Tractor and planter compaction cut yields
This year’s late, damp spring set the stage for irregular strips of stunted corn six rows wide that correspond to each pass of the tractor that pulled the planter. Pinch-row compaction is the culprit, and the consequences are more than aesthetic.
Pinch-row compaction damage might not always be visible
"In 2011, when we had enough soil moisture at planting to create compaction, we saw yield
decrease by 19.6 bu. per acre between pinch rows and wing rows on a center-fill planter planting in 30" rows," says Jason Webster, Beck’s Hybrids agronomist. "In 2012, the soil was a little dryer at planting, but we still saw an 8-bu. yield loss in the pinch rows. Even with a noncentral-fill planter, the pinch-row compaction from just the duals of the tractor showed a 2.2-bu. reduction."
A study of corn in 22" rows in Minnesota by DuPont Pioneer documented an average yield decrease of 11.3 bu. per acre in pinch rows compared to rows on the wings of planters.
Stunted roots from pinch rows on the left are dramatically smaller than the roots from corn planted by the planter wings.
While center-fill planters can increase pinch-row compaction, planters are merely accomplices, says Paul Jasa, University of Nebraska Extension engineer. In many situations, he estimates up to 80% of total compaction is caused by the tractor.
"If the tractor has already done damage to the soil structure," Jasa says, "then the planter doesn’t add much more."
Farm Journal Field Agronomist Ken Ferrie has been tracking the effects of pinch-row compaction in corn using aerial thermal imaging and penetrometers in conjunction with yield checks that compare yields between the center and wing sections of each planter pass.
Ferrie acknowledges documenting the effects of pinch-row compaction is difficult. "Pinch-row compaction, and whether or not center-fill planters are a contributing factor, is definitely a moving target," he says. "The more tillage a farmer does, the more we see the problem. Continuous corn growers who moldboard plow or disk rip in the fall, then field cultivate in the spring, have more pinch-row compaction than guys who no-till or strip till, which tend to have firmer soils.
"I’ve got farmers, who are in continuous corn and have to do a lot of tillage, who were so concerned about center-fill planters contributing to pinch-row compaction that they traded their single 36-row planters for two 16-row planters," Ferrie says.
Farmers worried about pinch-row compaction with center-fill planters have options. Some farmers only fill planters half full of seed when operating in soils prone to compaction.
The effects of pinch-row compaction weren’t visible on the ground, but the red stripes correspond to six-row-wide strips of corn stressed by compacted soil. To some degree, each planter pass is evident due to compaction-related root stress.
Some growers outfit planters with both conventional row-mounted seed hoppers and center-fill seed tanks. In dry soil conditions, the center-fill system is used. When soil conditions favor compaction, individual seed hoppers are used.
Kinze Manufacturing Inc. recently unveiled a new weight-transfer system on their center-fill planters that automatically transfers weight from the center frame to the wing frames. Used in conjunction with reduced air pressure in tractor tires to minimize compaction, Kinze product manager Rhett Schildroth says pinch-row compaction can be dramatically reduced.
"In extreme cases, compaction in the center rows can be reduced by a factor of 10 when utilizing reduced tractor tire pressures and planter weight transfer systems," Schildroth says.
In 2012, Ferrie used penetrometers to compare soil compaction behind a center-fill planter equipped with a weight-transfer system.
"The penetrometers showed a distinct difference in compaction when we turned the weight-transfer system on and off," Ferrie says. "Damage from pinch-row compaction may not always be visible, but pinch rows usually reduce yield to some degree."
You can e-mail Dan Anderson at email@example.com.