By Charles Hurburgh and Steve Johnson
Large amounts of soybeans will be stored on-farm and commercially this fall and well into 2019 — perhaps even through 2019. As with all grains, spoilage of soybeans will occur quickly if storage moisture is too high. High oil content makes beans more susceptible to spoilage than corn. Thus, soybeans need to be about 2 points drier than corn for proper storage.
In a normal year, using unheated air, a bin fan can dry soybeans to 13% moisture in the fall and lower in the spring. In cool and wet fall conditions, supplemental heat may be required.
This fall, the drier weather during the last two weeks of October took the need for supplemental heated air out of the picture. The key is knowing the grain temperature and following weather conditions, especially the dew point and the difference between dew point and temperature. That difference has been running at nearly 20 degrees F — very good for this time of year.
Be careful drying beans
Soybeans with less than 18% moisture content can be dried with bin fans if airflow is high enough for the moisture. Storing 18% beans is about like storing 20% corn. Also, remember beans are fragile compared to corn, and they can be damaged by air that’s too hot or too dry and by rough handling.
Soybeans have about 25% less airflow resistance than shelled corn, so fans sized for corn drying will produce greater airflow through soybeans. Greater airflow means faster drying. For soybeans, if you are drying with heated air, limit it to 130 to 140 degrees F range for commodity beans, and 100 to 110 degrees F for seed beans. The actual grain temperature of commodity beans should not exceed 120 degrees F; most dryers use air hotter than the actual grain temperature will reach.
Low-temperature dryers should have a full perforated floor and a fan that can push airflow of 0.5 to 1 cubic foot per minute per bushel, and progressively more up to 18% moisture beans.
To avoid overdrying and cracking of soybeans, size heaters on low-temp drying bins for no more than a 10-degree-F temperature rise, and use an in-plenum humidistat to shut off the heater when relative humidity of drying air is below 45%.
The concern with airflow and low-heat drying of beans (without stirring) is overdrying, which causes substantial economic loss when beans get below 13% moisture content. You can get very dry very fast with beans. As long as they are cold, they will keep well. See the table on Page 6 for allowable storage times for soybeans and corn.
Both temperature and moisture are important in grain preservation; but often, temperature control is the most immediately important if drying capacity is limited.
Drying time depends on airflow, weather and initial moisture content, but will probably be three to six weeks. If current conditions stay favorable, it may be only a week or two. Check the soybean moisture and condition every day. Resume drying in spring, if necessary. If you detect mold, heating or foul odors during drying, unload the bin and sell, or dry the beans at a high temperature. Keep in mind that once beans start to mold, it’s very hard to stop them, because oil rancidity reactions begin and continue beyond mold activity.
Other storage strategies
Here are a few more tips for soybean storage:
• Level off bins immediately after harvest; remove the center core.
• Avoid using worn augers and mechanical spreaders that will damage the seed while filling.
• Aerate bins as soon as they are filled to remove heat from stored beans, regardless of moisture. Get grain temperature into the 40s or below immediately. This shouldn’t be an issue this year. The dew point tells about how cold you can get them.
• Aerate stored beans to maintain grain temperature at 35 to 40 degrees F in winter and 40 to 60 degrees F in summer. This is probably not possible in summer, depending on dew point. Keep them cold as long as you can.
• Check bins every couple of weeks during the storage period; watch for crusting and aerate if needed. Be sure bins are ready for unloading before winter weather arrives, in case you need to move soybeans that are going out of condition.
Caution: With mold on beans coming from some fields this fall, don’t mix damaged beans with good-quality beans. For information on mold and moisture management, see Managing wet soybeans in a late harvest. Also, visit the Iowa Grain Quality Initiative.
Hurburgh is an ISU Extension grain quality specialist and director of the Iowa Grain Quality Initiative. Johnson is an ISU farm management specialist.