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Date Available

5-1-2026

Year of Publication

2026

Document Type

Master's Thesis

Degree Name

Master of Agriculture (MAgr)

College

Agriculture, Food and Environment

Department/School/Program

Soil Science

Faculty

Chris Matocha

Abstract

Like soil texture, clay mineralogy is considered a permanent or inherent characteristic of soils reflecting the influence of soil forming factors over long periods of time. Despite the importance of clay mineralogy in providing ecosystem services, much remains unknown about whether land use (native grassland sod versus no-tillage) can modify clay mineralogy under short periods of time. Furthermore, in no-tillage agroecosystems, lower crop yields are often ascribed to immobilization of added N fertilizer where inorganic nitrogen (such as ammonium) is converted to organic nitrogen. The possible role of clay mineralogy in retaining added ammonium has been overlooked in no-tillage systems. The objective of this study is to evaluate the role of land use (native grassland sod versus no-tillage) in shaping clay mineralogy and soil properties from soils over a climate gradient (MAP 450-1320 mm) and on ammonium behavior.  There is a clear difference in clay mineralogy between sites that is corroborated by the cation exchange capacity values and reflects differences in precipitation. In addition, moving from native grassland sod to no-tillage was accompanied by a shift in clay mineralogy, with greater illitic layer content at the Sidney and Kentucky no-till sites when compared with the sod. ‘The clay mineralogical changes with precipitation and land use were reflected in the soils’ affinity for ammonium based on sorption KD values, where sites with smectitic mineral layers have a much higher affinity for added ammonium. While the exact mechanism(s) of clay mineral alteration is not known, the role of biota in shaping the clay mineralogical suite has emerged. This calls for a shift in our perspective of clay mineralogy which is assumed to only change on geological time scales.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.212

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Funding Information

This research was supported by the Agriculture and Food Research Initiative (AFRI). 

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