University of Missouri Extension

G1280, Revised October 1993

Measuring and Reducing Soybean Harvesting Losses

Charles W. Shay, Lyle Ellis and William Hires
Department of Agricultural Engineering

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.

How to measure losses

To 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 (Table 1). A plastic clothes line and four pins made from number 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
8 feet 15 inches
10 feet 12 inches
12 feet 10 inches
13 feet 9.25 inches
14 feet 8.6 inches
15 feet 8 inches
16 feet 7.5 inches
20 feet 6 inches
22 feet 5.45 inches
24 feet 5 inches

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.

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 needed.

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 line 4.

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 square feet area Number of beans = 1 bushel per acre Your bean loss in bushels per acre
1. Total crop loss   40  
2. Preharvest loss   40  
3. Machine loss   40  
4. Gathering unit loss. Totals of:   40  
a. Shatter
b. Loose stalk
c. Lodged stalk
d. Stubble
5. Cylinder and separation loss      

Tips for keeping combine losses low

Your 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 minimum.

G1280, reviewed October 1993

G1280 Measuring and Reducing Soybean Harvesting Losses | University of Missouri Extension

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