By Steve Butzen, Clyde Tiffany and Darren Goebel, Pioneer agronomists
Management of corn residue should begin at harvest with uniform distribution of chaff and stalks behind the combine.
Uniform distribution has advantages for growers in no-till, minimum-till or conventional-till systems, including better erosion protection, less plugging of tillage or seeding equipment, and improved stand establishment. Success in uniformly distributing crop residue this fall also can help eliminate tillage passes next spring.
Today’s combines, with wider grain platforms and corn heads, concentrate a larger volume of plant material into the same narrow band exiting the combine. This material then must be spread back onto the wide harvest swath, making uniform distribution more challenging.
Combines with header widths of 20 to 30 feet or more may not be adequately equipped to uniformly distribute large volumes of residue. In such cases, adding manufacturer options or after-market equipment to more aggressively manage residue may be needed. Modifying, checking and maintaining existing equipment also may help improve residue management.
Residue spreading and management tips
• Both rotary and cylinder types of combines can distribute residue equally well if set properly, according to engineers.
• Refer to the operator’s manual or talk to your dealer about getting the most even distribution possible from a machine.
• Always check residue distribution patterns of newly purchased combines (whether new or used), and if necessary, add residue-spreading attachments.
• After setting residue choppers and spreaders, continue to check distribution as harvest conditions change.
• Overcorrecting for windrowing problems and spreading residue too far can result in residue concentration outside the harvest swath.
• Changing pulleys to increase the speed of straw spreaders can help achieve wider distribution.
• Inspect blades of straw choppers. If edges are rounded or dull, consider sharpening or replacing according to manufacturer recommendations.
• More aggressive treatment (chopping and shredding) of cornstalks at the corn head should aid in stalk degradation.
Straw and chaff
Every grain combine discharges two streams of material. Straw is the material that passes through the threshing and separating units of the combine. It consists of corncobs, husks and some cornstalk pieces. Chaff is the material which is blown or otherwise discharged from the cleaning unit (cleaning shoe) of the combine. It contains smaller “chaffy” pieces of plant stalks, cobs or hulls.
Spreaders and choppers
A straw spreader uses blades or rubber batts rotating in a horizontal plane to intercept the exit stream of straw and deflect it behind and to the sides of the combine path. Most pieces of crop residue remain intact. A straw chopper uses a series of metal flails or knives mounted on a horizontal shaft or drum rotating at high speeds to break or cut residue into smaller pieces before distributing. A chaff spreader typically uses spinning disks to distribute the fine residue coming from the combine sieves.
Straw spreader versus straw chopper
Straw spreaders and choppers are interchangeable on most combines, so growers can choose between the two (with some combines, a combination of both is available). While the spreader typically distributes residue more uniformly, the chopper can provide more residue cover, since it chops the residue into small pieces before spreading. Most combine manufacturers offer straw choppers as a standard item or option, and few after-market choppers are available now.
Chaff spreaders are most important for crops that produce a lot of light, fine crop material during threshing of grain, such as soybeans or wheat; but they also may be helpful for corn. Chaff is easy to distribute with hydraulically driven single or dual-spinning disks with rubber batts attached, mounted to the rear axle. However, because it is lightweight, chaff is difficult to spread beyond 20 to 25 feet with a single disk.
Consequently, for harvest swaths greater than 20 feet, dual chaff spreaders may be needed. Swath width and distribution patterns of chaff spreaders usually can be altered somewhat by adjusting: 1) the fore-aft position where material drops onto the spinning paddles, 2) the deflectors or shields at various points around the perimeter of the paddles and 3) the speed (rpm) of the spinners.
Locating spreaders and choppers
Commercial chaff and straw spreaders and straw choppers are now available to fit most combine models. Producers can obtain more information from equipment dealers, Cooperative Extension and private fabricators. A list is also available from the PNW Conservation Tillage Handbook Series at:
Stalk processing at corn head
One option for growers who find cornstalks challenging at planting is more aggressive treatment of the stalks at the corn head. Crushing, laceration and shredding of stalks at the combine may help in subsequent stalk degradation by exposing them to microbes and weather. Many equipment manufacturers offer optional “knife rolls” or more aggressive stalk rolls to replace standard stalk rolls on corn heads.
John Deere manufactures a knife roll that replaces the standard stalk roll on many John Deere corn heads. John Deere also produces a StalkMaster chopping corn head for
thorough chopping of stalks with a rotary blade.
New Holland offers optional “sharpened knife rolls” for corn heads to chop the cornstalk residue for more even dispersal on the field.
Massey Ferguson offers aggressive fluted snapping rolls as standard equipment. According to the manufacturer, these rolls adequately shred stalks to promote rapid decomposition of field residue, making tillage and/or seeding passes easier.
Case IH offers optional straight fluted stalk rolls that are more aggressive than tapered rolls.
Pixall knife rolls are an after-market item for John Deere combines that aggressively “condition” stalks at the corn head. Their use may eliminate a tillage pass and aid in planting in the spring, according to the manufacturer.
Geringhoff U.S. produces the Rota Disc corn head that thoroughly chops stalks as they pass through the head, eliminating the need to chop stalks post-harvest.
Some experts suggest leaving 12 to 18 inches of stalk in the row at combining. In no-till systems where next year’s crop will be planted between the old rows, this keeps more residue anchored and out of the row middles. Taller stalks may catch on planters or fertilizer equipment, however.