Iron slag, a byproduct of the steel manufacturing process with a high amount of iron (Fe), magnesium (Mg), manganese (Mn) and zinc (Zn), was used as a seed coating material to improve soybean nutrient quality and maintain yield during cultivation. Soybean yield (grain, aboveground, roots) did not differ significantly from the non-coated seeds, but nutrient concentration in soybeans, such as nitrogen, magnesium and manganese, were significantly increased in the iron-coated treatment, by 6%, 20% and 17%, respectively, than in the non-coated seeds. The application of iron slag as a protective seedcoat improved the nutrient concentrations of soybean seeds after harvest and maintained a good yield, implying that the material could be applied worldwide to improve the nutritional quality of soybeans in large scale production.
