How to improve drainage in clay soil

Updated March 23, 2017

Providing adequate drainage for plants in clay soil requires improving the soil's texture. Lighten clay soil texture with the help of organic materials. With appropriate amendments, clay soil can become a fit environment for healthy plant growth.

Select a large area of clay soil to amend. Adding a couple of bags of sand to a small patch of ground will not benefit the soil nor the plants. Plants need to be in sufficiently-amended soil to avoid contact with neighbouring clay soil. A larger amended area allows plants a sufficient extension area.

Measure the area you want to amend to determine how much material you need to add. Measure square metres by multiplying length by width. Add into your calculations how deep the layers of additives need to be. Added 7.5 to 10 cm (3 to 4 inches) of sand and organic matter.

Buy materials in bulk. Since you need to amend a large area, it is impractical to buy bags of sand and compost or manure. An average bag of sand covers about a couple of square metres. Bulk material is measured in cubic metres. Account for the distance plant roots spread over time. For example, roots of a fully grown tree can extend beyond a 30 metre (100 feet) area.

Amend clay soil with coarse materials for adequate drainage.Use builder's sand, which is coarser grade than sandbox sand, with coarse organic material, such as compost or aged manure. Coarse compost is made from leaves. Contact your local garden centre and ask about compost made from leaves.

Cover the area with coarse compost or aged manure. Till the material to a 15 cm (6 inch) depth. Spread coarse sand over the top of the organic material. Till again. As the compost or manure decays, it acidifies the alkaline clay soil. Regularly check pH levels and soil texture. Maintain levels appropriate for what you plant.


Amend clay soil when it is dry.

Things You'll Need

  • Tape measure
  • Coarse sand
  • Coarse compost or aged manure
  • Tiller
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About the Author

Alyson Paige has a master's degree in canon law and began writing professionally in 1998. Her articles specialize in culture, business and home and garden, among many other topics.