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Agronomy Journal Abstract -

Copper Industrial Byproducts for Improving Iron Deficient Calcareous Soils1


This article in AJ

  1. Vol. 68 No. 1, p. 79-82
    Received: Apr 23, 1975

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  1. J. Ryan and
  2. J. L. Stroehlein2



Laboratory and greenhouse experiments were conducted to evaluate an iron-rich surplus by-product (“jarosite”) from a copper refining process as Fe fertilizer. Combinations of H2SO4, which is a by-product from copper smelting, with “jarosite” were studied in order to see if the iron solubility would be increased. Acidification of the “jaroste” greatly enhanced Fe solubility. As the “jarosite”/H2SO4 ratio increased from 1:1 to 7:1, the amount of the material solubilized as Fe decreased from approximately 12 to 2%. At ratios wider than 7:1, negligible amounts of Fe dissolved. At “jarosite”/H2SO4 ratios < 1, Fe solubility increased but the end product could not be handled as a conventional pelleted or powdered fertilizer.

In greenhouse experiments using sorghum (Sorghum bicolor ‘Double Dwarf Yellow Sooner’) in an Fe-deficient calcareous soil, the 2:1 mixture of “jarosite”/H2SO4 was significantly more effective than either “jarosite” or H2SO4 alone in terms of increasing plant growth and chlorophyll content. The mixture compared favorably with conventional inorganic and chelated sources of Fe. Varying the ratio of “jarosite”/H2SO4 from 1:1 to 5:1 resulted in no differences in yield. Particle size of the mixture influenced plant growth. The < 1 mm fraction was most effective, the 1 to 2 mm and 2 to 6 mm fractions gave similar yields and the 6 to 12 mm fraction was least effective. Post-harvest analysis of the cropped soil showed that the “jarosite”/H2SO4 mixture significantly increased the levels of DTPA-extractable Fe.

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