Generally, onions appear insensitive to iron deficiency, with most soils supplying adequate levels of iron to meet crop needs. Under extreme deficiencies, leaves become completely chlorotic and bleached.

The most common symptom for iron deficiency starts out as an interveinal chlorosis of the youngest leaves, evolves into an overall chlorosis, and ends as a totally bleached leaf. Because iron has a low mobility, iron deficiency symptoms appear fi rst on the youngest leaves. Iron deficiency is strongly associated with calcareous soils, anaerobic conditions, and it is often induced by an excess of heavy metals.