Corn production is a journey from where you are now to where you want to be, figures Farm Journal Field Agronomist Ken Ferrie. Your destination is maximum profitability.
Tillage is a critical mile marker on the route to profitability. With tillage, the goal is to create uniform soil density so roots and water aren’t restricted.
The most common tillage systems include horizontal (conventional) tillage, vertical tillage, strip-till (including zone till) and no-till. Like roads, each system has obstacles you must negotiate.
Geography—topsoil depth, climate and soil drainage—might be one obstacle. So might farm size or the financial status of your operation.
Use these guidelines to help you choose your best tillage route to higher yields and profits.
Compared with a regular moldboard plow, miniature moldboard plows like this one from Salford can be set to leave generous amounts of residue on top of the ground. Both are a form of horizontal tillage.
Horizontal tillage, or conventional tillage, works soil uniformly in a horizontal plane. Years ago, horizontal tillage meant moldboard plowing. Today, it typically involves running a field cultivator, disk or soil finisher 3" or 4" deep in the spring before planting. Following soybeans, it often means doing no tillage in the fall and making one pass with a soil finisher before planting corn in the spring. It’s a reliable way to get fast emergence and uniform stands.
“The downside of horizontal tillage,” Ferrie explains, “is that it creates an abrupt change in soil density between the worked soil and the layer at the bottom of the implement’s working depth.”
Whether a density change becomes a problem depends on the year. “Heavy rains early in the season may pond on the sudden density change leading to nitrogen loss and plant health problems,” Ferrie says.“If it’s hot and dry in July and August and the first three sets of crown roots turn on the sudden density layer, you won’t have the root depth to get through a drought.”
Faced with that, should you switch to vertical tillage, strip-till or no-till? “It probably would be a good idea,” Ferrie says. Here’s why.
“One of our primary goals is to get the first three sets of crown roots deep into the soil,” he explains. “In vertical tillage, no-till or strip-till conditions, the first set of crown roots will go down. But, when we do horizontal tillage before planting—except in a few conditions like sand—no matter what we did in the fall, the first two sets of crown roots almost always turn on the dense layer. Hopefully, with fall vertical tillage, the third set will penetrate.”
An abrupt change to vertical tillage, no-till or strip-till may be too great a transition for some farmers. “So, the first step is to loosen the soil profile by doing some type of fall tillage,” Ferrie says. “After your spring tillage pass, there will still be a horizontal layer, but the difference in density will be less.”
There’s an assortment of fall vertical tillage tools, such as disk rippers, chisel plows and in-line rippers, on the market.
“Selecting the right one is critical,” Ferrie says. “Consider residue issues, the depth of your topsoil, timeliness and horsepower requirements.
“If you need to bury residue, as in continuous corn or corn following wheat, that rules out an in-line ripper, which simply picks up soil and drops it. However, if you’re in a situation like a corn/soybean rotation, and you need to leave residue to control erosion, an in-line ripper may be a good choice.”
In a corn/soybean rotation in most of the Midwest, such as in central Illinois or Indiana, you can run an in-line ripper 14" or 15" deep, Ferrie notes. But in areas with shallow topsoil, deep tillage may not work. “Shallow soils must be worked shallow,” Ferrie says. “If you need to maintain residue, you can still use an in-line ripper, but you must run it shallower. That requires reducing the shank spacing.”
To achieve good soil shattering with an in-line ripper, get into the field early before the ground gets wet. Chisel plows can run in wetter soil. In deeper soils like in central Illinois, you can use a large disk chisel or disk ripper.
After doing fall tillage, you must be patient in the spring. “Eighty percent of the compaction that I see in fields is put in by the first tillage pass in the spring,” Ferrie says.
After planting, check the crown roots. “If the third set of crown roots is turned, it indicates you worked the field too wet and smeared the soil, and your fall tillage was wasted,” he adds. Another way to transition to less tillage is to no-till soybeans.
