Take Action Against Compaction
Compacted soils cut crop yields, but technology and common-sense management can help reduce and mitigate the damage.
By Jason Jenkins
When Randall Reeder’s family bought their first tractor—a Ferguson TO-20—back in 1950, they didn’t worry about the 2,800-pound machine causing soil compaction on their West Virginia farm. The same was true a decade later when they bought a Massey Ferguson® 35, which weighed well under 2 tons.
Today, however, farm equipment is vastly larger, says Reeder, an Extension ag engineer at Ohio State University, as are concerns about the soil compaction that field operations can cause. Now, 20-ton row-crop tractors pull 7-ton planters, and 15-ton combines harvest and carry grain weighing nearly as much as the harvester itself. Add the weight of commodity carts, sprayers, grain carts and tractor-trailers, and crop fields are under a lot of pressure.
“Whether planting in spring or harvesting in fall, farmers are always anxious to get in the field, but they should ask themselves, ‘At what cost?’ when conditions aren’t right,” says Reeder, who has studied soil compaction since 1987. “Compaction reduces yields, and it costs money to correct it. That’s reason enough to avoid it.”
Compressed And Stressed
In general, soils with good structure are composed of roughly 50% mineral and organic material, 25% moisture and 25% air-filled void space. When soil is compacted, this important void space is decreased, lowering the soil’s porosity, says Mahdi Al-Kaisi, professor of soil management and environment at Iowa State University.
“Porosity is essential for air movement and for water movement to provide a healthy environment for the crop root system,” he explains. “When you compress the soil, you damage and destroy soil aggregates, which are the building blocks of any good structure in the soil, and it’s going to restrict the root growth physically.”
A dense layer of compacted soil can prevent water infiltration, leading both to a lack of moisture deeper in the soil profile and to increased surface runoff. Al-Kaisi says the decreased porosity also lowers the availability of oxygen, which negatively impacts microbial communities, as well as root system development and nutrient uptake.
“It’s very damaging to the yield,” he says, adding that compaction severity varies by soil type and soil moisture. “There is an estimated 10 to 20% reduction in yield with severe soil compaction.”
Both Reeder and Al-Kaisi note that many studies have found that the first pass of equipment causes 70 to 80% of total soil compaction. So what can producers do to stem the worst damage? Both researchers agree: Whenever possible, stay out of the field when it’s wet.
“Really watch the field condition,” Al-Kaisi says. He advises that before entering with equipment, a producer should simply take a handful of soil from the field and squeeze it. “If there is a trace of water in your hand, just stay away for a couple of days.”
Understanding soil types in each field can help a farmer determine which may be worked first after a rain and which need more time to dry out. Farmers also can adopt certain management practices to lessen and sometimes even avoid compaction, such as incorporating cover crops and no-till systems, as well as establishing controlled traffic lanes in their fields.
With controlled traffic, Reeder says a farmer designates specific permanent lanes in the field that all machinery—tractors, planters, sprayers and combines—will travel. Equipment is configured to the same track width and operating width (30 feet is common) so that compaction is concentrated only on those lanes and not where the crop grows. These lanes provide a firm surface on which to drive, he says, lessening rolling resistance. This, in turn, can equate to fuel savings over time.
“Controlled traffic will also let you get across a field sooner without causing any problems,” Reeder adds. “Say, for instance, you have an insect problem and need to spray, but you just had a 3-inch rain. Controlled traffic is going to let you do that spraying much sooner.”
An Equipment Edge
The potential for compacting soils increases as axle loads increase, Reeder says. He recommends that in less-than-ideal conditions, farmers should empty combines and grain carts before they are full to avoid extra weight. He adds that as farmers replace their equipment, they should consider machinery with track systems, as tracks can spread the load over a greater surface area than tires.
AGCO® offers a range of equipment with tracks, including the Challenger® MT700 and MT800 series tractors, the White Planters™ 9900 Series of large-frame planters and the all-new Fendt® IDEAL™ combine.
Machines equipped with tires also can lessen compaction by providing adequate flotation with reduced tire pressures. This allows the tire to bulge slightly and increase its footprint on the soil. However, the ideal pressure for fieldwork isn’t ideal for road transport.
One way to overcome this issue is with a central tire pressure inflation system, such as Fendt VarioGrip.® Available as a factory-installed option on the 800, 900 and 1000 Series tractors, the system allows a farmer to adjust tire pressure from 11.5 psi to 35 psi from inside the cab.
“When you’re in the field, you want to have a lower pressure to maximize the tire footprint and put more lugs to the ground,” says Andrew Sunderman, AGCO tactical marketing manager. “But on the road, that lower pressure creates additional friction and wear on the tire. VarioGrip lets you tailor the ideal pressure. You can even incorporate it into your headland management sequence.”
Once a soil is compacted, the effects can be felt for years to come. Larry Kuster, AGCO senior marketing specialist, says primary tillage tools such as the Sunflower®4500 Series disc chisel discs and the 4700 Series of in-line coulter rippers are designed for breaking up compaction.
In 15 years of research on conventionally tilled ground, Reeder found a benefit to subsoiling with a ripper every three or four years. “In 2002, we changed our research to no-till, and we found continuous no-till was better at resisting compaction than the subsoiled ground,” he says. “It makes sense because no-till has soil structure.”
Al-Kaisi says the best remedy for compaction is time. “Mechanical disturbance will break up compaction, but it isn’t going to cure compaction,” he says. “These soils need nurturing to build the organic matter, to build the soil biology. You need a stable environment.”
The Iowa State researcher advocates for minimal tillage and the addition of deep-rooted cover crops to a rotation as a way to begin breaking up compaction and improving the soil’s resistance to future compaction.
“Just give it time to heal,” he says. “You might get a hit on yield, but that hit in the long term is going to be less damaging than if you continue doing the same thing.”
Application Equipment Fighting Compaction
With its Challenger family of application equipment, AGCO offers even more innovation that helps reduce soil compaction. Learn more about the TerraGator®C Series and its ability to apply six products at variable rates in only one pass; and the RoGator®C Series, which features Auto-Track Adjust, a feature that allows an applicator to position the machine’s wheels for different row spacing and minimize compaction. Full information on both Challenger applicator series is here: http://www.challenger-ag.us/products/application/.