Supplementary file 1_Global meta-analysis reveals soil, climate, and management drivers of crop yield and nitrogen use efficiency under enhanced-efficiency fertilizers.docx

Improving nitrogen use efficiency (NUE) while maintaining high crop yields is a key challenge for achieving green and sustainable agricultural development. Enhanced-efficiency fertilizers (EENFs) have broad potential to improve crop yield and nitrogen use efficiency (NUE), yet their responses across diverse climatic, soil, and management conditions remain poorly quantified. Here, we present a global meta-analysis of field studies evaluating the effects of controlled-release urea (CRU), nitrification inhibitors (NI), urease inhibitors (UI), and their combination (NI+UI) on crop yield and NUE. EENFs increased average crop yield by 8.32% and NUE by 25.90%, with NUE consistently exhibiting greater relative gains than yield across treatments. Effect magnitudes varied by fertilizer type: NI enhanced yield by 7.69-10.44%; CRU increased NUE by 25.60%; NI+UI improved NUE by 34.00%; and UI alone increased NUE by 26.55%. Climate strongly modulated these effects. Yield responses to MAT and MAP were relatively stable, whereas NUE was highly sensitive to environmental gradients. Notably, NUE gains under NI+UI peaked at intermediate temperatures (7.5-15 °C), and yield responses were largest under MAP >1200 mm. Soil properties, including soil organic carbon, total nitrogen, and pH, further influenced both yield and NUE, with NI+UI showing the highest responsiveness in low-fertility soils. Crop type, fertilization frequency, and nitrogen application rate also modulated fertilizer effectiveness, with UI most effective for wheat and maize yield, and NI+UI consistently enhancing NUE in rice and other crops. Model analyses revealed that the relative importance of environmental, soil, and management factors differed among fertilizer types, with crop variety, soil nutrients, pH, and fertilization practices as key predictors. Collectively, EENFs reliably enhance crop yield and NUE across global agroecosystems, yet their efficacy is context-dependent, driven by the interaction of climate, soil, crop, and management factors. These findings provide quantitative guidance for optimizing fertilizer use to improve agricultural sustainability and reduce nitrogen losses.