TY - JOUR

T1 - Exploring the mechanisms of diverging mechanical and water stability in macro- and microaggregates

AU - Roosch, Svenja

AU - Felde, Vincent J.M.N.L.

AU - Uteau, Daniel

AU - Peth, Stephan

N1 - Funding Information: This study was conducted within the research unit “,” which is funded by the , project no. ). μCT scans of macroaggregates have been conducted with an X‐ray microscope that was financed by the (project no. ) at Leibniz University Hannover, Institute of Materials Science, by . Open access publication financed via project . We thank and (University of Bonn) for their help with the wet sieving of microaggregates and (University of Giessen) for conducting the element analysis of microaggregates. Three anonymous reviewers greatly helped to improve the manuscript. MADSoil—Microaggregate Development in Soil: Formation and turnover of the structural building blocks of soils DFG (Deutsche Forschungsgemeinschaft) (DFG RU 2179 276973637 DFG 316923185 Christoph Kahra DEAL Dymphie Burger Wulf Amelung Elke Müller

PY - 2024/2/8

Y1 - 2024/2/8

N2 - Background: Soil stability is often evaluated using either mechanical or hydraulic stress. The few studies that use both approaches suggest that these two types of stability behave differently. Aims: Our aim was to explore the mechanisms of aggregate stability regarding mechanical and water stability at the macro- and microscale, among other things, the effect of differing pore structure and soil organic matter content. Methods: Samples were taken from two adjacent plots that were expected to differ in stability due to land use, that is, cropped versus bare fallow (BF). The stability of dry-separated macroaggregates (8–16 mm) and microaggregates (53–250 μm) was determined via wet sieving and unconfined uniaxial compression tests. To explore the mechanisms of stability, 3D pore characteristics were analyzed with microtomography scans. Furthermore, the contents of carbon and exchangeable polyvalent cations as well as contact angles were determined. Results: Water stability of macroaggregates was much higher in the cropped plot (geometric mean diameter 0.65–2.37 mm [cropped] vs. 0.31–0.56 mm [BF]), while mechanical stability was very similar (median work 17.3 [cropped] and 17.5 N mm [BF]). The two size fractions behaved similarly regarding both types of stability, with more pronounced differences in macroaggregates. Several soil characteristics, like carbon, exchangeable calcium, and higher connectivity of pores to the aggregate exterior, contributed to water stability. Regarding mechanical stability, the destabilizing effect of lower carbon content and exchangeable calcium in the BF plot was counterbalanced by a lower porosity. Conclusions: Mechanical and water stability behaved differently in the two plots due to the different deformation mechanisms.

AB - Background: Soil stability is often evaluated using either mechanical or hydraulic stress. The few studies that use both approaches suggest that these two types of stability behave differently. Aims: Our aim was to explore the mechanisms of aggregate stability regarding mechanical and water stability at the macro- and microscale, among other things, the effect of differing pore structure and soil organic matter content. Methods: Samples were taken from two adjacent plots that were expected to differ in stability due to land use, that is, cropped versus bare fallow (BF). The stability of dry-separated macroaggregates (8–16 mm) and microaggregates (53–250 μm) was determined via wet sieving and unconfined uniaxial compression tests. To explore the mechanisms of stability, 3D pore characteristics were analyzed with microtomography scans. Furthermore, the contents of carbon and exchangeable polyvalent cations as well as contact angles were determined. Results: Water stability of macroaggregates was much higher in the cropped plot (geometric mean diameter 0.65–2.37 mm [cropped] vs. 0.31–0.56 mm [BF]), while mechanical stability was very similar (median work 17.3 [cropped] and 17.5 N mm [BF]). The two size fractions behaved similarly regarding both types of stability, with more pronounced differences in macroaggregates. Several soil characteristics, like carbon, exchangeable calcium, and higher connectivity of pores to the aggregate exterior, contributed to water stability. Regarding mechanical stability, the destabilizing effect of lower carbon content and exchangeable calcium in the BF plot was counterbalanced by a lower porosity. Conclusions: Mechanical and water stability behaved differently in the two plots due to the different deformation mechanisms.

KW - bare fallow

KW - computed tomography

KW - mechanical stability

KW - soil aggregates

KW - water stability

UR - http://www.scopus.com/inward/record.url?scp=85179370815&partnerID=8YFLogxK

U2 - 10.1002/jpln.202300245

DO - 10.1002/jpln.202300245

M3 - Article

AN - SCOPUS:85179370815

VL - 187

SP - 104

EP - 117

JO - Journal of Plant Nutrition and Soil Science

JF - Journal of Plant Nutrition and Soil Science

SN - 1436-8730

IS - 1

ER -