Soil and Landscape Factors Influencing Microbial Reduction of Iron Oxides.

We know that numerous factors can influence the development of reducing conditions in soils, including 1) the presence of appropriate soil microorganisms, 2) minimizing available oxygen through soil saturation, 3) the abundance and ease of alteration of oxidizable carbon, and 4) soil temperature effects on rates of microbial metabolic reactions.  There are also several approaches that have been utilized to assess the onset or presence of anaerobic or reducing soil conditions, such as measurements of redox potential with electrodes, the use of colorimetric dyes (such as alpha,alpha-dipyridyl), or more recently, the use of iron oxide coated IRIS tubes. Recent experimental work, however, suggests that use of the different methods may result in different conclusions.  This paper will propose an integrated approach for understanding the relationship between soil properties and environmental factors which together contribute to the onset of anaerobic conditions and the reduction of iron oxides in soils.