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The Y2K Harvest

Tuesday, August 1, 2000
filed under: Harvest/Storage

"Ten Tips for the Storage of Sunflower and Other Grains"

A generally favorable growing season, combined with low harvest prices, has resulted in a lot more calls to Ken Hellevang regarding grain storage.

The North Dakota State University extension ag engineer points out that each farmer's storage situation will be different, depending on crop mix, yield, storage capacity and marketing strategies taken.

Nonetheless, knowing the right steps for grain drying and aeration - and when to employ them -will go a long way toward helping protect the quality of stored sunflower and other grains. Whether storing grain temporarily (less than six months) or for the

longer term, here are 10 tips to keep in mind:

1) Covered is better than uncovered - Manitoba agricultural engineers have studied losses in small grains stored temporarily. While losses in an uncovered outdoor pile ran about 50 percent, losses were only one to four percent with temporary bins set on a plastic sheet and likewise covered with a plastic sheet.

2) Fill existing buildings, but at a safe depth - Pole buildings, empty barns and stud-framed shops or garages can be used for grain storage; but make sure the building location is well drained. If the building hasno concrete floor, place the grain on plastic to prevent moisture from the ground affecting the grain. Even with a concrete floor, plastic is advisable - especially if the floor is cracked and the ground beneath the concrete is moist.

Also, keep in mind most farm buildings are not built to withstand lateral loads, so may need to be strengthened to support grain pressure. (NDSU Extension Bulletin AE-84, "Temporary Grain Storage," has detailed guidelines on using existing buildings. The bulletin is available online at More online grain storage links can be found on page 11).

3) Grain going into temporary storage must be dry - Just because grain is stored for a shorter period doesn't mean drying shortcuts can be taken. Aeration cools the grain to enhance storability, but it is not adequate to remove moisture from grain.

4) Get airflow through the grain pile - "For every 10 degrees we can cool the grain, the allowable storage time is doubled," Hellevang advises. Put another way, the rate of grain deterioration doubles with every 10-degree increase in temperature. "Airflow is critical, and it doesn't require a lot. A little aeration can be of great benefit, and

any is better than none," he observes. The amount of time required for an aeration cooling cycle depends on airflow rate. The cooling time for corn and wheat can be estimated by dividing 15 by the airflow rate. For example, about 75 hours is needed

with an airflow rate of 0.2 cfm/bu. The cooling time for lighter crops such as sunflower can be estimated by dividing eight (8) by the airflow rate. Check the grain temperature at several locations to determine when the aeration cycle is complete.

5) Begin the natural air drying of harvested sunflower ASAP - "If we're able to dry in October weather conditions, when the average temperature is about 47 degrees, natural air drying (i.e., in-storage drying system which uses unheated air vented upward through the grain to dry the crop) works great. In November, however, when the average temperature is 27 degrees, that 20-degree drop in temperature doubles the drying time,"

says Hellevang, who adds that energy costs also are greater when it's colder. "Efficiency and speed of drying will be much less than if we can do it under warmer temperatures."

6) Heat can make sunflower too dry - Some producers who are harvesting sunflower into November add a heater when drying in order to to warm the grain as it dries. The problem is that the additional heat that warms the air by 20 degrees will cut the relative humidity roughly in half. "So instead of drying oil sunflower to around eight- or nine-percent moisture, it will dry to five or six percent, which is too dry," Hellevang explains. "Sunflower that is over-dried tends to shell abit more; and if it's confection, the market might not accept them. You'll also have less to haul to market. If you have 100 pounds of oil sunflower at 10-percent moisture and you dry it down to six percent, now we have only 95 pounds left. You lost five percent of the weight."

7) Target 20-25 degrees for winter storage - "By controlling the grain temperature, we can greatly enhance the storability of grain," says Hellevang. The ideal temperature for insect and mold growth in stored grain is about 80 degrees. Cooling grain below 70 degrees dormant. Mold growth is almost nil at temperatures below 40 degrees. Grain should be cooled to about 20-25 degrees for winter storage. Because about a 20-degree temperature differential in the grain mass will cause moisture migration, aeration should start before the average outdoor temperature is 20 degrees cooler than the grain tempera-ture, Hellevang recommends. "If stored sunflower is at 40 degrees and it's 20 degrees outside, you need to cool down the sunflower in storage to take advantage of the cooler outside environment."

8) Don't go with more fan than you need - More horsepower is needed for drying; less for aeration. A 20-horsepower fan would be needed to dry oil sunflower in a 36-foot-diameter, 25-foot-deep bin; but a 1.5-horse fan would be more than adequate for aeration in a bin that size. "A lot of guys have gone to big fans for drying. But if we're going to be

cooling grain as storage management, those big fans aren't needed," Hellevang remarks. Though large fans are not required for cooling, a large fan can be used to cool 'flowers in just a few hours.

9) Watch for "moisture rebound" in sunflower - A moisture meter can be fooled by sunflower with hulls that are drier than the kernels inside. "The moisture meter will say 10 percent, and all of a sudden you're up to 12 percent again," says Hellevang. "So especially with sunflower, moisture testing is important. Test it, and then come back a day or two later to make sure it's at the temperature you want."

10) Check it - Check the condition of stored grain about every two weeks while grain is cooling, then about monthly after it has cooled. A check should include measurements of moisture content and temperature at several locations. Moisture measurement accuracy is dependent on the grain temperature, so it is best to collect a grain sample, let it warm

to room temperature in a plastic bag or other sealed container, then check the moisture content. Also, be sure to cover fans and ducts prevent snow from blowing into the bins. - Tracy Sayler

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