What is the Bracha on Nature Valley Granola Bar, Bracha rishona and Bracha achrona?

The bracha rishona is Adama (שו”ע או”ח סי’ ר”ח סעיף ד). The Shulchan Aruch writes that the bracha achrona is Borei Nefashot . However, the Shulchan Aruch also quotes Tosfot who is unsure if the bracha achrona should be Borei Nefashot or Al Hamichya, and Tosfot writes that because of this safek one should only eat such foods during a meal, when one can say Birchat Hamazon afterward. Because of this safek, if one wishes to eat a granola bar and is not eating bread, it is best to eat less than a kzayit at a time so that there is no obligation to make a bracha achrona (see the OU website for more details). If one did eat more than a kzayit, one should make a Borei Nefashot (משנה ברורה סימן ר”ח ס”ק י”ח).

Tl;dr: Bracha rishona – Adama. Bracha Acharona – it is better not to eat a kzayit, so that one does not need a bracha achrona. If you did eat a kzayit – Borei Nefashot.