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Lower prices point toward more soybeans in storage

WITH A LARGE SOYBEAN crop expected in the South proper grain handling will be needed to protect farmersrsquo soybean investment
<p>WITH A LARGE SOYBEAN crop expected in the South, proper grain handling will be needed to protect farmers&rsquo; soybean investment.</p>
With the South&rsquo;s high temperatures and humidity, proper drying and handling are needed to protect stored soybeans against mold and insect damage. Moisture content and temperature are the two key factors that impact the safe storage of soybeans.

With 2014 harvest prices the lowest in years, expect more soybeans to go in the Commodity Credit Corp. loan, as growers wait on possible market rallies.

And it’s important to make sure those beans are handled and stored properly to meet the quality demands of buyers if prices do trend higher.

In southern production areas, that means drying beans to as low as 11 percent moisture, if possible, then aerating and handling them according to how they’ll be used.

With the South’s high temperatures and humidity, proper drying and handling are needed to protect beans against mold and insect damage, says Paul Sumner, retired University of Georgia agricultural engineer.

“Moisture content and temperature are the two principal factors that impact the safe storage of soybeans,” Sumner says.

“The amount of moisture in soybeans determines whether or not mold damage will occur. The higher the moisture and temperature, the faster mold growth and the more rapid the spoilage of soybeans will occur. Insect damage is also less in dry stored soybeans.”

Cooling a great benefit

Low temperatures offset the effects of high moisture, he points out.

“Cooling is one of the greatest benefits gained from moving and turning soybeans in elevators,” Sumner says. “This can be accomplished more effectively by aeration, which cools soybeans so damp beans can be held in storage for weeks or even months.”

The ability to dry soybeans enables growers to harvest the crop as soon as beans are ripe and mature. And this can avoid field losses.

“Soybeans should be harvested promptly when they are mature in order to reduce field losses and lessen chances of damage from bad weather,” Sumner says. “With adequate drying methods, soybeans can be harvested at a moisture content as high as 20 percent.

When drying from 20 percent to a safe moisture content, “a large amount of water must be removed, increasing the cost of the drying operation.

“High moisture grain loses this moisture rapidly in the field. So, for maximum returns, soybeans should be harvested when they have reached approximately 14 percent to 16 percent moisture content.”

Equilibrium moisture content 

Moisture evaporation requires heat energy that is normally supplied by air forced through soybeans. As airflow continues upward from the bottom of the storage facility, more of the soybeans begin to dry.

“A layer known as the drying zone is formed,” Sumner says. “The drying zone continues to move upward through the wet soybeans until it is passed through the surface layer.

“Relative humidity of the drying air determines the moisture to which grain will dry. At a given temperature and relative humidity, there is a corresponding moisture content below which grain will dry no more. This property of grains is referred to as the ‘equilibrium moisture content.’”

The final use of the grain should be considered in order to determine the safe maximum temperature of the heated air for drying any grain.

“For soybeans to be milled for oil, and those to be used for food, the temperature in heated-air batch driers should be limited to 130 degrees F,” Sumner says. “Soybeans to be used for seed should not be exposed to air over 110 degrees.

“The greater the moisture content of the soybeans, the greater the air flow required per bushel to dry beans to a safe moisture content before mold can set in.”

Iowa State University’s ag engineering specialists point out that soybeans are more fragile than corn, and can easily be damaged in the drying process.

Cool beans after drying

Beans can be damaged by air that’s too hot or too dry, as well as by rough handling, the ISU specialists say.

Soybeans have about 25 percent less airflow resistance than shelled corn, so fans sized for corn drying will produce greater airflow through soybeans, which means faster drying.

Sumner says soybeans should be cooled immediately after drying is completed. Aeration keeps the grain at a uniform cool temperature, which prevents “top sweating” in the top layer of grain in the center of the bin.

“Cooling should be repeated every two months during winter and once in spring on a cool, dry day,” he says. “After each cooling, all openings to the plenum under the floor should be closed and a tight cover put over the fan inlet to prevent any outside air circulating through the grain.”

The air can be forced up through the grain, as in drying, as long as condensation doesn’t occur on the bin roof.

It’s not always necessary to pull the air through the grain, as in aerating grain with smaller fans — in which case pulling is essential, Sumner says.

Avoid mechanical injury to seed

Also, mechanical injury to soybean seed should be avoided to prevent a reduction of germination and vigor.

“Injury to soybean seed results primarily from impacts of the seed with hard surfaces or other seed,” Sumner says.

“The extent and severity of mechanical damage are related to the moisture content of the seed, the velocity of the seed at the moment of impact, and the degree of hardness of the impacted surface.

“A single 10-foot drop of seed with less than 12 percent moisture against a metal surface can reduce germination by as much as 10 percent to 15 percent. Seeds with 14 percent or more moisture are relatively unaffected by impacts resulting from drops as high as 20 feet.”

Soybeans for use other than seed are also affected by dropping into a bin if moisture content is too low. A certain amount of splitting will occur each time they are dropped. Soybeans should be handled as little and as gently as possible.

Check grain weekly

Regular inspection will help identify problems before they get out of hand, say ISU specialists. When checking moisture of binned grain, use a 6-foot or 10-foot probe to collect samples from various depths. Go as deep as possible in the bin at several locations.

Don’t mix samples, because knowing the moisture content at different locations can help you find the drying front in drying bins or the trouble spots in storage bins, ISU says. If you don’t have a probe, at least take some samples at arm’s length below the surface.

For more on soybean and other grain drying and storage, contact your local or regional Extension agricultural engineer or agronomist.

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