Advantages: Less down pressure and fewer attachments required on planter; lower herbicide cost; more timely planting; quicker emergence; higher odds of a uniform stand
Disadvantages: Puts in a density layer, which may cause ponding and impede root growth, negating all the advantages
Obstacles to adoption: Should not be used on land prone to water or wind erosion or on drought-prone soils
Prerequisites for success: Access to tillage equipment
Management tips: Consider adding some deep tillage in the fall to break up the tillage pan, and transition toward less intensive tillage
The Great Plains Verti-Till is one of several hybrid tillage tools for corn-on-corn conditions. The new-style tools allow you to leave or bury varying amounts of residue, get even shattering and level the field all in one pass.
Vertical tillage tools have deep-digging shanks that break up compacted layers of soil, eliminating the density change layer put in place by horizontal tillage. Tools include in-line rippers, chisel plows, disk chisels and disk rippers, which are used with harrows in the spring to level the surface without putting in horizontal layers.
Determining how deep to run the fall tools depends on the depth of your topsoil. “Running 15" deep works great in deep topsoil, such as in central Illinois,” Ferrie says. “But in other areas, running that deep will break shanks and bring up rocks.”
In very shallow soil, deep tillage is only 7" to 8" deep. So, you are limited mostly to chisel plowing.
To get uniform shatter with vertical tillage tools, the depth must equal half the distance of the shank spacing. In other words, if you want to run a chisel plow 7" deep, place the shanks on 14" or 15" centers. It’s important to get shattering all the way across. “If you can only pull an in-line ripper 11" deep, stop and pull the shanks in so you get shattering all the way across,” Ferrie says. “Or switch to a chisel plow or disk ripper.”
The later you do vertical tillage, the tighter the window. Disk rippers, disk chisels and chisel plows provide a bigger window than in-line rippers because they work in wetter conditions.
“Uniform shattering is easier to attain with disk rippers and disk chisels because we have many shanks,” Ferrie says. Because uniform shattering is a function of depth, shank spacing, speed and soil moisture, you may have to set the machine for each field.
Because chisel plows, disk chisels and disk rippers have staggered shanks, they leave a pattern of peaks and valleys of untilled soil beneath the surface. “The peaks should be no closer than 4" to 5" from the surface,” Ferrie says. “Otherwise, you’ll wind up planting into peaks of unworked soil.”
With fall vertical-tillage tools, you want to leave the surface as level as possible because you will replace secondary tillage with harrows. You can add leveling devices to the rear.
“In some cases, when there is a horizontal layer, the soil wants to flip up like gravestones,” Ferrie says. “Usually, this happens the first time a farmer runs a vertical-tillage tool. Leveling devices can solve the problem.”
You want to come out of winter with peaks and valleys no deeper than 3". Deeper valleys lead to herbicide streaking, and dry peaks and wet valleys make it difficult to get soil uniform for planting.
Select chisel points based on what you want to accomplish. “To leave residue, run a straight point and move the shanks in closer,” Ferrie says. “To bury residue, use twisted shanks with a cutter on the front of the tool. Straight cutters leave more residue on the surface; slightly concave cutters seize and bury some of the residue.”
Final leveling is done in the spring, using a leveling harrow. “They do no horizontal tillage—just level the surface,” Ferrie says. “They don’t bury residue. If residue is a concern, you must decide how much residue to bury with your primary tillage.”
Vertical-tillage harrows are designed to run 7 mph to 12 mph. Tractors and sprayers should be equipped with flotation tires because there will be no opportunity to remove compaction caused by wheel tracks.
When you run your harrow in the spring, you’ll find out how good of a job you did with your primary tillage. “If the tractor rocks, you didn’t go deep enough; the peaks and valleys are too close to the surface,” Ferrie says.
“If you did it right, you should be able to drink a cup of coffee as you go across the field. You may fight to steer the tractor because of the softness of the soil, but you won’t bounce.”
Ferrie adds: “If you did a good job of primary tillage, it should be easy to set the right down pressure on your planter units. If you didn’t, it will be almost impossible because there will be hard and soft spots.”
