Landuse, Clay Mineral Type and Organic Carbon Content in Two Millisols-Alfisols-Vertisols Catenary Sequences of Tropical India

摘要

Soils under different land use attain a certain value of soil organic carbon (SOC) over a period of time. Research attempts to understand such value of major soil types of India are rare. The present study was therefore undertaken to find out SOC value in two Mollisols-Alfisols-Vertisols catenary sequences of Deccan basalt area in Central (Satpura Range) and Western Ghats regions of India. The results indicate that the Vertisols dominated by smectites, are usually under agriculture and has a SOC of~8 g kg-1 in the top 30 cm of soils. On the other hand the spatially associated Mollisols and Alfisols under forests and dominated by smectites, maintain relatively high SOC values of 12 to 26 g kg-1 in the top 30 cm of soils. The results show that SOC content is mainly a function of clay mineral type rather than clay content. The identification of smectite inter stratified with 0.7 nm minerals in these soils demonstrate its influence in SOC accumulation of tropical soils. Establishment of SOC values in relation to land use, and clay mineral type provides valuable hints about the upper limit of SOC sequestration in Vertisols of arid and semi-arid regions of India and elsewhere for their sustained productivity.