Originally Posted by maura
churumbeque is exactly right.
Standard rule is at least 1/3 of the post's length should be under ground.
Sinking them 1 foot will virtually guarantee that the posts will lean and fall over.
I would not go smaller than a 4" x 4" post either; something smaller will not support the weight of the 1" X 6". I'd recommend you go with 8' between your posts. You might get away with 10 or 12', but if you look at the cost of lumber; it might actually be cheaper to do 8' centers and 16' boards. This is also a more secure configuration than a having a join on every post.
If I am going with T post along the back side of the pasture and the side that's gona be near the woods, is it the same rule of thumb as far as how deep to knock them in the ground? I will get probably 8 ft t post and I guess go 3 ft in the ground? Or if I get 7 ft ones, then 2 ft