Advantages: Removes tillage pans, compacted layers, density changes and wheel tracks
Disadvantages: Requires a higher level of management than horizontal tillage
Obstacles to adoption: Requires significant horsepower with flotation on tractors and sprayers to avoid wheel-track compaction; planter must be able to handle residue; need to accomplish fall tillage before weather turns wet
Prerequisites for success: Control weeds with burndown herbicides rather than tillage; run staggered shank tools like disk rippers deep enough to keep peaks 4" to 5" below the surface; run in-line rippers deep enough to shatter from shank to shank; all tillage tools should have leveling devices on the rear
Management tips: Do vertical tillage behind the combine; adjust tillage tool shank spacing, depth and speed for moisture conditions in each field; also consider tillage depth based on depth of the topsoil
Strip-Till and Zone-Till
Strip-till offers a way to work part of the field, leaving the rest untouched. Rigs like this Redball strip-till machine make it possible to remove more residue from the strip, making the seedbed warmer in the spring.
With vertical tillage, you must have row cleaners on your planter because you are dealing with more residue than in conventional tillage.
If you farm in a wet or cold climate but want to minimize soil disturbance, consider strip-till or zone-till. Both tillage systems are just a step away from no-till. Strip-till is done 6" or 7" deep; zone-till uses parabolic shanks to go even deeper.
“Both systems let us break horizontal layers,” Ferrie says. “But, zone-till takes more horsepower than strip-till. With either system, you don’t eliminate compacted horizons, but you do create pathways for roots.
“Strip-till works when 80% of a field is ready to plant, but 20% is too wet. It is ideal in shallow soil where deep tillage hits rocks, and it allows poorly drained soils to warm faster. It’s a modified no-till program for use as we move north.
“The biggest obstacle to strip-till is whether you can build your strips in a timely manner in the fall. This becomes a bigger problem as you move north into northern Iowa or Minnesota where the ground may be frozen when you finish harvest.”
You need a person and a tractor available to run the strip-till rig while harvest is under way. “If you harvest all your corn and soybeans first, you may wind up strip-tilling in the mud,” Ferrie says. One way to solve that problem is to hire a custom strip-till operator.
If you farm in an area suited for fall nitrogen application, applying nitrogen when you strip-till makes the practice more feasible. But, there’s a catch.
“Soil must be dry for shattering and building the ridge, and that usually occurs right after soybean harvest,” Ferrie explains.
Timing is key. “Building the strip at the right time is an important factor to having a good seedbed next spring,” Ferrie says. “On the other hand, that may not be the best time to apply nitrogen. If you lose it, it’s harmful to the environment, and you’ll have to apply more later.
“If it’s too warm, you’re better off to shut off the nitrogen and build the ridge while it’s dry and apply nitrogen later. You can still apply phosphate and potash.”
Some farmers can’t do strip-till without nitrogen because the bar they use belongs to a fertilizer company, which insists on nitrogen use. Buying your own bar may not be practical because they cost $50,000 or $60,000.
“Once strips are in, the biggest problem is staying on the ridge when you plant in the spring,” Ferrie explains. “The person who makes the strips should also run the planter or use auto-steer. I recommend auto-steer if a custom applicator makes your strips.”
The better you stay on the strips, the easier it will be to set your planter, Ferrie adds. And, the more residue you move off the strip in the fall, the easier it will be to plant.
You must have a backup plan. “If the soil is wet, the strip-till bar will cut slots,” Ferrie says. “It will look like a ridge, but smears in the knife slot will still be there next spring. When someone strip-tills too wet, seeds fall 3" to 5" down in the slot. There may not be enough of them to hurt population a great deal, but it will hurt ear count due to uneven emergence. High ear count is a key to high yield.”
For plan B, Ferrie suggests moving strip-till to the spring. “If you do that, don’t apply anhydrous ammonia,” he cautions. “Switch to a nitrogen solution, or pull the bar and apply your nitrogen later. We’ve built strips in March and early April, and when we got rain to settle them we got a decent seedbed.”
But in dry years, spring strips may dry out too much, leading to germination problems. “If we make strips in early April and it doesn’t rain, we’ll no-till off to the side of the strip,” Ferrie says. “If it’s too dry to plant in the strips, it’s dry enough to no-till.”
