publication G01280 — Reviewed October 1, 1993
Measuring and Reducing Soybean Harvesting LossesCharles W. Shay, Lyle
Ellis and William Hires
Department of Agricultural Engineering, University of
Numerous tests of soybean combine losses show that up to 12 percent of the
soybean crop is lost during harvest. Harvesting losses cannot be reduced to
zero, but they can be reduced to about 5 percent. Combines can be operated to
reduce losses without affecting the harvesting rate. This guide describes the
major sources of loss.
When the reel speed is too fast or the reel is positioned too
far forward, soybeans are shelled in front of the combine. Reel peripheral speed
should not exceed forward speed of the combine by more than 25 percent.
Peripheral speed is easier to adjust on combines with variable speed reel
- Preharvest losses. These losses are beyond the combine operator's control
and cannot be called harvesting losses. Preharvest losses are caused by
lodging and shattering. In most years, 0.25 percent of the total crop yield is
lost before harvesting begins.
- Shatter loss at combine header. These losses occur when the header is
operated improperly or when the crop tends to shatter easily. Shatter losses
increase with crop dryness.
Consider shatter losses of 2 percent acceptable. Average losses are 5 percent
Stubble losses should be no more than 0.75 percent of the total
crop yield. Average losses are 1.5 percent or more.
- Stubble loss. Often many pods are left on the stubble because they have
been missed by the cutterbar and were not gathered into the combine. Overcome
this problem by keeping the field level and using a flexible cutterbar or
special row-crop head for soybeans.
- Lodged or loose stalk loss. Beans left in the pods on downed stalks or
those that are cut but do not pass through the combine should be only about 1
percent of the total crop yield. Minimum losses occur when the machine is in
top condition, the knife is sharp and the correct reel height is used. A
pickup reel reduces these losses. Average losses are 2 percent to 5 percent of
the crop yield.
- Cylinder loss. Beans left in pods that have passed through the machine are
the result of harvesting when the moisture content is too high or with
incorrect cylinder-concave settings. There should be no loss, but improper
operation can cause losses as high as 0.5 percent of the crop yield.
- Separation loss. Loose beans passing out of the machine can be held to a
minimum with the correct blower and sieve settings. These losses can be as
high as 0.5 percent but should be held to 0.25 percent of the crop yield.
How to measure lossesTo get satisfactory combine operation, you need to
identify and measure losses. Alone, you can check losses in about 10 minutes. If
you have help, even less time will be required. The extra soybeans in your grain
tank will more than pay for the delay.
To determine losses, count the unharvested beans in an area of 10 square
feet. An average of four beans per square foot equals one bushel per acre loss.
Make the area of 10 square feet equal in width to the combine header. (See Table
1.) A plastic clothes line and four pins made from No. 9 wire make excellent
material for forming the rectangle.
Table 1. Rectangular dimensions for 10-square-foot plot.
|Common machine swath
||Distance to enclose 10 square feet|
Before checking for losses, disconnect the straw spreader or chopper so you
can get a more accurate count. Stop the combine where the crop is representative
of the entire field. Stop the header and threshing mechanism. Back the combine a
distance equal to its length. Shut off the engine.
Place the rectangular frame across the machine swath and make counts for:
Step 1. Total crop loss. Place the rectangular frame
across the swath harvested at rear of combine. Count all loose beans as well as
the beans in loose and missed pods. Enter the number of beans per 10 square feet
in Table 2, line 1.
- Total crop loss (Step 1),
- Preharvest loss (Step 2), and
- Header loss (Step 4).
If the total crop loss is less than 3 percent of the crop yield, keep on
harvesting. You are doing a better than average job. If losses are greater than
3 percent, pinpoint the source of the losses to determine where adjustments are
Step 2. Preharvest loss. Determine the preharvest loss by placing the
rectangular frame in standing beans. Count the loose beans on the ground and the
beans in loose pods on the ground. Enter the number of beans per 10 square feet
in Table 2, line 2.
Step 3. Machine loss. Determine the machine loss by subtracting the
preharvest loss from the total crop loss. Enter this number in Table 2, line 3.
If the machine loss is 3 percent of the total crop yield, you are doing a better
than average job and adjustments are not necessary. If the loss is greater than
3 percent, check the header losses.
Step 4. Header loss. Determine header losses by placing the
rectangular frame across the swath harvested in front of the parked combine.
Place it over an area where there has been no discharge from the rear of the
combine. Then make bean counts as follows and enter the numbers in Table 2.
Obtain the total header loss by adding the losses for shatter,
stubble, loose stalks and lodged stalk losses. Enter the total header loss in
- Shatter loss. Count all loose beans on the ground and beans in loose pods
on the ground. Enter the number of beans per 10 square feet in line 4a.
- Loose stalk loss. Count all the beans in pods attached to soybean stalks
that were cut but not gathered into the machine. Enter the number of beans per
10 square feet in line 4b.
- Lodged stalk loss. Count all the beans in pods attached to soybean stalks
that were lodged and are still attached to the ground. Enter the number of
beans per 10 square feet in line 4c.
- Stubble loss. Count all the beans in pods still attached to stubble. Enter
the number of beans per 10 square feet in line 4d.
Step 5. Cylinder and separation loss. Determine cylinder and
separation loss by subtracting the total header loss from the machine loss.
Enter this difference in Table 2, line 5.
Table 2. Loss data table.
|Source of loss
||Beans found in 10 sq. ft. area
||Number of beans = 1 bu./acre
||Your bean loss in bu./acre|
|1. Total crop loss
|2. Preharvest loss
|3. Machine loss
|4. Gathering unit loss. Totals of:
b. Loose stalk
c. Lodged stalk
|5. Cylinder and separation loss
Tips for keeping combine losses lowYour best guide for correct combine
adjustment is your operator's manual.
Remember that more than 80 percent of the machine loss usually occurs at the
gathering unit. The following suggestions will help keep these losses to a
- Make sure that knife sections, guards, wear plates and hold-down clips are
in good condition and properly adjusted.
- Keep the seedbed level. Do not dig up soil around beans when cultivating.
- Operate the cutterbar as close to the ground as possible at all times. A
floating header unit or an automatic header control is nearly essential on
- Use a ground speed of 2.8 to 3.0 miles per hour. To determine ground
speed, count the number of 3-foot steps taken in 20 seconds while walking
beside the combine. Divide this number by 10 to get the ground speed in miles
- Use a reel speed about 25 percent faster than ground speed. For
42-inch-diameter reels, use a reel speed of 11 revolutions per minute for each
1-mile-per-hour ground speed.
- Reel axle should be 6 to 12 inches ahead of the cutterbar. Reel bats
should leave beans just as they are cut. Reel depth should be just enough to
control the beans.
- A six-bat reel will give more uniform feeding than a four-bat reel.
- Complete the harvest as quickly as possible after beans reach 15 percent
- A pick-up type reel with pick-up guards on the cutterbar is recommended
when beans are lodged and tangled.
request G1280, Measuring and Reducing Soybean Harvesting Losses (50
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Agriculture. Ronald J. Turner, Director, Cooperative Extension Service,
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