Now’s the time to correct soil compaction under your lawn

By Gene Sumi Homestead Education Coordinator

If your lawn looks barren of turf and the only green plants that are thriving are the weeds, your soil may be seriously compacted.  Compaction will appear as hard-pressed soil, almost as if it has been  turned into pavement.

If you want to successfully grow any plant, but turfgrasses in particular, you must have soil that is loose, which means it is filled with openings between the soil particles – openings that can hold water and air.  It’s the soil’s ability to hold water and air that means life and death to your lawn.  The clay will naturally want to come together and form this compaction.  You need organic matter mixed in the soil to keep the clay particles apart.  The long, hot summer this year has baked the clay soils of our region and those soils that have little or no organic matter are the ones that have turned into one big clay brick.  I have advised many homeowners to prepare the soil before planting a seed or sod lawn by mixing in organic material, particularly composts such as Leaf-gro® or Compro®, into the soil in adequate amounts.  Many, I am sure, do not do this and are paying the price each year is lawns that fail over and over again.

How to Remedy your Compaction Problem
If you have one of these lawns, you have the choice of two ways to greatly improve your lawns.  You can start over and dig up the lawn area and reseed or resod, being sure this time to add organic material, mixing it with the existing soil to a depth of at least 4 inches deep.  I recommend using a ratio of organic matter to soil of 1 part organic matter to 3 parts existing soil.  This means spreading about 1½ inches of compost on top the soil and tilling it into the soil to a depth of 4 inches.  This process will aerate your soil and mix in the material that will help to keep it aerated.


Your second choice, if you do not want to redo your entire lawn, is to mechanically aerate your lawn with a core aerator.  This device will cut cylindrical cores (1/2 inch across and 4 inches deep) out of your soil at 4-inch intervals.  Core aeration means removing those cores of soil, not just punching holes in the soil using a solid spike device (And about those hole-punchers?  Save your money.)  The openings left by the removal of the cores will relieve the compaction and open the soil to air, water and fertilizer down to the deepest roots.  Follow the aeration with an overdressing of compost, which will filter down into the holes and add needed organic matter.  You can rent a power drum core aerator machine at most equipment rental businesses.  If you have heavy soil, you should do this mechanical aeration every fall.

Make soil aeration a part of your yearly lawn maintenance program, along with watering, fertilizing, mowing, and pest control.

Photo credits: core aerator, and plugs from one.

2 Responses to Now’s the time to correct soil compaction under your lawn

  1. Nancy says:

    I had the same problem over and over on a slight hill (right at the back yard gate). I purchased sod several times, only to have it die. Last week, my Hubby and I got an axe and started chopping away at the soil. What we found was very tiny roots (about 2 inches from the surface) covering the entire area. Apparently they are from a Maple that is planted about 8 feet away. We removed all the roots from a 6×6 area and plan to condition the soil and lay sod again. Hopefully, it will survive this time. If you have any additonal suggestions, please advise. Thanks. Nancy

  2. Gene Sumi says:

    Dear Nancy:

    Root competition from larger plants such as well-established trees and shrubs make it difficult for newly-planted plant stock from getting themselves established (sort of like “possession is 9-points of the law.” You can help any plant that faces this newcomer disadvantage by mixing a reliable sources of Mycorrhizal fungi in with the backfill soil when you are planting. This fungi is nature’s way of helping new plants compete for root space with the big boys. The fungi attaches to the roots of your plants and establishes a symbiotic relationship with your plant that lasts a lifetime. The fungi get sap sugar from the green plant host and gives back by sending out very efficient roots systems of its own to supplement the feeder roots of the host plant. This means that at the start, your new plant has an added advantage in the root department and can sometimes out-compete the neighbor plant for water and nutrients. I recommend Espoma Bio-tone as the source for these natural, beneficial fungi.

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