Iron chlorosis in fruit stone trees with emphasis on chlorosis correction mechanisms in orchards: a review

Iron is one of the essential micro-nutrients for plants and trees because they cannot complete their life cycle without it; it cannot compensate by other nutrients and is directly involved in plant metabolism. It acts as a cofactor for enzymes involved in electron and oxygen transport. Iron deficiency is a global problem in fruit production in calcareous or alkaline soils, and approximately one-third of the total land area contains calcium carbonate. Despite the widespread presence of iron in the Earth's crust, the low solubility of iron compounds in many soils, especially at high pH, aerobic conditions limit the bioavailability of iron and cause symptoms of iron deficiency in plants, primarily in young leaves. Facial chlorosis has been observed between veins, reduced branch growth, leaf deformation during the growing season, and finally, tree death. In this regards, current study reviews various methods that have been mentioned for prevention and treatment of iron deficiency, including the use of iron efficiency cultivars, soil application of elemental sulfur with iron sulfate or iron chelate, the use of organic fertilizers and preservation of plant residues, foliar application with ferrous iron or chelated iron sulfate, and injection of iron ammonium citrate or ferrous sulfate into the tree trunk. Accordingly, at the first onset, the use of iron efficiency cultivars and suitable hybrids are the most appropriate methods to prevent the formation of iron chlorosis in fruit trees, especially in fruit stones. Secondly, other treatment methods such as consumption of sulfur fertilizer or iron chelate and trunk injection are important approaches.