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Is Desiccation Right for Your Farm?

Friday, August 21, 2020
filed under: Harvest/Storage

Reduced risk and losses are only a couple of reasons sunflower growers use desiccation as a harvest aid.

Using a desiccant on a sunflower crop can decrease a grower’s losses due to inclement weather, lodging and bird depredation, as it will speed up the drydown process, says Alison Pokrzywinski, Nuseed Sunflower Product Development Manager for North America.  However, desiccation as a harvest aid is underutilized in sunflower production, she adds.

“If a grower doesn’t desiccate, then they are at the mercy of Mother Nature, waiting for a hard frost to kill off the plants or natural drydown.  Sometimes growers are waiting until October or November for that to happen.”

According to Pokrzywinski, there are three important reasons growers should consider desiccating their sunflower crops prior to harvest: disease, unknown fall weather variables and blackbirds.  For example, if a crop is experiencing late-season stalk disease, getting it off as soon as possible will prevent further stalk damage.

Producers will also have peace of mind the earlier the crop is in the bin and not at the continued mercy of late-season environmental conditions.  This past year, 2019, was a prime example, where 24 inches of snow fell on some fields in the Northern Plains in early October.  

Additionally, blackbirds can settle into a field two weeks after petal drop, and once established, are hard to get rid of. Thus, getting the crop off earlier is the best solution to this difficult problem.

“Sunflower can get hit by a lot of issues in the fall, whether it’s disease, blackbirds, wind or rain.  Growers need to consider the maturity of their crops and how far from harvest they would be if they don’t desiccate,” says Pokrzywinski.
Growers who desiccate also have more control over harvest timing, and desiccation also helps even out moisture levels before harvesting, she adds.  “If you plant on the earlier side, you should automatically put desiccation into your budget.”
Maturity & Drydown
It’s important for growers to understand the maturity and drydown of their hybrids and that they sometimes don’t go hand in hand.  An early season hybrid with good late-season plant health or stay green is not necessarily going to have good drydown and vice versa.  And a fuller-season hybrid could dry down really well, depending on the hybrid.

“This is where desiccation can be important.  A medium-maturity hybrid with good late-season plant health may not look like it’s ready, but all the indicators for maturity are there and you can desiccate.  However, if you wait for Mother Nature, it could take a while.”

But desiccation is not for everybody and it’s not for every farm, adds Pokrzywinski.  For example, growers in South Dakota, who plant around June 20, likely aren’t going to desiccate—by the time the crop is mature enough for desiccation, fall has set in and the temperatures are much cooler, or it’s close to a killing frost.

A sunflower crop planted early in the season may be mature by the end of August.  In this case, desiccation is advantageous for growers because the crop can be harvested early and put in the bin before the elements or blackbirds decrease yield.

Waiting for a crop like this to dry down naturally, or for a killing frost, may take a long time, during which the sunflower is vulnerable.  Sometimes growers are waiting until October or November for a hard frost to kill off the plants, adds Pokrzywinski.
Desiccant Timing & Products
Desiccants can be applied to the crop once plants have reached physiological maturity.  At this stage (R-9), the back of the head turns yellow, the shoulders of the bracts turn brown, and seed moisture is about 35%.  Applying desiccant before physiological maturity may reduce test weight and seed quality.

Growers can often desiccate earlier than they realize, says Pokrzywinski, especially if the weather is sunny and warm. She recommends growers check their fields often under these conditions as their crops may be ready to desiccate.

Desiccation products for use on sunflowers include glyphosate; Gramoxone (paraquat), which is known as Reglone in Canada; Drexel Defol (sodium chlorate), which is only registered in the United States; Sharpen (saflufenacil), which is known as Heat in Canada; and Valor (flumioxazin), which is only registered in the United States.  Always follow registered uses on the product label, Pokrzywinski emphasizes.

One of the big differences among desiccation products is speed.  Usually growers can start harvesting about three weeks after applying glyphosate.  Alternatively, products like Gramoxone and Drexel Defol work faster, allowing growers to harvest about 10 days after application.

Another important difference between products is Gramoxone and Drexel Defol will remove the waxy layer on the back of sunflower heads, whereas glyphosate will not.  This waxy layer prevents water absorption into the head if it rains.

“If you get rain a couple of days after spraying, the sunflower head is going to absorb water and you could be waiting longer to harvest than if you hadn’t sprayed,” says Pokrzywinski.

Growers can typically harvest sunflower 10 to 14 days after applying a tank mix of Sharpen and glyphosate, she adds.

When considering desiccation as a harvest aid, growers should factor in planting date, weather, typical hard frost date and market.

“You have to weigh your odds on what the weather’s like, your potential for a hard freeze, when you planted and how much time you have.  For example, are you going to be waiting for a hard frost for 30 days or more?” asks Pokrzywinski. “The other part to consider is what the price of the crop is, and what market you’re going into.  Those in a higher value specialty market, like confections, want the highest quality to get the best price they can.”                                
Desiccation Fast Facts
  • Growers can harvest earlier with the use of a desiccant.
  • Physiological maturity (R-9) must be reached or test weight and seed quality will be reduced.
  • Apply desiccant when seed is at 35% moisture or below, or when bracts are turning brown.  This can be difficult to determine exactly as most hybrids are now the “stay green” type.  Thus, hybrids often have dry seed in the head but have the coloring of an immature plant.
  • Growers with later plantings likely don’t require desiccation.  For example, a June 20th planting in South Dakota would likely be close to a killing frost by the time the crop is mature.         
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