Crop & Pest Report


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Late Season IDC in Soybean (07/23/20)

The ‘normal’ time during the soybean growing season for the appearance of iron deficiency chlorosis (IDC) is from 1st to 3rd trifoliate.

The ‘normal’ time during the soybean growing season for the appearance of iron deficiency chlorosis (IDC) is from 1st to 3rd trifoliate. This is because the historically wettest period of our growing season is from mid-April thru mid-June. This year, although wetness resulted in late planting, for most areas June was rather dry. July, however, has been very wet for some. This week, a grower from Cavalier County noticed IDC for the first time on soybeans in the 6-8 leaf stage, well after flowering. The IDC effect does not care what stage of growth the soybean is in. If a soil has significant carbonates, then soils that are wet enough to dissolve carbonate, producing bicarbonate, prevent the uptake of iron (Fe) into the soybean. For a full explanation of the science and physiology of IDC in our state, please see the updated soybean fertility circular at:

There is no foliar Fe amendment that is effective on relieving IDC on soybean. Iron is not mobile within the plant, and an Fe amendment does not green-up IDC affected leaves significantly. The best to hope for is dry weather. As the soil dries, the IDC will reduce and may go away completely. A soybean that receives a ‘flash’ of wet-soil-induced IDC will probably suffer little yield damage. If the wetness persists and the IDC persists, yield damage may be significant.

To reduce the risk of early or later season IDC, follow these steps in the future:

  1. Choose the right fields to plant soybeans into. If soil pH is greater than 7, then IDC is a possibility. Fields with pH less than 7 will never have IDC. If a field has higher pH, then the soluble salts within the field is a major factor in North Dakota that affects the severity of IDC. Soybean is sensitive to salts (EC) anyway. Planting soybean into a soil with EC greater than 2 is a poor cropping choice. Soybean and EC sensitivity can be found in the newly updated ‘Managing Salinity in North Dakota’ circular

IDC combined with high salts is the poorest soybean planting field choice.            

  1. Choose a very North Dakota IDC tolerant variety. NDSU scientists rate soybean varieties on their tolerance to IDC under North Dakota conditions (high carbonates, high salts). Ratings from other states, particularly those to the south and east of North Dakota, do not usually consider salts. Choose a variety from the NDSU Extension published soybean variety trials based on best IDC ratings.
  2. Plant a companion crop of oats or barley at the same time as soybean. Soil nitrate when taken up by soybean interferes with the internal physiology of Fe oxidation within leaves. The greater the soil nitrate, the greater the IDC. A companion crop helps reduce soil nitrate, and also helps to dry out the soil, both reducing IDC severity. The companion crop should be terminated by V5, or earlier if the season is dry. The companion crop would not help a later season IDC occurrence as we see this year in some areas, but it is effective on early-season IDC.
  3. Apply an in-furrow, mostly ortho-ortho-EDDHA Fe fertilizer in furrow at planting. This fertilizer is effective for a long period in the growing season, unlike other fertilizers to date. Research is progressing on newly formulated products that might have similar effects.


Dave Franzen

Extension Soil Specialist


This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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