How much Iron in the form of Oxide do plants require for healthy growth?

Question

How much Iron in the form of Oxide do plants require for healthy growth?

Answer 1

It depends on the plant, but very little. Iron is a micronutrient and there is normally plenty in the soil and water. The most important factor determining iron nutrition is the pH of the soil.

At low pH (acidic soils) iron is much more soluble and therefore easily available to the plants. Other potentially toxic minerals also become more soluble, such as aluminium, and this is why many plants cannot survive in acidic soils.

Very calcareous soils (high pH) have much less available, dissolved iron and so iron deficiency can be a problem, especially to plants that have evolved to survive on more acidic soil.