Within-Field Variability in Nitrogen Losses:a case study in Denmark

Nitrogen (N) losses from agricultural fields, through nitrous oxide (N₂O) emissions and nitrate (NO₃⁻) leaching, pose environmental risks and reduce agricultural productivity. Understanding the spatial variability within fields is crucial for effective N management. This study aimed to quantify and explain spatial variability in N₂O emissions and NO₃⁻ leaching within a typical agricultural field in Denmark, identifying the key factors influencing this variability. Field measurements were conducted across two growing seasons (2023 and 2024), involving soil, plant, and environmental data collection at 24 and 48 sampling points, respectively. Random forest modeling was employed to analyze feature importance of predictor variables. The study revealed significant spatial variability in N losses. The key influencing factors included topographical features, plant N uptake, and climatic conditions. An inverse relationship was observed between N₂O emissions and NO₃⁻ leaching, indicating a trade-off in N loss pathways. Random forest models explained approximately 30% of variability for NO₃⁻ leaching (RMSE = 11.32; MAE = 8.89) and N₂O emissions (RMSE = 0.71; MAE = 0.21). These findings underscore the complexity of N loss dynamics and difficulty of the adoption of site-specific management strategies to mitigate environmental impacts and improve N use efficiency.