Technical ArticlesCHANGES IN QUANTITY AND COMPOSITION OF CRYSTALLINE CLAY ACROSS E-BH BOUNDARIES OF ALAQUODSHarris, W. G.; Hollien, K. A.Author Information Soil and Water Science Department, 2169 McCarty Hall, University of Florida, Gainesville, FL 32611. Dr. Harris is corresponding author. E-mail: [email protected] Florida Agricultural Experiment Station, Journal Series No. R-06633 Received Dec. 2, 1998; accepted March 26, 1999. Soil Science: August 1999 - Volume 164 - Issue 8 - p 602-608 Buy Abstract Theories of Spodosol formation emphasize chemical rather than particle translocation. However, some studies have presented evidence for particle as well as chemical migration in the formation of Bh horizons. In addition, abundant data for Florida Alaquods show that Bh horizons have significantly higher clay content than do eluvial and common subjacent horizons. This bulge in clay content has genetic implications if it is partially attributable to crystalline clay because it would be evidence suggesting that colloidal migration (lessivage) has occurred. This study was conducted to compare the amount and composition of crystalline clay contained in Bh and adjoining horizons of Alaquods. Data for more than 200 Alaquod profiles available from the Florida Cooperative Soil Survey database and complementary data generated for six of these profiles selected randomly from the pool were statistically analyzed. Pre-existing data included organic C; pyrophosphate-extractable C, Fe, and Al; citrate-dithionite extractable Fe and Al; and particle size distribution (pipette). Complementary data included particle size (centrifugal separation) and clay mineralogy (by X-ray diffraction and differential scanning colorimetry), each following H2O2 and ammonium oxalate pretreatment. Particle size data in conjunction with mineralogy confirmed a significant increase in resistant secondary phyllosilicates from the E to the Bh horizon, consistent with a physical redistribution of clay particles from the E to the Bh horizon. A possible source of these particles is sand grain coatings, which are absent from Alaquod E horizons but present in E horizons of most other sandy soils on better drained adjacent land-forms. Noncrystalline Al in grain coatings may be the source of Al accumulated in the Bh horizons of these soils, rather than weatherable minerals, which are nearly absent in the upper 2 m. © 1999 Lippincott Williams & Wilkins, Inc.