Contemporary pedogenic formation of palygorskite in irrigation-induced, saline-sodic, shrink-swell soils of Maharashtra, India
Hillier, Stephen (Macaulay Institute)
Pharande, A. L. (College of Agriculture)

Data:	2008
Resum:	Increasing use of irrigation in India has exacerbated the problems of soil salinity and sodicity. The present study was undertaken on shrink-swell soils from Maharastra State to determine if changes in soil chemistry due to irrigation have affected the clay mineralogy. Twenty six samples (15 locations) of irrigation-induced, saline-sodic, shrink-swell soils and 27 samples (22 locations) of normal un-irrigated (rain-fed) shrink-swell soils were studied using X-ray powder diffraction (XRPD), infrared spectroscopy (FTIR), and scanning and transmission electron microscopy (SEM, TEM). The XRPD analysis of the <0. 2 μm fraction of rain-fed, shrink-swell soils indicates a predominance of dioctahedral smectite with minor to trace amounts of kaolinite and chlorite. Traces of palygorskite (1-4%) were detected in three samples. In contrast, palygorskite is a common component (1-20%) of the fine-clay fraction of salinesodic soils. Quantitative analysis of palygorskite by XRPD in whole-soil (<2 mm) samples showed that saline-sodic soils contain up to 20 wt. % of palygorskite, whereas palygorskite was only detectable (1. 5 wt. %) in one sample of the rain-fed set. The SEM, TEM, and FTIR confirm the presence of Fe-rich palygorskite in saline-sodic soils and demonstrate that the fibrous palygorskite crystals are exceedingly small (∼0. 5 mm long). Delicate palygorskite fibers radiate from the margins of smectite plates suggestive of a pedogenic origin and a close genetic relationship between smectite and palygorskite. The compositions of saturation-paste extracts display a shift from the stability field of smectite in rain-fed soils to that of palygorskite in saline-sodic soils. Thus the occurrence and formation of palygorskite appears to be related to the change in land management from rain-fed to irrigated agriculture. This change has occurred over a period of no more than 40-50 y, implying that palygorskite formation in the irrigated, saline-sodic soils has been an extremely rapid process.
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Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Beidellite ; Irrigation ; Montmorillonite ; Palygorskite ; Pedogenic ; Shrink-swell ; Soil ; Smectite ; Vertisol
Publicat a:	Clays and Clay Minerals, Vol. 56, Núm. 5 (2008) , p. 531-548, ISSN 1552-8367

DOI: 10.1346/CCMN.2008.0560507

18 p, 1.5 MB  Accés restringit a la UAB

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