Soybean harvest is rapidly approaching, with plants changing color from dark green to yellow to brown as they mature.
Every year, challenges emerge during soybean harvest that need to be overcome, and it is difficult to get all the conditions perfect. When harvesting soybeans, you need to consider not only physical traits, but also the mechanical aspects of harvest to minimize harvest losses.
Harvest at correct physical maturity
Maturity encompasses the plants’ physical characteristics, such as stems and pods, as well as soybean grain moisture. Soybean grain moisture plays a key role in not only marketing, but also in preventing excessive harvest loss. The optimum soybean yield and marketability occurs at 13% moisture. Grain elevators will usually dock prices for grain with moisture content above 13%.
Harvesting soybeans at approximately 13% moisture — while ideal — is difficult to achieve. Soybean moisture content can fluctuate throughout the day. It can increase by several points with an overnight dew, or decrease by several points during the heat of the day accompanied by low humidity or windy conditions.
Sampling for moisture before harvest will allow you to determine the approximate levels within a field and how to proceed. If soybeans are at a higher moisture level, avoid harvesting during early mornings and late nights. If moisture levels are on the drier side, avoid afternoon heat.
Here is how moisture levels can impact yield:
- Soybeans harvested at 8% moisture can lose 5.4% of yield.
- Soybeans harvested at 9% moisture can lose 4.4% of yield.
- Soybeans harvested at 10% moisture can lose 3.3% of yield.
- Soybeans harvested at 11% moisture can lose 2.25% of yield.
- Soybeans harvested at 12% moisture can lose 1.1 % of yield.
Make combine adjustments
The physical plant characteristics of green stems and pods with low soybean moisture content has become more prevalent over the years. This is due to many factors, including genetic, environmental and field addition (biologicals and fungicides) changes to soybean production. No one factor is the complete cause.
While these characteristics do not usually limit yield, they can cause soybean harvest problems. Harvesting soybeans with green stems and pods is limited by the equipment available and combine capacity. If a farmer has enough header and combine capacity, these characteristics are not an issue.
However, adjustments must be made to harvesting techniques with smaller or older equipment. Ground speed must be reduced to compensate for the greater time needed within the combine. Green stems and pods tend to produce more potential for plugging and increase combine fuel consumption.
Though harvesting green stems and pods leading to potential losses is problematic, it is far less compared with potential header loss and shattering incurred by harvesting excessively dry soybeans. Every four to five beans on the ground per square foot equals about 1 bushel per acre lost. Be sure to stop and make adjustments as needed to help minimize this loss.
Mechanical combine adjustments during soybean harvest are critical to match the physical requirements of the beans and equipment available. Many farmers take the “set it and forget it” approach to combine settings. This approach may save time, but it will leave profits in the field instead of the bin, regardless of the harvesting machine used.
While grain losses can occur throughout a combine, field studies show 90% of soybean loss typically occurs at the head. With proper threshing and separating adjustments to combine draper heads, these losses can be greatly reduced.
Research identifies the cutter bar as most responsible for soybean losses within the header. However, reel speed and position and cross-auger operation also can affect losses. Ensure cutter-bar sections are sharp, in register with guard positions, and held firmly against the guard with hold-down clips. The reel speed index (ratio of peripheral reel speed to combine travel speed) is normally about 1.25 (25% faster reel than ground speed) but may be increased based on plant stem conditions or lodging.
If plants are shorter in stature due to drier conditions or variety, adjust the combine head height to ensure good header feeding. Although grain loss can be attributed to the combine head, other areas such as the rotors and sieves can prove to be costly if not properly adjusted for field conditions. Rotor speed can be raised or lowered to compensate for differing soybean plant conditions. This, in conjunction with adjusting ground speed, can greatly reduce losses.
Adjust combines with conditions
In order to maximize 2025 soybean yields, farmers need to make sure they scout fields and adjust their combines according to current field conditions. Each field and variety can differ, and striving to harvest during optimal conditions will ensure more soybeans go in the bin rather than on the ground.
Small changes can equal big gains by reducing yield loss throughout the field. Adjusting combines with conditions is a profitable usage of time.