To evaluate whether your inoculant is working, cut open several nodules and look at the color inside each one. You want to see a vibrant pinkish-red color. Nonfunctioning nodules can have white, green or even black interiors, the latter of which occur whe
Soybeans are a workhorse crop that are expected to produce solid yields with little or no TLC. With soybean prices in double digits today, however, farmers are looking for inputs, such as inoculants, to help boost yields from this easygoing crop.
Inoculants are made up of tiny bacteria called rhizobia that occur naturally in soils and are manufactured, as well, by various companies. In both cases, rhizobia partner with soybeans to boost nodulation and fix nitrogen.The better your soybeans handle these two tasks, the better they will tend to perform in the field.
A manufactured inoculant is applied on approximately 40% of all U.S. soybean fields annually,
estimates Ryan Locke, North American marketing manager for soybeans for EMD Crop BioScience Inc. That percentage is double what it was only 10 years ago, he adds.
When to inoculate. The challenge for most soybean producers is determining when it makes sense to use manufactured inoculants, which are based on the Bradyrhizobium japonicum strain of rhizobia.
"If I’m planting soybeans after a field has been in CRP [Conservation Reserve Program] or in a field that’s not had soybeans for three years, then I’m going to make the investment in a manufactured inoculant," says Bill Wiebold, University of Missouri soybean Extension specialist.
Wiebold’s colleagues in other Midwestern states, including Illinois, Indiana, Nebraska and Wisconsin, offer similar recommendations that range between three and five years.
The timing recommendations for manufactured inoculants vary based on how well the naturally occurring rhizobia work in various soils.
Flooded soybean fields are also candidates for an inoculant, depending on the length of time a field has been under water, according to Wiebold.
"Bacteria are aerobic, and when in water for prolonged periods of time, they drown," he says.
Some of the Extension specialists say a couple of the newer manufactured inoculant products, including Optimize 400 and Vault HP, provide additional benefits.
"These components can help with early plant growth, especially in cool and wet soils associated with early planting," says Shaun Casteel, Purdue University soybean Extension specialist. "However, while plant stand establishment can be improved, we usually do not see much of a yield benefit in a corn–soybean rotation."
University of Illinois soybean Extension specialist Vince Davis notes that a yield increase of 1 bu. per acre or less is common. "With $13 per bushel beans and a $2 to $4 per acre cost, it takes very little yield benefit to pay for itself," he says.
- Mid-February 2011