The stump of an oak tree can turn an otherwise clean lawn into an unsightly view. Often oak trees not only fill the soil below them with roots, but also extend gnarled roots upward above ground, making routine mowing, maintenance, and play in the yard difficult. While some landscaping projects would call for harsh chemicals or a bulldozer to remove the tree's roots, you can kill oak tree roots without chemicals with just a few supplies.
Cut the tree or stump down as close to the ground as you can with a chain saw. Make a horizontal cut if possible, but cut as you can safely.
With the largest drill bit you have, drill down into the stump as deeply as possible to form eight or nine holes in the base of the oak tree. Drill two or three holes into portions of the oak's roots that stick up, if it is safe to do so.
Spray over the ground all around the oak roots and over the stump surface to saturate the ground thoroughly. Allow the water to absorb for five to 10 minutes, then water the ground again. Let the water soak in for five to 10 more minutes.
Pour salt into the drilled holes, filling them as full as possible. Spread a tarp or black landscaping plastic over the cut surface of the stump and the roots to fully cover them.
Pile 3 to 4 inches of bark mulch over the tarp or plastic to cover it completely, locking in moisture and heat. Spray the mulch to soak it and weight down the plastic.
Pull back the mulch and tarp once a month to wet the ground and add salt to the drilled holes. Cover the tree again with the plastic, and wet the mulch. Repeat this monthly practice for six months to a year.