Detectability of degradable organic matter in agricultural soils by thermogravimetry

David Tokarski, Jana Šimečková, Jiří Kučerík, Karsten Kalbitz, Michael Scott Demyan, Ines Merbach, Dietmar Barkusky, Joerg Ruehlmann, Christian Siewert

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Sustainable agricultural land use requires an assessment of degradable soil organic matter (SOM) because of its key function for soil fertility and plant nutrition. Such an assessment for practical land use should consider transformation processes of SOM and its sources of different origin. In this study, we combined a 120-day incubation experiment with thermal decay dynamics of agricultural soils altered by added organic amendments. The aim was to determine the abilities and limits of thermal analysis as a rapid approach revealing differences in the degradability of SOM. The carried out experiments based on two independent sampling sets. The first sample set consisted of soil samples taken from non-fertilized plots of three German long-term agricultural field experiments (LTAEs), then artificially mixed with straw, farmyard manure, sheep faeces, and charcoal equal to 60 Mg ha−1 under laboratory conditions. The second sample set based on soil samples of different treatments (e.g., crop type, fertilization, cultivation) in LTAEs at Bad Lauchstädt and Müncheberg, Germany. Before and after the incubation experiment, thermal mass losses (TML) at selected temperatures were determined by thermogravimetry indicating the degradability of organic amendments mixed in soils. The results confirmed different microbial degradability of organic amendments and SOM under laboratory conditions. Thermal decay dynamics revealed incubation-induced changes in the artificial soil mixtures primarily at TML around 300°C in the case of applied straw and sheep faeces, whereas farmyard manure showed mainly changes in TML around 450°C. Charcoal did not show significant degradation during incubation, which was confirmed by TML. Detailed analyses of the artificial soil mixtures revealed close correlations between CO2-C evolution during incubation and changes in TML at 300°C with R2 > 0.96. Results of the soils from LTAEs showed similar incubation-induced changes in thermal decay dynamics for fresh plant residues and farmyard manure. We conclude that the practical assessment of SOM could be facilitated by thermal decay dynamics if modified sample preparation and evaluation algorithms are used beyond traditional peak analysis.

Original languageEnglish
Pages (from-to)729-740
Number of pages12
JournalJournal of Plant Nutrition and Soil Science
Volume182
Issue number5
DOIs
StatePublished - 1 Oct 2019
Externally publishedYes

Keywords

  • artificial soil mixtures
  • field experiments
  • microbial degradation
  • organic fertilizers
  • soil organic matter
  • thermal decay dynamics

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