Sustainable precision nitrogen fertilization in durum wheat: Insights from NNI and NDVI approaches

Durum wheat is a key staple crop globally, with increasing nitrogen (N) fertilizer use driven by the need to sustain rising food demand. However, inefficient N management not only reduces resource use efficiency but also contributes to environmental degradation. Precision agriculture technologies, particularly variable-rate fertilization (VRF) informed by satellite imagery, offer the potential to optimize N application while maintaining yield and quality. This study evaluated the effectiveness of different N fertilization strategies in durum wheat over four consecutive growing seasons (October 2018–July 2022) in Asciano, Siena, Italy. Four approaches were compared: a conventional uniform N rate, and three VRF strategies based on Sentinel-2 L2A spectral bands. The VRF approaches included one guided by the Nitrogen Nutrition Index (NNI), a proportional NDVI-based estimate (NDVIH), and a compensative NDVI-based estimate (NDVIL). Grain yield, quality parameters (including protein content and technological properties), N fertilizer use efficiency (NfUE), and economic performance were assessed. Results showed that the NNI-based approach achieved significant reductions in N input without negatively affecting grain yield or quality. This method improved protein partitioning and dough rheological properties, critical for pasta production and other end-uses. Moreover, the NNI consistently delivered the highest NfUE among all treatments. Economic analysis revealed that the NNI approach offered lower social costs and higher returns on investment compared to both the uniform rate and the other VRF methods. These findings demonstrate that satellite-guided VRF, particularly the NNI approach, can simultaneously enhance economic viability and environmental sustainability in durum wheat production. By optimizing N inputs to actual crop requirements, this technology reduces resource waste, mitigates environmental impacts, and supports long-term agricultural resilience. The study provides practical evidence supporting the adoption of NNI-based VRF as a sustainable fertilization strategy in durum wheat cultivation under Mediterranean conditions.