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Route 1: Beat the Spread
By Darrell Smith
3/11/2008
Have you ever seen a corn field that resembled a roller coaster as you looked across the horizon? The problem may have been caused by improper residue management from previous crops—not tillage or fertility issues as you may have originally suspected.
Uneven amounts of old-crop residue, on the surface or incorporated too shallow, can result in varying populations of soil microorganisms, explains Farm Journal Field Agronomist Ken Ferrie.
More crop residue equals more microbes in the soil. As the microbes decompose residue, they devour nitrogen from the soil. The microbes can deplete the nitrogen from the soil early in the season (although it will become available again later) at a time when corn plants are busy making crucial decisions about yield.
Strips of heavy residue also keep spring soils cold and wet. Ivan Riecke of Case IH documented 2°F to 7°F colder spring temperatures in soil covered by 6' to 8' swaths of soybean chaff. The cool, wet strips delay emergence, leading to uniformity issues with the crop, Ferrie points out.
In low-rainfall regions where moisture conservation can be an issue, uniform residue cover on no-till fields helps prevent plants from running short of water during the summer, says University of Nebraska agricultural engineer Paul Jasa.
Residue management starts with the combine, Ferrie and Jasa agree. “Even if you do shallow tillage, it is very difficult to correct the effects of uneven residue spreading,” Ferrie adds.
Full-width spread. Your goal should be to spread residue the full width of your combine head but no further. That’s easier to do with corn because you are dealing with large pieces of cobs and stalks and tougher with soybeans because you have to deal with lots of light chaff.
If you don’t spread residue uniformly, you have to turn to tillage to try to fix the damage, says Tracey Meiners, Case New Holland product manager for tillage. “If you leave residue in clumps, you’re asking for a host of problems, including plugging, fertility, seed placement, temperature, moisture, insects and disease, as well as extra work in the spring,” he says.
If you see streaks of residue behind the combine, adjust the chaff spreader and any residue spreading devices. “The most common problems are incorrect spinner speed and the position that the chaff hits the spinner,” Ferrie says.
Heavy streaks of residue inside the wheel track indicate residue is hitting the spinner too far to the rear, Ferrie explains. If residue collects behind the combine, but fails to fill the header pass, the most common cause is chaff dropping too far forward on the spinner.
“Especially in soybeans, consider how wind affects your spread pattern,” Ferrie says. “If residue is being blown into standing soybeans, you’re going to have streaks. You may have to combine from a different direction or from the other side of the field to minimize the effect of wind.”
Make sure your spreading capacity matches your header width. “If you will be harvesting soybeans with a new combine equipped with one of the new, wider heads, buy the higher-end stalk chopper and spreader,” Jasa says. “Some companies offer the high-capacity spreaders as options, rather than standard equipment.”
A high-capacity chopper and spreader is less critical with corn and wheat, Jasa notes. “With corn, the head processes the residue,” he says. “With wheat, you can run the head higher, so you take in less straw. But, in soybeans, you can’t avoid running the head low to get those bottom pods.”
A stripper header also works with wheat, Ferrie says.
“If you buy an extra-wide head from a third-party manufacturer and attach it to a combine made in the 1990s, you could find yourself short of spreading capacity,” says Brent Mueller, Case IH combine marketing specialist.
Case IH’s largest combines, the 7010 and 8010 series, include spreaders capable of spreading residue up to 45', and those heads cannot be cross attached to the company’s smaller 2500 series combines, Mueller adds.
John Deere STS operators who need to spread residue more than 30' can use the company’s Power Cast widespread tailboard, says Pat Duffy, senior marketing representative for combines. Its two rotating, hydraulically driven impellers spread residue up to 40'. Besides having sufficient spreading capacity, be sure to adjust the straw chopper for the proper length of cut in your crop and conditions, Duffy adds.
Continuous residue. In continuous corn, Ferrie, who is based in central Illinois, says doing some tillage to bury residue and help it decompose reduces the risk. “Those who need to strip-till or no-till need to emphasize the management of residue and disease,” he adds.
In the drier western Corn Belt, Jasa says no-till continuous corn can work, although it carries some added risk.
