24,000 to 26,000 an acre – 26,000 to 30,000 under optimal conditions and 22,000 to 24,000 where yield might suffer from things like late seeding.


However, seeding rate and plant population are not the same because not every seed planted produces a viable plant, de Rocquigny said.

“If you cut your seeding rate you’re going to have to employ a little higher level of management,” she said. “Basically you’re going to have to ensure the seeds that you have planted merge uniformly to maximize your yield potential.”

That means planting into a well-prepared seedbed and warm soils (at least 10C), seeding to the proper depth (1.5 to two inches) and making sure the seeds are evenly spaced. Even emergence is important and is compromised by cold and/or cloddy soils and uneven seeding depth. Slowing to four miles per hour instead of six helps with seeding depth.

“The thing to keep in mind is the longer the seed takes to get out of the ground the more time there is for things to go wrong,” de Rocquigny said. “Those smaller, later-emerging plants will almost act like weeds.”

One U. S. study concluded when one out of four plants emerges 10 days later yields dropped from 188 bushels an acre to 176. That’s similar to the yield hit that would occur had the ent i re crop been seeded later.

“That’s how important uniform emerge is to your production,” she said.


Even if the farmer does everything right, Mother Nature, in the form of weather, weeds, insects or diseases, can still reduce the plant population and the yield potential, de Rocquigny said. The impact isn’t as great when the plant population is optimal.

Farmers trying to trim their seed bill can also consider switching hybrids. Many are genetically modified to tolerate the herbicide Roundup as well as containing the Bt gene to kill attacking European corn borers. Corn borers haven’t been a major pest for several years in Manitoba. Farmers should assess whether they need that protection, de Rocquigny said. If not, they can save money planting a conventional hybrid.

But de Rocquigny added that option seems to be disappearing. In 2003, there were 42 hybrids assessed by the corn committee in Carman and of those 44 per cent were conventional. In 2008, only 19 per cent were conventional. Out of the 20 corn companies offering hybrids, for testing only four had conventional hybrids. [email protected]

About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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