Unless you know how much you are losing and from what part of the machine the loss is coming, you don't know how to make corrections. It is essential to measure losses and pinpoint their source to see where machine adjustments are needed. Always recheck losses after making adjustments to see if they had the desired effect. Once you learn the procedure, a loss check can be made in just a few minutes.
Preharvest Loss. Loose beans or beans in detached pods which are on the ground prior to harvesting.
Gathering Unit Loss. All beans which are attached to plants at harvest, but which never get into the combine. Most harvesting losses are in this category. There are four types of gathering unit losses:
Separation loss. Threshed beans which go out of the combine with the trash.
Bean counts are made in a 10-square-foot area. It is convenient to mark the area with a collapsible rectangular frame made from four stiff wire pegs and string, which can be rolled up and carried on the combine. Width of the rectangle should equal the swath width of the combine header. The length needed to enclose 10 square feet can be determined from Table 1.
1. Determine the total field loss. Stop the combine (do not clear), well in from the end of the field, where the crop is typical of the whole field. Disengage the gathering unit and back up about 15 feet. Place the rectangular frame across the harvested swath at the rear of the machine. Count all beans within the frame area and record in column A, line 1 of Table 2. Divide by 40 (in average-size beans) to get bu/a of preharvest plus harvesting loss and record in column B, line 1.
If the total field loss is not more than 3 percent of yield (1.2 bu/a in 40 bu/a beans), continue harvesting. If total loss exceeds 3 percent, follow steps 2 through 5 to see where the losses occur and make adjustments to reduce them.
2. Determine the preharvest loss. Place the rectangular frame in standing sbeans in front of the combine, and count all beans lying loose on the ground within the frame, both in and out of pods. Record the total count in column A, line 2 of Table 2. Divide by 40 to get bu/a, and enter in column B, line 2.
3. Determine the overall machine loss. Subtract the preharvest loss (line 2) from the total field loss (line 1) in columns A and B, respectively, of Table 2. If the machine loss is not more than about 3 percent of yield (1.2 bu/a in 40 bu/a beans), continue harvesting. If more, proceed with the remainder of the loss analysis and make adjustments to reduce losses where needed.
4. Determine the gathering unit losses. Place the frame across the harvested swath between the combine header and the standing beans. Make counts as follows:
b. Stubble loss. Count beans in pods attached to stubble, and enter in column A, line 4b. Divide by 40 and enter bu/a in column B, line 4b.
c. Lodged stalk loss. Count beans in pods attached to stalks which were not cut, and enter in column A, line 4c. Divide by 40 and enter bu/a in column B, line 4c.
d. Loose stalk loss. Count beans in pods attached to loose stalks or portions of stalks which were cut but not gathered by the header, and enter in column A, line 4d. Divide by 40 and enter bu/a in column B, line 4d.
5. Determine cylinder and separating losses. Subtract gathering unit loss (column B, line 4) from overall machine loss (column B, line 3), and record in column B, line 5.
Examine the various types of gathering unit losses, and the cylinder and separating losses to see where adjustments should be made. Comparison with the "acceptable" losses in column C, lines 4a-4d should be helpful in identifying the problem source. If your yield is much different from 40 bu/a, these "acceptable" bushel-per-acre losses should be adjusted accordingly. Make only one change in combine adjustment (i.e., reel speed, reel height, ground speed, cutter-bar height, cylinder speed, concave clearance, etc.) at a time, and recheck losses to see if the change improved performance. If not, go back to the original setting and try another approach, rechecking losses after each change. Only with this systematic approach can you isolate and correct the cause of excessive harvesting losses.
1. Keep ground speed to 3 mph or less. Long stubble, uneven cutting height and shatter losses due to knife stripping are indications that ground speed is too fast.
2. Operate cutterbar as close to the ground as possible at all times.s A floating flexible cutterbar with automatic header height control is virtually essential for low loss levels.
3. Keep knife sections sharp, and make sure guards, wear plates and hold- down clips are in good condition and properly adjusted. Narrow-section knives reduce shatter and may permit slightly higher ground speeds.
4. Operate reel about 25 percent faster than ground speed. Position reel axis 6 to 12 inches ahead of cutterbar. Bats should enter crop only enough to gain control.
5. Complete harvest as quickly as possible after beans first reach 15 percent moisture. When beans reach 13 percent moisture or less, take advantage of damp pod conditions brought on by dew, light rain or high humidity to reduce shattering.
6. Operate the cylinder at the slowest speed which will give complete threshing to reduce splitting. Check and adjust if necessary as conditions change from damp to dry.
7. Measure losses when field and crop conditions, varieties or machine settings change.
Table 1. Dimensions for rectangular 10-square-foot plot
Swath width Distance along row to enclose 10 square feet (ft) (inches)
8 15.0 10 12.0 12 10.0 13 9.25 14 8.6 15 8.0 16 7.5 18 6.7 20 6.0
Table 2. Soybean field losses
Column A Column B Column C ----------- ----------- --------------- Type of Frame location (or Beans in 10 Loss, Max. acceptable Step Loss How Calculated) sq-ft area bu/a* loss in 40 bu/a yield
1 Total Behind combine 1.2 2 Preharvest In standing beans 0.1 3 Machine Total minus 1.2 preharvest 4 Gathering Between header and 1.1 unit standing beans a shatter All loose beans 0.4 minus preharvest loss b stubble All beans in pods 0.3 still attached in stubble c lodged All beans in pods 0.2 stalk still attached to lodged stalks d loose All beans in pods 0.2 stalk still attached to loose stalks 5 Cylinder Machine minus 0.1 & gathering unit loss separation
* Beans in 10-sq-ft area divided by 40, for average-size beans.