Fragipan Degradation and Nodule Formation in Glossic Fragiudalfs of the Lower Mississippi River Valley

Abstract

Glossic Fragiudalfs comprise several million hectares of agronomically important soils within the silty uplands of the lower Mississippi River Valley (Major Land Resource Area [MLRA] 134). These soils are typified by a fragipan within 100 cm of the surface overlain by a 5‐cm‐thick, or more, glossic horizon containing bleached coatings (albic material) along primary ped faces, indicating fragipan degradation. Concentrations of Fe–Mn nodules also occur in horizons above the fragipan. There is limited documentation regarding the in situ morphology of the nodules or their relationship to the underlying fragipan. The objectives of this study were to document (i) the profile distribution of nodules, (ii) variations in nodule morphology with depth, and (iii) the role of fragipans in nodule formation. Nodules were most common and largest directly above the fragipan horizons. Field and micromorphological observations suggested the nodules formed in remnants of the brittle fragipan matrix as a result of the conversion of Btx material to E′ material (albic material) that isolated and surrounded brittle fragipan peds. The brittle peds that are the precursors to nodules appeared to decrease in size and became more highly impregnated with Fe and Mn oxides with distance above the fragipan. Spatial relationships of Fe concentrations and argillans within the nodules illustrated that the nodules were being formed in place and were not transported despite having distinct borders. With time the glossic horizon expands at the expense of the fragipan, resulting in a horizon consisting of Fe–Mn nodules and a few isolated brittle peds in a matrix of albic material.

Influence of redox processes on clay mineral transformation in Retisols in the Carpathian Foothills in Poland. Is a ferrolysis process present?

“…Additionally, the lower soil horizons are characterized by presence of many hard and soft Fe-Mn nodules, and many clay coatings on ped faces and clay infillings in channels (Table 2) (Szymański et al 2011(Szymański et al , 2012. Such a morphology of the soils is very typical for Retisols (Albeluvisols) occurring in different areas around the world (e.g., Brinkman 1979;Lindbo et al 1994Lindbo et al , 1995Lindbo et al , 2000Montagne et al 2008;Kalinina et al 2013;Sauer et al 2013;Nikorych et al 2014).…”

“…Thus, it is very likely that ferrolysis may take place in Retisols containing a fragipan, because of the high bulk density and low porosity of the pan (e.g., Witty and Knox 1989;Lindbo et al 1994;Ciolkosz et al 1995;Szymański et al 2011). The seasonal stagnation of water within Retisols causes the bleaching of soil material indicating reduction and dissolution of iron oxides and their subsequent re-oxidation and immobilization in the form of iron nodules, concretions, soft masses, and pore linings (Cescas et al 1970;Schwertmann and Fanning 1976;Rhoton et al 1993;Zhang and Karathanasis 1997;Lindbo et al 2000;Dixon and White 2002;Szymański et al 2011Szymański et al , 2012Szymański et al , 2014Szymański and Skiba 2013). Similar changes in the valence of iron may occur within the structures of clay minerals containing iron in the octahedral sheet (e.g., Rich 1968;Brinkman 1977;Rozenson and Heller-Kallai 1978;Gerstl and Banin 1980;Hardy et al 1999;Kohut and Warren 2002).…”

Suitability of Kabanyolo Soils for Fruit and Vegetable Production

“…Such morphology indicates that the pedons could have resulted from the translocation of colloids (clay minerals and iron oxides) and cyclic reduction-oxidation processes [25] [26].…”

Location and expression of fragic soil properties in a loess-covered landscape, Southern Illinois, USA

“…8c, d). Development of an eluvial horizon is common in horizons overlying or extending into fragipans, with degradation commonly occurring between coarse prismatic structural units (Miller et al, 1971;Lindbo et al, 2000;Weisenborn and Schaetzl, 2005b).…”