Combining soybeans is about harvesting soybeans at optimal moisture to capture the most bushels while reducing harvesting losses. It is also about making sure the combine is properly set and operated to reduce any mechanical losses.

Soybean yields can be increased by 5 to 10 percent by leaving fewer beans in the field after harvest. Combine harvesting loss of only 3 to 4 percent (1.5 to 2.5 bu/acres in 60-bushel beans) can be achieved with a properly set and operated combine. Taking extra care when combining doesn’t cost you more and the beans you save will add to your profits.

There are harvesting losses through the combine. To help pinpoint the cause of loss, you can measure how many beans did not make it into or through the combine and how many beans came out the back of the combine and into the bin. Make a square or round hoop to lay in the field, calculate its internal surface area and then use it to
count the number of beans lying on the ground. Depending on the size of the bean, 2 to 6 beans per square foot equals one bushel lost per acre. Try to measure an area of 10 square feet behind the combine to see what came out the back and just below the cutting head to see what did not make it in. Also stop the combine, back up and evaluate what was under the head and attribute that to field loss.

Field losses fall into several categories:

  • Field loss: Loose beans or beans in detached pods which are on the ground prior to harvesting. This can happen when a big storm comes through once beans mature and dry or when pods undergo several cycles of rewetting and drying before harvest.
  • Platform loss: Beans which are attached to plants at harvest, but which never get into the combine. Most harvesting losses are in this category. There are three types:
    • Shatter loss: Loose beans and detached pods resulting from harvesting when too dry.
    • Stubble loss: Pods remaining attached to the stubble or stems and below the height of the cutting head.
    • Loose stalk loss: Pods which were harvested, but did not make it through the rotor or cylinder and were discharged out the back.
  • Cylinder/Rotor loss: Beans which pass through the threshing unit but remain in the pod.
  • Separation loss: Threshed beans which go out of the combine with the trash.

There are ways to reduce these losses. Since most losses are at the head, pay the most attention there:

  • Go slow. Long stubble, uneven cutting height and shatter losses due to stripping are indications that ground speed is too fast.
  • Cut as close to the ground as possible at all times. A floating cutter bar with automatic header height control is essential for low loss levels.
  • Keep sickle sections sharp, and check to see guards are not worn and wear plates and hold- down clips are in good condition. Narrow-section knives reduce shatter and permit slightly higher ground speeds.
  • Operate the reel 25 percent faster than ground speed and position the reel 6 to 12 inches above the cutter bar. Do not let reel bats become too aggressive.
  • Harvest as soon as possible after bean’s moisture level drops to 14%. When beans reach 12% or less, take advantage of damp pod conditions brought on by dew, light rain or high humidity to reduce shattering.
  • Operate the cylinder/rotor at the slowest speed which will give complete threshing while not splitting beans. Check and adjust as conditions change through the day.
  • Check for losses when field and crop conditions, varieties or machine settings change.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at

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About the Author: Dan Davidson

Soybean agronomist Daniel Davidson, Ph.D., posts blogs on topics related to soybean agronomy. Feel free to contact him at or ring him at 402-649-5919.