|Prioritize fields to ensure tillage is completed on your most compacted areas.
Pinch-row compaction has existed since we first went to the field with a tractor. But today's heavy tractors and center-fill planters make it a growing concern, especially in wet springs like that of 2009, says Farm Journal Field Agronomist Ken Ferrie. It's just one more reason to adopt a tillage game plan this fall.
Pinch-row compaction results when soil next to a row is crushed by a heavy tractor wheel, restricting a root's growing space. "Two rows—one on each side of the wheel—can get hammered pretty hard,” Ferrie says. "The heavier the tractor and the wetter the ground, the more compaction you get.”
"We had never seen symptoms of pinch-row compaction caused by the planter before this year, but it was very noticeable in 2009,” says Aaron Gingerich of Lovington, Ill. "It looks like the streaks of stunted corn that sometimes show up in the wheel tracks you made where you field cultivated prior to planting,” he says. "But those streaks run across the field at an angle, while pinch-row compaction follows the row.
"The shortest row of corn was between the tractor's dual wheels, but the rows on each side were shorter, also,” Gingerich continues. "Six rows were affected with a 24-row planter.”
Gingerich dug up corn plants to examine the effect. "The roots were wider than the seed trench, but they were pinched on each side,” he says.
Yield hit. Hand-checking prior to harvest suggested yield loss in Gingerich's affected rows at 12 bu. to 15 bu. per acre, and much more where the compaction was aggravated by other problems, such as standing water.
Typically, corn rows affected by pinch-row compaction yield 7 bu. to 10 bu. per acre less than other rows in the field, Ferrie says. "If the compaction is severe, they can yield much less,” he adds.
Center-fill planters aggravate pinch-row compaction. "The weight of a full seed hopper, and starter fertilizer tanks if you have them, goes to the planter's carrying wheels—not to the depth wheels, as it does on planters with individual seed boxes,” Ferrie says. "That puts added weight on the tongue, which puts more weight on the tractor.”
The effect is severe enough to show up in normalized difference vegetation index (NDVI) images and to feel with a spade when you probe fields. "Pinch-row compaction is worse in tilled fields than in strip-till or no-till,” Ferrie says. "In conventional tillage, the ground is softer and the pinch-row compaction goes deeper.
"It's a problem in no-till and strip-till, too. You have to plant into those tracks next year. Pinch-row compaction can go deep enough that freezing and thawing may not help.
"There isn't much you can do to prevent pinch-row compaction. You can lighten the intensity by removing extra weight on the tractor and carrying less gallonage in the fertilizer tanks and less seed in the hopper—but most farmers don't want to do that,” Ferrie says. "If your planter has a center-fill hopper and individual row boxes, you could use only the boxes when running on wet soil. But mostly, pinch-row compaction is the price we pay for the convenience of center-fill planters. It just makes managing compaction that much more important.”
- Mid-November 2009