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| Home > Publications database > Using radiogenic and metal stable isotope ratios as new tools to assess nutrient cycling in agricultural systems |
| Conference Presentation (After Call) | FZJ-2026-03244 |
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2026
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-03244
Abstract: Ratios of radiogenic and metal(loid) stable isotopes are well-established tools in geosciences to trace geological transformation processes. Although these processes also occur in agricultural systems, the application of these isotope ratios in agriculture is still poorly constrained. Apart from the fact that the isotope composition of metal elements like iron (Fe) and magnesium (Mg) differ between soil compartments and plants, agricultural practices often alter biogeochemical processes and thus isotope ratios in agri-systems. Therefore, analyzing these stable isotopes can help understand the cycling and use efficiency of key nutrients under agricultural conditions. In this presentation, we will present several examples of such applications in the investigation of long-term agricultural land-use and sustainable subsoil management funded by the Deutsche Forschungsgemeinschaft (DFG, PaddyFe Project, No. 391749090) and the Bundesministerium für Forschung, Technologie und Raumfahrt (BMFTR, BonaRes-Projects Soil3, No. 031B0026C, 031B0515C, and 031B1066C).Using Fe stable isotopes we reconstructed Fe dynamics in a paddy chronosequence, revealing that long-term rice cropping and subsequent redox cycle altered the biological contribution in the terrestrial Fe cycle. Long-term liming reduced Fe availability to crops due to the increased soil pH and promoted the Fe uptake strategy of the crop through complexation of Fe(III) from the rhizosphere. Long-term liming also altered the exchangeable Mg pool of the soil and its Mg isotope composition by promoting Mg uptake.Using metal stable isotopes in the assessment of sustainable subsoil management allowed us to explore the potential of subsoil amelioration through deep loosening and compost injection in optimizing nutrient and water use efficiency for crops. We first conceptually showed that Mg use efficiency of crops can be solely quantified from Mg stable isotope ratios when lime is not applied. We further used the radiogenic strontium isotope ratio (87Sr/86Sr) to reveal changes of the nutrient uptake depth caused by subsoil management. A shift in the 87Sr/86Sr ratio of crops indicated that deep loosening with compost incorporation in a silty Luvisol deepened the depth of nutrient uptake, whereas no such shift was observed in crops grown in a sandy Retisol. This suggests that when water is not a limiting factor subsoiling with compost incorporation is an effective management strategy to improve nutrient utilization from the subsoil, whereas under water-deficit conditions subsoil amelioration primarily improves water uptake from the subsoil but not nutrient acquisition.We conclude that non-traditional metal stable isotopes are a powerful tool in agricultural sciences as they allow insights into biogeochemical cycling of nutrient elements.
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