July 06, 2004

SIUC Country Column: Scientist looks for ways to fight fungi in soybeans

by K.C. Jaehnig

Brian P. Klubek tweaked an old crop management technique to boost its yield potential from 15 to 29 percent, but he's not satisfied.

Klubek will bring charts and diagrams illustrating his work with soybean inoculation to SIUC's annual Farmers Field Day, set for July 15 at the Belleville Research Center. Farmers may talk with him under the big tent before the regular tours begin at 9 a.m. or after they end at 11 a.m.Now the Southern Illinois University Carbondale soil microbiologist is tweaking the tweak, hoping to make it fight fungal disease as well.

Inoculation involves coating soybean seed with bacteria that churn out nitrogen, a mineral the plants need to produce a bunch of beans. This works just fine in fields that have not had soybeans for years, if ever. But in fields where farmers grow beans year after year, other soil bacteria often reach the roots first.

In order to give "his" bugs an edge, Klubek turned to a soil organism that makes its own antibiotic.

"The antibiotic doesn't kill the native bacteria -- it just makes them sick, slows them down a little," he said.

After "breeding" strains of nitrogen-producing bacteria that could tolerate exposure to the antibiotic, Klubek and a graduate student began inoculating soybean seed with both his cream-of-the-crop bugs and the soil organisms -- a dynamic duo that led to some eye-popping yields.

In 2001, the Country Column reported his preliminary results. The following year, a Nashville farmer, who had read the column, asked if he could use the powerhouse combo in a demonstration plot on his own farm.

"The inoculated soybeans out-yielded the other varieties he was testing, even though Ma Nature was not very good to us in 2002," Klubek said.

"He got a 17 percent increase in yield. While most of his varieties were averaging 21 to 22 bushels per acre -- that's how bad it was that year -- the ones he inoculated with my bugs produced something like 28 bushels per acre."

These days, Klubek is looking to add a third inoculant to the mix: a particular kind of root-dwelling bacteria with a number of helpful habits.

"They are reported to enhance or stimulate more rapid seed germination and root development, and they're also reported to be antagonistic to fungal pathogens like SDS, which offers an additional advantage," Klubek said.

This year, he's testing various combinations of two of the bacterial strains he developed in his earlier work, the soil organism and the growth-promoting bacteria.

"As far as I know, we're the only ones using three different organisms in inoculation," Klubek said. "It's a first. It's unique."

He's also adding some ingredients to the inoculant stew -- sucrose, glutamic acid and an organic complex that keeps iron soluble -- all aimed at helping the microbes survive. And, in addition to the bean variety he used in the past, he's using a second variety to see if results obtained with the one hold true for the other.