You can switch to strip-till for all the right reasons but work against the benefits with a lax approach to soil preparation.
The appeal of strip-till is that it offers a profitable and more environmentally sound alternative to conventional tillage. It involves tilling narrow strips and building berms, or small ridges, 3" to 4" high. The operation is performed in the fall, and fertilizer can be banded in the strips.
To stack your odds for success, loosen compacted layers of soil, optimize pH and fertility levels and modify your weed control program. If you strip-till continuous corn, you'll want to pay special attention to disease management and harvest technique. You'll also need a backup plan in case weather prevents you from making strips in the fall.
Strip-till is becoming common around the Corn Belt. Tom Endress and his brother Mike, who farm near Tremont in central Illinois, began experimenting with strip-till in 1996. Now they use the technique on all their corn acres.
"We weren't happy with the soil finishing tools that were available in the late 1990s,” Tom says. "They often put in a compaction layer at 3" or 4".”
The brothers compared corn plants' root growth in strip-till and in their full-width tillage system, which included a disk ripper running shanks 14" to 16" deep. In strip-till, the roots of a corn plant less than 3' tall penetrated 42" into the soil. In full-width tillage, the roots penetrated only as far as a compacted layer 4" beneath the surface, then grew horizontally, putting plants at risk in a dry year.
"Strip-till also saves immensely on time, labor and fuel,” Tom says. "It makes your spring workload easy if you get strip-till completed in the fall.” So far, the brothers have always been able to do that.
After more than a dozen years in a corn–soybean rotation, strip-till corn yields as well as or better than corn grown with conventional tillage, Tom reports. In continuous corn, the brothers' strip-till yields have been less consistent (more on that later), but the improvement in soil condition keeps them strip-tilling.
The Endresses' experience parallels what Purdue University Extension cropping specialist Tony Vyn learned from research studies.
"My research has confirmed that strip-till is a viable alternative to the most common tillage practices in this area, such as chisel plowing and disk ripping,” Vyn explains. "That is true for either continuous corn or a corn–soybean rotation.”
"With corn following soybeans, strip-till doesn't necessarily produce a higher yield than conventional tillage,” he adds. "But compared to no-till, it provides more planting flexibility in the spring, along with earlier planting opportunities, which can increase yield substantially. Done correctly, strip-till yields better than no-till in high-residue environments, such as continuous corn or corn following wheat.”
In central Illinois, more than half of Mark Baer's clients at Sun Ag Supply are strip-tilling. "More than anything, farmers have adopted strip-till to save time and labor,” he says. "It also requires less equipment. Strip-till allows a 1,000-acre or 2,000-acre operator to farm with just one tractor or maybe one big tractor and a utility tractor.”
Not to be overlooked, Vyn says, are strip-till's conservation benefits. The system leaves two-thirds to three-fourths of the soil surface unworked and covered with protective residue.
Prepare to strip-till. "If you decide to strip-till, preparation is the same as for no-till,” says Farm Journal Field Agronomist Ken Ferrie. "We ask clients for three years to get a farm ready.
"The first step is to remove old plow soles,” Ferrie continues. "That includes all horizontal layers, especially the deeper ones. Strip-till over a plow sole doesn't work very well.”
While you're taking out compacted layers with vertical tillage, you can mix lime and fertilizer through the complete soil profile—something you no longer will be able to do with strip-till (except for knifing in phosphorus and potassium). "After you begin strip-tilling, plan to apply small amounts of limestone more frequently, as you would in no-till,” Ferrie says.
"It's easier to maintain a good soil pH from the surface than to fix an extremely acid one [after you get into strip-till],” Ferrie continues. "Our soil tests indicate lime moves downward about ½" per year through the soil. We have maintained uniform soil pH in no-till farms for more than 15 years.
"If you go into strip-till with acid soil that needs 3 tons of limestone per acre, it's almost impossible to fix the problem without tillage,” Ferrie adds. "If you apply 3 tons of lime, you'll wind up with a high-pH surface soil over an acid subsoil. The high pH at the surface will create problems with nitrogen management and cause phosphorus to become tied up and unavailable to plants.
