Summary
Humic and fulvic acids extracted from a mollisol and manure were used to determine their zinc-complexing capacity by ion-exchange equilibrium method. The simultaneous chelation of phosphorus by organic-matter preparations in the presence of complexed zinc was also studied. The results indicated that phosphorus is bonded to humic and fulvic acids in the presence of complexed zinc. Phosphate ions in such complexes probably act as additional ligands in bridging the organo-metal units. The stability constants of zinc complexes increased whereas the free-energy change accompanying their formation recorded lower negative values in the presence of phosphorus and at higher pH. Zinc fulvic salts and complexes being less stable but mobile should enhance the movement of zinc ions to plant roots and yield of crops in deficient soils.
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Dhillon, K.S., Sinha, M.K. & Randhawa, N.S. Organo-metallic phosphates. Plant Soil 43, 317–326 (1975). https://doi.org/10.1007/BF01928495
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DOI: https://doi.org/10.1007/BF01928495