Spatio-Temporal Variability Mapping for Variable-Rate Nitrogen Fertilization

Variable-rate nitrogen (N) fertilization has the potential to improve nitrogen-use efficiency and reduce losses in rainfed cereal systems, yet practical frameworks linking ground-based management zones with satellite time series remain limited. Here, we assess variable-rate N fertilization in a commercial winter barley field in Catalonia using Sentinel-2 optical and Sentinel-1 C-band SAR observations. Two variable-rate strategies were evaluated against the farmer’s uniform-rate (UR) practice. Spatio-temporal clustering of Sentinel-1 and Sentinel-2 time series was used to evaluate satellite sensitivity to within-field heterogeneity identified by proximal soil sensing, complemented by point-level time-series analysis to track site-specific crop development. For two seasons of winter barley, spatio-temporal clusterings revealed that GNDVI and NDWI produced the most heterogeneous spatial clustering, indicating potential sensitivity to spatio-temporal variability throughout the crop growth stages. 

This work promotes to implementation of freely available optical and radar satellite data for within-field farming practices integrated with ground based proximal sensing to support operational, site-specific nitrogen management in Mediterranean cereal systems.