Pyritic Lignite as a source of iron for soybean as influenced by variety and soil pH.

Iron deficiency chlorosis (IDC) is a frequent problem in soybean [Glycine max (L.) Merr.] production on calcareous soils. Greenhouse and soil incubation experiments were established to evaluate pyritic lignite efficacy to supply Fe as compared to Fe-EDDHA and Fe-EDTA sources across contrasting IDC tolerance varieties grown on a slightly acid and a calcareous soil. Soybean IDC incidence was influenced by the soil properties and variety tolerance. All iron sources increased plant dry matter accumulation on the Leeper soil, whereas on the Marietta soil only lignite at 0.672 kg ha-1 produced an increase. Lignite at 0.336 kg ha-1 successfully improved Fe availability to the plant as reflected by an increase in Fe content. Furthermore, no differences were found between the low rate of lignite and the commercial fertilizers on any of the evaluated parameters. Results from this study indicate that pyritic lignite may serve as an acceptable source of Fe on problem soils to prevent IDC