Characterization and Classification of Some Alluvium-Derived Rice and Associated Non-Rice Soils of Jorhat District of Assam

Abstract

A study was conducted to characterize and classify some traditional rice and associated non-rice soils of Jorhat district of Assam. Three locations (Borholla, Koronga and Alengmora) were selected for the purpose and alltogether six soil profiles, one each from rice and associated non-rice soils, were collected. The results showed only few differences in morphological, physical and chemical properties between the rice and associated non-rice soils. Soils were dark brown to brownish yellow in colour, sandy loam to clayey in texture and very strongly acidic to neutral in reaction. The organic carbon (OC) content was found to be higher in the surface horizons (10.3-18.1 g kg-1) as compared to the sub-surface horizons (1.2-15.5 g kg-1). Exchange acidity of the soils ranged from 0.50-3.25 cmol(p+)kg-1 and indicated dominance of exchangeable Al3+ (0.25-2.63 cmol(p+)kg-1). The CEC was invariably low (4.7-12.3 cmol(p+)kg-1). Rice soils of Borholla and Alengmora showed marginally higher pH than non-rice soils but OC exhibited an opposite trend. Exchangeable Al3+, exchange acidity and total potential acidity were slightly higher in rice soils of Borholla and Koronga than non-rice soils. The rice and associated non-rice soils of Borholla were qualified for Alfisols and classified as Oxyaquic Hapludalfs at subgroup level. Both rice and non-rice soils of Koronga and Alengmora were placed under Inceptisols and Entisols and classified as Oxyaquic Dystrudepts and Typic Udifluvents, respectively at subgroup level. An improvement in profile development was observed with the increase in the distance from the river Brahmaputra because of improvement in drainage condition and stability of landforms.