Grain sorghum response to plant residue?recycled iron and other iron sources

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Abstract
Inorganic Fe sources applied to the soil are usually not effective for correcting iron chlorosis unless extremely high rates are used. Certain synthetic chelates and some organically complexed Fe compounds are somewhat effective in soil applications but their use is not economically feasible except on high cash value crops, gardens and ornamentals. The most effective correction of Fe chlorosis on field crops is foliar spray applications with Fe compounds. However, in severe chlorosis, several separate spray applications may be needed. Field experiments were conducted on two soils supporting severely and slightly Fe chlorotic grain sorghum (Sorghum bicolor L. Moench) to determine the agronomic effectiveness of various Fe sources. Plant complexed Fe sources using post‐harvest grain sorghum stubble and iron‐efficient Amaranthus spp plants were compared with a synthetic chelate for efficacy in correcting Fe chlorosis on grain sorghum. Industrial byproducts containing acid and Fe were also compared. Sorghum growing on mildly Fe deficient soil produced highest grain yields when supplied with Fe‐enriched sorghum residue (Fe‐SR). Seedband placement of acidified mining residue (AMR) resulted in vegetative response but had no effect on grain yields. On severely Fe deficient soil, Fe‐enriched Amaranthus (Fe‐AR) was evaluated as a plant‐complexed Fe source. Highest dry matter and grain yields were associated with multiple foliar sprays, Fe‐AR and high rates of AMR. Data indicated that Fe‐AR was more effective than Fe‐SR while both sources induced a better plant response than Fe‐EDDHA.