A fresh look at preplant soybean management strategies may offer more yield potential. The top two student teams in last year's Illinois Soybean Association (ISA) yield challenge harvested a few more bushels by stressing root health and amending the soil.

"Ironically, the Gallatin County High School FFA in far southern Illinois near Junction, and the Heyworth FFA chapter from central Illinois both evaluated newer preplant variables in their plots for greater yields," says Jim Nelson, ISA Yield Challenge coordinator.

Nelson says the Gallatin County chapter amended their plot's soil, attaining 1.7 bu./acre

more than their control plot. Their yield also surpassed the of 41.5-bu. county average

by 11.4 bu./acre. The Heyworth chapter incorporated a seed treatment, which netted them an increase of 1.4 bu./acre more than the 55.4-bu. McLean County average.

Enhanced soils

The Gallatin County plot is near the Wabash and Ohio Rivers, close to where Illinois meets Indiana and Kentucky. John Sutton, one of the two school FFA advisors, says productivity is a challenge for the 30-acre plot that’s in a corn and soybean rotation. The field contains light-colored McGary soils and highly erodible land.

For the Yield Challenge, the field was divided into two, 15-acre fields -- one used as a control, and the other where a pre-plant application of SumaGrow from Bio Soil Enhancers was used. SumaGrow is a microbial blend that is designed to enhance soil and plant health, and is manufactured by the company based in Hattiesburg, Miss.

"SumaGrow is a natural soil product that contains humic acid and about 30 types of microbes that break down organic matter in the soil," says Sutton. "The company provided the product to us, and a local fertilizer company sprayed it at 1 gal./acre. A local farmer planted a Group 4.2 maturity Southern Cross variety soybean for us about 10 days after the product was applied. We had mostly normal growing conditions and good harvest conditions."

Sutton, who also raises soybeans, says he was encouraged with the plot's yield increase over the control. "We hope our efforts can help lead to a break in the soybean yield plateau," he says. "I also hope our students take home these strategies to implement on their own family farms. We are fortunate to have good community support and farmers that help us along the way."

Bill Raben, soybean farmer from Ridgway, Ill., recommended the 85-member FFA chapter try the preplant strategy. He used SumaGrow in both corn and soybeans on his own farm in 2011.

"I have attended some of informational meetings Bio Soil Enhancers have held at their facility in Mississippi. I had seen enough potential from their results that I thought it would be good for the FFA chapter and also on my own farm," says Raben. "As a kid, I always dug in the dirt and brought up shovelfuls of earthworms. You do not see that today, perhaps because farmers have overworked the soil."

Raben says use of SumaGrow is considered more of a long-term versus one-season investment. "I saw a variable 2-8 bu./acre in our corn, and maybe 2-3 bu. more in our soybeans. It was not cost-effective over just one season," he says. "I did not apply it in 2012, but I am anxious to see what effect it continued to have after analyzing 2012 results, although the drought may affect those results. You have to see it for the long-term impact for your soils."

Better roots

Heyworth students use a local farmer's field for their research trials. Jestun Nutter, the school’s FFA advisor, says the 23-acre field they use has sloping ground, which offers the students a chance to test strategies in both wetter and drier field spots.

"The field had been in continuous corn for nine years," he says. “Yield was declining, so the farmer suggested we put in a soybean plot. With the help of a local seed company rep, we decided to plant Beck soybeans with and without an inoculant. The seed company mixed the powdered product, Graph-Ex SA, with the soybeans. Our season was pretty dry. We saw a yield increase, but may have had higher yields in a good year."

Graph-EX SA has been commercially available for the last two growing seasons. Its bacteria live on plant roots, which Nutter says help protect against disease. Graph-EX SA is designed to expand the root system so the plant can increase moisture and nutrient intake.

"Graph-EX SA contains three strains of rhizobia bacteria and a strain of trichoderma with a patent pending from Cornell University. Of the rhizobia, one nodulates in cool soils, one works in warmer soils, and the third works in the presence of high nitrate levels from the previous corn crop," explains Dan Custis, president of Advanced Biological Marketing, the company that manufactures the product.

"Third-party research at Cornell and other universities shows an average 3-3.5-bu./acre yield increase in the Corn Belt, which provides about a 10:1 return on investment with soybean prices in the teens," he continues. "Farmers will see the most yield response on their marginal ground, but even good soils in central Illinois can see a yield bump."

Fabian Fernandez, University of Illinois soil fertility specialist, has not done any research with Graph-EX SA, but says general research with soybean inoculants shows that such products work best where soybeans have not previously been planted or not been planted in many years. He adds that soybeans have strong seed coats that keeps embryos safe and protects seed from dehydrating and abrasion from the soil.

Raben anticipates more farmers explore new management strategies to increase yields. "I think we could see more preplant strategies come back into play, especially as some of us put less emphasis on only post glyphosate treatments for weed control."