Nitrate-Induced Iron-Deficiency Chlorosis in Avocado (Persea americana Mill.) Rootstocks and Its Prevention by Chloride

Iron deficiency symptoms are commonly observed in avocado groves grown on calcareous soils. The uptake of iron by avocado at various levels of N03 and Cl in the nutrient solution was studied. Avocado seedlings were grown for 126 days in 10 L containers filled with sand and flushed with complete nutrient solutions containing 2,4,8 or 16 mM Cl. Each level of Cl was combined with 2,8 or 16 mM NO3, at a constant ratio of Mg:Ca:K of 1:5:2 in charge equivalents. An increase in the N03 concentration in the nutrient solution led to a decrease in uptake and accumulation of Cl in the leaves. Fe-deficiency chlorosis of the young leaves was induced and increased with time in the low CI:high N03 treatments. Increased concentration of Cl salts in the nutrient solution prevented the development of chlorosis and enhanced Fe content in the leaves.