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Piggyback Soybean Cyst Nematode Sampling With Fall Fertility Sampling

It’s a great first step in managing SCN-resistant soybean varieties that resist SCN.

Hopefully, one of these days the skies are going to clear in rain-deluged areas so farmers may harvest their soybeans. When that happens, a good follow-up step later this fall is to double up while pulling soil fertility samples. 

“It’s also a great time to pull soil samples for soybean cyst nematode (SCN) testing while you’re in the field,” says Sam Markell, North Dakota State University plant pathologist and leader of The SCN Coalition.

It’s the first step in actively managing SCN resistance, which is a growing problem for many soybean farmers, whether they realize it or not.

“With research showing that SCN populations are becoming resistant to the source of resistance (PI 88788) used in 95% of commercial soybean varieties, farmers can no longer assume that planting an SCN-resistant variety is controlling this pest,” Markell says. “That’s why the SCN Coalition recommends that farmers know their nematode numbers.” (Find a short animation showing how the SCN problem evolved here.) 

Since soybean boards in several states offer free SCN soil testing, it may cost little to nothing to test your fields, so you know your numbers. The following states offer soybean farmers free SCN soil testing: Arkansas, Michigan, Minnesota, Nebraska, Ohio, South Dakota, Tennessee, Texas, Virginia, West Virginia, and Wisconsin. 

“This list isn’t exhaustive, so check with your state soybean board,” Markell adds.

In states that don’t offer cost assistance, SCN tests generally cost $1 to $2 per acre. “The yield loss potential is $10 to $20 per acre, so testing makes economic sense,” he continues. “You can have yield losses of up to 30% from SCN with no above-ground symptoms.”

Fall is a perfect time to sample fields where soybeans were grown this year, as well as fields planted to corn in 2018 and slated for soybeans next year. “You’ll get information on this year’s crop, as well as data to help you make management decisions next spring,” says Markell. 

A similar sampling process

The SCN sampling process is similar to soil fertility sampling. Use a soil probe that’s a 1-inch diameter tube. Collect 20 cores or more from 6 to 8 inches deep.

“We’d like cores collected either in a zig-zag pattern, or you can pull cores from high-risk areas in the field,” Markell says. “Those include entryways, high soil pH areas, low spots, and areas that have previously flooded, as well as areas in the field with unexpectedly low yields that you can’t explain.” Put the cores in a bag and mail them to private or public testing labs.

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