Báez Lugo, Frances M.

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Hydroxy-interlayered 2:1 clays: A sink and a source of aluminum in an extremely acid Ultisol at the Coloso Valley Agricultural Reserve
(2024-05-06) Báez Lugo, Frances M.; Muñoz Muñoz, Miguel A.; College of Agricultural Sciences; O’Hallorans Castillo, Julia M.; Tirado Corbalá, Rebecca; Department of Agro-Environmental Sciences; Acuña Guzmán, Salvador F.
Exchangeable and extractable Al3+ fractions were evaluated in backslope and footslope profiles of Río Piedras soil (Typic Hapludults) at the Coloso Valley Agricultural Reserve in western Puerto Rico. Soil parameters evaluated were texture, clay surface area and mineralogy, pH, CEC, and Al3+ fractions extracted with 1 N KCl, 0.5 M CuCl2, 0.33 M LaCl3, and 0.33M Sodium Citrate at pH 7.3. The average soil pH for both profiles was 4.4, while the average KCl-exchangeable Al3+ was 10.9 cmolc kg-1 in the backslope and 9.2 cmolc kg-1 in the footslope. XRD analysis of the clay fraction indicated the presence of hydroxy-interlayered clay minerals and very low-intensity gibbsite peaks in most horizons. High soil acidity and the presence of expansible 2:1 clay minerals inhibit the formation of gibbsite and maintain high levels of exchangeable Al3+ and other extractable forms. The formation of hydroxy-interlayers in smectite and vermiculite confer these clay minerals high resistance to weathering, favoring their predominance over their ‘non-interlayered’ counterparts.