CHANGES IN NH4HCO3-DTPA-EXTRACTABLE ZINC AND IRON AS AFFECTED BY VARIOUS SOIL PROPERTIES

Abstract

The NH4HCO3-DTPA soil test of Soltanpour and Schwab can be used to separate Fe- and Zn-deficient soils from nondeficient soils. After 8 wk of crop growth in greenhouse studies, the test soils were resampled, and NH4HCO3-DTPA-extractable Fe and Zn concentrations were recorded. Objectives of the present work were to establish the ability of the NH4HCO3-DTPA soil test to measure the changes in Fe and Zn levels in soils fertilized with Fe-EDDHA (ferric ethylenediamine di-(o-hydroxyphenyl acetate)) and ZnSO4 fertilizers, and to relate the variability in levels of extractable fertilizer Fe and Zn to properties of the 40 Colorado [USA] soils. Extraction of fertilizer Fe and Zn by NH4HCO3-DTPA from soils receiving Fe-EDDHA or ZnSO4 averaged 43 .+-. 6% and 57 .+-. 8%, respectively, indicating that the NH4HCO3-DTPA soil test provides a measure of the residual value of Fe and Zn fertilizers. Multiple linear regression analysis successfully accounted for much of the variability in extractability of fertilizer Fe and Zn; multiple coefficients of determination were 76 and 70%. Clay content and presence of lime were the most important soil properties in explaining variability in fertilizer Fe extractability, and clay content and soil pH were most effective for fertilizer Zn extractability.