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Iron

Iron is a vital micronutrient crucial for chlorophyll production, photosynthesis, respiration, and energy transfer in both grass and broadleaf crops. Iron availability in soil depends heavily on pH and its balance with other nutrients. When soil pH rises above 7, iron shifts from a plant-available ferrous form to an unavailable ferric form, limiting uptake. Because of this, iron deficiencies are common in higher pH soils.

Iron deficiency shows as yellowing (interveinal chlorosis) on new growth since iron is not mobile within the plant. This symptom can resemble manganese deficiency, so soil and tissue testing are important to identify which nutrient is lacking.

Crops like corn and wheat generally utilize iron better than soybeans and sorghum. In areas with high pH and poor drainage, iron deficiency chlorosis (IDC) is more frequent and can impact yields.

To manage iron deficiency, growers can:

• Lower soil pH to increase iron availability
• Select crop varieties tolerant of iron chlorosis
• Apply iron fertilizers early in the season, preferably near the roots
• Use foliar iron applications for a quick green-up, but timing is critical to avoid yield loss
• Apply sulfur to reduce pH and free up iron

It’s also important to balance iron with manganese in the soil. Ideally, iron levels should be between 20–40 ppm and manganese between 10–20 ppm, with iron higher than manganese for best plant health. More plants and roots in the soil produce organic acids that help convert iron into a plant-available form, improving uptake naturally.