How to Improve Clay Soil

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I have heavy clay soil that becomes as hard as a brick when it dries, and my neighbors who also garden have asked me how to improve clay soil. What are the best methods for improving clay soil?

First, the good news: “Of the three major soil components — sand, silt and clay — clay has the highest nutrient content,” says Garn Wallace, president of Wallace Labs, a Improve Clay Soilsoil-testing firm in El Segundo, Calif. Clay soils retain minerals in forms that are readily available to plants and that aren’t water soluble, so rain and irrigation water are less likely to leach them away. The trouble is that clay lacks good porosity. Its fine-textured particles tend to clump tightly together. Air, water, roots and seedlings can have trouble moving through it, so crop yields may be lower. (Plus, clay is a pain to work in!)

Increasing your soil’s organic matter is the first and most important step toward improving heavy clay soil. Organic matter invites in more porosity-improving earthworms. Work in compost, grass clippings, shredded leaves or other organic materials. Plant and turn under cover crops, and safeguard your soil’s surface with an organic mulch to prevent crusting. Sand or peat moss can also improve soil texture, but they lack many of the other benefits of organic matter, such as beneficial microbial activity and nutrients for your plants to uptake. Plus, you’ll need a lot of sand to make a real difference (1 part sand to every 2 parts clay soil).

Photo by Dreamstime/Ian Nixon: Don’t be foiled by your heavy clay soil: Add organic matter to soften up your tough terrain.


Vicki Mattern is a contributing editor for MOTHER EARTH NEWS magazine, book editor and freelance magazine writer. She has edited or co-authored seven books on gardening, and lives and works from her home in northwestern Montana. You can find Vicki on .