Ammonia is very useful and in very high demand but who first invented it and when?

Fritz Haber
The Haber Process was discovered in 1918 by Fritz Haber. At this time the ingeniusness of the process earned Haber a Noble prize. This isn't the end though, because at the time nobody could use the process to efficiently and the technology wasn't available to provide the right parts for it to be worthwhile.

Carl Bosch
In 1931 Carl Bosch, a chemical engineer, came into the picture. He designed the chemical plant that could use the Haber Process efficiently enough to make it cost affective. Also the technology was also now available to provide the parts nessessary. In recognition of this Bosch was also awarded a Noble Prize for his application of the process.
Now the process developed is being used all around the world for the mass production Ammonia for use in fertilisers and a primary source of Nitrogen in the production of many chemicals.