How Many Bushels Is Your Combine Losing?

With harvest getting underway, here are some ideas on how to minimize harvesting losses. Rod Swoboda

Published on: Sep 20, 2005

While many combine operators routinely adjust concave clearances, rotor or cylinder speed, fan speed, and sieves, the majority of harvest losses occur outside of the threshing and separating unit – at the header. On the average, gathering losses at the head account for as much as two-thirds and nearly 90% of corn and soybean harvest losses, respectively.

That reminder comes from Shawn Shouse, an Iowa State University Extension ag engineer. Total losses as high as 6 bushels per acre in corn and 3 bushels per acre in soybeans are not uncommon, but that doesn’t have to be the case, he says.

Those are average losses; top combine operators reduce these losses by about 75%, leaving only a bushel and a half of corn and less than a bushel of soybeans in the field and increasing returns by about $10 per acre.

They get these results by keeping their headers in good mechanical shape and by making adjustments based on the condition of the crop. Read the operator’s manual and look for specific information for your header. Here are a few tips to get you started:

For harvesting soybeans:

  • Use a properly adjusted pickup reel to gather as much of the crop as possible. Reel axle should be located approximately 8 inches ahead of the cutter bar. Adjust chains and belts.
  • Adjust reel speed to 1.5 times ground speed using the following formula: reel speed (rpm) = combine speed (mph) x 504 / reel diameter (inches).  Example: If ground speed = 3 mph and reel diameter = 42  Reel speed= 3 x 504/42 = 36 rpm 
  • A reel that turns too fast will cause shattering. A reel that turns too slowly will drop bean stems.
  • Use a well-maintained flexible floating cutter bar to cut as low as possible.
  • Adjust wear plates, hold-down clips and guards.
  • Knife sections and ledger plates should be sharp.
  • Adjust chains and belts.

For harvesting corn:

Stay alert and on the row. Weaving off of the row by as little as a couple of inches can account for gathering losses of at least a bushel per acre.

Under poor field conditions, consider adjustments to corn head components to minimize header losses. If possible, slow snapping roll speed when operating under adverse conditions such as a lodged crop. After-market reels for corn heads can quickly pay for themselves when harvesting wind-damaged areas. With all the potential stalk rot this fall, let's hope it is not windy.

Drought and other poor growing conditions that result in small ears also increase gathering losses due to shelling at the snapping rolls. Adjust the spacing of the snapping roll bars if possible to minimize shelling losses at the head, and increase travel speed under good field conditions to keep the combine near capacity. Hopefully most of you will find that the ears are decent sized this fall.

Remember: safety first and always

Finally, be alert and aware of the location of others during harvest. With it looking like we may continue to have dry fields this year, please be sure you carry fire extinguishers and that they are in good working order and carry a cell phone with you. We have already had a few fires with the limited number of acres harvested, so be careful! Have a safe and happy harvest.