In order to receive an agricultural subsidy, do you have to use a Monsanto fertilizer/product?

No. Subsidies are granted for certain commodities and programs. Its a very complicated system. These subsidies come from the Farm Bill. here is the website: a href="http://www.usda.gov/wps/portal/farmbill2008?navid=FARMBILL2008" rel="nofollow"http://www.usda.gov/wps/portal/farmbill2…/a