CLAY MINERALOGY OF SHRINK-SWELL SOILS OF PATHARDI TAHSIL
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Date
29-06-02
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MAHATMA PHULE KRISHI VIDYAPEETH, RAHURI, DIST. AHMEDNAGAR. 413722. MAHARASHTRA STATE, (INDIA)
Abstract
Important and widespread Shrink-swell soils of Pathardi Tahsil were assessed for the clay mineralogy, bulk soil mineralogy, morphological characters and physical and chemical properties during the year 2001-2002. The data on important morphological, physical and chemical characteristics of soils used confirmed the Vertisols, Inceptisols and Entisols nature and were derived from basalt/basaltic alluvium and slightly conditioned by topography. They were categorized as very shallow to very deep, silty loam to clay, yellowish brown to dark gray brown in colour, moderately alkaline, highly calcareous in nature, low in organic matter, which decreased with depth, having no salinity and sodicity problems. The CEC of Vertisols and Inceptisols were found higher than the Entisols. The composition of saturation paste extract (SPE) analysis of Shrink-swell soil series indicated predominance of Ca2+ and Mg2+. Among the anions CI- and S04 2- were dominant. From the SPE analysis it was observed that these soils were free from salinity and sodicity features. The X-ray diffractograms of clay fractions of different soil series of Vertisol, Inceptisol and Entisol revealed the dominance of smectite in clay fractions (>95 per cent) with little proportion of kaolinite (5 per cent). The Greene-Kelly test confirmed the predominance of beidellite species of smectite rather than montmorillonite. The smectite clay mineral of Vertisol, Inceptisol and Entisol soil series of Pathardi Tahsil was predominated by iron rich beidellite-nontronite series. The X-ray of bulk soil indicated the presence of smectite, kaolinite, ilmenite and haematite with dominance of smectite followed by labradorite. Thus, Vertisol, Inceptisol and Entisol soil series showed variation in properties, such as morphological, physical and chemical characteristics but had negligible effect on clay mineral and bulk soil mineral assemblage. The quantitative data of X-ray powdered diffractograms of bulk soils indicated the predominance of smectite (40.3 per cent) followed by labradorite (21 per cent), quartz (9.8 per cent), calcite (8.2 per cent), kaolinite (7.4 per cent), augite (5.7 per cent), ilminite (2.7 per cent) and haematite (2.4 per cent). The Entisol soil series comparatively showed lower content of smectite, but higher content of kaolinite, quartz, labradorite, augite and haematite than Vertisol and Inceptisol soil series. The soil mineralogical assemblage was similar throughout the depth and no definite trend in respect of mineral content was observed.