Researchers explain the science behind coated seeds
The trend of increasing seed treatments means farmers will have fewer products to apply at the planter.
Treated seeds epitomize the old adage that good things come in small packages. Applying a layer of chemicals and biologicals on corn, soybean and other row-crop seeds shields them from diseases and pests in the early stage of growth and pushes yields higher.
"The fungicide treatment is kind of cheap insurance," says Mike Cerny, who farms near Walworth, Wis. That’s because the treatment protects newly emerged soybeans in soils that are wet and tight.
Like a package, while wrapping options are virtually limitless, the space in which researchers can work is finite, experts say. As a result, farmers can expect seeds to be wrapped in new treatment mixes that offer an increased spectrum of activity. Treatments will be applied more precisely and with smaller chemical doses.
"The trend is to continue to have fewer products that the farmer has to apply at the planter," says Mark Miller, U.S. seed treatment application lead for Monsanto Company.
To understand where treatment mixes are headed in the future, it’s important to know a little bit about seed biology, treatment activity and environmental stewardship.
First, seed coats can only handle so many treatments.
"There is a limit of 8 oz. per cwt. of the total mix (seed treatment, water, etc.) that can be on soybeans since the seed coat of the soybean is less absorbent than other seeds," explains
Emmanuel Byamukama, South Dakota State University Extension plant pathologist. "Corn is similar to soybeans. In wheat, since it is a little more absorbent, it can take 10 oz. per cwt. to
12 oz. per cwt. total mix without the seed becoming slimy and the seed treatment not sticking
to the seed."
Protection threshold. While technology exists to apply treatments to a seed in layers, says Miller, most Monsanto treatments are applied after being mixed together. Corn is packaged with three fungicides, an insecticide that’s strength is selected by the purchasing grower and polymers that bind the treatment to the seed. Each contributes to what he calls the "total load" that a seed can support. Soybeans get three fungicides—different from those used on corn—and producers can choose to add an insecticide and a nematicide.
Seed retailers can manage active ingredients in treatments down to the milligram per seed using a touchscreen control panel, Miller says. That wasn’t possible 20 years ago.
In general, high loading seed treatments account for 0.5% to 1% of the total seed weight, says Bill Hairston, director of product development for SeedGrowth at Bayer CropScience.
- Seed Guide 2013