Copper Industrial Byproducts for Improving Iron Deficient Calcareous Soils
1976
Ryan, J. | Stroehlein, J. L.
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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