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The Cost of Moisture Shrink

Wednesday, September 1, 2010
filed under: Harvest/Storage

Shrinkage is a desirable development when it involves your waistline. But when it brings the moisture of your market-bound sunflower seeds down below 10%, it’s costing you money.

Sunflower producers know that harvesting their crop at moisture levels below 10% can be detrimental in at least three ways. First, it likely will result in more shattering and seed loss at the header. Second, if low enough (7-8%), it will increase the risk of combine fires. And third, a low-moisture crop will weigh less than a 10% or higher one, meaning fewer dollars at the marketplace.

It’s thus another reason, too, not to overdry seeds beyond what is prudent for short- or long-term storage, depending on your market timing intentions.*

Some shrinkage takes place at the elevator or other delivery site. Foreign material aside, there inevitably is a certain amount of handling loss (spillage, dust blowing off the piles, etc.). These are items over which the producer has no control, and they’ll vary from site to site. The elevator typically factors in such shrinkage into its handling charges.

But then there is “moisture shrink.” This term refers to the weight loss in grain resulting from the drying of that grain down to a particular moisture content. Moisture shrink is a straightforward number, points out North Dakota State University extension ag engineer Ken Hellevang. “We have an equation that tells us that if we remove a given quantity of water from our grain — be it sunflower, wheat or corn — we’ll have a certain weight loss associated with it. That weight loss is what we call ‘moisture shrink,’ ” he notes.

Table 1 on the following page shows the percentage reduction in weight — a constant value — based upon the final moisture content of the grain. Table 2 indicates the actual pounds one loses (or gains) at crop moistures below and above 10%. (See separate PDF file for website article.)

“If working with sunflower, whose market standard is 10% moisture, the shrink is going to be 1.111% for every point of moisture removal,” Hellevang points out. “If we take off five percentage points, we know our shrink will total 5.555%.” So drying 100 pounds of sunflower seed at 15% moisture down to 10% would result in a cumulative moisture shrink loss of 5.56 pounds, for a net seed weight of 94.44 pounds.

Hellevang advises producers to familiarize themselves — in advance of harvest — with their elevator’s shrink and other discount policies. And remember, he says, that while moisture discount schedules can vary from elevator to elevator (and also from date to date at the same facility), “moisture shrink” is a constant value. — Don Lilleboe

• Ken Hellevang points out that though the market moisture content is 10%, oil sunflower seed will need to be at 8% moisture content to safely store through summer. Storing 10% sunflower during the summer would be similar to storing 15% moisture wheat.

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