How to Improve Clay Soil For Lawns

Amending Clay Soil For Lawns

claysoilTo improve clay soil for lawns, you will need to apply organic matter by a process called topdressing.  Topdressing is generally performed once or maybe twice a year in some cases. For correct topdressing you apply a thin layer of organic matter over your grass. Applying a layer of 1/4 inch to 1/2 inch thick usually works best depending on the mowed height of the grass. Up to 1 inch may work for grasses maintained at 3 or more inches. If you completely cover the grass with compost growth may be restricted and the grass will suffer.

Core Aeration

It helps greatly to core aerate the lawn before topdressing. Core aeration pulls out a plug of soil approximately ¾ inches wide by 3 inches long. Pass the aerator over the grass several times in different directions. It will seem like you are over-aerating, but you are not. If the soil is largely clay, remove the cores before topdressing. Once you begin top dressing, allow the organic matter to fill the holes. This gets the amendment down into the soil instead of only on the surface.

Using  Soil Amendments For Large Areas

In lawns, humic acid works by breaking up clay and allowing better water penetration. It helps with water retention in sandy soils as well.For the organic matter to do any good it needs to be worked down so it touches the soil. Brushing the grass with the backside of a rake is usually enough. While top dressing is extremely beneficial at every stage, it may take several years before you would be able to increase the soil organic matter to a satisfactory level. Humic Acid is also used to relive compaction. It is a term that describes the bio-chemically active ingredients of humus and is derived from many decomposed organic materials.

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Sand and Compost

Using sand to blend into clay soil as an amendment is not recommended. Although it is given as advice, it can have an opposite affect by making the clay harder and almost impossible to work with. Finer sand particles can fill the tiny holes in clay structure producing something like concrete. For sand to be effective, use the largest coarse sand particle size available. Sand based soils have sand volumes at least half of the volume of clay. To produce your own sand based soil you would need a tremendous amount of sand for a home lawn.  Using a sand and compost mix as topdressing is also an option.  Using a wheel barrel and a shovel to scatter a thin layer is still the most common method used.

Recommended Soil Amendment Materials

Compost, or humus, is decomposed plant material. It makes an excellent organic amendment for clay soils.

  1. From your lawn and garden: save yard waste, grass clippings, spent annuals, etc.
  2. From your trees: save raked-up leaves in fall, and grind them up by making several passes over them with the lawn mower. Leaves will decompose much more rapidly when ground up.
  3. From your household: save vegetable peelings, canning wastes, coffee grounds, etc. (but not meat or animal by-products).

For large areas you can till the lawn and start fresh by mixing a variety materials.  If your lawn has heavy compacted clay soil and you need to amend large areas of your lawn. Call Ryno Lawn Care for help.

PDF Version of this Post – Improve Clay Soils in Lawns

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