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RESEARCH ARTICLE (Open Access)

Podzolisation affects the spatial allocation and chemical composition of soil organic matter fractions

Agnes Krettek https://orcid.org/0000-0002-3119-4923 A B , Ludger Herrmann A and Thilo Rennert https://orcid.org/0000-0003-1435-2157 A
+ Author Affiliations
- Author Affiliations

A Department of Soil Chemistry and Pedology, Institute of Soil Science and Land Evaluation, University of Hohenheim, D-70593 Stuttgart.

B Corresponding author. Email: agnes.krettek@uni-hohenheim.de.

Soil Research 58(8) 713-725 https://doi.org/10.1071/SR20164
Submitted: 10 June 2020  Accepted: 11 August 2020   Published: 25 September 2020

Journal Compilation © CSIRO 2020 Open Access CC BY-NC-ND

Abstract

Podzols are soils that display a unique vertical distribution of soil organic matter (SOM). We hypothesise that podzolisation, as a pedogenetic process, influences or even controls content, allocation and quality of SOM. We determined soil organic carbon (SOC) and nitrogen (N) contents in six SOM fractions obtained from mineral horizons of five soils with increasing degree of podzolisation: sand and stable aggregates (S + A), particulate organic matter (POM) > 63 µm and <63 µm, silt and clay (s + c), resistant SOC and dissolved organic matter. We applied infrared spectroscopy to evaluate SOM decomposition state, relative abundance of functional groups and SOM-metal complexation. In topsoil horizons, relative SOC allocation shifted from the larger to the smaller size POM fraction with increasing podzolisation. Accompanied with size reduction, the POM < 63 µm fraction was progressively less decomposed, as derived from infrared spectroscopy and C : N ratios. In illuvial subsoils, the proportion of SOC in the S + A fraction increased with increasing podzolisation, implying SOM accumulation in aggregates and coatings on sand grains. Elevated abundance of carboxylate and aromatic C in the s + c fractions of subsoil horizons indicated their preferred sorption. Additionally, metal-carboxyl complexation increased during podzolisation.

Additional keywords: fractionation, infrared techniques, Podzols.


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