Comparing Performance of Mn-Coated and Fe-Coated IRIS Devices.

Over the last decade, Fe-coated IRIS tubes have moved into common use for documenting reducing conditions in soils, and have been approved by the NTCHS for use as part of the Technical Standard for Hydric Soils. However, Fe oxides are reduced only under strongly reducing conditions, while important hydric soil (and wetland) functions and services (such as denitrification) occur under less intensely reducing, anaerobic conditions. Thus, there has been interest in exploring Mn-coated tubes to document moderately reducing soil conditions. Recently, a Mn oxide (birnessite) paint was developed that can be applied to PVC much like the Fe oxide (ferrihydrite-goethite) paint, such that a durable coating is easily achieved. As part of the NE1438 Multistate Research Project (Hydropedology of Vernal Pool Systems) both Fe-coated tubes and Mn-coated tubes were tested at 8 locations across the country. Five replicate tubes of each type were installed (paired) in plots along 3-point transects that spanned a range in hydrological conditions. This paper and poster will report on the performance of the Mn-coated and Fe-coated devices relative to each other and also in comparison with environmental variables.