Manure and peat based iron-organo complexes - I. Characterization and enrichment

Earlier studies have shown that some naturally occuring organic materials can be used as an Fe source for plants. The aim of this research was to study enrichment procedures that would result in complex formation in common, low cost organic materials and to determine the maximum attainable Fe enrichment levels. Three organic materials-farmyard manure (FYM), poultry manure (PM) and Huleh Valley peat (PE) were studied for their characteristics as Fe, Mn and Zn carriers for plant uptake. Various enrichment procedures were investigated. These studies have shown that the enrichment level depends on the metal, pH and the water soluble fraction (WSF) of the organic materials. Maximum enrichment levels (at pH=3.5) were measured after the excess of inorganic salts was removed by leaching. These levels were 5.8-6.6% for Fe, 3.0-3.4% for Mn and 6.0-6.3% for Zn. An infrared spectrum of the Fe enriched WSF showed that most of the ligands in the complex formed are polysaccharides or polysaccharide-like compounds.