"Keeping the proper pH at the soil surface also helps stalks to decompose as rapidly as possible.”
Ready the profile. If you build phosphorus and potash to proper levels throughout the soil profile, stratification in the top couple inches will be less of an issue after you switch to strip-till and surface application, Ferrie says. "In that situation, stratification at the surface becomes almost like banding fertilizer—it makes nutrient feeding by the roots more efficient. If you have problems with nutrient tie-up in the soil, surface stratification actually becomes a plus.
"However, if subsoil phosphorus and potassium levels are low when you start strip-tilling, they'll stay that way. With low phosphorus and potassium levels in the subsoil, roots may not find the nutrients they need when they are forced to feed deep in a dry year.”
If you have a situation where phosphorus gets tied up because of high pH or high iron levels, strip-till does allow you to band some fertilizer in the strip, Ferrie says. "Not all strip-till bars are set up for banding, but some are,” he notes.
Protect ridges. To avoid damaging your ridges, Baer recommends applying lime and broadcast fertilizer before you strip-till in the fall. Contact your dealer early so they can schedule your field for timely application.
"If you strip-till first, the only other alternative is to wait for the ground to freeze before broadcasting lime and fertilizer,” Baer says. "Even if the soil is partially frozen, you may still mash down the strips.”
An advantage of strip-till is that you can apply nitrogen as you build your strips. On the flip side, there's a potential conflict. "Depending on your locality, the best time to build strips may not be the ideal time to apply fall nitrogen,” Ferrie says. "Poor nitrogen management can offset the benefits you gain from strip-tilling.”
The primary mistake strip-till farmers make is pushing up the time of nitrogen application to late September or early October. "Even if you apply a nitrification inhibitor, you can lose nitrogen if the soil stays too warm for too long,” Ferrie says. "You may find you have to go ahead and build your strips and apply your nitrogen in the spring or by sidedressing.
"Growers should consider using a nitrification inhibitor with fall-applied nitrogen,” Ferrie emphasizes. "If you don't, you may wind up with flaming yellow plants in the summer.”
Remember, especially in continuous corn, you will pay a carbon penalty because of all the crop residue left on the surface. When soil microbe populations expand to decompose the residue, they tie up mineral nitrogen in the top few inches of soil, making it temporarily unavailable to corn plants. That causes the plants to turn yellow and grow slower. The nitrogen you applied in the strip will be too deep for the small plants to reach.
"Eventually, the plant roots will reach the applied nitrogen, and the nitrogen tied up by the microbes will become available again later in the season,” Ferrie says. "But you can avoid yellow, uneven early stands by applying some nitrogen on the soil surface and in starter fertilizer.”
Weed control. If you switch from conventional tillage to strip-till, you may need to manage winter annual weeds in the fall (just as in no-till) because you won't be controlling them with spring tillage.
"If your field has a history of winter annual weeds, it's wise to treat them in the fall,” Baer says. "Winter annuals don't show up as much the first year you strip-till. But after three or four years, populations take off.
"A fall herbicide treatment is pretty economical,” Baer continues. "Several products kill all three of the primary winter annuals: henbit, chickweed and marestail. In the spring, after the weeds have been growing all winter, they'll be ten times as difficult to control.”
In the spring, you will want to add a burndown herbicide to your residual product, Baer adds.
In continuous corn, if harvest is late and some ears fall off, you may wind up with volunteer corn in the following crop. "Although this situation doesn't happen often, volunteer corn could be an issue if you're growing Roundup Ready hybrids back-to-back,” Baer says. "The only solution would be to switch to a LibertyLink hybrid.” You can minimize the risk by scouting fields and prioritizing which ones need to be harvested first.