In either locality, you need to size the corn residue because small pieces decompose more readily. Your combine head starts the process, Jasa points out. “Knife-to-knife snapping rolls process residue more thoroughly than intermeshing rolls, and tapered rolls do a more comprehensive job than straight ones,” he says.
You can chop up more of the cornstalk by running your head close to the ground, rather than just below the ear, Jasa says. For an additional investment, you can increase residue processing with stalk-chopping corn heads, available from various manufacturers. “If you do a good job with your combine header, one shallow pass with a disk will really size the residue,” Jasa says.
Recent years have brought an array of new fall tillage tools. All of them can be helpful, Ferrie says—or you can use a traditional disk chisel or disk ripper, equipped with a leveling device, followed by a vertical tillage tool in the spring. “After overwintering, you want no more than 3" from the tops of the peaks to the bottoms of the valleys,” he says. “From the soil moisture perspective, not having deep rills lets the ground dry uniformly. In continuous corn, the valleys tend to fill with high amounts of residue, which gets buried and may cause seedbed issues.”
Examples of spring vertical tillage tools include the Till-Lite from Phoenix; the To The Max from Landoll; the Turbo-Till and the Ultra-Till from Great Plains Manufacturing; the Reel Till, Reel Disk and Spiral Reel Stalk Chopper from McFarlane Manufacturing; the Phillips Rotary Harrow; Yetter Manufacturing’s Vertical Tillage Attachment and new Vertical Tillage Tool; and Case IH’s new 330 Turbo.
“It’s hard to write a general prescription for spring tillage tools because there’s a lot of management involved,” Meiners explains. “A tool may work great in one field and do nothing but create clods in another soil type a mile away.
Meiners continues: “You need to select the tool that does the best job in your conditions. Read about tools on the Internet, visit industry specialists and talk to neighbors who have run various tools. Nothing beats a demonstration of a tool on your own soils.”
In a no-till or strip-till situation, be aware that if you shred stalks in the fall and detach them from the ground, they may move with wind or water, Ferrie says. “This happens more frequently with Bt hybrids that are slow to decompose,” he says. “And, fungicides, which keep corn healthy, result in tougher stalks in the fall.”
Theoretically, residue management may be easier with non-Bt corn hybrids. But, Ferrie and Jasa agree, especially in continuous corn, yield potential and disease resistance are most important.
In the spring, in continuous corn, remember that residue (even when properly spread and mixed with soil) will result in booming microbe populations, which can immobilize nitrogen in the top few inches of soil. Ferrie recommends surface applying 60 lb. to 100 lb. of nitrogen per acre to make sure the corn plants don’t run short. The application may be split between fall and spring, he adds.
Since residue decomposes slower in acidic soils, watch pH, too. For decomposition, pH should be 6.3 to 6.5.
“In strip-till and no-till, plant in between the old rows,” Ferrie adds. “Think about your combine’s wheel tracks as you harvest. You may have to wait a day for the ground to dry, run duals, put bigger tires on the back of your combine or even go to tracks.”
In the eastern Corn Belt, in continuous corn, Ferrie and others consider residue removers on a planter to be essential equipment. Set them so they move residue but not soil.
In Nebraska, spoked residue removers, set to move residue but not soil, can warm up poorly drained soils or even up non-uniform residue cover, Jasa adds.
But, when cold, wet soil is not an issue—the usual case in Nebraska—Jasa often tells no-tillers to omit residue removers, even in continuous corn. “If residue is already spread uniformly, moving it can do more harm than good,” he says. “If residue blows or washes back over the row at planting, it creates non-uniform conditions for the seed. Emerging corn may leaf out under the residue and fall behind other plants.”
That advice also applies in sandy soils in the eastern Corn Belt, Ferrie says. “But, you need to cut the residue,” he says. “When I want residue to stay put, but not be pinned by the opener, I use a very sharp, slightly fluted or bubble-type coulter without a row cleaner.”
Operators who deal with cold, wet soils in the East or warm, dry soils in the West all have one thing in common: In Jasa’s words, “Uniformity in every operation all season long is the goal. It begins with harvest.”
For More Information
To compare the various makes of chaff spreaders, visit the following manufacturers’ Web sites:
To read a report on chaff spreaders published by the Manitoba, Canada, Department of Agriculture, visit
www.gov.mb.ca/agriculture/soilwater/soil/fbd01s06.html.
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