Reduce Harvest Losses in Soybean and Corn

September 3, 2019

  • Some mechanical damage is expected at harvest.
  • Grain loss behind the combine should be measured to determine the need for combine adjustments.
  • Careful operation and adjustment of combines can reduce harvest losses to an acceptable level.

Corn kernels and soybean seeds left behind when the field is combined represent a loss of profits. Harvest losses cannot be completely eliminated, but can be reduced to 1 to 2 bu/ acre by checking the performance of your combine.

CORN: How to Measure Harvest Loss

Determine total ear loss by counting the number of fullsize ears, or the equivalent, in a 1/100 acre area (Table 1). Each full-size ear represents about 1 bu/acre loss.4

To measure kernel loss, count the loose kernels on the ground and those still attached to threshed cobs in a 10 square foot area for each row behind the combine. The area should have width equal to the planted row width (Table 2). Two kernels per square foot equals a 1 bu/acre loss.4

Reduce Corn Harvest Loss

Proper combine settings can help maximize income by reducing harvest loss and reduce volunteer corn issues for the next growing season. Mechanical losses may be due to ear drop, stalk lodging, and kernel loss from threshing and cleaning. Mechanical losses are expected, but keeping them to a minimum of 1% for ear loss, 0.3% threshing loss, and 0.5% loose kernel loss should be the goal.1 Altogether, a 1.8% mechanical loss from a 150 bu/acre corn yield would be 2.7 bu/acre or an average of 5.4 kernels/ square foot.

Ear loss can be minimized by setting snapping rolls to fit stalk width and running snapping rolls at the same speed as ground speed. Cylinder or rotor speed can be adjusted to minimize threshing losses and kernel damage. Loose kernel losses can be affected by fan and shoe settings, and combines should be adjusted where stressed plants produced lighter kernels. Follow manufacturer’s settings to minimize losses.

SOYBEANS: How to Measure Harvest Loss

Losses are determined by counting the number of soybeans on the ground in a 10 square foot area (Table 3).4 The number of soybeans lost per square foot can be determined by counting soybeans in this area and dividing by ten. Approximately four soybeans/square foot equals 1 bu/acre loss.2,3 Therefore, dividing the number of soybeans/square foot by four will give the loss result in bu/acre. Make loss determinations at several locations and calculate an average.

Reduce Soybean Harvest Loss

Soybean combine losses can be as much as 15%. Careful maintenance and operation can help keep soybean harvest losses to 3%, which would be 1.35 bu/acre in a 45 bu/acre crop (or 5.4 soybeans/square foot). Most of soybean harvesting losses occur at the gathering unit of the combine between the header and standing soybean plants.2 Loss at the gathering unit is often from shattering.

Shattering loss can be reduced by harvesting soybeans as quickly as possible when soybean moisture reaches 15%.3 Ground speed should be reduced to 3 miles/ hour or less, and reels should operate about 25% faster than ground speed. The best guide for correct combine settings and adjustments is your operator’s manual.


Each harvest season producers have the opportunity to save yield potential through combine adjustments and careful machinery operation. While some grain loss is expected during harvest, mechanical losses should be kept to a minimum. Measurement of grain left behind the combine is the key to making adjustments to combines and proper combine operation.


1McNeill, S. and Montross, M. Corn harvesting, handling, drying, and storage.

2Beasley, E.O. Reduce soybean harvest losses. North Carolina State University.

3Staton, M. and Harrigan, T. 2011. Reducing soybean harvest losses. Michigan State University Extension.

4Shay, C., Ellis, L.V., and Hires, W. 1993. Measuring and reducing corn harvesting losses. University of Missouri Extension. G1290.

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