I'd say its capable of doing that but it is not a brush hog so several trips across the field will be necessary as taller grass will just bend over as the deck pushes it down going over it.
You need a DR trimmer type of machine or a sickle bar, not a lawnmower deck
A brush hog type of mower would be ideal.
As far as fire suppression, any dry vegetation will burn, the only answer to that is bare ground.
