Lime-Induced Chlorosis

Lime-induced iron chlorosis in citrus and avocado trees may be controlled by chelating agents, such as EDTA-ethylene-diaminetetraacetic acid. Chelating agents have the ability to form complex compounds with metal ions-iron, zinc, manganese, and magnesium-holding the metals in a soluble form in various degrees of tenacity. Iron is held most firmly and, for this reason, the prospects may be best for the control of iron chlorosis-perhaps the most difficult nutrient deficiency to correct. EDTA has the ability to hold iron as a chelated complex in acid, neutral, and, to a certain extent, in mildly alkaline and calcareous soils. It has proved successful in soil applications in correcting iron deficiency, mostly in the glasshouse, on several plant species including citrus, avocado, azalea, macadamia, and Leptospermum. Several species of chlorotic trees and shrubs in calcareous soil the field have become green following soil applications. Care must be taken in making soil applications of EDTA. Some plantscitrus, avocado, azalea, macadamia, Leptospermum, and corn-were severely burned by large applications.