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The Best Soil Amendments for Gardens With Clay

By Hollan Johnson ; Updated September 21, 2017

Clay soil is soil made up of over 50 percent of clay. If you have clay soil, things aren’t all bad. Clay soil holds in moisture well and contains a lot of nutrients, which your garden needs. However, clay soil also drains slowly and has very little air in it. There are soil amendments for clay soil that will improve the aeration and drainage of your garden over time.

Coarse Sand

Thick, coarse sand will improve drainage in clay soils and aid aeration by breaking down the clay soil’s bond with water. Add 4 to 5 inches of coarse sand for every square foot of clay soil in your garden, and work it into the soil to a depth of at least 8 inches for the best effect. Do not use fine-grained sand as it will just make the clay soil worse.

Compost or Aged Manure

One of the best amendments for clay soil is organic material. It adds air and helps break up clumps of clay. Compost and aged manure are both fast-working organic materials that will break down quickly and improve clay soil right away. For the best results, add 4 inches of compost or aged manure to every square foot of clay soil and work it into the garden to a depth of 6 inches.

Organic Mulch

Organic mulch is another form of organic material, although it will break down more slowly than compost or aged manure. However, as organic mulches such as pine chips, bark or sawdust break down, they amend clay soil by adding more organic material to the topsoil, helping create a rich airy loam. Do not try to work organic mulch into the soil; just allow it to work itself in over time.


About the Author


Hollan Johnson is a freelance writer and contributing editor for many online publications. She has been writing professionally since 2008 and her interests are travel, gardening, sewing and Mac computers. Prior to freelance writing, Johnson taught English in Japan. She has a Bachelor of Arts in linguistics from the University of Las Vegas, Nevada.