I need to approach the chemistry of fertilizer, I am a chemistry and I don't have any idea about this topic. I would start to approach this field. Any comments are welcome.
In addition to the Book suggested by Dr. Anil Kumar Singh, I recommend the following book for you:
Yawalkar KS, Agarwal JP and Bokde S (2002) Manures and Fertilisers (Ninth Edition). ISBN 81-900392-2-9. Agri-Horticultural Publishing House, Nagpur- 440010, India.
I am sure you'll find the book very interesting and useful.
Suggest you access the American Society of Agronomy website and the Digital Library listed therein. Digital versions of book chapters are available. Some books you might find useful include "Fertilizer Technology and Use" and several on specific nutrients such as "Phosphorus in Agriculture", etc. Good luck.
I think all important books on the topic has been covered by the colleagues. Beside this you may consult another good book " Fertilizing for maximum yield by G. W. Cooke".
Are you only interested to fertilizer chemistry or also to fertilization and soil-fertilizer interactions? Are you interested to mineral or organic fertilizer chemistry? If you could better detail your interest, I and our colleagues could be more useful in suggesting you interesting books.