Well, Soldier background seems to be of somehow limited use to... soldiers, or rather classes that already have high BaB, Fighters in particular.

I think that Rural/naturalist bonus doesn't have to deal with animals necessarily, as it will always be somehow clunky the way 3.5 rules are built...

Maybe some bonus against getting fatigued and similar? As from background generally connected with constant, monotonous physical activity.

Power of Earth seems fine, useful both in combat and outside, but can't get abused easily.

"Ground" needs clarifying, though.