Agriculture 44.6% Foreign 31.7% Traffic 11.9% Industry & buildings 8.7% Ammonia from sea 3.0%
Also note that this is separate from greenhouse emissions, the nitrogen reduction is needed to allow our nature to recover from decennia of neglect. There was a recent study showing that over 50% of our nature is in bad/poor condition, amongst the worst across the EU.
In 2019 an important ruling was made against the governmental policy to deal with nitrogen. This policy is what allowed highway speeds to increase from 120 kmh to 130 kmh, residential buildings to be build and overall industry to continue. Since 2019 several additional rulings have been made that put everything on hold. For every activity that impacts nature in a negative way, the nitrogen deposits need to be offset.