Correcting soil compaction in lawns

Bonnie Kirn Donahue, University of Vermont Extension

The summer months are a time when many of us enjoy lawns. From playing sports to picnicking, lawns can be an important part of our summer experience. With all this activity, lawns can be sensitive to overuse, and soil compaction may become an issue.

What is soil compaction? Soil compaction is when the amount of pore space in the soil is reduced when particles of soil are forced together. This commonly occurs when lawns have a lot of foot traffic or are driven over with vehicles.

Photo by Bonnie Kirn Donahue When lawns receive a lot of foot or vehicle traffic, soil may become compacted, which affects the health of plants, which need oxygen to spread out their roots, respire, take up nutrients and grow.
Photo by Bonnie Kirn Donahue. When lawns receive a lot of foot or vehicle traffic, soil may become compacted, which affects the health of plants, which need oxygen to spread out their roots, respire, take up nutrients and grow.

When soil is compacted, soil and plant health decreases. Plants need oxygen to spread out their roots, respire, take up nutrients and grow.

Air pockets in the soil also help water infiltrate into the ground. Compacted soil means that it is more difficult for water to infiltrate and foster plant growth, increasing stormwater runoff and pollutants running into nearby rivers, ponds and lakes.

You will know if your soil is compacted if it looks hard and cracked and is difficult to dig. There may be areas with standing water or places where sediment has collected. Plants like turfgrass may be sparse, discolored or struggling to survive.

How can you avoid or correct soil compaction and have healthy, usable lawns?

One way is to avoid driving over lawns as much as possible. If this must happen, giving the lawn and soil some time to recover without additional compression can help. If possible, avoid driving on lawns when the soil is wet, as this can make compaction worse.

You can create small holes in the surface of the soil using a pitchfork or aerator. The holes allow air and water to infiltrate into the ground easier. An aerator is a machine that creates holes by extracting small soil cores. If you have ever wondered why there are little holes in sports fields and see little cores of soil, this was likely done with an aerator.

Another way to avoid compaction is to increase the amount of organic matter in your soil. Leaving grass clippings or leaf mulch (after being chopped fine by a lawn mower) over time provides necessary nutrients and organic matter that feeds the soil and breaks down to create more air space.

Additionally, lawn areas can be lightly topdressed with compost, sand or a combination. Apply about a one-fourth to one-half inch layer over the turf area and gently rake into the soil. For larger projects, and if possible, you may want to consider renting specialized equipment or hiring a landscape contractor to help.

Raising the blade of your lawnmower deck also can help. According to Lake Champlain’s Lawn to Lake initiative, keeping grass height at least 3 inches tall will promote longer roots, which can help combat soil compaction while stemming stormwater runoff and resist drought and weed pressure.

Looking for more information about correcting soil compaction? Check out “Combating Soil Compaction” from the University of Delaware for more ideas. Or contact the University of Vermont Extension master gardener helpline for more advice.

(Bonnie Kirn Donahue is a UVM Extension master gardener and landscape architect from central Vermont.)