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Plasmic fabric and calcium carbonates of Vertisols in a climosequence from humid to arid environments of Peninsular India

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Title Plasmic fabric and calcium carbonates of Vertisols in a climosequence from humid to arid environments of Peninsular India
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Creator Maurya, U.K., Raja, P., Bhattacharyya, T., Chandran, P., Ray, S.K. and Pal, D.K.
 
Subject Plasmic fabric, calcium carbonates, Vertisols, climosequence, humid, arid, environments, Peninsular India
 
Description Not Available
Micromorphological studies of 22 thin sections of seven benchmark Vertisols, formed mostly in the alluvium of the Deccan Trap basalt in humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic zones, were undertaken. An attempt has been made to understand the possible reasons for their differences in plasmic fabric and CaCO3 despite their common shrink–swell properties as evidenced by the presence of slickensides and high clay content.

Soils of HT climate indicated strong plasma separation with poro/parallel/ granostriated b-fabric. Soils of SHM climate indicated strong plasma separation with parallel/reticulate/ crescent striated with some stipple-speckled b-fabric whereas soils of SHD climate indicated mostly crystallitic and stipple-speckled with some granostriated b-fabric. Soils of SAM indicated mostly crystallitic and mosaic-speckled with some parallel/granostriated b-fabric whereas soils of SAD climate showed primarily mosaic/ stipple-speckled with some parallel/granostriated b-fabric. Soils of AD climate showed primarily crystallitic with some granostriated b-fabric. It was observed that plasma separation is more pronounced around grains and in voids in all soils of HT, SHM, SHD, SAM and SAD climates. Poor plasma separation in the soils of AD climate can be attributed to weak swelling of clay smectite which is sufficient for the development of slickensides but not adequate for the development of poro/parallel striated b-fabric.

Study indicated that all the soils have variable quantity of discrete calcium carbonate glaebules with and without Fe/Mn coating. The former is non-pedogenic CaCO3 (NPC) and the latter form is pedogenic (PC). All the soils under study except one of HT climate in Western India have both NPC and PC in the upper 100 cm of the profile. In general the content of PC increases with decrease in mean annual rainfall (MAR) and shows an higher values than NPC. The nearness between NPC and PC indicates the formation of PC at the expense of NPC. But the soils of AD climate have significant amount of calcite crystals which were absent in soils of other climates. This indicates that plasma separation is weak and in a state of disorganization in soils of AD climates. High clay content induces cracks and distinctive structural elements in the major body of Vertisols but their b-fabric are not identical in the Bss horizons. The gradual degradation of plasma separation in soils from HT to AD climates appears to be related to the presence of CaCO3 that was thought hitherto to inhibit the swelling. But the release amount of Ca+2 ions from CaCO3 in alkaline environment of Vertisols is negligible and unable to contract the diffuse double layer required for swelling of smectite. This may thus be attributed to less number of swell-shrink cycles due to low content of stored moisture.
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Date 2020-06-27T01:29:49Z
2020-06-27T01:29:49Z
2006-12-01
 
Type Presentation
 
Identifier Maurya, U.K., Raja, P., Bhattacharyya, T., Chandran, P., Ray, S.K. and Pal, D.K. (2006). Plasmic fabric and calcium carbonates of Vertisols in a climosequence from humid to arid environments of Peninsular India 15th Annual Convention and National Symposium on “Clay research in relation to Agriculture, Environment and Industry” of the Clay Minerals Society of India, BCKVV, Mohanpur, West Bengal, December 1-2 2006, pp10.
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http://krishi.icar.gov.in/jspui/handle/123456789/37489
 
Language English
 
Relation Not Available;
 
Publisher Clay Minerals Society of India