Most urea (fertilizer)is produced in Russia and China.I would like to
know which companies have the lowest prices world-wide.I prefer direct
sources and contact information on these companies.Thank you for your
assistance in this project.

Your very much right about lowest pricing of fertilizer. Here are the
very good links where you can find out companies details. I'm giving
only china based companies details. As far I know russia have some
export rule problems in fertilizer products.

http://www.chinatech.com/commodity.htm
http://www.made-in-china.com/prod/catlist/?for=listcatprod&sub_cat_id=114050

My suggestion is you try Indian based manufacturers also, Becoz India
also producing very good amout of Urea every year. Following link is
providing information about NFL -- who have more then 80% production

http://www.nationalfertilizers.com/services.htm

Let me know If want any information