Interestingly, the thoughts on boosters have shifted a lot and the recommendation to receive every ten years may soon be dropped, since the vaccine is considered to have a longer effect than originally thought.

Since Clostridium tetani is anaerobic and in fact can't survive in the presence of oxygen, a lot of the things people suspect could give it to them likely can't. Unless you cut yourself while digging it's pretty unlikely you've been exposed to tetani.

And not to downplay your fears too much, but untreated tetanus is ~7% fatal versus 99.9% with rabies.