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Iron Deficiency Chlorosis in Soybean (06/14/18)

After an initial dry start to the soybean growing season, rainfall in the last week or two has provided conditions for iron deficiency chlorosis (IDC) to show up in the region.

Iron Deficiency Chlorosis in Soybean

After an initial dry start to the soybean growing season, rainfall in the last week or two has provided conditions for iron deficiency chlorosis (IDC) to show up in the region. Although there is usually enough iron (Fe) available in the soil, young soybean plants may not be able to take up enough Fe. The symptoms of IDC usually start to show when the plant is at the first or second trifoliolate growth stage (see photo on next page). The cotyledons and unifoliate leaves normally will stay green. In trifoliate leaves, the symptoms appear as yellowing leaf tissue between the veins while the veins may remain green.

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Severe IDC cases may turn leaf tissue brown and cause necrosis (Graph 1). Plants with chlorosis are often stunted and behind in growth and development compared to healthy plants. Chlorosis is common when soybean plants are grown on high pH calcareous soils, especially when salt levels are elevated. For a description about the need for Fe in soybean and why IDC develops, consult Extension publication SF1164.

Soybean plants may grow out of the chlorosis and become green again, however yields might already be reduced due to IDC. The most important management practice is selecting chlorosis tolerant soybean varieties. NDSU scientists use a rating of 1 to 5 to score the IDC symptoms in plants where 1 is green, 3 is yellow, and 5 is dead tissue (Photo 2).

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A listing of IDC ratings of varieties tested in 2017 can be found in the NDSU soybean variety trial results publication A843. The IDC scores for varieties tested in 2018 will be available this fall. If a field has IDC this year, it is critical to note which variety is used and what tolerance the variety has to IDC expression. It is vital to grow soybean tolerant varieties in fields more prone to IDC.

Hans Kandel

Extension Agronomist Broadleaf Crops

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