Effects of plant iron recycling on iron chlorosis of grain sorghum grown on calcareous soils

Abstract

Chlorosis of grain sorghum (Sorghum bicolor L. Moench) due to a deficiency or unavailability of soil iron limits yields of grain over an extensive area of Texas. Standard corrective treatments in the past have called for frequent foliar sprays to correct the deficiency. Soil applications generally have not been economically satisfactory‐ The purpose of this study was to develop a practical and economical means of improving Fe nutrition of grain sorghum. Soil applied as well as foliarly applied treatments were evaluated. Ferrous iron from foliarly applied inorganic Fe sources was complexed by plant metabolites and cycled back to the soil as organic residue. In addition to the sorghum plant, weeds were compared for their Fe complexing abilities. Sorghum plant response and Fe uptake were compared with coitmercial Fe chelates and foliar Fe sprays. Growth responses in the greenhouse experiments were in the following order: Plant complexed Fe > FeEDDHA. > foliar sprays. The degree of plant response to Fe was associated with the severity of Fe chlorosis. Amaranthus, spp, a commonly occurring weed in Fe chlorotic areas showed higher Fe complexing ability than sorghum. Subsequent applications of the various Fe‐treated plant residues to soils of medium to severe Fe chlorosis problems indicated Amaranthus, spp, was a better Fe carrier than the other sources. Data indicate plant uptake of Fe by the sorghum crop from plant complexed sources equaled or exceeded that from FeEDDHA. Field tests evaluating the new organic sources have been initiated.

Key words:

• Iron chelate
• grain sorghum
• genotype
• manure
• ferrous sulfate
• polyphosphate
• extractable Fe