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Initial soil aggregate formation and stabilisation in soils developed from calcareous loess

Pihlap, Evelin; Steffens, Markus and Kögel-Knabner, Ingrid (2021) Initial soil aggregate formation and stabilisation in soils developed from calcareous loess. Geoderma, 385, p. 114854.

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Document available online at: https://www.sciencedirect.com/science/article/abs/pii/S0016706120326094?via%3Dihub


In soil, carbonates are important inorganic binding agents, controlling aggregate formation and soil structural stability. Until today, a clear understanding of the aggregate forming mechanisms in calcareous soil is missing. The objective of this study was to elucidate the initial aggregate formation in calcareous loess from the point when soil organic matter content was low and soil properties were mostly controlled by the parent material. We used a space-for-time chronosequence approach on agriculturally reclaimed loess soils in an open-cast lignite mining area in Garzweiler, Germany. We selected six time points from 0 to 24 years after reclamation in order to investigate the early processes of soil aggregate formation. Samples from two sampling depths (1–5 cm and 16–20 cm) were wet sieved into four size classes: silt- and clay-sized fraction (<63 µm), large microaggregates (63–200 µm), small macroaggregates (200–630 µm), and large macroaggregates (>630 µm). Each aggregate size class was characterized for soil organic carbon, total nitrogen and CaCO3 content. Organic matter amendment induced the formation of large macroaggregates (>630 µm), but we did not detect an accumulation of soil organic carbon neither in microaggregates nor in the silt- and clay-sized fraction. The silt- and clay-sized fraction contained large amounts of CaCO3 throughout the whole space-for-time chronosequence. This finding shows that in undeveloped loess material, microaggregation is controlled by cementation by carbonates inherited from the loess. These carbonates were likely easily dissolved during contact with water, therefore, aggregates in the early stage of soil development were not water-stable. Soil aggregate formation on young calcareous soils consists of two main mechanisms, 1. fresh soil organic matter predominantly contributes to macroaggregate formation, and 2. intrinsic cementing of loess through carbonates affects microaggregate stability. Therefore, the early stages of soil development in loess material do not show an aggregate hierarchy as we would expect in soils with high silt and clay content, such as Cambisols and Luvisols.

EPrint Type:Journal paper
Keywords:Aggregate size distribution, Carbonates, Reclamation, Soil organic carbon allocation, Aggregate stability, Abacus, FiBL10125
Agrovoc keywords:
organic matter
Subjects: Soil > Soil quality
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil > Soil quality
Germany > University of Munich - TUM
Deposited By: Forschungsinstitut für biologischen Landbau, FiBL
ID Code:42760
Deposited On:09 Nov 2021 08:40
Last Modified:11 Jan 2022 12:44
Document Language:English
Refereed:Peer-reviewed and accepted

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