Don’t Leave Soybean Yield Behind at Harvest

By Jane Fyksen Crops Editor
Thursday, September 18, 2008 7:39 AM CDT

Soybean growers should take “extraordinary precautions” this year to check combine settings throughout the harvest day, especially if they switch maturity groups, urges UW-Madison soybean specialist Shawn Conley.

“Much of the rainfall that occurred in the dry areas of Wisconsin occurred too late to aid early maturity group soybeans. These soybeans were physiologically mature (R7 growth stage) prior to rain,” he discusses. “However, many late maturity group varieties were still in the R6 (grain fill) growth stage and may have benefited from the late August-Early September rainfall.”

Conley says as growers proceed in harvest, a quick in-field estimate can be performed to assess where yield losses are occurring. The three areas of concern are: Pre-harvest loss (i.e. standing soybeans), header loss (harvested swath in front of the combine), and machine loss (harvested swath behind the combine). In each area, count the number of beans per 10 square feet. Forty seeds per 10 square feet equates to about a bushel of lost yield.

In most years, 0.25 percent of the total crop yield is lost before harvesting begins.

Harvest losses of 12 percent can easily occur if combine operators don’t pay close attention to equipment adjustments and operation, agrees Michigan State University Extension educator Mike Staton, who suggests harvest management strategies to limit losses to 3 percent or less.

“Shatter losses at the header account for most of the harvest losses,” says Staton in Van Buren County. “The best way to prevent shatter losses is to harvest as much of your crop as possible before the moisture level in the beans falls below 13 percent. When soybeans undergo repeated wetting and drying cycles after initially drying below 13 percent moisture, the pods become brittle and shatter easily.”

In a study conducted at Penn State University, a yield loss of 20 bushels per acre occurred when harvest was delayed three weeks. They also measured preharvest losses of 12 percent due to premature shattering when harvest was delayed three weeks in another field. As a result, they recommend harvesting soybeans one week after 95 percent of the leaves turn brown, even though some green leaves may still remain on the stalks.

Staton suggests growers incorporate the following in order to be able to market more of their 2008 soybean crop:

- Begin harvesting when the moisture level in the beans reaches 15 percent.

- Keep knife sections sharp and tight, and make sure that all guards wear plates and hold-down clips are in good condition and properly adjusted. Consider replacing standard knife sections with narrow knife sections to reduce shatter losses.

- Operate the cutter bar as close to the ground as possible.

- Keep the ground speed at three miles per hour or less.

- Adjust the reel to run about 25 percent faster than the ground speed.

- If the crop is standing well, position the reel axis 6 to 9 inches ahead of the cutter bar and adjust the reel height so that the tips of the fingers operate about 12 inches above the ground. If the plants are tangled or lodged, position the reel axis 9 to 12 inches ahead of the cutter bar and adjust the height so that the reel runs about one inch above the ground. Raise the reel if plants are riding over the top of it.

- Take advantage of conditions that create damp pods, such as dew, light rains or high humidity, to reduce shattering.

- Maintain the slowest cylinder speed possible that produces complete threshing.

- And, as Conley notes, check header losses periodically by backing the combine up 10 feet and counting the number of beans per square foot on the ground in front of the header. (Remember that you are losing a bushel per acre for every four beans per square foot you find on the ground.)

University of Missouri ag engineers add to the discussion, noting that when the reel speed is too fast or the reel is positioned too far forward, beans are shelled in front of the combine. Reel peripheral speed shouldn’t exceed the forward speed of the combine by more than 25 percent. They consider shatter losses of 2 percent “acceptable”; average losses are probably 5 percent or more.

Overcome “stubble loss” (missed by the cutterbar) by using a flexible cutterbar or special row-crop head for beans. Stubble losses should be no more than 0.75 percent of total yield; average losses are generally 1.5 percent or more.

There’s also lodged or loose stalk loss n beans left in pods on downed stalks or not cut. This type of loss should be only about 1 percent of yield. Keep your machine in top condition, the knife sharp. Use the correct reel height and a pickup reel to reduce this loss. Farmers typically lose 2 to 5 percent of yield this way.

Cylinder loss is beans left in pods that have passed through the machine. It’s the result of harvesting when 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, according to the Missouri ag engineers.

Separation loss or 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.

Alone, a farmer 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, the experts assure.

As noted, count the unharvested beans in an area of 10 square feet. A plastic clothes line and four pins made from No. 9 wire can form your rectangle.

Rectangular dimensions to enclose a 10-square-foot plot for various machine swath widths are: Machine swath of 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 total crop loss, preharvest loss and header loss as follows:

- Total crop loss - Place rectangular frame across the swath harvested at rear of combine. Count all loose beans as well as the beans in loose and missed pods. 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.

- Preharvest loss n Place the frame in standing beans. Count the loose beans on the ground and the beans in loose pods on the ground.

- Machine loss - Determine by subtracting preharvest loss from total crop loss. If the machine loss is 3 percent of total 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.

- Header loss n Put the 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: For shatter loss, count all loose beans on the ground and beans in loose pods on the ground. For loose stalk loss, count all the beans in pods attached to soybean stalks that were cut but not gathered into the machine. For lodged stalk loss, count all the beans in pods attached to soybean stalks that were lodged and are still attached to the ground. For stubble loss, count all the beans in pods still attached to stubble. Obtain the total header loss by adding the losses for shatter, stubble, loose stalks and lodged stalk losses.

- Cylinder and separation loss - Determine cylinder and separation loss by subtracting the total header loss from the machine loss.

More information on reducing and measuring harvest losses is available online at web1.msue.msu.edu/soybean2010. Michigan’s Soybean 2010 web page seeks to help growers increase soybean yields and farm profitability by 2010.

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