Edge Yields Upward

November 27, 2008 06:00 PM

Harvesting with one row of a three-row head, Bob Recker has found a 20 bu. to 30 bu. yield variation between rows.

Some people spend their golden years playing golf. Bob Recker plans to spend his figuring out why one row of corn yields less or more than others. For several years, Recker has documented row-by-row yield variability on seven farms in northeast Iowa. He harvests one row at a time, all the way across the field, using a tiny John Deere 3300 combine, a weigh wagon and a grain cart.

"I've found dramatic yield variation from row to row—often 20 bu. to 30 bu. per acre,” he says.

Recker plans to collect more data before speculating about the causes of yield variation. In the meantime, he has documented another phenomenon that might help farmers net extra profits right now: the edge-row effect.

Edge rows often yield more because they receive more sunlight. Recker confirmed that—but he also found that poorly managed edge rows may yield less. "On one farm, an edge row yielded only 150 bu. per acre, compared to the field average of 200 bu.,” he says. "The only difference was that weeds and grass encroached from the adjacent roadside.”

Recker calculated how profit might be affected by edge-row management on a supposed 1,000-acre farm. The imaginary farm has twenty-five 40-acre fields, each with a ¼-mile waterway. Half the fields are planted to corn in 30" rows. The outside rows of each field and the edge along both sides of the waterways total 11.4 acres of corn.

"If every edge row yielded 50 bu. per acre less than the field average, the farm would produce 570 fewer bushels of corn,” Recker says. "With $3 corn, that's $1,710 lost profit. With $5 corn, it's $2,850 lost profit.”

In a real-world field where outside rows were kept free of weeds, Recker found the edge row yielded 250 bu. per acre, and the second row in from the edge yielded 220 bu. per acre—averaging 235 more bushels per acre than the field average of 200 bu. (The remaining rows yielded the field average.)

Because two outside rows are involved, these rows constitute twice as many acres as in the previous example, or 22.8 acres. They produce 798 more bushels of corn—worth $2,394 at $3 per bushel or $3,990 at $5 per bushel.

An "accidental test plot” on another farm made Recker wonder what might happen if you applied more inputs to the outside rows to use the additional sunlight. The operator accidentally planted 60,000 seeds per acre, instead of 36,000. To salvage the situation, he applied extra nitrogen. He kept the edge free of weeds and grass. The outside row yielded more than 400 bu. per acre and the second row almost 300 bu., while the field averaged 200 bu.

"Using the same 1,000-acre farm layout, I assumed the operator switched from 30" rows to 20" because narrow rows are recommended if you are trying to exceed 300 bu. per acre,” Recker says. In this case, the two outside rows of corn around fields and waterways total 15.2 acres.

"If you average 150 more bushels per acre on 15.2 acres, that's 2,280 more bushels of corn—worth $6,840 at $3 per bushel or $11,400 at $5 per bushel (minus the cost of additional seed and fertilizer),” Recker says.

Sure, this is "blue sky” brainstorming. But no doubt you'll someday have the technology to give edge rows special management. For now, it might pay to make sure you don't let weeds and grass sneak in.

For More Information

Following his retirement as a tractor design engineer, Bob Recker is devoting his time to analyzing row-by-row yield variation. His company, Cedar Valley Innovation, is based in Waterloo, Iowa. Contact Recker at cvi@forbin.net.

You can e-mail Darrell Smith at dsmith@farmjournal.com.
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