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What Is Clay Soil?

By Charles Pearson ; Updated September 21, 2017
Clay is one of the most difficult mediums in which to grow plants.

Clay soil is difficult to use when gardening because the clay is sticky and has a difficulty developing a good structure. Clay also makes it difficult for plants to absorb nitrates, phosphates and sulfate. Excessive clay causes water to remain in the soil for too long, but according to the University of California Davis, moderate amounts of clay soil can be beneficial by helping the soil retain moisture.


Clay is created by the gradual chemical weathering of quartz, feldspar and mica. These weathered products have the finest sized particles, causing clay to be sticky. Clay has a tendency to attract positive ions while repelling negative ions. Clay also has a tendency to attract water.


Plants in clay soil need extra space. The hole that is dug for the plant should be twice as wide as the root ball. The roots should be below the surface when the soil is poured back into the hole. The original soil can be mixed with compost or peat moss in order to increase the chances that the plant thrives, though the old soil should always be mixed into the added soil in order to prevent the soil from draining unevenly. The soil that you add probably will be drain efficiently, while the clay soil has a tendency to not drain well. The fertilizer that is added to the clay soil should be a slow-release product in order to provide the plant with plenty of nutrients throughout the year.


Lime should be added to clay soil in areas where there is heavy rain if the soil is very acidic but should otherwise not be used. Mulch can be added to the surface to prevent moisture from being lost and to also prevent soil erosion.


Clay soil should be handled carefully. Heavy clay soil that has no organic matter on it can lose its form if it’s tilled or walked on when wet. A spading fork should be used to break up clumps of clay when tilling the soil in areas where the soil is clumpy. The clods of clay soil can be broken up by adding moisture, raking the clods and then letting the clods air-dry before repeating the process. While doing this, organic matter can be gradually added to the clay soil in order to improve the structure.


The types of organic matter that can be added to the clay soil are animal manures, compost and leaf mold. Slowly decaying material like peat moss and sawdust should be avoided because it has a tendency to deplete the nitrogen in the soil, which will be in short supply in clay soils. There are many plants that can survive in clay soils. But these plants usually have particular soil pH levels and other requirements.


About the Author


Charles Pearson has written as a freelancer since 2009. He has a B.S. in literature from Purdue University Calumet and is currently working on his M.A. He has written the ebooks "Karate You Can Teach Your Kids," "Macadamia Growing Handout" and "The Raw Food Diet."