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Iron Deficiency Chlorosis in Soybeans

Iron Deficiency Chlorosis (IDC) is expressed in new leaf tissue as an interveinal yellowing while the veins remain green.  As the deficiency progresses, leaf tissue and even the growing point can die. 

North Dakota soils usually contain an abundant amount of iron for plant functions. However, iron is rather insoluble and with increased soil pH, the iron solubility becomes even lower and the plant is unable to uptake the required amount of iron. 

Soil conditions which are prone to IDC are: high pH soils containing calcium carbonate; cool wet soils; poor drainage; saline soils; and high nitrogen fertility level fields.  Other non-iron related soybean yellowing causes are loss of sulfur, poor inoculation of first-year soybean fields or soybean cyst nematode.

If IDC symptoms are observed, the best course of action is to take note of problem fields for future management plants and just wait for sunnier days.  Rescue iron chelate sprays are not economical and not recommended.  

IDC is minimized by choosing a tolerant variety, using an ortho-ortho-EDDHA fertilizer at planting, such as Soygreen™, planting in wider row spacings, using a cover crop at the time of soybean seeding, and not applying N to the soybeans or at least choosing fields with lower residual soil nitrate levels.  Managing crop drainage and salinity levels also can improve conditions. 

Use of ortho-ortho-EDDHA fertilizer at planting has been successful.  However, farmers are encourage to read fertilizer information carefully.  Many products on the market contain ortho-ortho EDDHA and ortho-para EDDHA fertilizer.  The para- chemical formulation does not increase iron solubility to become effective against IDC.  Use only ortho-ortho formulations. 

Resources: "Iron Deficiency Chlorosis in Soybean", Crop and Pest Report 6/23/11, H. Kandel and R.J. Goos.

"Iron Chlorosis in Soybeans", Crop and Pest Report 6/30/11, D. Franzen.

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