Micronutrient Spotlight – Iron (Part 5 in series)

Oct 10, 2022 | Latest news

Micronutrients can maximize crop performance
Andrea Rice, Director of Research, Education, and Outreach
Missouri Fertilizer Control Board

Image description:  Field with areas of iron deficiency.
Photo credit:  cropnutrition.com

How is iron used by the plant?
Iron is a catalyst for the formation of chlorophyll and acts as an oxygen carrier in the nodules of legume roots.  Symptoms of iron deficiency first appear on the younger leaves at the top of the plant.

Deficiency of iron is usually associated with areas of high soil pH, free calcium carbonate, and low organic matter.  These soils frequently have had topsoil removed by erosion or leveling.  Cool, damp settings worsen iron deficiencies and are most severe in young seedlings.

How can an iron deficient field be identified?
When viewed from a distance, iron-deficient fields have irregularly-shaped yellow areas.  Corn and sorghum present a definite striped appearance with yellow leaves and dark green veins.  If the deficiency is severe, the entire plant may be impacted and turn a very light yellow or even white.  Plants with moderate deficiencies occurring early in the season tend to recover well.

Image description: Iron deficiency in corn.
Credit: International Plant Nutrition Institute

How should iron be applied?
Soil treatment for iron deficiency is not effective.  Therefore, it is recommended to spray the crop with iron when the deficiency is noticeable and while the crop is efficient at absorbing the iron.

Foliar spray of iron can be effective in restoring green color to plants, but there may not be a correlating restoration of high yields.  It is most effective to apply iron sprays to young plants and repeat at 10-14 day intervals.  Ferrous sulphate or iron chelates can be used for spray application.  It is best to check with advisers and ag retailers for specific sources, amounts, and timing.

 Is iron more useful in specific areas of crop production?
Missouri crops most affected by iron deficiency are corn and sorghum with alfalfa and wheat being least sensitive.  Iron deficiency may also be a problem in landscaping and ornamentals such as lawns, shrubs, and orchards – specifically peach trees.