In acid soils, iron is usually available to all plants. In neutral or alkaline soils, iron may be so insoluble that some plants can’t absorb enough for their requirements. Iron is often unavailable in soils to which high amounts of soluble phosphates have been added. Iron may also be precipitated as insoluble iron phosphate. This is more likely in sandy soils. Clay soils tend to “fix” excessive soluble phosphates.
Iron is an essential microelement that is needed for chlorophyll production.
Symptoms in broadleaf plants are young leaves uniformly yellow (chlorotic) with narrow green veins; older basal leaves remain darker green. Leaves are small, bleached with apical and marginal scorch. Symptoms are severe during cold, wet spring weather. Shoot length usually normal but of small diameter, Twig dieback and defoliation are common in severe cases. Fruit has poor coloring in some species; citrus fruit drop is heavy.
Symptoms in Conifers are the new growth is stunted and chlorotic. Older needles and lower crown remain green. Cotyledons of seedlings remain green.