Wetter springs and falls, heavier equipment all add up: Compaction

Written by Jonathan Eisenthal

A “Tires, Traction and Compaction” Field Day in West Central Minnesota drew about 200 farm operators to learn more about how compaction of soil can reduce yields, and to find out ways to limit the effects of compaction.

University of Minnesota Extension Educator Jodi Dejong-Hughes, along with a committee of volunteers, spent many hours creating an area of layered soils ending in a ditch that created in essence a cutaway view of the soil profile. And then they ran heavy farm equipment on the soil to demonstrate how compaction can vary.

Proper tire inflation is the key to limiting compaction and the yield losses associated with it, according to Ken Brodbeck, a representative of Firestone Ag Tires in DesMoines.

“You’re tire pressure gauge is an essential tool. Carry it with you and use it,” said Brodbeck, who noted that operators often have their tires inflated for proper wear and fuel use on paved and gravel roads, but that once the equipment rolls out onto the field and the operator unfolds the planter, a whole new set of tire pressures are recommended by manufacturers.

The basic rule of thumb is to reduce pressure, sometimes by as much as two-thirds, in order to broaden the footprint of the tire and achieve the best possible distribution of the weight. A tire inflated for the roadway has a smaller footprint and along that footprint it exerts a lot more pressure on the soil. Brodbeck demonstrated this effect with pieces of foam board–the more highly inflated tire left narrower but much deeper impressions.

Brodbeck gave an example of a customer in Iowa who plants 5,000 acres of corn, and who noticed a marked difference in the plants along his wheel tracks where compaction had taken place. By noting the difference in height and number of ears, and using current market prices last year, he was able to calculate that his yield loss in his wheel tracks amounted to $100,000 worth of grain.

Part of the effect was, in order to get that much grain planted in a timely way, the operator had gone to 36-row equipment, and to carry that much weight he had placed truck tires on the planter. 

Prof. Randy Taylor from Oklahoma State University presented information about compaction studies from across the country that have found that as much as 80 percent of the compaction effect happens in the first pass. So another key takeaway is to make sure you use the same wheel tracks again and again to limit to the minimum the area of the field affected by compaction. Also noted was that compaction is much less on dry soil. Comparisons were offered between equipment with tires and equipment on tracks, but the evidence is not yet conclusive in favor of one versus the other.

“If you are filling a grain cart on the go–and grain carts are often the heaviest piece of equipment we have in our fields–make sure once it’s full to follow the wheel tracks back out of the field and avoid driving a diagonal and creating more compaction,” said Jerry Larson, a farmer in Elbow Lake who attended the field day.

Larson this month wraps up his tenure as a member of National Corn Growers and Minnesota Corn Growers Association boards, after many years of active involvement.

“This is an excellent event,” said Larson. “It’s well worth the investment and I hope they stage more compaction field days in other parts of the state.”

Brodbeck noted that heavier equipment is a fact of life for farmers that need to get a lot done in a short period of time. But there is a solution on the horizon. The major equipment manufacturers have become interested in a technology already in use in Europe that allows the operator to vary the tire pressure from within the cab–on the go. A toggle switch would deflate the tires for field pressure, and then another turn of the switch would re-inflate them for roadway pressure. The technology came into use a decade ago in Germany when farmers insisted that manure trucks used to drain lagoons and then drive across fields and inject the manure in the soil do so without creating deep wheel ruts. According to Brodbeck the tires are built to go through this cycle of deflation and inflation several times in an hour. And a related development would include sensor technology that would adjust tire pressure for ambient air temperatures and soil temperature so that in the course of the day, as heat increases tire pressure, the sensor activates the system and releases air from the tires.

“If you figure that my customer with the 36-row equipment could reduce the wheel-track compaction by half, this is a technology that would pay for itself in a very short time,” said Brodbeck. Brodbeck believes the major manufacturers may offer this technology in the US in the next three-to-five years.

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