Before moving into strip-till, ask yourself: Can you manage disease? Are you willing to take the time to adjust your planter for conditions in each field? Can you control gully erosion in strips on rolling ground? Can you control weeds with a burndown herbicide? Decide how to manage your traffic so you don’t drive over the strips with herbicide and fertilizer applications.
Equip your planter as you would for no-till. “If the ridge is uneven, your planter must be able to roll dry soil back into the ridge and level it,” Ferrie says. “I prefer floating row cleaners with depth-band wheels so they stay engaged all the time.”
Balance pH before moving to striptill, Ferrie advises, because you will no longer be mixing soil. After you begin strip-tilling, apply smaller lime applications more frequently.
Advantages: Breaks up horizontal layers; can equalize planting conditions when part of a field
is wetter than the rest; provides a seedbed while protecting most of the soil surface with residue cover; works better than no-till in corn-on-corn fields because it reduces competition from old roots
Disadvantages: Narrow window of application in the fall, especially in northern latitudes
Obstacles to adoption: Cost and availability of strip-till bars; requires more management
Prerequisites for success: Have access to a strip-till bar; have sufficient manpower and horsepower to strip-till in timely fashion (or use custom strip-till); manage weeds and disease without tillage; balance pH before strip-tilling
Management tips: Have a backup plan in case you can’t get strips made in the fall; have the same person who builds the strips run the planter or use auto-steer; manage traffic patterns to avoid compaction from wheel tracks
No-till is similar to strip-till and zone-till, but it requires more management. Farm size often is an issue.
“Some of the most profitable farms I know use no-till,” Ferrie says. “But, they are sized and equipped to plant in a timely fashion. With 7,000 acres, when you’re farming 35 miles from home, you can’t wait for a field to dry.”
Before committing to no-till, ask yourself: Can you manage weeds and disease without tillage?
“As with strip-till, you need to control the first flush of weeds with a burndown herbicide instead of a soil finisher,” Ferrie says. “In addition, you may need to apply a burndown treatment in the fall.”
Disease becomes a bigger issue, especially as you move south from the latitude of central Illinois. “If you select genetics for disease resistance, scout fields and know when to spray fungicides, you’ll be OK,” Ferrie says.
Continuous corn is not impossible with no-till, but it is more difficult, especially as you go north. “From central Illinois south, you get more residue decomposition during the winter,” Ferrie explains. “Never plant the same genetics back to back.”
Your planter must be equipped to handle residue. “The idea that you’ll just give no-till a shot without row cleaners and adequate down pressure is a recipe for failure,” Ferrie says.
As with strip-till, balance pH, phosphorus and potassium before you start no-tilling. Then make frequent, smaller lime applications.
Be flexible and patient with the decision making. “I know farmers who have been successful with
no-till for decades,” Ferrie says. “But if they get in trouble—from a wet fall that results in compaction or a manure application that causes wheel tracks—they go back to vertical tillage to eliminate the problem. They may have to do that every five or six years.”
Have a backup plan. “If waiting for fields to dry forces you to plant in June, your yields will suffer,” Ferrie says. A backup plan may include switching to soybeans or carrying crop insurance.
Advantages: Minimizes field passes and soil disturbance; excellent erosion control; lowers fuel cost
Disadvantages: Fields are slower to dry out and warm up for planting
Obstacles to adoption: Requires the highest level of management; requires row cleaners, ample down pressure and specialized closing wheels on planter; farmers who have fields that are spread out over many miles might not be able to wait for fields or portions of fields to dry out to head in with the planter
Prerequisites for success: Remove compacted layers and balance pH, phosphorus and potassium before you no-till; equip your planter to plant through residue; have the ability to manage weeds and disease without tillage; fields must be well-drained
Management tips: Be patient and let fields dry before planting (even if conventional tillage neighbors are planting); have a backup plan if fields don’t dry out; do vertical tillage if you create compaction during a wet harvest season
After you switch. What if your new tillage system comes up short on uniformity of stand and on ear count? “I’ll take a uniform stand over soil density improvements any day,” Ferrie says. “Above all else, keep the planting pass sacred.”
This article by veteran editor Darrell Smith first appeared in Farm Journal in 2015.