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Desiccation: The ’08 Experience

Thursday, January 1, 2009
filed under: Optimizing Plant Development/Yields

By Don Lilleboe

Assigning a letter grade to the 2008 Northern Plains experience with sunflower desiccation is difficult, if not impossible. It truly was a case-by-case scenario, with the results largely depending on one factor: timing. For those growers fortunate enough to get their desiccant applied and working before the wet autumn weather set in, the experience commonly graded out as an “A” or “B.” But for those whose timing was not as fortuitous, the report card more than likely registered a “C,” “D” — or perhaps even, gulp, an “F.”

“It was all over the board,” affirms Breckenridge, Minn.-based Mycogen Seeds agronomist Bruce Due. “There were some growers [for whom] desiccation worked very well. There were some [for whom] it didn’t work at all. And, there were some who said, ‘I’ll never do that again!’ ”

Good intentions often fell victim to Mother Nature’s decision to soak and delay the 2008 row-crop harvest across much of North Dakota and northwestern Minnesota. Due, for instance, advised one north central North Dakota grower, whose fields were beginning to lodge, to apply Gramoxone® in an effort to get the ’flowers off before the lodging got worse. “The forecast at that time sounded pretty good,” Due recalls. “Well, he put Gramoxone on — and three days later the rain moved in.” By the time his neighbors had finished their harvests, this grower’s crop was still sitting in the field at 20% moisture. Due did not receive a Christmas card from him in December.

At the same time, Due refers to another grower, located in northeastern North Dakota, who treated his entire sunflower acreage with Gramoxone — and ended up harvesting a crop whose moisture was low enough that he didn’t have to run any of the seeds through the dryer. “So he’s thinking he made a smart decision” by desiccating, the seed company agronomist remarks.

After a positive experience in 2007, quite a few Northern Plains growers applied preharvest glyphosate to their 2008 ’flowers as well. Glyphosate products are labeled for “weed control” only, not for “desiccation.” But since the herbicide works on a sunflower plant similarly to the manner in which it works on weeds, the effect is the same. And as long as the sunflower is physiologically mature, there is no yield loss. The bottom line, under suitable environmental conditions, is a faster plant drydown and earlier harvest.

Again, though, “a suitable environment” proved elusive for many producers last fall. Mike Clemens of Wimbledon, N.D., hired glyphosate applied to his first field on September 24. “I wanted to get it done during that time frame because there were about five days that were pretty warm and dry,” Clemens says. “I knew if I was to wait a week, the the temperature would be down around 50 degrees. At that point, I could just as well wait for a killing frost.”

A prolonged cool, wet spell — coupled with the absence of a killing frost until late October — resulted in Clemens not being able to harvest that field until a month after the glyphosate treatment. Still, he thinks the treatment “bought me about a week of time.”

Will he desiccate again in the future? “If I can spray in early September, it certainly would be an option to consider,” Clemens says. “But the closer we get to October, the less excited I am about it.”

Bruce Due says one of the problems with using glyphosate for sunflower desiccation purposes is the fact that the label states the plants must be physiologically mature (e.g., 35% seed moisture or less) for application. “But the only way glyphosate is taken up is for the plant to be actively growing,” he points out. “If the plant is ‘physiologically mature,’ there’s no reason for that plant to grow any more; it’s time to die.”

Glyphosate did do the job for northeastern Colorado grower Doug Imhof in 2008. To qualify for crop insurance, the Haxtun area grower needed to get his winter wheat planted by no later than October 15. That meant getting his irrigated confection sunflower acreage harvested earlier. So Imhof applied 22 oz/ac of glyphosate (Roundup) when the sunflower seed moisture was around 28-30%.

Dave Crossland, Imhof’s landlord and the person who drilled the ensuing winter wheat crop, says they harvested those ’flowers about two weeks sooner than some nearby fields that were not desiccated. “I figure we got almost 20 days earlier planting on that wheat, which is critical,” Crossland says. The glyphosate also took out some weed pressure (cocklebur, Canada thistle and grasses), “so it was a ‘double bang,’ ” he adds.

Gene Kleve of nearby Holyoke had a positive experience with sunflower desiccation as well this past fall — though he used Gramoxone instead of glyphosate. Like Imhof, Kleve’s primary motive was to get his confection ’flowers off earlier so he could drill winter wheat in time to beat the October 15 insurance cutoff. Spring rains had delayed his sunflower planting, and the crop’s development lagged accordingly. Kleve chose to use Gramoxone because he believed it would work faster than glyphosate — “and the cost wasn’t that much different.”

Kleve’s sunflower was sprayed when the seeds were around 30% moisture. “After 48 hours, [the plants] were brown,” he says. The field was harvested within one and a half weeks following the treatment, and he got his wheat in the ground in time to qualify for insurance. He would not have made it without the desiccation treatment, he remarks.

As an added bonus, “I think we actually tricked the birds,” Kleve chuckles. About two weeks after the sunflower field was harvested, blackbirds showed up in droves. They ate whatever seeds were left on the ground; but their missed timing cost them what would have been a much bigger feast.

Mike Bretz, agronomist with SunOpta Sunflower at Goodland, Kan., says his company neither encourages or discourages the desiccation of sunflower. He does understand why some growers choose to use the practice. For those who double-crop ’flowers after wheat, it’s a way to get the crop harvested earlier — especially in the absence of a killing frost. For those producing full-season sunflower (like Imhof and Kleve), it’s the best way to get the sunflower off in time to plant winter wheat on that field.

While he’s aware of more fields being treated with Gramoxone than with glyphosate, Bretz agrees that the High Plains environment — typically warmer and drier in the fall compared to the Northern Plains — makes glyphosate a good option for some sunflower growers.
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