When Strip-Tillage first emerged as a method to conserve soil on Midwest farms, the setup was pretty simple. Mole knives — named for their ability to form a tunnel underground — were attached to shanks on an anhydrous ammonia toolbar to till narrow strips of soil while fertilizer was applied. Closing discs, mounted behind the knives, would catch the loosened soil and form a raised mound that served as the seedbed for next year's crop.
This decade-old setup has worked well for tilling ground planted to low-residue crops like soybeans and wheat. And it was designed for such a rotation.
However, in the last two years since the corn ethanol wave, more Midwest growers have wanted to plant consecutive years of corn to take advantage of higher prices. “Two years ago hardly anyone asked if our strip-till equipment could handle corn on corn,” says Tony Randall, sales manager with Redball. “This year at farm shows, it was one of the first questions asked.”
These growers have tested the limits of the old units. Equipment companies responded by developing a new breed of strip-till equipment that is heavier and more aggressive to handle tough cornstalks.
Not your daddy's rig
More than 18 manufacturers make strip-till equipment, with price tags anywhere from $15,000 for a 12-row up to $120,000 for both the rig and air cart to deliver fertilizer. On average, the price for a 12-row unit is around $24,000 to $36,000.
However, not all units sold are designed to work in corn on corn, according to Jodi DeJong-Hughes, University of Minnesota Extension educator and organizer of the 2007 Northern Strip-Tillage Expo held in Rothsay, MN.
“I would say buyers definitely need to look at the newer strip-till machinery, because it has changed drastically in the last few years,” DeJong-Hughes says. “Companies have done a lot of research and tweaking to make sure they do a good job clearing the row and handling residue.” What used to be a glorified anhydrous bar has transformed into a bonafide piece of equipment, she adds.
All of this equipment, including the older stuff, works on a corn-bean rotation, resulting in yields comparable to those gained from chisel plowing on well-drained soils, according to university research conducted in Minnesota, Iowa and Wisconsin. But farmers growing corn on corn should look for the new, more aggressive models if they want to achieve the same yield results.
Just how aggressive? DeJong-Hughes says growers who are planting continuous corn should look for equipment that leaves behind less than 10% residue on the raised mounds or “berms.” Amounts more than that could leave the soil too wet or cold and delay emergence of the corn crop.
Four major design changes set the new rigs apart from the previous generation, reports Mark Hanna, agricultural engineer, Iowa State University. They are described on page 51.
Hanna says these enhancements can also be found on other types of tillage equipment. And because strip-till subscribes to no standard depth, the tillage categories are starting to blend.
“For example, strip-tilling 12 to 14 in. deep is not going to look, act or feel to your tractor a whole lot different than pulling a subsoiler or ripper at that same depth,” Hanna explains. “In both cases the tractor is pulling an inch-wide piece of steel about a foot deep, requiring similar tractor horsepower. And both implements probably have a cutting or straight coulter in front of the shank, resulting in about the same drawbar load. So fuel use and tractor horsepower required for both field operations may be the same.”
Skip the semantics
Because the categories are blending, Hanna advises growers to not get hung up on what a particular unit might be called and instead look at the soil-engaging components it features and what each component does to the soil.
Buyers need to decide which components are required based on region and soil types, because units vary according to how much they disturb the soil. “For example, on poorly drained, irrigated or compacted soils, deeper tillage may be desirable,” Hanna says. “Growers on well-drained soils may want shallower tillage to avoid potential for dry soil under the seed and limit power requirements.” (See page 52.)
Hanna adds that options and attachments offered for strip-till will allow these units to be adapted to different preferences and conditions. What might be important to someone in central Nebraska on an irrigated field may be entirely different from southwest Wisconsin's more humid climate and different soil types.
New units displayed
The first of these new aggressive units were unveiled at winter farm machinery shows in late 2006 and were demonstrated at the two major strip-tillage expos in summer 2007. Even John Deere joined the market this year with its first strip-till unit designed for corn, which some people say validates strip-till as an accepted form of tillage.
“All the new units have things that are real positives,” reports DeJong-Hughes. “So I can't say one machine is better. It just depends on your situation.”
The companies building these units report that consumer interest in them has increased. Redball's Randall says the percentage of inquiries for the company's strip-till model 2000 designed for corn rose from 10 to 15%, to 80 to 95% in the last 24 months. He says most of the leads are coming from no-tillers looking for a more aggressive tillage system. But he adds that an increasing number of minimum- and conventional-till growers have started to inquire due to higher fuel and fertilizer costs.
Strip-till, a form of minimum-till, can require less diesel fuel than conventional- or minimum-till because tillage and fertilizing with phosphorus and potassium are done in the same pass. Conventional systems, generally chisel, require at least two to three field passes for fertilizing and secondary tillage operations to create the seedbed for planting.
“Plus strip-till allows for banding with reduced rates of phosphorus and potassium compared to broadcast with conventional-till,” according to Les Everett, University of Minnesota agronomist. However, there is no recommended reduction for nitrogen. Corn will need the same amount of nitrogen to produce a certain number of bushels regardless of the tillage method.
Experts do caution some growers about strip-till. Northern areas that lack adequate tile drainage can hinder performance, according to Gyles Randall, University of Minnesota soil scientist, Waseca, MN. “For instance, on the well-drained silt loam soils of southeastern Minnesota, strip-till has worked quite well for some farmers with continuous corn,” Randall says. “But on the poorly drained soils of south-central Minnesota, strip-till would be expected to be problematic for continuous corn without adequate tile drainage.”
He says results will depend on the amount of residue, the adequacy of drainage, slope, and weather conditions shortly before planting and in the month following planting. “In other words, the risk of crop failure increases as these situations become less forgiving,” Randall says.
4 Design changes
New strip-till rigs that are able to handle corn-on-corn work generally include four design features that are changes to the previous generation of strip-till equipment.
- Increased down-pressure through heavier frames or the addition of heavier springs on parallel linkage between row units, which may require more horsepower.
- A larger lead coulter (often greater than 20 in. in diameter) to provide a better attack angle to cut through cornstalks. Smaller coulters tend to push rather than cut the residue.
- Additional ground clearance and spacing between tillage components to allow room for stalks to flow through.
- Wider range of attachments and the ability to adjust components so units can work in different soils and conditions. (For example, rock trippers are desirable in glaciated areas with rocky soils.)
4 Components of strip-till
Strip-till units usually are equipped with several different ground-engaging components:
- Tillage shank
This is the primary soil-engaging component. Choices range from a subsoiler point on a straight or parabolic shank to a mole knife attached to a heavy-duty C shank. Buyers must determine what operating depth is desirable and whether working depth is adjustable.
- Cutting coulter
Mounted ahead of the tillage shank, the coulter cuts residue. It may be wavy, fluted or straight as long as it is sharp and at least 20 in. in diameter to handle corn stubble.
- Row cleaners
A set of row cleaners to move residue out of the way in front of the shank is desirable for corn residue but optional in soybeans. They are also called residue managers or trash whippers.
- Closing discs
Behind the shank is some kind of closing device used to form a structured berm on the strip-tilled row. Generally the berm should be 3 to 4 in. tall and consist of less than 10% residue. Closing discs should be adjustable to work in different soils and conditions.
Here are just a few of the manufacturers marketing strip-till rigs designed for corn on corn.
Alloway Ag Systems
Blu-Jet, Thurston Mfg.
Brillion Iron Works
Case IH - DMI
Dawn Equipment Company
Environmental Tillage Systems
Twin Diamond Ind.
Unverferth Manufacturing Company