What Kind of Dirt to Fill Holes in Yard?

By Janine Soriano, Master of Science in Forestry, government environment researcher

Sometimes you may spot holes across your lawn that seemingly appear out of nowhere. They can come in a variety of sizes, and ignoring them can lead to more lawn problems. Filling any holes in the yard is important not only for aesthetics but to prevent accidents as well. Here are some tips including what kind of dirt should you use.

Why they’re there

Before filling any holes, it’s important to know what causes them to appear in the first place. Most of the time, they form as a result of mechanical activity or disturbance by wildlife on your lawn. To determine what animal(s) is responsible, you should examine the lawn first. Ask yourself these questions – what kind of holes do you see? Are they big or small? Do you see any signs like droppings or burrowing patterns? Next, try to poke them with a stick. Is it deep? Are they connected? That may be a clue – animals like squirrels, moles, rats, and skunks visit to feed on insect larvae underground (and sometimes on lawn plants).

Holes may also be caused by previous landscaping activity. Lawn machines may leave marks if left on the ground for a long time. Earth-balling also involves taking out a chunk of the root ball of trees and shrubs, leaving deep cavities. In the worst cases sinkholes may develop, which are large depressions that happen when the outermost layer of the soil collapses because the loose soil underneath gets oversaturated with water. Sometimes, the culprit of sinkholes is buried tree stumps or any large organic debris that has decomposed over time.

What dirt should you use to fill them

Now that you have carefully assessed your yard, it is time to fill the holes with dirt. Keep in mind that the type of dirt you are going to use depends on their condition. For small-sized and shallow ones caused by burrowing animals, the filling material can simply be the topsoil from the lawn itself. Aside from being the cheapest method, the topsoil is rich in nutrients compared to the subsoil that lacks organic matter. A mix of fine river sand and compost can also be applied to help the surrounding grasses volumize its root. Using this potting mix allows easy penetration of fine roots into soil pore spaces thus hastening its recovery from disturbance. For moderate holes, it is not recommended to use stones and gravel alone. Use fill soil with sand. In the case of sinkholes, the advice of landscape experts, geologists and engineers would help you determine the suitable fill material – they can recur if the wrong fillers are used. Usually, they would recommend different rock sizes, concrete, and topsoil.

How to fill them in

To fill small holes, the first step is to prepare the fill soil, sand and compost materials. Next, remove any evidence of underground grubs so as not to encourage animals to rake through the soil. Pour in the soil mixture, making sure that the lowest portion is compacted. Add the remaining topsoil and the sod. Water the filled holes to establish the turf. In restoring common lawn sinkholes, the depression must be cleared of any debris to ascertain the extent of the damage. If the sinkhole is relatively shallow, filling it with compacted soil can do the job. On major sinkholes, using a combination of rocks and dirt would be needed. Drill through the hole using a rig to apply cement which will bind any open cracks within the limestone surface. Fill the lowest gap with large rock sizes followed by pebbles, sand, and dirt. Make sure that everything is well-compacted. Plant the sods over then water at field capacity. It is advisable to refrain from planting big-sized trees over the treated hole to prevent collapse.