The Distribution of Micronutrient Cations in Soil Under Conditions of Varying Redox Potential and pH

Abstract

A laboratory study was conducted to determine the influence of redox potential and soil pH on the distribution of Fe, Mn, Zn, and Cu in Mhoon silty clay loam soil (Typic Fluvaquents) and to provide insight into factors affecting micronutrient dissolution and mobility in soil. Generally, greater amounts of Fe, Mn, Zn, and Cu were found in the Na acetate (exchangeable) and pyrophosphate (organic) extractions at low pH and Eh than at high pH or Eh. In contrast, the amounts (except Mn) in the water‐soluble, NH2OH·HCl, and oxalate fractions were greater at high pH or Eh. Although the micronutrients were brought into solution at low pH and Eh, much of the soluble cations soon associated with the exchangeable and organic fractions. After reduction, mobilized Fe associated about equally with the exchangeable, organic, and NH2OH·HCl fractions; mobilized Mn with the exchangeable and water‐soluble fractions; mobilized Zn with the organic fraction; and the mobilized Cu with the organic and water‐soluble fractions. Separation of the water‐soluble fraction into free ions and those complexed by soluble organic matter indicated that micronutrient cations were complexed by organic matter to a greater extent in reduced soil.

Mechanism of Iron Uptake by Peanut Plants

“…In long term studies, however, much lower concentrations of iron chelates (<10 LM) are sufficient to cover the iron demand for optimal growth (8, and unpublished data). In soil solutions, depending upon the pH and the redox potential of the soils, a high proportion of iron can be observed as complexed iron (17). Concentrations of complexed iron in soil solutions as hydroxamate siderophores between 10-8 and 10-7 M were found by Powell et at (13).…”

Factors influencing metal bioavailability in soils: preliminary investigations for the development of a critical loads approach for metals

“…Sulphide minerals are normally oxidised to sulphates at higher Eh levels (Evans, 1989). Sims and Patrick (1978) observed that water soluble Zn decreased at low Eh. However, the opposite was recorded by these authors for Cu and exchangeable (sodium acetate-extractable) concentrations of both Zn and Cu increased at low Eh.…”

Fracionamento, dessorção e extração química de zinco em latossolos

“…Em solos ácidos, como também observado por Xiang et al (1995) (Sims & Patrick, 1978;Iyengar et al, 1981).…”