Gypsum soils—Their morphology, classification, function, and landscapes

60 Pags.- 1 Tabl.- 17 Figs. The definitive version is available at: http://www.elsevier.com/books/book-series/advances-in-agronomyGypsum soils are both a problem and a puzzle, which is precisely why they deserve attention. Gypseous (high-gypsum) soils generally occupy sparsely populated land with minimal land use intensity in arid and semiarid climates. Gypsum content in agricultural soils results in restricted water and nutrient retention and the potential for dissolution piping, primarily in response to irrigation. The corrosive effects of gypsum soils on concrete, metal, and building materials are also problematic. On the other hand, understanding the genesis and function of gypsiferous (low-gypsum) and gypseous soils is interesting and challenging, and our grasp of processes involved in the formation and behavior of these soils is critical for proper management for agricultural, rangeland, engineering, and construction purposes. The objective of this review was to examine the physical and chemical properties of gypsum and the impacts of these properties in the soil environment. The particular properties that gypsum presence imparts to soils affect soil development, including soil morphology. Accumulations of pedogenic gypsum influence water-holding capacity, nutrient and water availability for plants, root growth, and the standard concepts of soil texture and rupture resistance. Gypsum precipitation is also affected by the presence of more soluble salts. The development of physicochemical models that explain the formation and function of gypsiferous and gypseous soils is necessary if we hope to properly manage and maintain these unusual soils and their landscapes.We gratefully acknowledge the commitment and contributions of the National Cooperative Soil Survey (NCSS) Gypsum Soils Task Force, established in 2007 under the auspices of the USDA-NRCS-Soil Science Division (SSD), to address the mapping, description, taxonomic classification, interpretations, laboratory methodology, and soil–geomorphic relationships on gypsiferous and gypseous soils, although the Task Force is currently inactive. A number of field photos were provided by Philip J. Schoeneberger, a member of this Task Force. We particularly appreciate the efforts of Sharon W. Waltman and Paul Reich, USDA-NRCS-SSD staff, for their assistance in preparation of the map and tabulated data on extent of gypsum soils in the United States and worldwide, respectively. The collaborative effort behind this manuscript is reinforced by a Letter of Intent between the College of Agriculture and Natural Resources, Texas Tech University, and Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC), Spain, with the intent to foster joint academic programs and research activities.Peer reviewe

Evaluation of portable x-ray fluorescence for gypsum quantification in soils

The use of field portable X-ray fluorescence (XRF) spectrometry as a quantification tool for gypsum content in soils of West Texas and southern New Mexico, USA, was evaluated. Six sites were evaluated with gypsum contents ranging from less than 10% to greater than 90%. Samples collected from each site were scanned in the field using XRF and then transported to the laboratory for additional XRF scanning. Variables that might affect XRF scanning results, such as scanning time, particle size, moisture content, and so on, were evaluated. Both gypsum (CaSO4 • 2H2O) and calcite (CaCO 3) were quantified using standard laboratory techniques. Three data sets were compared: (1) soil characterization data, obtained from the National Soil Survey Laboratory Research Database in Lincoln, NE; (2) quantitative X-ray diffraction; and (3) portable XRF (PXRF). The best correlation of gypsum XRF data (via Ca quantification minus calcite content) and laboratory data was between PXRF and quantitative X-ray diffraction (R = 0.96). On average, PXRF provided results within 6% of soil characterization data, the current laboratory standard for gypsum quantification. Field PXRF shows considerable promise as a rapid, quantifiable measure of gypsum in soils. © 2009 by Lippincott Williams & Wilkins, Inc.Peer Reviewe