Predicting Native Plant Copper, Iron, Manganese, and Zinc Levels Using DTPA and EDTA Soil Extractants, Northern Great Plains

Abstract

Abstract The utility of DTPA (0.005 M , pH 7.3) and EDTA (0.01 M , pH 7.0) extractants for measuring the availability of Cu, Fe, Mn, and Zn from uncultivated A‐ and C‐soil horizons to western wheatgrass ( Agropyron smithii Rydb.), silver sagebrush ( Artemisia cana Pursh), and above‐ground biomass was assessed at 21 geochemically diverse sites in the northern Great Plains. Positive relationships between the extractable or the total concentration of these elements in soils to concentrations in plants, as measured by multiple regression, were limited. A‐horizon DTPA‐extractable levels of Fe and Mn were significant positive independent variables in the prediction of Fe and Mn levels in wheatgrass. C‐horizon DTPA extractable levels of Mn and Zn were significant positive independent variables in the prediction of Mn and Zn sagebrush levels. Multiple regression techniques never gave significant relations between EDTA‐extractable element levels and plant element levels; however, strong relations were observed between soil pH and metal concentrations in plants. The relation between plant metal concentration and A‐horizon pH was always positive and apparently related to soil levels of metal carbonates. These data indicate that caution should be used in the formulation of regulations for plant available levels of these metals in Great Plains soils based solely on extractable levels.