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The climate change and land degradation are both individually and in combination have profound influence on natural resource based livelihood systems and societal groups, but this land degradation is caused by land use changes and unsustainable management. The different land use systems practiced in southern agro-climatic zones of Karnataka have significant impact on soil carbon and fertility status of soils, a study was carried out to characterize and classify the soils of southern agro-climatic zones of Karnataka. Five pedons, one from each agro-climatic zone from cultivated land use were selected for the study. Soils of Hiriyur pedons were moderately shallow and rest were deep to very deep, red, well drained and appreciable amount of gravels were observed in all the pedons. Clay illuviation in sub-soil layers was observed hence sub-soil layer contained more clay than surface. The soil texture varied from sandy clay loam to sandy clay and clay. Bulk density of soil varied from 0.86 to 1.86 Mgm-3 in the surface. In all the profiles, bulk density increased with depth. Soil reaction varied from very strongly acidic to moderately acidic in Balehonnur and Brahmavara, moderately acidic to neutral in Hassan and Tiptur, neutral to moderately alkaline in Hiriyur. Cation exchange capacity was low and exchange complex was dominated by hydrogen and aluminum. Dominant cations were calcium and magnesium hence base saturation was high in the pedons due to leaching of bases and deposition in sub-surface horizons within the solum except in Brahmvara and Balehonnur was observed.

Microorganisms give life to the soil and provide a variety of ecosystem services to plants. Soil bacteria are the strongest candidates for determining soil health. Bacterial communities are important for the health and productivity of soil ecosystems. Therefore, we must have a thorough knowledge of the diversity, habitat, and ecosystem functioning of bacteria. In this chapter, we will discuss the functional, metabolic, and phylogenetic diversity of soil bacteria and highlight the role of bacteria in the cycling of major biological elements (C, N, P, and S), detoxification of common soil pollutants, disease suppression, and soil aggregation. This chapter also underlines the use of soil bacteria as indicators of soil health. We have concluded the chapter by taking note of the present agricultural practices that call for concern regarding the natural soil microflora and steps to return biological activity to the soil.