Comparison of different methods for assessing effects of soil interparticle forces on aggregate stability

Abstract

Soil interparticle forces, involving in van der Waalsattractive force, and surface hydration and electrostatic repulsive forces, greatly influence the soil aggregate stability. However, current studies on methods for evaluating the impact of soil interparticle forces in aggregate stability are scarce. This research was aimed to examine the impact of soil interparticle forces on aggregate stability using diverse methods for different soil types. Soil aggregate stability was tested through the pipette method, wet sieving, and rainfall simulation, respectively characterized by aggregate stability index (ASI), mean weight diameter (MWD), and splash erosion mass (SE). Soil interparticle forces were adjusted by the changing concentrations of NaCl solution. The results showed that all three approaches can be applied to study the impact of soil interparticle forces on aggregate stability. The ASI, MWD, and SE showed little change below 10−2 mol L−1 NaCl concentration and then ASI and MWD increased at a high rate above 10−2 mol L−1 concentration of NaCl, while the SE showed the opposite trend. These results were as expected for soil interparticle forces. Moreover, for a single soil, a substantial correlation existed between the aggregate stability indicators obtained from three methods. However, the order of soil aggregate stability, measured by three methods were varied among soil types. Our results suggest that a single method cannot be applied to determine the aggregate stability of all soil types even if the breakdown mechanism was identical, because organic matter content and particle size distribution of soil are important factors influencing aggregate stability. Hence, in order to compare the difference in aggregate stability between various soils, multiple methods should be considered to investigate the impact of interparticle forces of soil on its aggregate stability. If a single method was to be chosen, wet sieving may be a good choice as it was not only relatively simple and time-saving but also reflected more comprehensive information about sizes and amount of fragments released from soil aggregates.