Soybean Harvest Yield Loss

Soybean yield loss at harvest can be a result of either delayed harvest issues (shattering, lodging, etc.) and/or mechanical losses from the combine. With a 12”x12” square you can categorize how much yield you are leaving in the field.

Michigan State University recommends that we target 3 percent or less yield loss from mechanical harvest. If we consider that four beans laying on the ground per square foot is equal to roughly 1 bu/Ac yield loss, we want to see less than six beans per square foot in a 50 bu/Ac field (Figure 1). Generally, mechanical yield loss is the number of beans on the ground after the harvester minus the number of beans already on the ground before the harvester, but here is how you can drill in deeper:

1. Stop the combine in the middle of a pass and back out after the machine has cleared out.
2. Toss your square on the ground in the following areas and count the beans inside it. Do this at least three times in each area to get an average.
   • Ahead of the combine in unharvested crop: The number of beans on the ground is the shatter loss. Include beans that were in dropped pods. If beans are shattering or lodging ahead of your combine pass, it’s a harvest timing issue in most cases.
   • Under the machine to capture header losses
     • Stubble count: The number of beans in pods still attached to the cut stubble. They were too low to the ground for the header to cut and pick up.
     • Escaped plant count: The number of beans on plants that were cut but not gathered by the head. Are stems too wet? Are reel settings tuned?
     • Lodged count: the number of beans on plants that were not cut by the header.
     • Loose bean count: Now the total of header shatter and environmental shatter.
   • Behind the machine loose bean count: Now the total of environmental shatter, header shatter and threshing loss. Avoid the chaff pile from when you stopped.
3. Do some math and adjust. Remember that 4 beans per square foot is ~ 1bu/Ac.
   • Note that remedies for individual issues are listed above.
   • Thresher Loss = (Behind the machine loose bean count) – (Loose bean count). Consult manufacturer resources to optimize thresher settings.
   • Total Mechanical Loss = header loss + thresher loss = (Under the machine – Ahead of the combine) + Thresher Loss. Target 3% of yield.

Figure 1. Six loose beans in 1 square foot.

Reference: https://www.canr.msu.edu/news/measuring_soybean_harvest_ losses