www.IndianJournals.com Members Copy, Not for Commercial Sale Downloaded From IP - 14.139.59.53 on dated 18-Feb-2014 Clay Research, Vol. 29, Nos. 1&2 pp. 57-62 (2010) Smectite Distribution in Three Representative Vertisol Pedons of Different Agroclimatic Regions of India P.L.A. SATYAVATHI, S.K. RAY, P. RAJA, T. BHATTACHARYYA AND D.K. PAL Division of Soil Resource Studies, National Bureau of Soil Survey and Land Use Planning, Amravati Road, Nagpur 440 010, Maharashtra Abstract: Three benchmark Vertisol pedons pertaining semi-arid (moist), semi-arid (dry) and arid regions of India were studied for the depthwise distribution of smectite in different soil size fractions. Smectite content is more in semi-arid (moist & dry) soils comparing with arid soils and its content increased with depth and in BC horizon it decreased. Smectite dominates the clay fraction of Bss horizons and the depth distribution of smectite indicates illuviation of fine clay smectite in the studied soils. More than 2350000 km 2 of clayey soils high in smectites are distributed over the world (Buol et al., 1997). The occurrence of smectite in soils has been reviewed extensively by Jackson and Sherman (1953), Pal and Deshpande (1987), Wilding and Tessier (1988), Bhattacharyya et al. (1993). Appreciable amounts of smectite exist in soils in any of the four B’s: 1) basins, 2) B horizons, 3) Super B horizons, and 4) in basic rock-derived soils (Jackson, 1965). In each of these environments high Si and basic cations occur; conditions necessary for smectite formation and/or preservation. Leaching is often at a minimum (Jackson and Sherman, 1953). Reduced leaching simply protects smectite from weathering (Borchardt, 1989). The mineralogy of almost all soils classified as Vertisols by the USDA is dominated by smectite (Soil Survey Staff, 1975; Blokhuis, 1982; Dixon, 1982) and it plays a major role in establishing the physical and chemical properties of these soils. A knowledge of depthwise distribution of smectite is essential to understand about the properties of Vertisols. Hence, the present study was undertaken. Materials and Methods Three benchmark Vertisols were selected for the study. These soil series are Bhatumbra in Bidar, Karnataka representing semi-arid (moist), Semla Gondal, in Rajkot, Gujarat representing semi-arid (dry), and Sokhda, in Rajkot, Gujarat representing arid region. These soils were developed in the alluvium of weathered Deccan basalt.