Lessons learned from the twinning TwinSubDyn collaboration.

Widening European countries face persistent limitations in scientific infrastructure, international scientific integration, and interdisciplinary training. The Horizon Europe Twinning project "Twinning excellence on organic soil amendments effect on nutrient and contaminant dynamics in the subsurface" - TwinSubDyn addressed these gaps by strengthening conceptual, analytical, and interpretive capacity at the University of Novi Sad Faculty of Sciences (UNSPMF). This was achieved through collaboration with four leading Universities and research institutes with EU: University of Vienna (UNIVIE), Forschungszentrum Jülich (FZJ), Martin Luther University Halle-Wittenberg (MLU), and Spanish National Research Council (CSIC). Focusing on organic soil amendments (OSA) and their effects on soil organic matter (SOM), nutrient dynamics, hydrology, and contaminant fate, the project operated in field-relevant conditions where OSA effects are highly context-dependent and challenging to interpret. TwinSubDyn applied integrated and concept-driven research, combining mobility of scientists, expert visits, collaborative research, trainings, workshops, and a summer school. Although the research component was modest, it provided essential focal points for training, joint interpretation, and mutual learning. Collaborative activities produced multi-scale insights into OSA aging, SOM transformations, nutrient mobility, and sorption processes. Mobility of scientists and expert exchanges substantially strengthened UNSPMF's analytical confidence and interdisciplinary reasoning, while the partners gained comparative insights into Western Balkan scientific capacity, research organization, and region-specific environmental conditions. The project fostered new research collaborations, enhanced institutional preparedness, and broadened engagement with policymakers, practitioners, and the public. TwinSubDyn demonstrates that twinning efforts achieve greatest impact when conceptual training and applied research are tightly integrated, offering a transferable model for future scientific development initiatives.