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Research article2017Peer reviewed

Soil aggregate breakdown in a field experiment with different rainfall intensities and initial soil water contents

Shi, P.; Thorlacius, S.; Keller, T.; Keller, M.; Schulin, R.


The breakdown of soil aggregates under the impact of rainfall is an important process in water erosion of agricultural soil. It determines the size characteristics of the disintegrated fragments and thus their availability for size-selective sediment transport and deposition. However, little is known about the dynamics of aggregate breakdown and its dependence on soil and rainfall properties under field conditions. In this research, we carried out artificial rainfall experiments to quantify the dynamics of aggregate breakdown in an agricultural field at two levels each of rainfall intensity (RI) and initial soil water content (IWC). In all treatments, the temporal dynamics of aggregate breakdown followed the same two-stage pattern: a steep exponential decrease in fragment mean weight diameter (MWD) during the first few millimetres of rainfall continued as a slow linear decrease at the second stage. The fragment mass size distribution (FSD) at the end of the rainfall events differed significantly among treatments. Slaking appeared to be the dominant breakdown mechanism in initially dry soil and was particularly strong at the higher RI, whereas mechanical breakdown was more prevalent in prewetted soil with no clear dependence on RI. We propose an empirical model that describes the effect of RI, IWC and initial aggregate stability on the decrease in MWD during the two stages of the breakdown process. The calibrated model successfully predicted the final MWDs in additional experiments, showing its potential for incorporation into erosion models to predict the size characteristics of surface soil fragments resulting from rainfall-induced aggregate breakdown for various initial soil moisture conditions.Highlights Rainfall-induced aggregate breakdown was investigated under field conditions. A two-stage breakdown pattern was observed in all treatments. Slaking appeared to be the dominant mechanism at the first stage, and mechanical breakdown at the second. A simple empirical model gave good predictions of aggregate fragmentation.

Published in

European Journal of Soil Science
2017, Volume: 68, number: 6, pages: 853-863
Publisher: WILEY

    Sustainable Development Goals

    SDG15 Life on land

    UKÄ Subject classification

    Soil Science

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