Optimising mineral nitrogen (N) use in crop production is inevitable target as mineral fertilisers reflectone of the highest inputs both in terms of economy and energy. The aim of the study was to comparethe relationship between the rate of N fertiliser application and different measures of energy parame-ters exemplary data for spring-wheat in boreal climate condition in Estonia in 2006–2010. The effect ofmineral N with rates 0, 40, 80, 120 and 160 kg N ha−1was studied on the background of composted cowmanure and without organic fertilisers. Univalent parameters, energy gain (EG) (energy output − energyinput) and energy ratio (ER) (energy output/energy input) were calculated. To aggregate parameterswith different units (ER and EG) we proposed two standardisation approaches for combined indices. ERmaximisation gave both organic fertilisation background optimum N norms significantly lower than EG(p < 0.05) optimisation. Both the new combined indices gave optimum N norms in between the rate ofER an EG. Composted cow manure background did not affect mineral N optimisation significantly. Wesuggest optimisation of mineral N according to bi-dimensional parameters as they capture important fea-tures of production efficiency and are more objective using as advisory tool for sustainable productionsystems.