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Tips for gauging sunflower drydown

Sunflowers can be a tricky crop to harvest. They’ve got to be dry (9% to 10% moisture is ideal for storage), but if they get too dry, heads can start shelling out, and there’s the risk of fire when you combine.

How can you gauge when it’s time for harvest, or if you need to apply a desiccant to aid sunflower drydown? The first step is to monitor maturity and moisture across the field.

“You’ve got to get a good cross section from the field. Go into four or five different areas of the field and test the moisture on a variety of heads — 10 inches, 8 inches, 4 inches,” says Max Dietrich of Benchmark Seeds Inc., an independent distributor of Pioneer seed products.

The sunflower plant is physiologically mature when seed moisture is about 32%. This usually occurs about 30 to 45 days after bloom, and when the head turns brown on the back, seeds are usually ready for harvest.

Dietrich says as the bracts curl and turn brown, they are an indicator that seed moisture is drying down, but he says the only way to accurately determine seed moisture is to shell out several seed heads from around the field. He says, “Looking at the plant will not tell you what the seed moisture is because some hybrids stay greener longer than others.”

Desiccant decisions

Should you apply a desiccant to help the drydown process? That’s a decision that really hinges on weather. “In cool weather a desiccant may not work as well; the drydown can be slower and the stalk rubbery,” says Kent McKay, a technical service representative with BASF.

On the other hand if it’s going to be hot, a desiccant might help you get to harvest stage faster. McKay reports that applying Sharpen to a sunflower crop mid-September followed by 90-degree-F weather produced beautiful results. “So you really need to watch the weather,” he says.

Research has shown harvest can occur as much as 10 days earlier in North Dakota with the use of a desiccant. Research results were not as significant in South Dakota or Kansas, where the numbers indicate no difference to a seven-day-earlier harvest with use of a desiccant.

Labels specify desiccating at less than 36% seed moisture for Sharpen and other labeled products. Research indicates spraying too late when seed moisture is under 30% does not provide much advantage in earlier harvest compared to the control of “no desiccant.”

The 2010 harvest season was the first year the Sharpen desiccant was available. In 2011, its label was revised to include more water in the mix — changed from 3 gallons per acre to 5. And the adjuvant rates and application timing are being studied again this year, with some changes anticipated for 2012, according to McKay.

McKay says a desiccant can be especially useful in situations where blackbirds are a problem.

“Time is money if you’ve got blackbirds feeding out there, so put it on at about 36% moisture, and it may help you get the crop harvested quicker.”

Gordon writes from Whitewood, S.D.

This article published in the February, 2012 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.