Spatially Explicit Assessment of Crop Production, Nitrogen Use Efficiency, and Environmental Footprint in Iran

Crop production, nitrogen use efficiency (NUE), and environmental footprint are not only of great significance for ensuring food security, but also serve as key determinants for achieving the integrated governance of agricultural development and environmental protection. However, Iran is currently facing challenges such as production in an arid climate and on degraded land, low NUE, and associated ecological and environmental pollution. Current agricultural nitrogen (N) management research is mostly limited to single crops or dimensions, leaving a gap in integrated multi-crop, multi-dimensional spatiotemporal analyses and grid-scale high-resolution spatial assessments of regional heterogeneity. Therefore, from the perspectives of food, resources, and the environment, this study systematically assessed the sown area, yield, N application rate, NUE, N surplus, and greenhouse gas emissions (GHG emissions) of six major crops (wheat, rice, barley, maize, sugarcane, and cotton) in Iran for the years 2000, 2010, and 2020. The aim was to assess the current status and spatiotemporal evolution of cropland N management in Iran. The results of this study indicate that the total N application rate in Iranian cropland exhibited an overall upward trend from 2000 to 2020, increasing from 1.095 × 106 t to 1.1937 × 106 t over this period. The NUE improved in some regions but remained generally low, increasing from 31.7% to 41.8%. Provinces in northern and southern Iran were characterized by high N application rates, low NUE (20–40%), substantial N surplus accumulation, and high GHG emissions. The multi-dimensional comprehensive assessment framework proposed in this study provides a scientific basis for N management in regions aiming for coordinated governance of food security and the ecological environment.