DISSOLUTION OF FERRIHYDRITE BY DISSOLVED ORGANIC COMPOUNDS DERIVED FROM SOME CROP RESIDUES | ||||
| Journal of Soil Sciences and Agricultural Engineering | ||||
| Article 3, Volume 25, Issue 10, October 2000, Page 6557-6566 PDF (369.66 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jssae.2000.259818 | ||||
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| Authors | ||||
| M. E. Saleh,; A. A. Abdel Salam | ||||
| Department of Soil and Water Science, College of Agriculture, University of Alexandria, El-Shatby, Alexandria, Egypt. | ||||
| Abstract | ||||
| The solubility of iron oxides and hydroxides is too low to cover the plant requirements especially in calcareous soils. Various attempts were carried out to overcome Fe deficiency in these soils. In the present study, the dissolved organic compounds (DOC) extracted from gramineous (rice, wheat, and corn) and legumeneous (peanut, faba bean, and clover) crop residues using water, 0.01M CaCl2, or 0.01M CaSO4 were used as DOC extractants to dissolve the laboratory-synthetic ferrihydrite-Fe. The results of infrared analysis for DOC showed a similarity in all residues with respect to the functional groups but different in their concentrations. The resulted DOC had a wide range of pH (7.0-5.1 in water, 7.1-5.3 in CaCl2, and 6.9-5.2 in CaSO4 solutions). Ferrihydrite showed a high affinity toward DOC; and different quantities of DOC were adsorbed on its surface. The DOC extracted by CaSO4 was adsorbed in greater quantities than water- and CaCl2-extracted ones. On the other hand, Fe dissolution by DOC indicated that the high ferrihydrite-Fe dissolution was observed with water-DOC of faba bean (1660.75mg Fe g-1 mineral), clover (336.45), rice (245.14), corn (85.49), and peanut (18.13) then the CaCl2-DOC of faba bean (533.18), clover 17.26), and corn (12.70). Ferrihydrite also showed a high affinity to adsorb the soluble Fe from wheat extracts and CaSO4-DOC extracted from all residues. This result confirms that Fe was adsorbed in soluble complexes with DOC. The results indicate that effectiveness of DOC to dissolve ferrihydrite-Fe is dependant, firstly, on the type of crop residue, the ionic strength of residue extracting media and the abundant ionic species. Secondly, it depends on the characteristics of DOC such as pH, type and concentration of the functional groups, reducing capacity, and the degree of lability (low or high molecular weight-DOC). The results concluded that legume crop residues and corn stalks are considered efficient sources, as organic amendments, for ferrihydrtie solubilization and maintaining high levels of soluble Fe in solutions. | ||||
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