if your going to use fish and smelly materials, make sure to berry it about 2 1/2 to 3 feet deep before planting. I've never had problems using organic liquid concentrated fertilizers outdoors as long as you don't leave any containers out there. Best advise is to build a fence around your property.
A good rule of thumb to follow when it comes to outdoors plants and their root systems is this. Basically a mirror image of whats above ground. Of course different soil textures and hardpan level effect this some. But roots are pretty tuff, I mean they can split rocks...That's wayyy tooo deep. Roots don't even go that deep. Stick with a foot and a half.