Determination of critical nitrogen loss zones in drinking water protection areas with satellite-based algorithms

High nitrate concentrations in groundwater, driven by agricultural nitrogen (N) fertilization, remain a significant concern. This study introduced an N uptake algorithm for winter wheat at harvest, designed to calculate site-specific N surpluses as an indicator of nitrate losses. The algorithm integrated data from plot combine harvesters, Sentinel-2 satellite imagery at various dates, and georeferenced soil properties. A comparison of two statistical models revealed high correlations (R²=0.77–0.84) and low errors (MAE=8–13 kg/ha) in calculating N uptake. Site-specific N  alancing, using the developed algorithm and N fertilization data, enabled the identification of high nitrate leaching risks in low-yield areas within a drinking water protection area (N surplus >90 kg/ha).