Engineering Notes Index

Minnesota/Wisconsin Engineering Notes
Spring 2000

Conditioning Soybeans for Seed

Bill Wilcke, Minnesota Extension Engineer

A number of farmers are interested in conditioning soybeans from their 1999 crops for use as seed in 2000. Here are some soybean seed conditioning tips gleaned from a variety of articles and extension bulletins and from the Iowa State University Seed Science Center.

• Make sure that you are not violating an agreement with the company from which you bought the 1999 seed, or that you are breaking some other seed law by using soybeans from your bins or your neighbor’s bins.
• Avoid using seed from fields that had disease problems that might be transmitted with the seed.
• Conduct a germination test before going to the trouble and expense of conditioning soybeans for seed.
• There are a number of custom seed cleaning operations in the region and it might be worth hiring them to condition soybeans for you. Late winter can be a busy month for seed handlers, however, and it might be difficult to get on their calendars.
• Normal grain augers, which have steel flighting, can cause a lot of seed splitting, seed-coat damage, and germination loss. If you must use steel augers when you move seed beans, run the augers slow and full. Pneumatic conveyors can also cause a lot of damage to seed; if you use a pneumatic conveyor, adjust the air to seed ratio for minimum damage and avoid bends—especially sharp ones, in the tubing. Also, avoid use of centrifugal bucket elevators (ones that operate at high speed and throw material from buckets at the top of the elevator). Belt-type conveyors and augers with nylon bristles attached to the outer edge of the flighting cause less damage to soybean seed than other types of conveyors.
• High-speed impacts damage seed and reduce germination. Minimize rough handling and long drops when moving beans and try to limit the number of times that beans are moved. Flow retarders in down spouts and bean ladders in storage bins can reduce bean velocity and damage during bin filling. Avoid use of mechanical grain spreaders during bin filling because spreaders sling seeds at high velocity and cause more impact damage.
• More seed damage and germination loss occur when soybeans are handled at moisture contents below 10% moisture (wet basis). Seed damage tends to be lowest when beans are handled in the 11 to 14% moisture range. Beware though, that mold damage can occur when soybeans are stored above 12% moisture during warm weather.
• More seed damage and germination loss occur when soybeans are handled at low temperatures. A study at Iowa State University showed greater damage to beans handled at 17° to 26°F than at 65°F. If stored soybeans are much colder than 50°F, it might be worth aerating them with 40° to 60°F air to warm the beans before they are unloaded from the storage bin and conditioned. Be careful, though, because condensation occurs when cold seeds are aerated with warm, humid air; make sure the fans run long enough to move the warming front all the way through the bin and re-evaporate the condensed moisture.
• If you are only going to use one piece of seed conditioning equipment, the air-screen cleaner appears to be the best machine to use for soybeans. The glossary in an extension bulletin on seed conditioning says that an air-screen cleaner “separates seed on the basis of size, shape, and density; uses multiple screens to first scalp the seed and finally grade it; and contains fans to remove light, chaffy material.” Additional equipment that is sometimes used in soybean conditioning includes spiral separators, gravity separators, and aspirators.

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