Ban Bean Anemia

Plan Ahead to Manage Iron Deficiency Chlorosis in Soybeans

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Yellow (chlorotic) soybeans are an early sign of iron deficiency chlorosis. In severe cases, plants will become stunted. (DTN photo by Pamela Smith)

ROCKVILLE, Md. (DTN) -- Imagine sitting famished in front of a big, juicy steak -- with no utensils in sight. Welcome to the sad world of the soybean plant suffering from iron deficiency chlorosis (IDC).

Unlike other plant nutrient deficiencies, where the desired nutrient is scarce or missing altogether, iron is plentiful in soils. But under certain soil conditions, a soybean plant can't access it.

Fortunately, researchers like University of Minnesota agronomist Dan Kaiser have honed in on some valuable utensils to give your famished beans ahead of time -- namely, varietal tolerance, companion crops and some in-furrow products.

HUNGRY BEANS. A range of factors influence IDC. They include soil pH, too much calcium carbonate, and soils with a build-up of bicarbonate, which forms from carbon dioxide trapped in poorly draining soils.

Iron is a component of chlorophyll that all plants need to grow. Without it, soybean leaves turn yellow (chlorotic) and in severe cases, plants will become stunted. The problem is a familiar and frustrating one to growers in parts of the northern and Western Corn Belt, mainly Iowa, Minnesota, the Dakotas and Kansas, where IDC is most common.

Symptoms often appear early in the growing season, when moisture is plentiful -- and the problem is beyond management.

HELP BEANS DIG IN. Consider varietal tolerance to IDC the steak knife for the soybean. "IDC-tolerant varieties are an essential starting point," Kaiser said. He recommends consulting your local seed salesman to best understand their rating system.

IDC can be field-wide, but in many regions it is a patchy phenomenon within fields. Soybean varieties with a greater tolerance to IDC will typically result in lower yield when grown on field areas where IDC is not present, Kaiser said. If possible, he recommends using variable rate planting to put an IDC-tolerant variety in the field's problem patches, and a more susceptible variety -- that may have greater yield potential -- elsewhere.

"Variety tolerance provides a layer of insurance as applying iron fertilizers do not consistently increase yield," Kaiser said.

GRAB A FORK. The steak knife is handy, but adding a fork is even better. Kaiser has had good success pairing IDC-tolerant varieties with other management options to improve yield in IDC fields.

Research has backed up the benefit of using an in-furrow EDDHA iron chelate product, with the majority of the iron chelated as ortho-ortho EDDHA, Kaiser said. All EDDHA products do not contain the same percentage of ortho-orhto EDDHA so the exact rate of a product required for maximum yield potential will vary.

Because high soil nitrates seem to exacerbate IDC, researchers have honed in on companion crops that can help by reducing nitrate levels and drying out soils early in the season.

Kaiser found that seeding 1.5 bushels per acre of oats, at or before soybean planting, can increase soybean yields in the IDC-affected sections of fields. The oat companion crop does require greater management, and the timing of oat termination is key, Kaiser warned. "Spray the oat crop too early and it will not provide the desired result, and let it grow too long, and it will over compete with the soybean crop," he said. "Spraying the field when the oat crop is 10 inches tall is critical."

For more information, see this University of Minnesota article on managing IDC here:….

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Emily Unglesbee