Soil structure and strength characteristics in relation to slope segments in a degraded Typic Ustroschrepts of northwest India.

摘要

It is imperative to understand the soil structure and strength characteristics of a watershed with respect to rainfall-runoff processes and adoption of suitable land management strategies. A study was conducted in an agricultural watershed of Typic Ustochrepts of northwest India to evaluate the role of soil organic carbon (SOC) and clay content in predicting soil structural and strength characteristics in three different slope segments. The bulk soil and undisturbed aggregates were sampled from shoulder, backslope, and footslope positions at 0 to 15 and 15 to 30 cm depth and used for laboratory analysis to evaluate SOC, clay content, and soil structural and strength characteristics in different slope segments. The SOC, clay content, and mean weight diameter (MWD) increased significantly down the slope. The soils in the footslope showed 5.36 times higher amount of macroaggregates (>2 mm) than the shoulder. The MWD was better explained with SOC (r2=0.85) than with clay content (r2=0.11). The MWD predictive model developed in the study was reasonably validated (r2=0.71) by another set of MWD values of samples collected nearby. Down the slope a decreasing trend of bulk density (BD) was observed, and it was reasonably (r2=0.60) predicted by SOC. The modulus of rupture (MOR) increased significantly by 75.5% in the backslope and 153.1% in footslope compared to the shoulder. Clay played the most determining factor (r2=0.85) to evaluate the MOR in terms of soil strength.