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Agronomic Update: Handling, Drying and Storing Wet Soybeans
Oct 30 2009
Harvesting wet soybeans is a 2009 reality across Pannar country due to a very cool growing season, delaying maturity coupled with on-going wet conditions. Many growers are more familiar with handling wet corn while wet soybeans are more unusual. Therefore, guidelines for handling, drying, and storing wet beans follow.
Optimum soybean harvest moisture ranges from 13% to 15%, for maximum weight and minimum field loss. Iowa State University reports soybeans can generally be harvested any time after the seeds are mature and the foliage is dry. However, when moisture is above 18%, threshing can cause additional loss by crushing or bruising some seeds.
Artificial drying is necessary when soybeans are harvested with a moisture content much above 13%. In addition, wet beans require special attention during storage. As a guideline, Dr. Bill Winkle, Extension Engineer with the University of MN, reports that soybeans in storage tend to act about the same as corn that is 2% greater in moisture content. For example, soybeans at 16% moisture could be expected to act like corn at 18% moisture.
Handling wet soybeans
Soybeans are fragile and can split from rough handling. The best options for gentle handling include belt conveyors, bucket elevators, and drag or mass conveyors. But normal grain augers can be used if they are operated slow and full, and pneumatic or air-type conveyors can be used if the air-to-grain ratio is set properly and if lines are laid out with a minimum number of very gradual curves.
Avoid long drop-heights in bean handling by frequently adjusting the position of conveyors or by using bean ladders or other devices that break long drops into a series of shorter drops. In food-grade soybeans, a grower recommended 10 feet as the maximum height for any single drop. Grain spreaders are suitable for commercial soybeans but not for seed beans. When a spreader isn’t used accumulated fines can be removed by a process called coring, which levels the grain by unloading several loads from the center of the bin while simultaneously
filling the bin.
Drying wet soybeans
In cool, damp years like this one, soybeans harvested with higher moisture content will require supplemental drying from either low-temperature or high-temperature drying. However, care must be taken not to over-dry the beans causing them to split. In most cases, dryers that were designed for corn can be adapted for use with soybeans. Nevertheless, dryers that re-circulate or stir grain constantly should be avoided. Fans sized for corn drying will produce greater air-flow through soybeans resulting in faster drying.
Low-temperature drying guidelines from Iowa State University, University of Minnesota and North Dakota State University:
- Low-temperature dryers should have a full-perforated floor and a fan that can push an airflow of one to two cfm/bu up through the grain. A drying front will develop near the floor and move slowly upward where drying time depends on air flow, weather, and initial moisture content but will probably be three to six weeks.
- To avoid an increase in splitting, do not increase air temperature by more than 3° to 5°.
- Prolonged relative humidity values less than 40% can cause excessive splitting. For every 20° F the air is heated, the relative humidity is cut approximately in half. Therefore, it doesn’t take long to reach a relative humidity < 40%.
- Run the fan continuously until the drying front reaches the top layer of beans or average outdoor temperatures fall below freezing. Turning the fan off when weather is cold will keep beans cold during the winter. If needed, drying can resume when average temperatures climb above freezing in the spring.
- Bigger fans should be installed so that drying can be finished earlier in the fall when weather is better.
- To avoid overdrying and cracking of soybeans, adjust heaters on low-temperature bins for no more than 20° F temperature rise and use an in-plenum humidistat to shut off the heater when relative humidity of the drying air is below 45%.
- Use manual or automatic controls to turn off the fan during periods of high humidity. Fan control will increase the amount of time required for drying, but it will result in drier beans.
High-temperature drying guidelines from Iowa State University, University of Minnesota and North Dakota State University:
- The same drying equipment may be used for both corn and soybean if temperatures are reduced to 120° to 140° F for commercial beans, and 100° to110° F for seed beans to avoid killing the embryo.
- If soybeans are dried too fast or at high temperatures, they may split very easily.
- Beans should be examined as they are leaving the dryer and temperatures should be reduced if too many splits are observed.
- Avoid dryers that recirculate the crop during drying.
- Retention time in a dryer’s heat section should be less than 30 minutes.
- To help avoid excessive moisture differentials from top to bottom in batch-in-bin dryers, shallow batch depths (two to three feet) should be used when drying soybeans. If the bin has the ability to stir, one stir is recommended.
- Cool soybeans that have been dried in gas-fired dryers within a day or so to remove dryer heat. This can be done in the dryer or in aerated storage bins. Stored beans should be aerated again later in the fall to cool them to 20° to 30° F for winter storage.
Storage
As stated earlier, keeping fines or debris out of the bin will help deter mold, disease, and insect invasion during storage. To do this, set combines for maximum cleaning or run the seed through a grain cleaner on the way into the bin. Use grain spreaders to fill bins by frequently moving spouts during bin filling or by coring bins after they are full.
Storing soybean seed at a moisture content that is too high can also result in rotten seed or decreased germination all in just a few days. Due to their higher moisture content, soybeans are more susceptible to spoilage compared to corn. Consequently, soybeans need to be about two points drier than corn for the same storage period. Iowa State University indicates the following moisture contents for different storage periods:
- 13% or less for commercial storage during winter storage
- 12% or less for up to one year
- 11% or less for more than one year
- 12% or less for soybean seed stored one planting season
- 10% or less for carryover seed
After soybeans have been dried to the proper moisture, it is important to make sure the seed is at the suggested winter storage temperature of 20° to 30° F for the upper Midwest. This can be accomplished with aeration fans. The University of Minnesota believes it is best to cool them in 10° to 20° stages as average temperatures drop in the fall. For example, if beans are harvested at 55° F, you could wait a few weeks until average outdoor temperatures drop to 40° F and run the fans long enough to cool all the beans in the bin to 40° F. Then shut the fan off for a few more weeks and repeat the cycle when average outdoor temperatures fall to about 25° F.
After reaching the desired storage temperature, check the bins every two to four weeks during the winter. Check for maintained temperature, mold, insects, and crusting. If temperature fluctuates, the aeration fan can be used during 20° to 30° weather to adjust the temperature. If keeping the soybeans into the warmer season, increase the frequency of bin checks to once a week. If aeration is needed during the summer, run it during the coolest weather available and make sure to keep the soybean temperature less than 60° F.
Sources:
Hurburgh Jr., C. 2008. Soybean Drying and Storage. Iowa State University Extension Publication PM-1636; Maier, D.E., 1993. Grain Quality Fact Sheet #16, Drying Soybeans Requires Special Considerations,. Purdue University. September 28, 1993. Available On-line: http://www.ces.purdue.edu validated 10/21/09.; Wilcke, B., Morey, V., Hellevang, K. 2005. Soybean Drying, Handling, and Storage. University of Minnesota and North Dakota State University. Available On-line: http://www.soybeans.umn.edu validated 10/ 21/09.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible.
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Pannar Seed Inc.
40329 US Highway 14 East
Huron, SD 57350
866-PANNAR1(726-6271) or 605-352-8791
Fax: 605-352-8361
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