Corn+Soybean Digest

Inoculants Help Soybeans Get Their Fix Of Nitrogen

Inoculants are an effective and profitable alternative method of providing soybean plants with nitrogen (N), according to Ohio State University Extension research.

Based on 64 Ohio field trials, the average yield increase from soybean inoculants is 1.94 bu./acre and produces a profit of about 300 percent when beans average $6/bu. and when inoculation materials cost $3/acre.

"We've been testing inoculation products since 1995," says Jim Beuerlein, an Ohio State University Extension agronomist. "Last year we tested over 30 commercial and experimental products. If you take a look at all of the work we've done over a period of about 10 years, what the data says is that over the long haul, someone who uses inoculum continuously year after year should pick up a minimum of two bushels per acre.

"It usually only takes about a half bushel yield increase to break even, and a 2-7 bu./acre yield increase is not uncommon if the seed is inoculated properly and planted in a timely manner."

Inoculants contain legume bacteria, or rhizobia, which, added to the seeds prior to planting, enable the soybean plants to fix nitrogen from the air.

"Depending on the protein content, a bushel of soybeans will contain between three and four pounds of nitrogen," Beuerlein says. "The production of a 60-bushel/acre crop requires in excess of 300 pounds of nitrogen, and with nitrogen running about 50 cents a pound right now, that's about $150 out of a farmer's pocket. The bacteria, which will cost a grower $3-$4, will give that nitrogen to you for practically nothing."

Inoculants come in two forms – dry or liquid. A wide range of inoculant products are available to growers, from materials that improve production over a wider range of environmental conditions to extenders that allow application to seed 30 days, 60 days or even 90 days prior to planting without loss of productivity.

"Inoculants, combined with seed fungicide treatments make for an effective soybean package," Beuerlein says. "Many fungicide treatments can be mixed with inoculation materials and applied at the same time."

Fungicide treatments applied to seed before planting are designed to protect the plants from root rot diseases such as Phytophthora, as well as improve plant stands and provide a healthier root system.

"Fungicide seed treatments are extremely important and over the long haul will generate good profit for the grower," Beuerlein says. "We test fungicide seed treatments and get on the average about a bushel and a half per acre yield increase. Many growers, however, can get four to six times that amount."

It's estimated that the loss of soybean productivity from diseases averages more than $150 million a year in Ohio. Producers lose from 5-8 bu./acre a year. By the time symptoms of a particular disease appear, the yield loss has already reached 7-10 percent, and there are significant yield losses when no disease symptoms are evident.

Additionally, in cases of replanting due to disease loss, it costs a producer between $80 and $100/acre due to extra costs and lost yield.
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