Soil organic matter pattern in an olive orchard with different management practices for 21 years

Climate change and resource depletion due to population growth emphasize the need for conservation-based agricultural practices to prevent soil degradation. Studying soil organic matter (SOM) dynamics across different land uses is essential for assessing soil health and guiding sustainable agriculture. This study examined the physicochemical properties of soils from a Mediterranean olive orchard sustainably (Smng) and conventionally (Cmng) managed for 21 years. The focus was on SOM in aggregates at three depths (0-5, 5-15, 15-30 cm) and across three aggregate size classes (1-0.250, 0.250-0.063, <0.063 mm). Smng soils had higher total carbon (+50.7%) and nitrogen (+74.9%), as well as a greater aromatic OM component (+76.0%) in the 0-5 cm layer compared to Cmng soils, suggesting slower transport of organic matter into deeper layers. This effect was especially pronounced in micro-aggregates (<0.063 mm), with increases in carbon (+59.3%), nitrogen (+86.7%), and aromatic OM (+87.7%) in Smng soils, likely due to their ability to bind small colloidal particles. Smng soils also showed increased bacterial abundance and different accumulation of organic compounds from microbial fermentation, reflected in the OM’s qualitative profile. Soil tillage in Cmng caused mineral alterations, whereas Smng soils retained higher crystallinity. Examining the quality, stability, and interaction of SOM with mineral components, helps to understand its degradability and ecological behavior, which is crucial for mitigating climate change impacts and promoting land conservation. This study was carried out within the Agritech National Research Center and received funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022). This work reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for them.