How does sodium nitrate make soil alkaline?

Our lecturer told us that when Sodium Nitrate is added as a strait fertilizer the soil becomes alkaline with time. How does this happen? She didn't give any explanation and asked us to find out. So far I had no luck with it. The possible answer I've found is that Nitrate turns to nitrite , then nitrite reacts with water to give HNO2 and H+. But I'm not sure whether thats entirely right. Help!