4. Soils of the Indo-Gangetic Alluvial Plains: Historical Perspective, Soil-Geomorphology and Pedology in Response Climate Change and Neotectonics

Indian earth scientists and soil scientists based on large number of well-presented pedons in the Indo-Gangetic Alluvial Plains (IGP), spread along the west hot arid climate to per-humid climate in the east, have led to new perspectives on the historical development of the IGP and the soils therein. This addresses the hitherto little known subtleties of pedogenesis and polygenesis due to recorded tectonic, climatic and geomorphic episodes and phenomena during the Holocene. Based on degree of development, five geomorphic surfaces, with soil ages 0.5, 0.5–2.5, 2.5–5.0, 5.0–10, >10 ka respectively, are mappable in the IGP and correspond to the post-incisive chronosequences that evolved in response to interplay of fluvial processes, climatic fluctuations, and neotectonics during the Holocene. The polygenetic signatures, illuvial clay pedofeatures, pedogenic carbonates, clay mineralogy, and stable isotope geochemistry, suggest the evolution of the IGP soils witnessed two humid phases (13.5–11.0 and 6.5–4.0 ka) with intervening dry climatic conditions. The IGP soils with varying climate from hot-arid to per humid belong to Entisols, Inceptisols, Alfisols, and Vertisols orders. Addition and depletion of OC, formation pedogenic CaCO₃, illuviation of clay particles and argilli-pedoturbation are the major pedogenic processes in soils of the IGP during the Holocene. The IGP soils are, in general, micaceous, but the soils with vertic characters are smectitic. A better understanding of the pedology of the IGP soils and their linkage to climate change, and landscape stability appear to be potentially useful as guideline for their management. Thus the new knowledge base has potential as a reference for critical assessment of the pedosphere for health and quality in different parts of the world and may facilitate developing a suitable management practices for the food security in the 21st century.