Which sport is played on the largest field?

The largest sports field is obviously a golf course.

A golf driving range typically needs 4–7 acres of land and a golf course course with a driving range typically with 30 to 200 acres.

A Polo field is the second highest with a dimension of 300 Yards x 200 yards.

You can get the dimension of sports field here. 

Association football (soccer) is typically played on the largest field, with dimensions of 100-130 yards  in width and 100- ...Football, the field of play, or the playing area, is rectangular and is 110-120 meters long and 70-80 meters wide. This makes association football the sport that is played on the biggest field in monkey type  terms of ar ea While "pitch" is the most common term for a soccer field, there are a few other terms that are sometimes used. These include: Field: This is a more general term that can be used to describe any playing area. Ground: This term is also general and is often used in the UK.

Australian rules football is played on the largest field, with an average size of 150 meters by 135 meters.