Replicability of aggregate disruption by sonication—an inter‐laboratory test using three different soils from Germany

Abstract

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 (e.g., 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−1 and 400 J mL−1. 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 < 63 µm. Despite differences in sonication devices and protocols used by the participants, only 16 in 216 tests of samples of the size fractions 2000–200 and 200–63 µm were identified as outliers. For the size fraction < 63 µm, fewer outliers were detected (8 in 324 tests). Four out of nine laboratories produced more than two outliers. In these laboratories, sonication devices differed from the others regarding oscillation frequencies (24 or 30 kHz compared to 20 kHz), sonotrode diameters (10 and 14 mm compared to 13 mm), and sonication power (16 W compared to > 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−1) provides replicable results despite the variations regarding procedures and equipment.

Wet sieving versus dry crushing: Soil microaggregates reveal different physical structure, bacterial diversity and organic matter composition in a clay gradient

“…This has a great influence on aggregate properties. The size composition of wet‐sieved size fractions was shown to be highly reproducible by Graf‐Rosenfellner et al (2018). This homogeneity, however, appears to be the product of the wet sieving procedure with sonication.…”

Clay content modulates differences in bacterial community structure in soil aggregates of different size

“…This has a great influence on aggregate properties. The size composition of wet-sieved size fractions was shown to be highly reproducible by Graf-Rosenfellner et al (2018). This homogeneity, however, appears to be the product of the wet sieving procedure with sonication.…”

From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils

“…Thus, the overall elemental composition of the bulk soils can directly be linked to the 13 C isotopic composition of the fresh and more decomposed POM fractions. In Arctic ecosystems, N 2 fixation is known as the major N input into ecosystems (Granhall and Selander, 1973;Rousk et al, 2017Rousk et al, , 2018 with N fixation rates between 1 and 29 kg N ha −1 a −1 , depending on which N 2 -fixing species (e.g., free-living or moss-associated cyanobacteria) is dominating (Rousk et al, 2017). Furthermore, Arctic soils are known to be dominated by organic N cycling rather than mineral N cycling (Hobbie and Hobbie, 2008), while atmospheric N deposition is low in this region (Hole et al, 2009).…”