By H. Mark Hanna, Extension Ag Engineer
Objectives when setting and adjusting the combine are to harvest all crop available in the field while maintaining grain in quality condition for storage. Past field measurements show that field losses due to the combine should be 1 bushel per acre or less if the crop is standing reasonably well. Each two kernels of corn per square foot (or 3/4 pound of corn ear per 1/100 acre) or four soybeans per square foot equals 1 bushel per acre loss.
Most losses occur at the gathering head, about 2/3 of machine losses for corn and 90% of losses for soybeans, so particular attention should be paid there to avoid loss. In soybeans, a flexible cutterbar with header height control helps to control uncut stubble loss. An extra inch of height equates to about 1 bushel per acre loss. Knife sections should be sharp, held down closely to guard shearing surfaces, and the cutterbar in good register with guards. Avoid outrunning the cutterbar at too high of a travel speed and shearing pods off stems.
The reel axis should be about 8-12 inches ahead of the cutterbar. Reel fingers should go deeply enough into the crop to guide it into the platform, however, reel fingers should come no closer than 2 inches to the cutterbar in its raised position. Peripheral reel speed is normally about 25–50% faster than combine travel speed, except in lodged crops where reel speed may be increased to about twice the travel speed to help pull and lift crop onto the grain platform.
On the cornhead, deck plates over snapping rolls should be adjusted wide enough to allow stalks to pass through, but narrow enough to avoid kernel shelling on the butt end of ears. About 1 3/8-inch width is a common starting position. Maintaining flexible ear-saver flaps at the lower end of stalk rolls helps to avoid the loss of a whole ear with several hundred kernels.
Coarse grains, such as corn and soybeans, are relatively easier to thresh and separate than small grains. Threshing action should be just adequate enough to separate corn from the cob or soybeans from the pod, but avoid being overly aggressive to the point of damaging seed coats, which can reduce grain quality and storability. Start from the lower point on the suggested range of rotor speed in the operator’s manual and the wider concave setting. Increase rotor speed and/or reduce concave clearance in small steps, only enough to avoid unthreshed cobs or pods behind the combine or in the grain tank.
In the cleaning shoe, start with suggested sieve opening settings and near the maximum fan speed to assist pneumatic separation of grain. Lower fan speed only enough to avoid blowing whole grain from the rear of the combine. If the tailings return has significant amounts of whole grain, open sieve settings or increase fan speed to avoid re-threshing.
Harvest safety is a major consideration to avoid injury and machine downtime. Don’t attempt to clear a head or auger unless power is disengaged and make sure to mechanically block the head before getting under it. Maintain guards. Although getting caught in or under the machine grabs headlines, a far more common harvest injury is falling off combines or bins. Use handrails, keep steps and platforms clean, and use good footwear with slip-resistant soles.
Maintain lighting and marking including red tail and amber warning lights and reflective tape as well as SMV emblems. Take a periodic break to clean debris for fire safety, check adjustments and maintain a sharp mental focus. Two ABC-type fire extinguishers are recommended, a smaller 5-pound model in the cab and a larger 20-pound model at ground level. Know the 911 emergency addresses for each field location.
Weather and other factors beyond our control create challenges at harvest. Accept the effects of adverse weather and adjust your equipment, speed and attitude accordingly.