Chapter 5 Mineralogy and chemistry of vertisols

摘要: Summary Mineralogy and chemistry are important aspects of Vertisols. Their great diversity in terms mineralogical chemical properties makes it difficult to develop, adapt transfer technology from one region another. Factors soil formation: (1) parent material, (2) climate, (3) topography, (4) vegetation (5) time the primary basis for utilization management Vertisols, vertic intergrades. Vertisols may develop a variety materials. The latter, associated with environmental conditions provide generally high fine-clay content (high external surface area) often base status. also occur under wide range climatic conditions. Climate is weathering processes governs duration intensity dry-wet cycles necessary shrink-swell behavior. Topography do not influence regional distribution but have an impact on moisture regimes hydrology, i.e. water availability, leaching potential, depth, mineralogy, etc. dependent factors cited above, particularly type material Under certain few hundred years sufficient Vertisol. five forming complex interdependent. Therefore, comprehension formation genesis requires that prediction their behavior based by scientists others be site specific since more than pathway lead Vertisol formation. A large spectrum minerals originating inheritance, transformation or neoformation Kaolinite, illite, smectite hydroxy-interlayered (HIS) phases reported as abundant throughout world. Clay must small size area. smectites, particular, iron-rich, layer charge thermodynamically stable smectites geological origins. Many other phyllosilicates Vertisols; presence strongly depends origin past present These Vertisols' physical properties. either acid, neutral alkaline reaction; this impacts use interpretations. Cationic exchange capacity ranges between 20 45 cmol kg -1 (soil) attributed organic carbon, clay present. Exchangeable cations reflect pH Aluminum, magnesium exchangeable acidity when calcium proportion sites. Cation anion agronomic interest. Potassium ammonium subject strong retention micas, vermiculite, high-charge interstratified these components. Phosphorus limiting due its low most propensity sorption mineral surfaces. Nitrate sulfate mobile pollute groundwater. Organic matter 5 lOOgkg depending many factors. amount involved complexes molecular macroscopic levels. Inappropriate practices such continuous cultivation, enhanced salinity, etc., negative aggregate stability progressive structural degradation Shrink-swell phenomena result interactions among mineralogical, Major volume changes normal modification microstructure, pore content. Interparticle intraparticle porosity microstructure largely responsible soils. popular beliefs expansion/collapse interlayer space diffuse double slight very chapter attempted discuss exhaustive review soils (Vertisols intergrades) around Some regions world, however, been described widely reported. Efforts direction should done near future. Also, mentioned our discussion, further research related consider: o particle classification relation reactivity, properties; behavior, e.g. dispersion, sorption, desorption, retention, anions different phyllosilicates; pedobiology, location derived land utilization; control soils; stress accumulation-relaxation shrinking-swelling processes; clay-water systems saturated cation electrolyte concentrations; resihency, regeneration degraded