Lightening a heavy clay soil

Question: The soil on one side of my house is heavy clay and plants don’t seem to do well in it. What’s the best way to improve this soil?


Adding compost is a great way to improve a clay soil. Photo by Kate Kurtz

Answer: Organic matter is your best tool to lighten a heavy clay soil. Composts or biosolids soil products should be available either from your local nursery or municipality. You can put compost on the soil to about 6 inches deep and use a tiller to incorporate it. It does not need to be mixed well; one or two passes will suffice.

Do this for a few years and you will see improvement over time. You can also make a “lasagna” on your soil: Layer leaves, straw, and manure in the fall on the surface of the soil. Cover it with burlap so it stays tidy. In the spring, you should be able to turn the soil with a shovel. Again, you will see improvements over time.

–Answered by Sally Brown, University of Washington, and Kristen McIvor, Pierce Conservation District, Tacoma, WA

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3 responses to “Lightening a heavy clay soil

  1. The more difficult thing is to improve compacted urban soils where trees are already present. I don;t like the idea of tilling and disturbing the roots of heritage trees …. or choking the roots with too much material. I guess it is just a question of mulching and being patient?

  2. I agree that you certainly don’t want to disturb trees in an effort to lighten your soil. Trees themselves will do a great deal to help your soil, both by their roots creating pores for water movement and by adding organic matter to the soil. With that said, a surface application of compost every year will also help the soil over time. It will provide nutrients for the trees and also gradually increase the soil organic matter. Also a surface mulch will help by slowing down the rain water and giving it a chance to soak into the high clay soil. It will also help for dry periods as a great way to let moisture stay in the soil.

  3. Pingback: Himalayan mapple(Acer oblongum Wall.ex DC) | Find Me A Cure·

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