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  • 1
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2018, Vol.181(6), pp.894-904
    Description: Sonication is widely used for disruption of suspended soil aggregates. Calorimetric calibration allows for determining sonication power and applied energy as a measure for aggregate disrupting forces. Yet other properties of sonication devices (., oscillation frequency and amplitude, sonotrode diameter) as well as procedure details (soil‐to‐water ratio, size, shape, and volume of used containers) may influence the extent of aggregate disruption in addition to the applied energy. In this study, we tested potential bias in aggregate disruption when different devices or procedures are used in laboratory routines. In nine laboratories, three reference soil samples were sonicated at 30 J mL and 400 J mL. Aggregate disruption was estimated based on particle size distribution before and after sonication. Size distribution was obtained by standardized submerged sieving for particle size classes 2000–200 and 200–63 µm, and by dynamic imaging for particles 45 W). Thus, these sonication device properties need to be listed when reporting on sonication‐based soil aggregate disruption. The overall small differences in the degree of disruption of soil aggregates between different laboratories demonstrate that sonication with the energies tested (30 and 400 J mL) provides replicable results despite the variations regarding procedures and equipment.
    Keywords: Disaggregation ; Particle Size Fractions ; Reproducibility ; Round‐Robin Test ; Ultrasound
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 2
    In: European Journal of Soil Science, May 2019, Vol.70(3), pp.454-465
    Description: Soil structural traits provide links between soil structure and ecosystem functioning. The size and stability of soil aggregates are assumed to provide information on aggregate formation and turnover. A standard method to analyse these traits is to determine the mass distribution on sieves. The major drawback of this method is the small size resolution because of a small number of size classes. A promising, yet still unexplored, method for size distribution analysis in soil science, is dynamic image analysis, which foremost allows a much larger diameter resolution and the assessment of both size and shape distributions. The aim of our study was to validate the applicability of dynamic digital image analysis in combination with sonication to characterize the size and shape distribution and the stability of aggregates. We used two different heterogeneous reference materials and three different soil samples with different aggregate stabilities to test this method. The soil samples were chosen based on increasing clay, humus and calcium carbonate contents. The method yielded reproducible results for diameter and shape distributions for both reference materials and soil samples. The most important improvement compared to well‐established methods was the extremely large size resolution. This allows specification of the pattern of diameter‐dependent breakup curves by relating them to specific soil properties. The information on sphericity adds supplementary information on the aggregates released. We found much lower sphericity of 1‐mm aggregates mobilized from topsoil samples formed from the activity of living organisms than aggregates mobilized from subsoil samples formed mainly by physicochemical processes. Highlights Our aim was to validate dynamic digital image analysis to characterize soil aggregates.Dynamic image analysis allows high resolution and shape analysis compared to established methods.The method yielded reproducible results for diameter and shape distributions.We established high‐resolution disruption patterns of aggregates enabling new approaches in future research.
    Keywords: Aggregate Breakdown Dynamics ; Particle‐Size Distribution ; Ultrasonic Dispersion
    ISSN: 1351-0754
    E-ISSN: 1365-2389
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