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Tips for Evaluating Your Corn Yields

August 6, 2012
By: Boyce Thompson, AgWeb.com Editorial Director google + 
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A kernel count puts farmers one step closer to an accurate yield estimate.  

Hot, dry weather won’t be the only thing depressing yields this year. You need to get out in the field to make an accurate prognosis.

 

Drought conditions have depressed corn yields in many parts of the country. That much is dead certain. But what will be much less obvious amid the carnage are the specific reasons corn plants didn’t grow to their full potential, produced stunted cobs, or are missing many kernels.


Agronomists at the recent Corn College events in Coldwater, Mich., presented the farmers in attendance with the tips they need to do proper forensic science on their corn crops. They also gave the audience plenty of sound advice to improve yields next year, when, as everyone hopes, conditions will be better.


When asked if they could project their ear count today, only a few farmers raised their hands. Farm Journal Field Agronomist Ken Ferrie told attendees that they need to be in their fields once a week, with a tape measure, shovel, hatchet, knife, planting schedule and historical data.


"I’m a big believer in evaluating the situation, trying to figure out how much we might have over-sold," he says. "If we changed our corn program, and we aren’t counting things, how do we know if we had success?"


Everyone needs a regular, objective measure of crop progress, especially today.


"I don’t want my morning coffee with a bunch of depressed farmers to affect what I see in the field. You need to open your eyes and take an accurate appraisal of the situation."


The drought won’t be the only critical factor negatively affecting yield this year, Farm Journal Field Agronomist Missy Bauer told the group. Some corn plants may not have received proper care and feeding during their early stages.


"I suspect this year we’ll have some of the biggest swings—field to field, hybrid to hybrid—that we’ve had in years," she says. "You could have 100 bushel swings from one hybrid to the next, depending on the timing of stress."


The secret to a high yield is stopping stress from the get-go, says Bauer, who strongly recommends using starter fertilizer.


"It advances the maturity of the corn, sometimes by 5 to 7 days. At a minimum, it should include nitrogen, phosphorous, and zinc. You get a bigger, greener plant by advancing maturity from the get-go."


There are many reasons why farmers would want to advance maturity, not the least of which is that plants will be in a better position to withstand early frost and dry conditions at harvest. They may also go through pollination sooner, improving the chances for big yields.


The healthiest corn has the best root growth, and lateral seminal roots—not just main roots—are a key part of that equation, Bauer explained. Having four roots rather than two will dramatically affect the size of corn. "We see a lot of correlation between what seed roots look like and the final corn looks like," she says.


Drought conditions no doubt prolonged pollination in many regions this year, depressing yield. "It’s not super common, but I suspect we’ll have some fields where this happened this year."


Other yield may be lost because pests interfered with pollination. "We need a half-inch of silk at all times to get pollinated," Bauer says. "If you have silk clipping at 40% pollination, you need to do something. It’s not such a big deal at 90%."


In a typical year, Bauer points out that more kernels are lost after pollination. "After pollination, you get into R2 blister stage. If we get drought and heat stress during this stage—about 10 to 14 days after silking—we can lose lots of kernels."


"This is a tricky thing. If you are out there and doing kernel counts, you might just count the yellow. You are going to lose the white ones. If you don’t understand kernel abortion, you can dramatically over-count your yield."


The key to any forensic process, Bauer says, is to know what stage your corn was at when you had bad weather.


While hot, dry conditions will depress yields, so will poor planting techniques, says Ferrie. When the agronomist visits farms for inspections, he wants to see uniform growth, a picket fence of photocopied plants. It helps with root growth and pollination.


He doesn’t want to encounter double stalks, skipped spaces, or poor spacing, which usually occur because of planting irregularities. "Doubles usually do not produce a harvestable ear. With drought stress, we lose them both. Yet the plant continues to suck up water and nitrogen."


Ferrie advised the farmers to weed out random uneven plants. He showed a picture of a row of corn, with two stalks in V5 development, bookmarking a stalk in V3. "Plants that are more than a collar behind are not going to put on an ear."


Planting irregularities usually occur because planting equipment wasn’t calibrated correctly or the planting process went too fast. Ferrie emphasized the need to set up and maintain planters properly, and to calibrate meters, aiming for target standard deviation of no more than 2 inches.


But he finds that speed is the biggest problem. "You need to slow the planter down. You need to plant at 5 miles per hour, instead of 7, and follow it through to the end, even if you look over and see your neighbor has lapped you."


It’s all about ear count, Ferrie says. "In the end, the one with the most ears wins the game."

See a photo gallery of farmers in the field at Corn College:

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See full coverage of this week's Corn College events at www.FarmJournalCornCollege.com.
 
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Thank you to the 2012 Soybean College sponsors:

Agrotain, BASF, Great Plains Mfg., MANA, Novozymes, SFP, Precision Planting, Pioneer

 


 

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