What Amends Clay Soil?

Clay soil commonly dries to a hard, compact texture like cement.

Clay soil presents the gardener problems that cause plants to decline and even die. This type of soil is prone to compaction, which squeezes air from around the roots. Compaction happens when clay soil is worked when it is wet. Clay soil also tends not to drain well because of its density. On the plus side, clay soil is usually full of nutrients. Amending clay soil fixes the problems and enables plants to grow. It takes two to three years of amendments before improvements begin to show.

Compost

Compost is one of the best amendments to use in clay soil. It adds bulk and slow-release nutrients to clay soil. Compost recycles yard and kitchen waste by turning it into dark, rich material. Add shredded deciduous leaves, conifer needles, straw, fruit peels and raw vegetable waste to the compost pile. Grass clippings should be dried before adding them to the pile. Spread out the grass in a 1/2-inch layer so it dries quickly. Turn the compost pile often so the compost ingredients break down quickly.

Wood Byproducts

Shredded bark, sawdust, wood shavings and other woody products can bulk up clay soil to create a coarser texture and aerate the soil so the plant roots have more access to oxygen. Decomposing wood steals nitrogen from the surrounding soil, causing nitrogen deficiencies in surrounding plants. This problem is solved by adding nitrogen fertilizer into the wood byproducts, but the best solution is to only use composted wood products that have finished decomposing.

Peat Moss

Peat moss is commonly used to amend clay soil to fix drainage problems and aerate the soil around the roots. This amendment increases the acidity of the soil when it is added. Peat moss gives the soil a more granular feel, which makes it easier to work with. While peat moss increases soil drainage, it also holds more water, making it accessible to plant roots. Additions of peat moss encourage root growth and are a long-term soil improvement. Commercially available peat moss is usually weed-free.

Manure

Manure holds more nutrients than peat moss, is lower in acidity and does not last as long as other types of organic materials. Manure can be an inexpensive addition to clay soil if there are cow farms in the local area. Fresh manure may be a source of weeds when added directly to the clay soil. It is best to use composted or well-rotted manure that is free of weeds; aged manure won't cause plant burn, which is caused by the heat of decomposing fresh manure.

Sand

Sand is an inorganic amendment that improves drainage, aeration and texture. Sand is added in 2-inch layers along with organic material. When used alone, sand and clay mix together to form a type of concrete. Construction grade or coarse sand is used to amend clay soil, because fine sand will increase the clay soil's tendency to compact. It takes a lot of sand to improve heavy clay soil. Peat moss or compost is usually a better and more inexpensive solution.

References

• Utah State University Cooperative Extension; Preparing Garden Soil; Duane Hatch; 1990
• University of Missouri Extension; Improving Lawn and Landscape Soils; Manjula V. Nathan; April 2010