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This year’s harvest was challenging in most areas. The soybeans matured fast, dried down rapidly, and now have been rained on in many areas. Seed producers are challenged by harvesting soybeans that have dropped from the ideal of 12 to 13% seed moisture to the 7% and 8% range or leaving in them in the field and hoping for some moisture gain.

Soybeans never improve in quality from the time of ideal harvest moisture. “Weathering” of soybeans leads to declines in physiological integrity, fungal infection, seed staining, cracked seed coats, and diseases such as purple seed stain. After the point of ideal harvest moisture, it is a gamble to harvest with low seed moisture and risk extensive mechanical damage, or leave them in the field and risk “weathering” problems and the associated declines in seed vigor. Neither option is good! Your experience with the seed crop, equipment, and weather in your area will be what you have to base the answer on.

Soybeans that have dried down past the reasonable harvest moisture point are highly resistant to gaining moisture at first. The cellular structure of the seed coat is designed to protect the seed. However, with each re-exposure to moisture, the seed coat becomes more and more permeable and moisture levels rapidly move up and down. These changes in seed moisture accelerate the deterioration of the seed tissues and cause a loss of viability. Fungi, such as phomopsis spp. commonly colonize the surface of green soybean pods, but the fungal infection cannot penetrate the living green tissues. Once the pod yellows and the tissue is dying, the fungus mycelium can penetrate and begin infection of the seed. Allowing the penetration of the fungus causing phomopsis infection, leads to extremely detrimental conditions for high quality seed production and complicates seed testing. Under severe conditions, it is not uncommon to have seed lots with infection levels in the 20 to 40% range with many dead seeds. Many infected seeds will be elongated, shriveled, discolored (sometimes salmon colored) and covered with a whitish mold growth, but even normal appearing seed can be infected. Slight infections of phomopsis usually can be solved by seed storage and seed treatment is always an option.

Mid-West Seed Services analysts observe and note fungal infections, types of abnormal seedlings and other factors that have limited the germination potential. The additional information that is available on your analysis report provides information helpful in making your management decisions.

Mid-West Seed Services recommends having a sand germination test and an accelerated aging test done on all your soybean seed lots in addition to the standard warm germination used for labeling. If these show moderate to severe infections of fungal spp., I recommend you request a new germination with seed treatment. This will provide you supplemental information about the potential field emergence and vigor of the seed lot.

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