If you're converting from conventional tillage to strip-till, you will also need to spend a little more effort on disease management because disease organisms overwinter in corn residue. "In the Farm Journal Corn College demonstration plots, we found two to three times as much disease in the strip-tilled corn as in the plowed ground,” Ferrie explains.
"Disease threats vary by region; a major one here in central Illinois is gray leaf spot,” Ferrie continues. "But disease is not a big deal if you understand the situation and manage around it. Select hybrids with higher disease pressure in mind. Plan to scout fields to determine whether a fungicide is needed.”
Continuous corn. When strip-tilling or using any other tillage system, continuous corn is tougher than a corn–soybean rotation.
"Successfully strip-tilling continuous corn depends on your location,” Ferrie says. "In northern latitudes, with a great deal of residue, it is a challenge—you have to fight a lot of residue in the spring because less of it decomposes in the fall, and the residue increases disease pressure. In southern latitudes, strip-tilling and no-tilling continuous corn is easier.”
In one field of continuous corn, the Endresses found strip-till yields were not keeping up. "So we tilled the field,” Tom says, "pulling the same type of ripper tool we had used in conventional tillage. In those days, our tractor struggled to pull it; but after strip-tilling for a few years, it walked right through.
"Although tillage helped boost yield that year by getting rid of some of the residue, we decided the damage to the soil structure wasn't worth it. So we went back to strip-tilling. In addition, we have also seen a field of strip-tilled continuous corn produce our best yield.”
Although it's not practical in every field, the brothers have found that pasturing cows after harvest makes it easier to strip-till continuous corn by reducing the volume of residue. "Our best continuous-corn yields are in the fields that are pastured,” Tom says.
In continuous strip-till corn, harvest technique takes on added importance. Wheel tracks from combines and grain carts (as well as manure spreaders) can make it hard to apply ammonia. "Strip-tilling into ruts doesn't work,” Ferrie says. "You can't build a good ridge in a 6" rut. If you're applying anhydrous ammonia, the soil won't seal.
"If a landlord demands that you mud a crop out, you'll have to till to fix the ruts. I continue to see growers try to strip-till into rutted fields, and the result usually is a disaster.”
Backup plan. You'll need a backup plan for strip-tilling and nitrogen application if weather prevents you from making strips in the fall. "If you don't get strip-tilling done in the fall, you'll have to do it in the spring,” Ferrie says. "We recommend against applying anhydrous ammonia with spring strip-tillage; the risk of seedling root burn is too great. Run only the strip-till bar, and don't take a chance on nitrogen smoking your corn stand.”
The ideal setup for your strip-till bar will depend on your soil and conditions. A number of manufacturers make toolbars and planter attachments for strip-till application.
A properly built strip is the key, Ferrie emphasizes. "The better job you do of making the strip, the better it overwinters, and the better you maintain depth as you plant, the better stand you will have,” he says.
"When you make your strips, if your tractor has extra power, resist the temptation to go too fast and explode the soil,” Tom adds.
Good strips provide a seedbed almost identical to conventional tillage. "We like a row cleaner with a depth gauge on our planter,” Tom says. "But you really don't need to modify your planter much. A planter that works in conventional conditions should work for strip-till.”
Ferrie recommends row cleaners in any tillage situation, not just strip-till. "Whether or not you need a coulter with the row cleaner depends on your soil type and how well you built the strip,” he says. "If you run a coulter, don't set it too deep; run it ¼" to ½" above where you place the seed.”
An auto-guidance system for your tractor makes it easier to stay centered on the row when you plant, Ferrie says. At Purdue, Vyn observed higher in-row soil temperatures when RTK auto-guidance was used to place corn rows directly in the center of the strip. His three-year study involved corn planted into soybean residue.
Auto-guidance also makes it possible to control traffic and keep wheel passes between the rows, Vyn says.
Be cautious about using strip-till on slopes greater than 5% or so, he says. Especially following soybeans, it may not leave enough residue cover to protect against erosion.
You can e-mail Darrell Smith at firstname.lastname@example.org.
- October 2009