scotiabank says: potash to be top pick in 2011, page-8

You first need to see phosphate prices move significantly north before you can hope for potash to follow. Potash is ALWAYS the last nutrient applied to a crop once it is planted, particularly given retail prices in non US denominated countries reflect carry-out priced from the last obscene peak in 2008.

Bet on rock and nitrogen first, then worry about potash ...