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Storing sunflower into Summer

Saturday, April 15, 2006
filed under: Harvest/Storage

The business adage about processing supply – “you can’t make all of the corn flakes in one year” – is certainly true of the sunflower industry today. In past years, the crop was crushed in the first five months of the year and the oil was exported. This is not the case in the domestic market these days, for either oils or confections.

The way the market has evolved and looks to continue into the future, growers may be asked and encouraged by contract price to store ‘flowers longer into the summer.

Even if contracts don’t specify this, prices in the open market may compel it, with better profits achieved by storing until prices improve.

However, there are management considerations for sunflower stored into the spring and summer. Sunflower – any grain in storage, for that matter – near the top surface and along the south bin wall will be warmed by solar heat gain. Temperatures in these areas may be much warmer than outdoor temperatures. This can result in problems if the grain went into storage at a higher moisture content then what’s recommended for long-term storage.

For example, Ken Hellevang, extension agricultural engineer at North Dakota State University, talked with a sunflower grower at the onset of spring; the sunflower went into storage last fall at about 12% moisture, had ‘caked up’ at the top, resulting in flowability problems in trying to remove it.

“Assuming aeration is done the way it should be, normally crusting shouldn’t be a problem, especially when we’re normally looking at winter temperatures near or below zero. But we’ve had some warmer temperatures this winter, resulting in some solar heat gain in the bin head space. And if you’ve got sunflower sitting there at 12% moisture, pushing the margins of recommended storage, there could be problems.” Particularly at the top of the grain mass, resulting in a layer of crusting. This can become both a quality and a safety issue.

“Once it does let loose, it comes down quick with a lot of force that can cause injury as well as suffocation danger,” Hellevang says.

A probe or long, lightweight pole probe can be used to break up a crusted surface or grain sticking to the sides of a bin. Beware of nearby or overhead electrical service wires when carrying a long pole into the bin. If working from the top of a bin, consider tying the pole to a rope which in turn is tied to the bin or something else, so you can retrieve the pole if you drop it.

Never stand in the center of a bin that may have been partially unloaded. Grain that forms a crusted layer on top with an open cavity underneath is sometimes referred to as bridged grain. A hollow may develop under crusted grain when it’s is removed from the bin, forming a “bridge” of grain. When the bridge collapses under your weight, you will be buried in seconds. If grain has been removed, but there is no sign of a cone at the top, suspect bridged grain, and do not enter the bin. If you must enter the bin, have someone else on hand outside the bin to assist if needed.

Long-term storage: moisture is key

Sunflower is a late-season crop that is often harvested above 10% moisture, and in fact, harvesting at a higher moisture can have its advantages, such as avoiding bird damage, lodging, or shelling.

Hellevang says sunflower can be stored for short periods at 12% with adequate airflow to keep the seeds cool. However, oil sunflower should not be stored above 10% moisture during the winter and 8% during the summer. Confection sunflower should not be stored above 11% moisture during the winter and no higher than 10% during the summer (better for confections to be closer to 9% or 9.5%).

For growers more familiar with safe storage moisture levels of wheat than for sunflower, Hellevang says a rough rule of thumb is that there’s about a 5 point difference between oil sunflower and wheat. Thus, oil sunflower at 8% moisture is roughly equivalent to about 13% moisture wheat; oil sunflower with 10% moisture would be equivalent to about 15% moisture wheat; and oil sunflower with 12% moisture akin to about 17% moisture wheat.

“Even though ten percent moisture sunflower is often viewed as a market standard, it is roughly equivalent to 15% moisture wheat. Most realize the danger of trying to hold 15% moisture wheat into warmer temperatures. Well, trying to hold 10% moisture sunflower at warmer temperatures is going to be about the same thing.”

In the past, some advised warming grain up in the spring for summer storage – this is no longer recommended. If your stored sunnies were cooled down to the proper temperature last fall, about 20° to 30° F, then there’s no need to do anything further this spring or summer, although it would be wise to check the condition of stored sunflower periodically.

However, if your stored sunflower moisture is higher then what’s recommended for summer storage, then you’ll need to get fans going to dry the grain. In North Dakota, the average temperature in April (about 42º) and average humidity level (around 65%) is about the same as conditions in October, which Hellevang says should work well for bringing stored sunflower moisture down to the optimum level needed going into summer, to limit mold and insect growth potential.

“If we’re looking at the need to dry down sunflower, we should get as much of that done in April as possible, before outdoor temperatures get too warm,” Hellevang says.

Cover fans or ducts after you’re done drying or cooling the sunflower (or if they were left uncovered over winter) to keep warm air from blowing into the fans and ducts. Remember, the goal is to keep the stored sunflower cool, not to let it warm up.

As outside temperatures increase in the summer, monitor for insect activity. When the top surface warms to temperatures exceeding 70°F, operate fans periodically for a few hours during cool summer mornings, pushing air up through the bin, to cool sunflower near the top of the bin to reduce the potential for insect infestations. “Then, cover up the fans and ducts again to keep the grain cool.”

Colorado State University extension agronomist Ron Meyer says the same advice applies to storing sunflower into the summer in the High Plains. “Actually, we usually have a lot less storage problems than our northern neighbors when it comes to moisture,” says Meyer. “Our falls are so warm and dry, we’re often taking 6% moisture seeds and it’s rare for us to be binning seeds above 10% moisture here. It does happen, and we do recommend harvesting early and putting air to them just because we can dry them so easy here. But lots of times we’re below 10% moisture by the time we get the seeds in the bin.”

Still, it’s a good idea for even High Plains producers to look in on their ‘flowers before summer. “Just to make sure you don’t have a hot spot going on,” Meyer says.

Consider a fumigant if needed (check to see if it’s permitted for sunflower under contract, or if there are any product or application restrictions). Hellevang notes that a certain temperature is needed for a fumigant to work successfully. The bin needs to be well ventilated after fumigating to remove all the fumigant to prevent a health hazard to grain handlers. In most cases, a fumigant is a restricted-use pesticide that is professionally applied. NDSU’s 2006 Crop Production Guide lists aluminum phosphide (available under trade names such as Fumitoxin and Phostoxin) as a fumigant labeled for sunflower seed. – Tracy Sayler

Online Resources for Grain Storage Information (search publications for “grain storage”) (NDSU Field Crop Insect Management Guide – scroll down to ‘fumigants’ link)

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