106570 Identifying the Possible Control of Clay Mineralogy of Soils in Some Southern US States over the Fluctuations in Potassium Fixation.
Poster Number 1317
Monday, October 23, 2017
Tampa Convention Center, East Exhibit Hall
Soil potassium (K) exists in solution, exchangeable, and non-exchangeable forms that are in dynamic equilibrium with each other. The majority of total K budget in soils is controlled by primary K-bearing silicates such as illite and other mica, interstratified illite-smectite, and K-feldspars. The extent to which K is fixed in the phyllosilicates capable to host it (illite, I-S, smectite) depends on the exact type of clay mineral, its cation-exchange capacity, mineral charge density, the degree of interlayering, the moisture content, the concentration of K+ ions, the concentration of competing interlayer cations, and the pH of the ambient solution. A study was conducted using the incubation method to determine the potential for K fixation in representative soils in some selected Southern US States. The results demonstrated a 30-60% potential K fixation by the soils across the different locations. Soils in the study area have pH in the slightly acidic to slightly alkaline region. A preliminary XRD analysis of the bulk soil sample showed the presence of illite-like phases and feldspars, with the possible presence of some minor illite-smectite and kaolinite. A separation of clay fraction is to be conducted to determine its mineralogical content. Clay minerals that dominantly control the K content in analyzed soils will be identified, which will ultimately lead to the understanding of the role of decisive parameters responsible for K-fixation in soils (exchange reactions, availability under various dry-wet cycle situations, time, and temperature).
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