Carefully select topsoil when doing fall yard work

Not all topsoil is created equal.

Select topsoil carefully when making fall lawn renovations, says Manjula Nathan, director of University of Missouri Extension’s Soil Testing and Plant Diagnostic Services. A soil test is the best way to measure topsoil quality.

Topsoil is the uppermost 3 to 10 inches of soil. Most surface soil has higher organic matter content than subsoil, but not all surface soil is ideal for lawns and gardens, Nathan said. If you have poor soil, consider adding a few inches of good topsoil with added organic matter, nutrients, lime or sulfur on the surface or on your raised bed gardens. Base these additions on your soil test results and consider what plants you are growing.

Topsoil is available in bags or bulk. Most garden centers and discount stores sell topsoil in 40- to 50-pound bags. Bagged topsoil may already have added nutrients and organic matter. Bulk topsoil is native soil taken from the surface and sold by the truckload.

Nathan shares the American Society of Landscape Architects’ guidelines for choosing topsoil:

• Topsoil should be free of weeds and plant pathogens.

• Check topsoil for three main physical and chemical properties: organic matter, texture and pH (a measure of acidity or alkalinity). Reject topsoil that does not meet recommended standards. It costs little money to test topsoil before using it to amend to renovate your lawn or garden. If you don’t know what you are getting in your topsoil, you may end up spending a considerable amount of money and time to improve it, Nathan says.

• For accuracy, measure soil pH with an electrode, not paper test strips. Ideal levels are 6.0-7.0. However, some acid-loving plants such as azaleas, rhododendrons and blueberries prefer pH below 5.5.

• Soil texture refers to the percentage of sand, silt and clay-sized particles in soil. Texture influences water-holding capacity, aeration, drainage, tilth, compaction and nutrient-holding qualities. Ideal soil texture is loam and silt loam.

• Organic matter improves the soil structure, nutrient- and water-holding capacity, soil aeration and infiltration, and it reduces compaction and helps retain plant growth. Organic matter should be 3 percent or more, Nathan said. Soil rich in organic matter will be dark or black.

For reliable results, Nathan recommends using a state-certified lab such as the Soil and Plant Testing Laboratory at 23 Mumford Hall on the MU campus. For more information, contact the lab at 573-882-0623 orsoiltestingservices@missouri.edu, or visit the lab’s website at soilplantlab.missouri.edu/soil. County extension centers also accept soil samples, and county extension staff are available to help review test results. For a list of state-approved soil testing labs, visit soilplantlab.missouri.edu/soil/msta.aspx.

Source: Manjula Nathan, 573-882-3250

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