Equipment Adjustments for Harvesting Soybeans at 13%-15% Moisture

Equipment Adjustments for Harvesting Soybeans at 13%-15% Moisture

Also see the companion article, Plan Harvest to Deliver Soybeans at the Optimum Moisture, in this week's CropWatch.

Combine feeder chain
Figure 1. The worn feeder house chain on the left won’t grip and pull green stemmed soybeans into the thresher as well as the new one on the right.  Replace worn parts on the combine to keep the materials flowing through the machine during harvest.

Everyone knows it is impossible to harvest all your soybeans at exactly 13%, but that should be your goal to optimize potential income. If you're harvesting soybeans at 14%-15% moisture and pods are mature and stems are still green, consider the following equipment recommendations to help assure a good harvest.

  1. When harvesting tough or green stems, make combine adjustments and operate at slower ground speeds. Make combine adjustments several times a day to match conditions as they change. The following combine adjustments are suggested when harvesting higher moisture soybeans or soybeans with green stems:
    • To increase “grip” on the green stems to pull them through the combine, replace rounded or worn parts in the thresher, especially worn feeder house chains (Figure 1) and rasp bars.
    • Increase cylinder/rotor speed to make threshing more aggressive to break open green pods and pull the green material through. Do not close down concave clearance as that reduces room for the green materials to pass through the thresher.
    • Insert filler plates or wires in the front portion of the concave to keep the green pods in the cylinder/rotor chamber longer for better threshing. If not, the pods will fall through to the sieves unopened. Consider closing down the top sieve slightly to send the green pods out the back if you are not threshing them properly.
    • Increase fan speed as the green stems are heavier and need more airflow to keep them suspended above the sieves to allow for proper cleaning and to blow the green leaves out.
    • Close down the lower sieve slightly to keep green pods out of the grain tank and send them back to the cylinder/rotor for rethreshing.
    • Install disrupter bars on rotary combines to improve green stem flow through the rotor and to reduce “roping." On some rotary combines, you can retard the material flow by adjusting the vanes on the rotor cage or by installing reverser rasp bars to keep the material in the rotor longer to allow more time for threshing and separating.
    • Consider adding an air reel to the head to have airflow help feed the soybeans into the combine and reduce bunch feeding.  More uniform feeding will improve threshing.

  2. Begin harvesting at 14% or 15% moisture. What appears to be wet or green from the road may be dry enough to harvest. Try harvesting when some of the leaves are still on the plant as the beans may be drier than you think. Soybeans are fully mature when 95% of the pods are at their mature tan color. When storing the first harvested, wetter beans on-farm, running the aeration fan will help drive moisture from the wetter beans upward to help rehydrate any dry beans in the top of the bin. 

  3. Harvest under optimum conditions. Moisture content can increase by several points with an overnight dew or it can decrease by several points during a day with low humidity and windy conditions. Avoid harvesting when beans are driest, such as on hot afternoons, to maintain moisture and reduce shattering losses. Harvesting immediately after a rain, if field conditions allow, will result in higher moisture contents.  However, several wetting and drying cycles from rain events will make the soybeans more susceptible to shatter losses from pods splitting open.

  4. Avoid harvest losses from shattering by harvesting before the beans become overly dry. Four to five beans on the ground per square foot can add up to one bushel per acre loss. Many times, the dock for delivering beans over 13% moisture content may be less the shatter losses from harvesting overly dry soybeans.

  5. If there are green leaves and green pods in the grain, they are considered foreign matter at the marketplace which can result in dockage.  If placed in on-farm storage, they can cause challenges in a grain bin at the edges. Avoid dockage and spoilage by doing the following:
    • Reset the combine as outlined above to provide a cleaner harvest.
    • Use a grain cleaner to remove the foreign matter before marketing or storage.
    • Use a grain spreader when putting beans into storage to better distribute any foreign matter.
    • In storage, operate the aeration fan to dry the leaves and green pods to a safe storage moisture content. The pods and green beans will dry quickly and help rehydrate any overly dry beans. The fans need to be operated for temperature management anyway.

  6. Don’t place “all of your eggs in one basket” when it comes to selecting the maturity of soybean seed at planting time. Select your varieties and schedule your planting to spread out plant maturity and harvest. Plant your early maturing varieties first.

Good luck and hopefully you'll have a safe harvest and an excellent crop of 13% moisture soybeans.

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