ZINC, MANGANESE, AND COPPER IN SOIL FRACTIONS

Abstract

An understanding of the distribution of microelements among various fractions of soils is important to understanding microelement soil chemistry and to the development of better soil extraction techniques. This study was undertaken to find methods to distinguish between chemical and physical forms of Zn, Mn, and Cu in soils and to apply these methods for eight southeastern soils. Successive extractions were made to solvate the Zn, Mn, and Cu in the exchangeable, organic matter, and Fe oxide fractions. The residue was separated into sand, silt, and clay size particles, and these, along with whole soil samples, were totally dissolved and analyzed for Zn, Mn, and Cu.The proposed fractionation scheme was satisfactory for most soils, but is still considered to be preliminary. The data for the sums of fractions agreed well with the whole soil data. The Zn, Mn, and Cu contents were higher in fine-textured, higher organic matter soils than in coarse-textured, low CEC soils. The fine-textured soils had a large proportion of their Zn and Cu in the clay fraction, but the coarse-textured soils had relatively higher percentages in the organic matter fraction. Fertilizer Mn was found mainly in the exchangeable and organic matter fractions. Percent Cu was highest in the organic matter and clay fractions when averaging the data over the eight soils studied. An understanding of the distribution of microelements among various fractions of soils is important to understanding microelement soil chemistry and to the development of better soil extraction techniques. This study was undertaken to find methods to distinguish between chemical and physical forms of Zn, Mn, and Cu in soils and to apply these methods for eight southeastern soils. Successive extractions were made to solvate the Zn, Mn, and Cu in the exchangeable, organic matter, and Fe oxide fractions. The residue was separated into sand, silt, and clay size particles, and these, along with whole soil samples, were totally dissolved and analyzed for Zn, Mn, and Cu. The proposed fractionation scheme was satisfactory for most soils, but is still considered to be preliminary. The data for the sums of fractions agreed well with the whole soil data. The Zn, Mn, and Cu contents were higher in fine-textured, higher organic matter soils than in coarse-textured, low CEC soils. The fine-textured soils had a large proportion of their Zn and Cu in the clay fraction, but the coarse-textured soils had relatively higher percentages in the organic matter fraction. Fertilizer Mn was found mainly in the exchangeable and organic matter fractions. Percent Cu was highest in the organic matter and clay fractions when averaging the data over the eight soils studied. © Williams & Wilkins 1979. All Rights Reserved.