We examined two Ultisols formed from glauconitic sediments of Eocene age for chemical, physical, and mineralogical characteristics. The parent glauconitic sediments have been subjected to intense weathering that has resulted in the release of large quantities of iron and the alteration of glauconite sequentially to vermiculite → smectite → hydroxy-interlayered vermiculite. These soils exhibited high capacities to adsorb K and P. Most of the naturally occurring K was adsorbed on high-energy-specific adsorption sites. Fertilizer K would be expected to be strongly retained by the clay minerals in these soils. Phosphorus adsorption was proportional to the clay and iron oxide content, exchangeable Al3+, and surface area. Adsorbed P was not easily removed by extraction with dilute CaCl2, indicating that it was not readily utilized by plants.
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