『Abstract
　Traditional nitrogen (N) management practices with excessive N fertilizer application and higher N losses to the environment are more widely used than the recommended best management practices (BMPs) across the nitrogen vulnerable zone (NVZ) of the Mediterranean region of Valencia. Since reported underground concentrations for this region are as high as 100 mg NO3-N L^-1, nutrient managers and policy makers need quick tools that qualitatively rank N management and their respective N losses to the environment in order to implement BMPs across the region. Our hypothesis was that a new tier one GIS N index tool (GIS NIT-a), based on quantitative N mass balance and qualitative rankings, can be used to assess N management practices across the NVZ. The new GIS NIT-a assessment tool was able to simulate N uptake, hydrology characteristics (water leaching), N dynamics and NO3-N leaching across several sites of the NVZ (P ＜0.001). This study suggests that the GIS NIT-1 can be used to quickly identify practices that produce very low to moderate N losses to the environment from those with high and very high N rankings.

Keywords: Ammonia volatilization; Denitrification; Nitrate leaching; GIS; NUE; Nitrogen index』

Introduction
Materials and methods
　Study area
　Nitrogen index tier one tool connected to GIS (GIS NIT-1)
　　Hydrologic soil map
　　Precipitation map
　　NO3-N irrigation map
　　Crop management map
　　Nitrogen management scenarios
　Nitrogen index calibration - validation
　Sensitivity analysis
Results and discussion
　Calibration - validation
　Sensitivity
　Management scenarios
　　System nitrogen use efficiency (NUE)
　　Effects of hydrologic groups-soil texture on NO3-N leaching and atmospheric N losses
　Nitrate leaching maps
　Comparison of N leached map with groundwater nitrate content
Conclusions
References