The profile distribution of total and DTPA‐extractable copper in selected soils in Louisiana

Abstract

In most of the relatively young soils, the highest concentration of total Cu occurred in the upper soil horizons. In older soils there was an increase in total Cu with increasing depth in the profile. The concentration of total Cu apparently varied more with the clay constituents of the soils and the parent materials than with soil depth. The majority of the soils had the largest amount of total Cu in the B horizons. The range in total Cu for all soils and horizons was 3.0-49.0 ppm. In the majority of the soils the highest concentration of DTPA [diethylenetriamine pentaacetic acid]-extractable Cu was in the surface Ap horizon. There was a decrease in the extractable Cu content with increasing soil depth in most of the soils. Soils developed in Red and Mississippi River alluvium contained relatively large amounts of extractable Cu, particularly in the surface horizons. The DTPA-extractable Cu in all of the soils and horizons ranged 0.10-5.12 ppm. There were highly significant positive correlations between extractable and total Cu and between Cu and organic matter in the soils developed in alluvium. Significant correlations were not obtained between extractable Cu and soil pH in Ap horizons in any of the soils studied.