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.
NORTHFIELD – 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 of this activity, lawns can be sensitive to over use, and soil compaction may become an issue.
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.
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.
Increasing the amount of organic matter in lawns and mowing to a grass height of at least 3 inches will promote longer roots, which in turn will help combat soil compaction while also reducing stormwater runoff.
How can you avoid or correct soil compaction and have healthy, usable lawns?
One way to avoid soil compaction is to eliminate 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.
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. When there are little holes in sports fields with 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 the 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 top-dressed 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, consider renting specialized equipment or hiring a landscape contractor to help.
Raising the blade of the 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.
For more information about correcting soil compaction, see “Combating Soil Compaction” at go.uvm.edu/compaction from the University of Delaware for more ideas, or contact the UVM Extension Master Gardener Helpline at go.uvm.edu/gardenquestion.
Bonnie Kirn Donahue is a UVM Extension Master Gardener and landscape architect from Northfield.
Bonnie Kirn Donahue
