Predicting soil organic matter stability in agricultural fields through carbon and nitrogen stable isotopes

Author(s)

Tim De Clercq, Maria Heiling, Gerd Dercon, Christian Resch, Martina Aigner, Leo Mayer, Yanling Mao, Annemie Elsen, Peter Steier, Jens Leifeld, Roel Merckx

Abstract

In order to evaluate the sustainability and efficiency of soil carbon sequestration measures and the impact of different management and environmental factors, information on soil organic matter (SOM) stability and mean residence time (MRT) is required. However, this information on SOM stability and MRT is expensive to determine via radiocarbon dating, precluding a wide spread use of stability measurements in soil science. In this paper, we test an alternative method, first developed by Conen etal. (2008) for undisturbed Alpine grassland systems, using C and N stable isotope ratios in more frequently disturbed agricultural soils. Since only information on carbon and nitrogen concentrations and their stable isotope ratios is required, it is possible to estimate the SOM stability at greatly reduced costs compared to radiocarbon dating. Using four different experimental sites located in various climates and soil types, this research proved the effectiveness of using the C/N ratio and δ¹⁵N signature to determine the stability of mOM (mineral associated organic matter) relative to POM (particulate organic matter) in an intensively managed agro-ecological setting. Combining this approach with δ¹³C measurements allowed discriminating between different management (grassland vs cropland) and land use (till vs no till) systems. With increasing depth the stability of mOM relative to POM increases, but less so under tillage compared to no-till practises. Applying this approach to investigate SOM stability in different soil aggregate fractions, it corroborates the aggregate hierarchy theory as proposed by Six etal. (2004) and Segoli etal. (2013). The organic matter in the occluded micro-aggregate and silt & clay fractions is less degraded than the SOM in the free micro-aggregate and silt & clay fractions. The stable isotope approach can be particularly useful for soils with a history of burning and thus containing old charcoal particles, preventing the use of ¹⁴C to determine the SOM stability.

Organisation(s)

Isotope Physics

External organisation(s)

Katholieke Universiteit Leuven, International Atomic Energy Agency (IAEA), Fujian Agriculture and Forestry University, Soil Service of Belgium, Agroscope

Journal

Soil Biology and Biochemistry

Volume

88

Pages

29-38

No. of pages

10

ISSN

0038-0717

DOI

https://doi.org/10.1016/j.soilbio.2015.05.011

Publication date

09-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

103014 Nuclear physics, 106002 Biochemistry, 405001 Agroecology

Keywords

ASJC Scopus subject areas

Soil Science, Microbiology

Sustainable Development Goals

SDG 15 - Life on Land

Portal url

https://ucrisportal.univie.ac.at/en/publications/15232010-0b1e-4675-83ea-c3e624017f42