Integrating Vegetation Indices and Nitrogen Use Efficiency to Assess Organic Wheat Performance Under Mediterranean Conditions

Food security requires increasing crop productivity while improving environmental sustainability. This study evaluated the performance of organic (ORG) and conventional (CON) winter wheat systems under Mediterranean conditions by integrating nitrogen use efficiency (NUE) indices with Sentinel-2-derived vegetation indices. The comparison was conducted under real farm management conditions, capturing the combined effects of nitrogen inputs, fertilization strategies, and agronomic practices. The ORG system produced a yield of 1.77 t ha⁻¹, lower than the CON system, but exhibited higher apparent NUE indices, including Partial Factor Productivity (PFP = 126.6) and Nitrogen Utilization Efficiency (NUtE = 22.6), largely reflecting reduced external nitrogen inputs. Conversely, the CON system achieved higher yields but showed evidence of nitrogen surplus. Vegetation indices effectively captured crop development and highlighted clear differences between systems, with the strongest relationships between VIs and NUE indices observed at the flowering stage (BBCH 61–69). These results identify flowering as a key stage for assessing nitrogen status and crop performance using remote sensing. Overall, the findings reveal a trade-off between productivity and nitrogen efficiency and demonstrate the potential of integrating vegetation indices with NUE metrics to support improved nitrogen management in organic systems. This approach provides a valuable framework for advancing precision management strategies under Mediterranean agroecosystems.