Driving around farm country at the end of grain harvest can be an enlightening experience. Most fields are mainly covered with corn stover, the stalks and leaves left after the combine passes through the crop.
Every so often, however, you see a field that looks like the farmer is trying to grow another crop. One field in the upper Mississippi Delta this fall looked like the corn left in the field after combining had emerged to a near-perfect stand.
As interesting as such sights might be, they can also mean the producer left way too much grain in the field, as much as 20 bushels of corn per acre, according to Extension agricultural engineers.
“We suggest growers try to keep losses to no more than 1 bushel per acre in corn or soybeans,” says Mark Hanna, an Extension agricultural engineer at Iowa State University.
For openers, combine operators should set the correct stalk roll speed, and adjust spacing to snap ears about one-half to two-thirds of the way up the snapping bars.
“Snapping bars should be spaced narrower in front than in back to prevent wedging,” Hanna notes. “Spacing of 1-1/4 inches in front and 1-3/8 inches at the back is satisfactory under average conditions.
“If a wider spacing is used, small ears will wedge between the snapping bars and shelling losses will increase. Make sure stalk roll spacing and snapping bar spacing are the same on all rows.”
Gathering chains should be adjusted so the flights are opposite each other and extend about 1/4 inch beyond the snapping bars. Also, keep trash knives adjusted close to the stalk rolls.
Corn losses can also be reduced by maintaining proper field operation. “Gathering snouts should barely touch the ground under normal field conditions,” Hanna says. “If corn is badly lodged, slow down and let the snouts float on the ground.
“Under good field conditions, growers should maintain a field speed that uses much of your combine’s capacity. Avoid overloading. Check chaffer, sieve and fan adjustments and reduce travel speed if necessary to keep separating losses under 0.3 bushels per acre.
“Watch for ears lost at the header and reduce travel speed if more than one ear per 1/100 acre is dropped.”
Adjustments should also be made to rotor or cylinder speed to where it is just high enough to adequately thresh corn without excessive damage. “Try not to break cobs into more than three or four pieces for better separating,” Hanna says. “Start with wider concave clearance to promote crop-on-crop threshing and narrow it only as necessary to limit threshing losses.”
Make sure the cutterbar is in good condition. “Be sure knife sections and ledger plates are sharp and that wear plates, hold-down clips and guards are properly adjusted,” Hanna says. “Keep chains properly adjusted and belts tight. Lubricate bearings and roller chains when they’re warm to get better lubricant penetration.”
On a standard header, Hanna says the reel axle should be 8-12 inches ahead of the sickle. “A pickup reel should be used with a floating cutterbar, and the reel axle should be 8 inches ahead of the sickle,” he says.
“A bat reel should be operated just low enough to tip cut stalks onto the platform. If it is too low, stalks may be carried over the reel and dropped on the ground. The tips of the fingers on a pickup reel should clear the cutterbar by about 2 inches.”
Hanna points out that properly governed engine speed is essential for proper separator action. The operator’s manual should list the proper speed for the right job. Speed should be measured with on-board sensors or at the proper shaft with a tachometer when the engine is at operating temperature.
“Proper reel speed in relation to ground speed will reduce gathering losses,” Hanna adds. “A 40-inch reel should rotate about 12.5 rpm for each 1 mph of forward speed; a 42-inch reel, 12 rpm; and a 44-inch reel, 15 rpm. The reel will shatter beans if it turns too fast, and stalks may be cut and dropped if it turns too slowly. Reel speed should be increased in lodged conditions.”