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By Sujana Silwal

I joined the research unit POLISES at the Department of Ecological Modelling, Helmholtz Centre for Environmental Research (UFZ), with the intention of working more closely at the intersection of agriculture, policy, and environmental systems. Coming from a background in sustainable agriculture, I was curious about how abstract policy ideas can be translated into models that help us understand farmers' decisions, environmental impacts, and the trade-offs between them. I knew this would challenge me technically, as understanding large decision flows, and long-standing logical codebases were outside my comfort zone. Still, I wanted to engage more closely with this complexity and understand how dynamic systems are built, used, and interpreted within a modeling framework.

During my internship, I worked with the SNAg ecological–economic modeling framework, using nitrogen yield response curves derived from the LPJmL crop model. My goal was to explore how uniform and targeted nitrogen reduction policies vary in their cost-effectiveness and yield impacts across maize systems in Germany. The most challenging aspect of this work was not the mathematics or the coding framework alone, but developing a coherent understanding of a complex system while learning how its different components fit together. Constructive guidance from my supervisor, Kaja, helped me navigate this process, ask better questions, and build confidence in my approach. Working with the Latin Hypercube Sampling results was a turning point for me. Seeing the full distribution of outcomes made the structure of the model much clearer and helped me understand how uncertainty and heterogeneity shape policy effects.

Beyond the project itself, the internship gave me a meaningful introduction to the research work culture in Germany. Regular internal talks and guest lectures exposed me to a wide range of interdisciplinary perspectives, expanded my understanding of how methodological, theoretical, and applied approaches have come together in environmental research. Outside the formal academic work, simple daily interactions like having lunch together, taking post-lunch walks, joining junior brunches, and participating in holiday parties created space for relaxed exchange across the whole research community in the department. These kinds of interactions aren't always visible in academic settings, and they meant a great deal to me as a short-term international researcher in the department.

Looking back, I'm proud that I helped move the project forward and feel lucky to have had this opportunity to grow within such a supportive research environment. These three months at UFZ confirmed that I have a knack for working where science, policy, and real-world decision-making meet. Working on nitrogen policy made me more aware that modeling is not only about optimization, but also about how uniform policy designs interact with heterogeneity, shaping trade-offs and outcomes across regions. It was a deeply positive experience, both professionally and personally.