Rut Woes

March 18, 2010 07:00 PM

Pam Smith, Farm Journal Seeds & Production Editor
Farmers joke about it, but ruts became the extent of the "tillage” done in many fields last fall.
Dale Crawford, Sullivan, Ill., counts himself fortunate this spring because he doesn't have a lot of widespread ruts, but he does have a few ponded areas. "If it dries out enough prior to planting, I'll probably try to level with some sort of vertical tillage,” says Crawford. "If not, I'll probably no-till straight in and try to fix things this fall. I figure there will be less waiting around this year for a perfect seedbed after last year.”
Spring, fall and winter blurred into one muddy mess for much of the Heartland and the fix is far from certain science. Here are a couple of opinions on some ways to proceed this spring:
Emerson Nafziger, University of Illinois Extension agronomist, says much of the corn in Illinois was planted into wet soils last year, creating a considerable amount of compaction. "Because many farmers couldn't till in the fall, much of this compaction remains. In addition, many fields had ruts cut into them during harvest. Finally, a large number of cornstalks remain in the field, insulating the soil and slowing rates of drying,” he notes.
Nafziger says, typically, compaction can be relieved some by natural causes. Each freeze-thaw cycle decreases compaction a small amount. Surface soils experience numerous cycles of freezing and thawing, but at depths of 6 inches or more, there are few freeze-thaw cycles. He warns that farmers cannot expect much relief of deeper compaction from natural causes this year.
"We simply need to live with most of the compaction and hope we can do a good job of deep tillage next fall to relieve it,” he said.
"Without an early period of warm, dry weather in 2010, it remains unlikely soils will be dry enough to allow effective tillage before planting starts. Soils don't dry rapidly until soil temperatures are in the 50s and 60s, usually in April or even May,” Nafzinger adds.
In the meantime, he says it will be helpful to find ways to disturb the soil surface and to cut and move, and perhaps bury, some of the residue. This will help dry the surface soils to allow earlier and more uniform planting.
"Chisel plows are unlikely to work, and field cultivators will probably not get through standing cornstalks,” he says. "Lighter disk harrows might work better than most alternatives to perform shallow tillage of cornstalks. Disk-rippers might be adjustable enough to work, but implement weight should be as light as possible to avoid causing more compaction.”
Some believe spring disking is the reason for compaction. But Nafziger argues that heavy equipment causes this compaction, not the shallowness or pattern of secondary tillage. The only real "blame” a relatively light tillage implement earns is by being run shallow, making the break between the tilled and untilled soil easy to find, he says.
Vertical tillage may be possible as these shallow-tillage implements are typically run at high speeds (often about 10 mph). They consist of rolling blades that chop stalks and cut into the soil, ripple or wavy coulters, rolling spikes of some sort, and in some cases leveling boards or blades. They do not produce a distinct break between tilled and untilled soil like the disk or field cultivator.
"If the surface is dry and relatively level, these implements do a good job of breaking residue and improving seedbed conditions,” he says. "If it's not dry or if there are ruts, these implements might not work well.”
If strip tillage is performed, Nafziger believes it may be best to remove the knives and use this implement to clear some residue off the rows and do light tillage, leaving small berms. He cautions farmers from placing anhydrous ammonia into wet soils during a spring strip-till operation, as it will stay concentrated and may well move back toward the roots if the soil dries out.
Tillage may be necessary to handle cornstalks and ruts. The rate of microbial breakdown in cornstalks will be slow until soil temperatures are back in the 60s and 70s, Nafziger says. The late maturity and cool temperatures after last fall's harvest meant little stalk breakdown. He thinks it may be necessary to till to get stalks under control to allow planting and use trash-movers during planting.
To make a good seedbed to plant into, farmers must find a way to fill in ruts completely without leaving pockets that interfere with seeding uniformity. In the majority of cases, tillage might be needed to do an adequate job of filling ruts.
Soybeans may be a better option than corn in untilled fields of cornstalks, Nafizger says. "It's easier to establish an adequate stand of soybeans with little or no tillage of cornstalks than it is to establish a good corn stand.
"Soybeans suffer less yield loss with planting delays than corn. Some farmers may choose to line up seed of both crops just in case and switch to soybean if the spring starts to resemble 2009,” he adds.
Iowa State University agricultural engineer Mark Hanna says ruts deeper than planting depth will definitely need to be leveled before planter operation. "A good strategy may be to wait until a week or two before planting and use a light tillage pass such as with a field cultivator, light disk, harrow or soil finisher,” Hanna says. "If only a portion of the field is rutted, consider tilling only that area to avoid re-compacting subsoil in other parts of the field.
Waiting until warmer weather allows potential for some drying of the top two or three inches of soil and avoids further compaction of wet, plastic soil on the surface. If compaction effects are observed during the 2010 growing season and soil is dry after harvest, tillage next fall (2010) may be considered deep enough to break through the compacted layer.
No-till farmers that have rutted fields may have to bite the bullet and do a little tillage, Hanna adds. "I would wait until spring and carefully evaluate field conditions,” he advises. "Obvious visible ruts more than a couple of inches deep will be too big of a challenge for the planter and will require some light tillage with a harrow, field cultivator or lightweight disk to level the ruts. I would till no larger area than is required though,” he adds.  If newly planted rows will be in last year's old rows rather than rutted areas, tillage may be avoided. 
Farmers with large wet spots in the field need to consider those areas too. If loose residue has washed into these areas and is more than an inch thick, Hanna recommends moving the build up or incorporating into the soil with some tillage before attempting to plant.
Read Farm Journal agronomist Ken Ferrie's thoughts on spring soil conditions: What A Mess!

You can email Pam Smith at

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