production of ammonia 1946-2007
<a href="//commons.wikimedia.org/wiki/User:Orci" title="User:Orci">Orci</a>
Eigenes Werk (own work), data from <a rel="nofollow" class="external text" href="https://minerals.usgs.gov/ds/2005/140/nitrogen.pdf">usgs-nitrogen (fixed)-Ammonia statistics</a>