Solubility relationships of iron, manganese, copper and zinc in alkaline and calcareous soils

Abstract

The solubility relationships of the native forms of iron, manganese, copper, and zinc in alkaline and calcareous soils were determined by a modification of the chelate equiIibrium method proposed by Norvell. The experimentally determined activity product (Fe3+)(OH-)3 in soils was found to vary within the reported range of solubility products of amorphous hydrous ferric oxides. Soils which undergo alternate cycles of reversible, oxidation-reduction processes were found to maintain higher solubility of iron and manganese than other soils. Soil pH and organic matter content were found to significantly affect the solubilities of all the four micronutrient cations. The solubility relationships of manganese, copper, and zinc have been expressed as a function of soil solution pH. Probable mechanisms controlling the solubility of these metals in alkaline and calcareous soils are discussed.