Olive cultivation is a crucial driver of the economy in the European Mediterranean basin, particularly in Spain, where it occupies about 2.75 million ha [1]. In recent years, there has been an expansion of super-intensive olive farming, which ensures high productivity but requires irrigation and is expected to increase organic waste generation and water demand. Consequently, it is imperative to adopt more sustainable approaches to manage the agricultural waste generated during olive harvesting and agro-industrial processing. To tackle that challenge, there is a renewed emphasis on utilizing organic amendments derived from agricultural residues. Biochar (B), a highly aromatic carbon obtained through biomass pyrolysis, has the potential to sequester carbon in the soil for extended periods and its unique physical properties increase soil porosity [2]. Nevertheless, B effects on SOM composition and functionality in the medium and long term are largely unknown. Additionally, green compost (Cp) is rich in nutrients and labile organic carbon, making it a valuable soil amendment for improving soil fertility, structure, and moisture retention. The two main goals of this study are: i) To discern the effects of transforming traditional olive orchards into bushrow olive cultivation on soil organic matter (SOM) composition, which plays an essential role in the carbon cycle and on soil quality, and ii) To assess the effects of of B and Cp on SOM composition two years after application. With such purposes, soil samples were taken from super-intensive olive orchards (1650 trees/ha; irrigated 30% water needs) amended with (B), green compost (Cp), a combination of B+Cp, as well as control plots [3]. Soil samples were also collected from traditional olive orchards in the same farm (La Hampa, Coria del Río) for comparative purposes. The free lipid fraction and volatile SOM were studied by using GC/MS and analytical pyrolysis (Py-GC/MS) respectively. Control soils, particularly those from the traditional olive orchards, exhibited higher total and relative abundance of fatty acids (including unsaturated fatty acids) and sterols (including α-Tocopherol). In contrast, the chromatograms of soils amended with B and to a lesser extent with Cp showed higher relative abundance of linear n-alkanes. Preliminary analysis of analytical pyrolysis data also indicates a greater soil functionality in the soils from the traditional olive orchards, which also exhibited the greatest total C and N contents. References [1] MAPA. Superficie y Producción. Aceite de oliva. (2023) https://n9.cl/ktqax [2] J.M. De la Rosa, S.M. Pérez-Dalí, et al., Agronomy 13 (2023) 1097. doi:10.3390/agronomy13041097 [3] J.M. De la Rosa, P. Campos, A. Diaz-Espejo, Agronomy 12 (2022) 2321. doi:10.3390/agronomy12102321

The Spanish Ministry of Science and Innovation (MCIN) and AEI are thanked for funding the project RES2SOIL (PID2021-126349OB-C22). The European Joint programme EJP SOIL from the EU Horizon 2020 R&I programme is thanked for funding subprojects EOM4SOIL, MAXSoil-C and MIXSoil-C (Grant agreement Nº 862695).

Póster presentado en XXII Meeting of the Spanish Society of Chromatography and Related Techniques 16-18 oct, 2023, Mayorca (España)

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