Soil Disintegration Characteristics on Ephemeral Gully Collapsing in Lateritic Belt of West Bengal, India

Abstract

Gully erosion has become a menace to agricultural and other development in the world. In the tropical and subtropical region of India, it is of very importance because of its advancement due to collapsing of head and gully wall. Quantification of different soil physico-chemical properties and soil disintegration characteristics within different weathering profiles (surface layer, red soil layer, sandy soil layer and detritus layer) and its relationships with different soil physico-chemical properties is necessary to understand the mechanism of the forming process and development of the collapsing gully. In this study, three collapsing gullies under red soil region of subtropical India were analysed for their physico-chemical properties and their relationships with the disintegration ability of the gully. The anti-disintegration ability of the different weathering profiles with two different moisture conditions (the natural state soil moisture condition and the air-dried condition) was determined by the anti-disintegration index (K c) and measured by the submerging test. The results showed that surface soil layers are high in finer soil particles and organic matter; and the sandy soil layer and the detritus soil layer are rich with coarser soil particles. The anti-disintegration coefficient gradually decreases with the increase in soil depth. The anti-disintegration coefficient decreases sharply with the increase of soil moisture. Therefore, sandy soil layer and detritus layers are vulnerable to disintegration due to the effect of external factors compared to the upper two layers. The anti-disintegration coefficient is positively correlated with clay and soil organic matter. Therefore, in soils with high clay and organic matter content smaller gully can be noticed, which is a common fact, and thus been established in this study with the help of anti-disintegration coefficient.