Increased nitrogen use efficiency (NUE) is important as a specific consideration to decrease negative impacts of nitrogen (N) on the environment and provide better crop quality. Therefore, in many European countries N is used with restrictions due to UE regulations, set to increase NUE. This is particularly important in wheat production because this crop in EU accounts for 48% of cereal production and uses about 25% of total N-fertilizer applied. One of the methods applied to increase NUE is the use of sensor-based diagnostic information for variable N application (VNA). However, due to the complex N turnover, NUE is difficult to measure at field level and thus to assess environmental effects of different N management approaches, including VNA. Calculation of NUE as grain production per unit of N applied has the disadvantage that NUE increase is not directly proportional to N rate increase. However, implementation of VNA does not always reduce N rates in comparison with uniform N application. On fields showing high spatial variability of N soil availability (Nmin), the use of VNA often redistributes N within the field to minimize N surplus (N_sur). Therefore, to assess the environmental effect of VNA, field strip-trials were conducted using: early spring soil Nmin sampling, an active optical sensor (AOS – OptRx Ag Leader®), spatial grain yield data, and dense spatial information on wheat N content in straw and grain to calculate N_sur. Strips were fertilized alternately with a variable or uniform N dose. The use of AOS did not significantly reduce N_sur. However, the site-specific N balance maps indicate where the areas more prone to N_sur are located within the fields. This allows to investigate which site-specific factors are most responsible for N_sur in these regions and what could be done to reduce the N_sur in the future.