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Emily Unglesbee DTN Staff Reporter
Wed Jan 28, 2015 01:44 PM CST
(Page 1 of 2)

ST. LOUIS (DTN) -- It's time to consider getting inoculated.

Growers who plant soybeans after years of continuous corn this spring should be prepared to inoculate their beans and supplement their soil to reach proper pH and potassium levels. (DTN photo by Katie Micik)

Flu season may be winding down, but first-year soybeans will require some doctoring this spring, Michigan State University Extension Educator Mike Staton warns.

As some growers consider a move from continuous corn fields to soybeans, they will need to consider a host of management steps, agronomists told DTN. Inoculation will be the most important one, Staton stressed. Checking on proper nodulation this summer will help growers gain that oft-reported bean yield bump following corn. Growers should also test soil for the proper levels of pH, phosphorus, and potassium, and some may need to plan ahead for managing heavy corn residue during planting.


If you've been out of the soybean game for three to four years, a soybean inoculant is imperative, Staton told DTN.

Like the friendly legume they are, soybeans are able to create a mutually beneficial relationship with the microscopic bacteria living in the soil around their roots, Staton explained.

"The soybeans give bacteria the food it needs, and the bacteria takes atmospheric nitrogen, which is not usable to the soybean plant, and converts it to a form that is usable," he said.

After years of no soybeans, the neglected bacterial population of your soil will decline, and their departure can hit you in the pocketbook, Staton added.

"Soybeans need so much nitrogen that if you don't have that bacteria functioning properly, you're going to lose a tremendous amount of yield, 10 to 12 bushels," he warned.

University of Arkansas soybean specialist Jeremy Ross has done extensive studies of inoculants on the market and said there seems to be little difference between the available products, so finding a good inoculant shouldn't be difficult. Their benefits are so well established that university agronomists in Michigan and Ohio actually recommend using an inoculant every year, regardless of your rotation, Staton said.

Don't relax once the seed is inoculated and in the ground, Staton warned. "Producers really should dig up some roots in representative areas in the field just before the plants blossom, in late June to early July, and look for these root nodules on the roots," he explained.


Dig -- don't pull -- the plants up, and carefully clean the delicate root system off. Look for small, hard nodules on the roots. If you find roots sprinkled liberally with these nitrogen-fixing bumps, you're in good shape. If you don't see at least seven nodules on the roots, your beans will need supplemental nitrogen, as soon as possible, Staton warned.

The nitrogen needs to be applied at R1 (first blossom) or R2 (full bloom), or growers won't see benefits, he added.

Nodulation can be unsuccessful for several reasons, Staton noted. The bacteria in the inoculant may not be viable, soil pH levels could be too high or low, soil conditions could be too wet or dry following planting, or residual nitrogen in the field could be too high.

"Residual nitrogen from manure or commercial fertilizer will make soybeans lazy," Staton explains. "If they have nitrogen available -- the magic number is 40 pounds per acre in the soil at planting time -- those plants might not nodulate."

You can find more information on identifying and responding to poor nodulation in this article from Michigan State University Extension's Field Crops website:….


Continuous corn can lower the pH of a field faster than other crops, thanks to the acidifying nature of the added nitrogen those fields require, Staton warned.

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