BOOK OF ABSTRACTS 165 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Friday, 28 August 2026 / Hall C Travel Awardee Presentations TA3 Land-Use Impact on SOM Transformation Agnieszka Grabusiewicz1, Maria Jerzykiewicz2, Irmina Ćwieląg-Piasecka3, Jerzy Weber3, James J Leahy1 1 Department of Chemical Sciences, University of Limerick, V94 T9PX Limerick, Ireland 2 Faculty of Chemistry, University of Wrocław, Joliot−Curie 14, 50−383 Wrocław, Poland 3 Institute of Soil Science, Plant Nutrition and Environmental Protection, Wrocław University of Environmental and Life Sciences, Grunwaldzka 53 St., 50-357 Wrocław, Poland The primary objective of our research is to identify the factors that correlate humins, humic and fulvic acids in soils across different land uses. The investigation aims to determine what has a dominant influence on the structure of selected fractions of soil organic matter: soil origin, fertilization type (organic or inorganic), or crop variety. By combining classical and advanced analytical methods, this approach could be effective and promising for uncovering the influence of agricultural practices on SOM composition and the impacts on soil health and productivity. By understanding these relationships, we can develop more sustainable agricultural practices that enhance soil quality and promote ecosystem resilience. This study investigates the compositional and structural changes in SOM influenced by varying land-use management across three long-term experimental fields: BRO - Broadbalk (UK) field experiment with mineral and manure fertilization (178-years), Chromic Luvisol SKI - Skierniewice (PL) field experiment with manure fertilization (100-years), Luvisol NO - Noreikiškės (LT) field experiment with mineral and organic fertilization (54-years), Cambisol. Humins, humic, and fulvic acid fractions were extracted using the method recommended by IHSS. The isolated fractions were then subjected to qualitative and quantitative analyses using advanced techniques (NMR, FTIR-ATR, EPR) and elemental analysis. Principal Component Analysis (PCA) was used to visualize the complex analytical data. The elemental composition of humin showed a higher O/C ratio in soil without organic fertilization. Manuring significantly increased the H/C ratio compared with NPK and the control, reflecting the higher aromaticity of SOM fertilised with organic fertilisers. The results correlated with the calculated areas of FTIR-ATR spectra. 13C CP MAS NMR spectra also confirmed these findings; however, the lower content of aromatic structures of samples from crops treated with manure without NPK indicated the importance of inorganic soil additives. Results of Principal Component Analysis showed that the greatest impact on the structure of different fractions of
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