High Iron (Fe) levels in plants may cause a bronzing of leaves with the potential for tiny brown spots on the leaves. However high iron levels in the soil can cause issues without any visible signs.
The treatment of high soil iron, can be just as complicated as the treatment of iron deficiency. Firstly, the soil pH should be checked an amended if required ‑ aim for a neutral pH unless the plant you’re growing requires acidic (or alkaline) soil. Soil drainage should also be improved if possible and where there is waterlogging the soil should be aerated if it is compacted. If the area is irrigated be careful to only water when necessary.
A balanced soil is the best method to elevate high iron levels in the soil. If soil tests reveal that the soil is deficient in major elements, then these should be corrected after pH and drainage. Pay particular attention to Zinc (Zn) or Potassium (K) deficiencies, as these can be the cause of iron toxicity or could make it worse.
Silica can buffer the soil by binding with iron and aluminium to nutrients like phosphorous to be more plant available. Pacific Fertiliser has some silica products suitable for agriculture.
