Foot sliced while submerged in dirt in dog pen. it's shallow, but gouged out a mm deep, a mm wide and 3/4ths an inch long. any chance of tetanus?

Yes, & Infection.: You should seek immediate medical treatment at the closest urgent care or ER, as your wound should be properly cleaned, possibly repaired, and you may benefit from prophylactic antibiotics as well as a tetanus vaccine (if you are not up-to-date on your vaccines).

Tetanus Concern: The aim of the tetanus shot is to give you protection by creating antibodies within your blood to neutralize tetanus toxins. You probably got a whole slew of tetanus vaccines as a child, but after that, you have to have a booster shot every 10 years or so, to maintain that immunity. If you have not had a booster shot in 10 years, it is not late to go today and get one. If you forgot when, get one.