Effects of soil porosity on water stability of aggregates

Abstract

Soil pore structure is a fundamental determinant of water infiltration, flow, and storage, and it is intricately linked to soil stability and erodibility. Understanding the interplay between soil pore structure and aggregate disintegration is vital for refining the erodibility factor in soil erosion prediction models. This study aimed to examine the differential impacts of pore volume on aggregate disintegration by employing three soil samples with controlled internal pore spaces at various initial moisture contents (air-dried aggregates with 3 %, 5 %, 10 %, 15 %, and 20 %). Computerized Tomography (CT) scanning technology was utilized to visualize and quantitatively assess the aggregate pore structure. The results indicated that the number of pores, as measured in three-dimensional (3D) space and fractal dimension (FD), initially increased and then subsequently decreased with rising moisture content. An increase in moisture content was associated with a decline in aggregate anisotropy values. The resistance of aggregates to slaking (RSI) diminished progressively with increasing moisture content. A significant negative correlation was observed between moisture content and anisotropy, mean weight diameter in the slow wetting (MWD_sw), MWD in the pre-wetting followed by shaking (MWD_ws), and RSI. Conversely, anisotropy, MWD_ws, and RSI exhibited significant positive correlations. This study not only enhances our understanding of the relationship between soil pore structure and stability but also has substantial practical implications for predicting water infiltration, flow, and storage in soil during natural rainfall events, as well as for assessing the stability and erodibility of soil aggregates under varying humidity conditions and improving soil erosion prediction models.