Stability and Erodibility of Some Soils of West Bengal in Relation to their Aggregating Agents

Abstract

Aggregate stability is a measure to evaluate the ease with which soils erode by water and/or wind to predict the capacity of soils to sustain long-term crop production. In the present study, soils of four different agroclimatic zones of West Bengal, viz. terai, new alluvial, red-laterite and coastal saline having two different cropping systems, viz. rice-vegetables and rice-fallow were used to quantify the soil organic and inorganic aggregating agents and to identify the major agents responsible for the aggregate stability as well as the erodibility. Rice-vegetables cropping system showed significantly higher mean weight diameter, geometric mean diameter, aggregate stability and aggregate ratio as compared to rice-fallow system. Soil organic carbon (SOC) was the major organic binding agent ranged from 4.78 to 12.27 g kg-1, followed by polysaccharide (2.03 to 3.96 g kg-1), easily extractable glomalin (0.25 to 0.70 g kg-1) and phenol (0.011 to 0.053 g kg-1), respectively. The Ca2++Mg2+ was the major inorganic binding agent ranged from 0.78 to 3.07 g kg-1, followed by CaCO3 (0.09 to 2.04 g kg-1), Al2O3 (0.09 to 0.52 g kg-1), Fe2O3 (0.08 to 0.32 g kg-1), Na+ (0.10 to 0.34 g kg-1) and phosphate (0.01 to 0.10 g kg-1), respectively. Terai and new alluvial soils possessed higher SOC (11.0 and 10.3 g kg-1) and polysaccharides (3.81 and 3.24 g kg-1). Soils of new alluvial and coastal saline zones produced significantly higher water stable aggregates with SOC and sesquioxides as prime aggregating agents that increased clay flocculation ratio. Soils of red-laterite zone had an increased aggregate diameter with the help of Fe2O3 as primary agents that decreased stability with a plenty of water dispersible clays. Among the total binding agents, the relative abundance of organic and inorganic agents was 77 to 81 and 19 to 23%, respectively, indicating that the binding agents and their tying mechanisms cohere with soil particles to form aggregates depending on the climate, land use and soil environment.