Grain sorghum response to iron sources applied alone or with fertilizers

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Abstract
Several greenhouse pot experiments were conducted on Fe‐deficient soils to determine agronomic effectiveness of various Fe sources applied alone or with fertilizers. Grain sorghum (Sorghum bicolor) response was greatest with FeEDDHA in all experiments. Several industrial byproducts containing Fe generally were not effective, but seed application and soil application of a natural organic complex containing Fe were somewhat effective in providing Fe to the crop. Effectiveness of FeS04 or FeHEDTA band applied with fluid fertilizers decreased in the order: polyphosphate suspension, orthophosphate suspension, urea‐ammonium nitrate solution. Crop response was greater with FeHEDTA than with FeSO4, in all fertilizers. Band application of urea‐phosphate (UP), an experimental acidic phosphate fertilizer containing urea, cogranulated with FeSO4 (to contain 4% Fe) was somewhat effective for grain sorghum. Crop response to UP‐Fe products decreased with level of water‐soluble Fe and percentage of the total Fe remaining in the ferrous form. Results show that agronomic effectiveness of Fe sources applied with fertilizers varies widely, depending upon chemical reactions which occur during manufacture or after soil application.