Development of In-Field Diagnostic Methods for Identification of Spodic Materials

Abstract

Using field methods to determine a soils specific properties has been used for many years. Spodic soil horizons in particular are often identified in the field via the Munsell color chart and by looking for eluviation in the horizons layered above the suspected spodic material. Spodic horizons have rich concentrations of sesquioxides (iron and aluminum) chelated with organic matter, and they are often identified by a reddish hue indicating these sesquioxides. Plus, darker colors may indicate an especially high accumulation of humus (organic matter). The portable x-ray fluorescence (pXRF) is an instrument that detects specific elements within a soil sample and tells the user the abundance of each element. The pXRF has the capability to accurately measure iron and aluminum content within a soil sample. Eight sites suspected of having spodic materials in Schmeeckle Reserve, Stevens Point, WI were dug out and a sample from each horizon was collected. The samples were then described via typical field sampling methods. The samples were then ground down and the lab analyses of pH, loss on ignition and pXRF were performed. A comparison was made between the results from the field methods and the lab methods. If the in-field soil description methods of Munsell color, organic matter estimation via color, and Hellige-Truog pH estimation can be accurately correlated to the laboratory methods of loss on ignition, pH by electrode and portable x-ray fluorescence for sesquioxide concentrations and organic matter, then these stated in-field methods can be trusted for identifying spodic materials. Utilizing these field methods could conserve time, money, and labor by reducing duplicate tests that me be performed in the field and then again in the laboratory.