Effects of Fe–EDDHA application on iron chlorosis of citrus trees and comparison of evaluations on nutrient balance with three approaches

Iron deficiency chlorosis occurred frequently in many fruit trees grown on calcareous soils with a high pH. A field experiment of Fe–EDDHA application and a nutritional status survey on citrus orchards were conducted to observe the effects of Fe–EDDHA application on iron chlorosis of citrus trees. Three approaches, i.e., Sufficiency Range Approach (SRA), Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND), were performed to evaluate the nutrient balance status of citrus trees. DRIS and CND were suitable to diagnose and evaluate nutrient balance status of citrus trees grown on calcareous soils with a high pH. The diagnosis results revealed that Fe–EDDHA application significantly improved Fe nutrition and decreased Zn in chlorotic citrus trees. The nutritional status of Zn, Mn, Fe, P and Mg were at the deficient levels and Cu, N, Ca and K at the excessive levels in iron treatment citrus trees. The results demonstrated that the leaf chlorosis of citrus trees grown on calcareous soils with a high pH was mainly caused by iron deficiency, but it was not the single cause leading to the nutrient imbalance in iron chlorotic citrus trees. DRIS and CND were suitable to diagnose and evaluate nutrient balance status of citrus trees grown on calcareous soils with a high pH. The results revealed that Zn and Mn deficiencies became the new limiting factors in iron deficiency citrus trees after iron chlorosis correction.

► This paper studied the effects of EDDHA application on chlorotic citrus leaves.
► DRIS and CND were suitable to diagnose and evaluate the nutrient balance status.
► Iron deficiency was the main reason for the chlorosis.
► The deficiency of Zn and Mn could be the new limiting nutrients after iron correction.