BOOK OF ABSTRACTS 245 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.18 Historical Land Use and Soil Carbon Dynamics in a Mediterranean Olive Orchard Under Different Agricultural Management Schemes Laura Gismero-Rodríguez1, Angel Valverde2, Nicolas Brüggemann3, Otávio dos Anjos Leal3, Heike Knicker1 1 Instituto de la Grasa – Consejo Superior de Investigaciones Científicas (IG-CSIC), Seville, Spain 2 Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA-CSIC) 3 IBG-3: Agrosphere – Forschungszentrum Jülich (FZJ), Jülich, Germany Corresponding author: heknicker@ig.csic.es Soil loss in olive groves is a widespread problem in Mediterranean climates. This is particularly critical in southern Spain, the world’s leading olive oil-producing region. To mitigate erosion between olive trees, traditional tillage has increasingly been replaced by cover cropping. Whereas this practice is known to protect the soil structure, its effect on soil organic matter (SOM) and carbon dynamics remains insufficiently understood. This study aimed to investigate how long-term management practices influence the degradation capacity of SOM. Soil samples were collected from an olive orchard under three management regimes established since 2009: conventional tillage (CT), natural cover (MC), and herbicide-based (TL-Herb). Given the sloping nature of the field, soils were sampled from both the upper and lower positions along the slope. A 40-day microcosm experiment was conducted using these soils, both alone and amended with wheat residues (13C-enriched and unenriched), to investigate carbon turnover and organic matter dynamics. Preliminary results based on CO2 flux and δ¹³C-CO2 measurements during incubation indicate higher respiration rates in MC soils and in samples from the lower part of the slope. These differences became less pronounced over time, likely reflecting the depletion of more labile, pristine organic matter. Additionally, lower δ13C-CO2 values in MC treatments suggests a greater contribution of native SOC to microbial respiration. To further interpret these patterns, mixed-effects model will be applied to quantify fast- and slow-cycling carbon pools and the priming effects across treatments. In parallel, solid-state 13C CP/MAS NMR spectroscopy are used to evaluate the impact of long-term management on SOM composition. Together, these approaches will provide insights into the role of cover cropping in shaping SOM dynamics and support the development of sustainable soil management strategies and robust soil health indicators.
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