Research Highlights

Exploring Desiccant Usage for Better On-Farm Decision Making

In this article, you’ll find details on:

• This Science for Success project looks at desiccants, or harvest aids, to improve yield in the South and whether they are feasible to use in the North.
• Extension Soybean Specialists are comparing desiccant application timing and maturity groups for best management practices.
• When finished, these trials will provide two years of data gathered from 14 states so farmers can adapt desiccant usage accordingly. 

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By Carol Brown

For the most part, crop farming is the same across the country, but there are distinctions depending on the crop and the geographical location. Some crops grow better in certain areas, some fields need irrigation to achieve a good yield, and some soils need additional inputs such as fungicides or herbicides for crop success. 

Using desiccants or harvest aids, for example, is almost a given practice in southern states but nearly unheard of in the North. Soybean extension specialists have received some farmer inquiries about these products, which led the Science for Success group to address them in a project that explores the impact of desiccation use and harvest timing. 

Science for Success is funded by the soy checkoff at state and regional levels and supports several projects annually that involve numerous states and researchers. Most projects use identical trial protocols so researchers from the participating states can amplify local findings and evaluate regional differences. However, the desiccant project is slightly different as it differs in protocols between northern and southern states.

“Farmers in the South use harvest aids as a way to speed up soybean harvest while keeping seed quality high,” says Shawn Conley, Wisconsin state soybean specialist and project leader. “We are taking this opportunity to look at harvest aid use to maximize yield and help farmers manage their fields in a timely fashion.”

The 2024 crop season will be the first fully funded year for this Science for Success project. In the previous crop season, some researchers conducted preliminary trials, supported by their respective state soybean organizations, to learn safe handling and to establish protocols for this year.

Southern Project Goals

The southern soybean specialists are exploring soybean varieties and maturity groups with desiccant application timing to see what combinations work best. 

“One of the things we’re looking at in the South is whether a harvest aid can preserve any seed quality and how harvest aid use may impact commonly grown maturity groups,” says Michael Plumblee, Extension soybean specialist at Clemson University in South Carolina. “In our trials, we’re looking Maturity Group 4 (indeterminant), MG 5, which could be determinant or indeterminant, and MG 6, a determinant variety. Among the two protocols, we are exploring different harvest timings within these maturity groups as well as the maturity group combinations with and without a harvest aid.”

In the Southeast, where Plumblee is located, farmers are interested in MG 4 soybeans, but they haven’t experienced the same success as those in the mid-south and southern states. MG 4 soybeans don’t do as well when left in the field to dry down naturally to 13% moisture for harvest, Plumblee says, therefore using a desiccant is a given. 

“We’ve learned there isn’t a big yield advantage from using the early maturity groups as opposed to using determinant varieties. In normal production conditions, there may be some exceptions in certain high yield situations,” Plumblee says. “We want to learn if it is worth the risk yield-wise if we use an MG 4 and a desiccant, or plant an MG 5 and not use a harvest aid.”

Northern Project Goals

The goals in the northern states are to study different timings of desiccant application to determine if harvest timing can be hastened without decreasing soybean yield. 

In Minnesota last year, Seth Naeve conducted desiccant trials funded through the Minnesota Soybean Research Promotion Council. He is the state soybean specialist and an agronomy professor at the University of Minnesota, and he is continuing the work this year with the Science for Success group. His results from 2023 illustrate the importance of desiccant application timing. Soybeans had a yield loss between 20 and 30% when a desiccant was applied at R6, approximately 20 days before maturity. When he applied a desiccant at R6.5, yield was reduced between 5 and 10%. Desiccants applied at R7 did not affect yield.

Conley says that last year in Wisconsin, he used a desiccant that also caused yield loss. Additionally, the product didn’t hasten harvest timing as they applied it too early. This year, he is trying different harvest aid products to hopefully find more effective options. 

“The product we tried last year works fine in the southern states, but we just don’t have the heat in the North to make it work as well,” Conley remarks. “If other products don’t work well again this year, the research may reinforce the idea that desiccants just don’t pay in the North.”

Desiccant Benefits and Drawbacks

Farmers in the South have more “pros” on their desiccant usage list than “cons.” 

“These harvest aids help the soybean crop to reach harvestable conditions faster. In the South, we often make management decisions to mitigate risk whether it’s drought, nematodes, insects, disease, or hurricane season approaching,” says Plumblee. “In this case, we want to keep soybean quality as high as possible at harvest. Desiccants could help us get the crop out of the field quicker to preserve seed quality.”

In the northern states, farmers are using a wide variety of maturity groups, depending on their cropping goals, and there are advantages to using desiccants that can help their production systems.

“Those who plant early soybean varieties may want to get a cover crop planted or put manure on their fields in the fall,” says Naeve. “Using a harvest aid can hasten the soybean development to get those applications done. Or if farmers are delayed in spring planting, a desiccant can help push the maturity before a hard freeze can do damage.”   

There are also drawbacks to using harvest aids. Higher soybean maturity groups that are grown in northern states are indeterminate plants, which continue to add yield up until harvest. There is a greater risk of losing soybean yield in the North when using a desiccant, Naeve says. 

“In the northern states, farmers aren’t as accustomed to making as many trips across the field as the southern farmers. Adding another application creates more expenses with product and fuel costs,” Conley says. “Northern farmers also have larger fields, meaning more acres to cover with each input.”

Plumblee also points to economics when considering desiccant drawbacks. They must consider the cost of the product as well as the applicator fees if they don’t apply it themselves. They need to consider safe chemical handling as well. 

Timing May Be Everything

The researchers agree that timing of desiccant application is crucial no matter where the geographic location. Spraying too soon can impact yield and spraying too late doesn’t allow the product to work fully. 

“In the South, when the harvest aid was sprayed too early, we left yield on the table,” Plumblee comments. “We probably lost 10 to 15% yield by spraying at the wrong growth stage. I think it’s important that farmers know how to check growth stages correctly to ensure that harvest aid applications are not limiting yield. This is something we will continue to look at in our research.”

States involved in the Science for Success desiccant study: 
Alabama
Arkansas
Georgia
Illinois
Iowa
Kentucky
Louisiana
Michigan
Minnesota
Mississippi
North Carolina
Ohio
Pennsylvania
South Carolina
Wisconsin

Published: Sep 9, 2024