Hypotheses Concerning Iron Chlorosis

Abstract Iron chlorosis was studied in two plant species grown on calcareous Quinlan, Tripp, and Millville soils. Two types of Fe chlorosis developed: ( 1 ) Iron deficiency accentuated by improper microelement balance appeared to be the causative factor controlling the development of Fe chlorosis in milo grown on Quinlan and Tripp soils. The Cu uptake by milo from all three soils and two NaDTPA chelate treatments was more than double that taken up by PI‐54619‐5‐1 and Hawkeye soybeans. The Fe/Cu + Mn ratio was much lower in the soil extracts of Quinlan and Tripp than the Millville soil. ( 2 ) An abundance of available P and Ca appeared to be the controlling causative factors of Fe chlorosis in PI‐54619‐5‐1 soybeans grown on the Millville soil. PI‐54619‐5‐1 and Hawkeye soybeans differed in their susceptibility to this type of chlorosis. It was suggested that new chlorosis‐resistant varieties through plant breeding, Fe chelates economically feasible for field application, controlled fertilizer, water, and cultural practices might all lend themselves to correcting Fe chlorosis in the field.