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Do You Really Need to Plant Higher Corn Populations?

July 22, 2014
By: Rhonda Brooks, Farm Journal Seeds & Production Editor
missy talks farmers CornCollege 2014
Missy Bauer tells farmers to evaluate hybrids and make their selections based on an overall systems approach to corn production and management.  

In the rush to boost corn yields to meet an ever increasing need for more food, fuel and fiber, farmers are experimenting with increased plant populations in the field. In some instances, agronomists say those higher populations are counter-productive.

With today’s improved corn genetics, conventional wisdom increasingly says you should push corn populations ever upward to boost yield results. Based on the hybrids you plant, that may be the right strategy for your farm. But sometimes conventional wisdom is wrong, says Ken Ferrie, Farm Journal Field Agronomist.

"I’m probably one of the few guys who’ll tell you that you may need to pull back on your plant populations," he says. "You don’t want to arbitrarily increase them for no reason."

There’s a logical reason why. Corn ear type and plant architecture differ between hybrids and can make a big difference in how each hybrid absorbs nutrients, sunlight and moisture.

Those were key messages Ferrie and Missy Bauer, Farm Journal Associate Field Agronomist, conveyed today to nearly 200 farmers attending the 2014 Corn College near Heyworth, Ill. This year marks the seventh season for the event, which is hosted by Farm Journal Media.

A balancing act. Farmers need to understand the characteristics of each hybrid they select, so they can determine the ideal population range for their ground, notes Bauer.

"It’s not just a matter of picking a high-yielding hybrid; you have to evaluate it comprehensively as part of a systems approach to selection and management," she advises.

Take the matter of water use by hybrid, for instance. Bauer tells farmers to assess both above-ground and below-ground factors.

"Look at row spacings, populations, ear type and plant architecture above ground," she says. "Below ground consider whether you have uniform soil density, which allows for better root growth and improved water movement up and down the soil profile. All those things can make a difference."

Ferrie adds: "The higher the plant population, the more transpiration or water usage. Likewise, lowering the plant population reduces the crop’s daily water needs."

Ferrie says a (pendulum) leafy plant is best suited in soils with a lower water capacity. The larger canopy of the plant blocks the soil from sunlight, decreasing the amount of water that is lost to evaporation. An upright variety does best in soils with higher water holding capacities where water is not a limiting factor.

Sunlight absorption plays a role in planting populations, too. Once a crop is able to capture about 97% of the available light, Ferrie says, farmers are not able to boost yields substantially by simply increasing the plant population of that hybrid in that field.

"Light interception is a really big deal," agrees Kyle Holmberg, a field agronomist with DuPont Pioneer, based in Nashville, Tenn. "Ken and Missy both talked about light interception and the importance of achieving that 97% level with hybrids. That’s something that definitely impacts yield at the end of the season and something we need to tell growers. That’s been my biggest take-away so far this morning."

Here are additional considerations that Bauer and Ferrie shared with Corn College attendees. Keep in mind there is no one size fits all hybrid for every scenario, and you’ll need to make adjustments based on your individual farm needs:

• High plant populations with an adequate water supply need an upright leaf structure to maximize sunlight interception. However, upright leaf structure can work against you in drought conditions. In addition, while low populations work for you in a drought, they work against you in normal years because of the lower ear count.

• When you lower plant populations, the ear type (flex, semi-flex or determinate) has to be considered. Flex-eared hybrids can make up for lower populations, as the individual ear per plant will be larger. Flex-eared hybrids often can’t take the stress of over planting or under fertilizing. Determinate ear hybrids need to be pushed to maximize yield and can usually handle more stress. Semi-flex hybrids split the middle.

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