In many areas of the US, Iron Deficiency Chlorosis (IDC) is a common limiting factor for soybean yields. It is usually identified by the yellowing of leaves between the veins, with the veins remaining dark green. Unlike other nutrient deficiencies, there is usually iron in the soil, but only a small amount is available to plants.
Key Takeaways
- Iron Deficiency Chlorosis (IDC) affects several areas in the US.
- IDC cannot be solved with fertilizer applications like other nutrient deficiencies.
- The first line of action to manage IDC is choosing more tolerant soybean varieties.
“Wet and cool growing seasons can lead to a higher incidence of Iron Deficiency Chlorosis.”
Cause
Iron (Fe) in the soil is typically in a low solubility form (Fe3+) and cannot be absorbed by plants. However, soybean plants have a strategy for iron uptake (Figure 1). The roots of soybeans make the soil around them more acidic and release enzymes that change the iron in the soil to a more soluble form (reducing Fe3+ to Fe++), making it accessible to the plant¹. This strategy is restrained when there are carbonates (CO ) in the soil. As the soil becomes wetter, the amount of dissolved carbonates increases, producing more bicarbonate that neutralizes the soil acidity, preventing the plant from absorbing iron². This is the reason why wet and cool growing seasons can lead to a higher incidence of IDC. Moreover, higher nitrate levels in the soil are also thought to contribute to IDC.
Management Options
- Variety Selection
- Choosing a tolerant variety is the best way to address IDC. If you have a field with a history of IDC, select the most tolerant variety available. IDC scoring methods may vary among companies, so it is best to consult university IDC variety trials. While there are other management strategies, none can compensate for choosing a susceptible variety.
- In-furrow Application of iron Chelate
- Applying ortho-ortho-EDDHA Fe chelate with water in the furrow at seeding has been shown to reduce IDC. The chelate delivers iron to the plant root early in the season but cannot compensate for choosing a susceptible variety over a tolerant one3. Another way of applying iron is through foliar sprays. However, these are generally not effective in correcting a deficiency as iron is not mobile within the plant4.
- Denser Plant Stands
- Higher soybean seeding rates or wider row spacing while keeping plant populations constant have been found to decrease the severity of IDC. However, the impact of increasing the seeding rate is relatively minimal and varies across different environments. The decrease in IDC with higher seeding density might be due to reduced soil moisture beneath the rows or greater acidity in the root zone, which promotes the activity of iron-reducing compounds secreted by soybean roots5.
References
1. Mallarino, A.P., M.U. Haq, D. Wittry and M. Bermudez. 2001. Variation in soybean response to early season foliar fertilization among and within fields. Agronomy Journal 93:1220-1226.
2. Schmidt, W. 1999. Mechanisms and regulation of reduction-based iron uptake in plants. New Phytologist 141:1-26.
3. Lovas, S.E.H. 2013. Laboratory and greenhouse evaluation of FeEDDHA fertilizers of
differing quality. North Dakota State University, Department of Soil Science MS thesis.
4. Chatterjee, A., S. Lovas, H. Rasmussen and R.J. Goos. 2017. Foliar application of iron
fertilizers to control iron deficiency chlorosis of soybean. Crop, Forage & Turfgrass
Management. Volume 3. https://doi.org/10.2134/cftm2017.05.0037
5. Goos, R.J., and B. Johnson. 2001. Seed treatment, seeding rate and cultivar effects on
iron deficiency chlorosis of soybean. Journal of Plant Nutrition
Author: Ana Carcedo, North Dakota State University June 2025.
