Microtopographic controls on soil formation in the Punjab region, India

Abstract Evolution of Alfisols in Punjab in genetically isolated pockets on concave landforms is a unique phenomenon. Our objective was to investigate the properties and genesis of these Alfisols. These soils are developed on alluvial parent materials of Pleistocene to Holocene age and are found alongside Inceptisols. These soils are largely a product of microtopographic differences which modify distribution of water across the landscape. The soils are deep, show A–Bt–C profiles, are lithochromic and have strong structural B horizons. The depth of Bt horizons, organic matter content and root distribution increase with rainfall and decreasing temperature. Textures of surface horizons are loam to sandy loam and subsurface textures are finer. The soils are slightly acidic to slightly alkaline. The minerals identified are quartz, micas, feldspars (plagioclases and alkali feldspars) with minor amounts of ferromagnesian silicates in the sand and silt fractions. Illite, smectite, kaolinite, vermiculite and chlorite are identified in the clay fractions. The soils are allocated to the classes Typic Hapludalfs, Typic Haplustalfs and Udic Haplustalfs. The concavity of land surface and heavy rainfall events during the monsoon months (July through September) facilitate argillic horizon development.