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Are corn plants spaced as evenly as you think they are? You could be losing bushels and money.

Tom J Bechman 1, Editor, Indiana Prairie Farmer

April 28, 2020

3 Min Read
young corn plants
HOW GOOD IS SPACING? These rows were planted with a modern planter with a sophisticated monitor. That still doesn’t guarantee uniform plant spacing. Tom J. Bechman

With electronic seed metering row by row and monitors reporting singulation, why talk about even plant spacing today? It made sense 30 years ago when Bob Nielsen discovered many farmers weren’t achieving “picket fence” stands. The Purdue University Extension corn specialist found much of the lack of uniformity related to sloppy planter maintenance. A cottage industry sprang up, with companies making test stands so dealers could test row units and make repairs or adjustments as necessary.

Today, you can do diagnostics on many high-tech planters, row by row, before ever going to the field — you don’t even need a test stand. So, again, why talk about spacing uniformity? Because not everyone runs high-tech planters, and not everyone has sophisticated monitors. And even if they do, when it’s crunch time, just getting the crop planted sometimes take precedence over checking actual placement row by row.

If you don’t wind up with uniform stands, you can give up bushels and dollars, Nielsen says.

“Several Midwestern corn specialists examined farmer fields beginning in the late 1980s and found that the spacing wasn’t as accurate in many of them as most people thought,” Nielsen explains. “Then we conducted research trials to determine if uneven spacing reduced yield. We discovered that in many situations, you could lose 2.5 to 5 bushels per acre just due to uneven spacing alone. That doesn’t address uneven emergence.” Combinations of erratic spacing and uneven emergence can cost 7 to 15 bushels per acre, according to research results.  

Even a 2.5-bushel-per-acre loss at $3.50 corn amounts to $8.75 per acre in lost revenue you never see. On 1,000 acres of corn, that’s $8,750; on 2,000 acres, it’s $17,500. That’s money that could pay a lot of bills this fall.

Measuring plant spacing

Check yourself to see how you’re doing, even if you think you have your high-tech planter dialed in, Nielsen says. Simply measure plant-to-plant spacing in inches over a long length of row. Repeat the process several times in the field. Write those numbers down in a spreadsheet.

“To get a handle on if you’re doing a good job of planting, calculate standard deviation once you have those numbers,” he says. If your eyes are glazing over right now, blink! It’s not as difficult as it sounds, Nielsen says.

“One way to visualize it is that it describes how close the majority of the plant spacings you recorded occurs around the sample average,” he explains. “It’s calculated in the same units as you measure spacings. So, if you measure in inches, you will calculate standard deviation in inches.” Most Microsoft Excel spreadsheets can calculate this for you, he notes.

Suppose your planter is perfect and every plant is 7 inches apart. Then the average spacing is 7 inches, and the standard deviation is zero. That’s not real-world, Nielsen says. In fact, he says a good goal is to obtain a standard deviation in plant spacing of 2 inches or less. If you reach the goal, you’re likely not losing yield due to erratic spacing.

However, for every inch of standard deviation above 2, you’re losing about 2.5 bushels per acre, just due to uneven spacing alone, based on research. If the standard deviation of plant spacings is 3.5 inches, you could be forfeiting nearly 4 bushels per acre.

You won’t know unless you check, Nielsen concludes.

About the Author(s)

Tom J Bechman 1

Editor, Indiana Prairie Farmer

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