Wikipedia gave me similar information:
http://en.wikipedia.org/wiki/Fertilizer
(You probably want a better source than wikipedia, try looking at the sources at the bottom of that page).
I don't think you can truly say who invented fertilizer, unless you are talking specifically about the fertilizers we use today. People have been using manure and other sources of nutrients to fertilize their crops for many many years.
But including a history about the industry and who discovered what components were useful and why would be good. I'd also include a brief discussion on older civilizations that used manure, fish, etc. for fertilizing crops (if you can find anything).