Characterization and classification of soils under different land use systems in the upper Brahmaputra valley of Assam

Abstract

For characterization of soils, soils were collected from Jorhat and a Golaghat district during 2016-2017under different land uses systems i.e. bamboo, sugarcane, tea and rice. Results indicated that surface soils of different land use systems varied from greyish brown (10YR 5/2) to brownish yellow (10YR 6/8).The structure was found predominantly sub-angular blocky and loam to clay loam in texture. The soil soils of all horizons of bamboo, tea plantation and rice were extremely acidic (pH <4.5) except sugarcane horizons (strongly acidic pH 5.0-5.50).Soil cation exchange capacity(CEC) in bamboo, sugarcane, tea plantation and rice varied from 6.20 to 7.29 cmol (p+)/kg, 8.19 to 9.92 cmol (p+)/kg, 5.54 to 6.88 cmol (p+)/kg, and 6.99 to7.58 cmol (p+)/kg, respectively due to variation in clay content. Sugarcane and tea plantation soils showed clay alleviation with more than 1.2 times in sub-surface horizon over surface horizon with low base saturation <35%to place them in the Ultisol and classified as fine-loamy, mixed, hyperthermic family of Typic Hapludults.In bamboo plantation, the soil had cambic horizon with base saturation <35%and classified as coarse loamy, mixed, hyperthermic family of Typic Dystrudepts, whereas, in case of rice soil, the gleyed sub-surface horizon was observed with base saturation <35% and classified as loamy, mixed, hyperthermic, Typic Endoaquepts.The correlation coefficient (r) among physico-chemical of soil properties in profiles under different land use systems in upper Brahmaputra valley of Assam showed organic carbon was positively and significantly correlated with base saturation. The pH showed positive and significant correlation with CEC and clay content.