# Define Loam & Topsoil
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Topsoil
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Geologically speaking, topsoil is pretty self-explanatory. It is a layer of ground up rocks, decomposed plant and animal matter, dust, microbes, minerals and nutrients that has accumulated on the Earth's surface. Commercially speaking, there are no guidelines dictating what is sold as "topsoil," according to several universities, including the University of Connecticut. Topsoil sold commercially can be just about anything and come from anywhere. Instead of being comprised of the rich, organic matter gardeners seek, it can contain weeds, trash, rocks and even pesticides or herbicides.
Tips for Buying Topsoil
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Just because topsoil isn't regulated doesn't mean you have to accept a substandard product. Purchase topsoil from reputable suppliers. If the topsoil has been amended, ask what was added and in what amounts. Ask if the soil was tested, find out its pH and the concentrations of sand, silt and clay. Ask for a sample and test it yourself. Soil tests often are available from your local university's extension. Test the texture. Take a ball of dirt in your hand and squeeze it -- it should break apart easily when released. If it smells like chemicals, don't buy it. Take a sample home and see if seeds germinate in it. This will help you determine whether or not there are herbicide residues in the soil.
Loam
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Loam is a term used to define soil with a mixture of sand, clay and silt. Topsoil can be loam, depending on its contents. Loam is all about texture, according to horticulturists at the University of Connecticut. Technically speaking, loam is 7 to 27 percent clay, 28 to 50 percent silt and less than 52 percent sand. A mixture of these three types of soil in important because it holds moisture while allowing for drainage. Depending on the percentages, soil can be called sandy loam, sandy clay loam, silt clay loam or any combination corresponding to the mixture.
Common Soil Amendments
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It is unreasonable to think that purchased topsoil will be perfect for gardening, according to the University of Connecticut. Most of the time lime and fertilizer will be needed. Organic matter, like compost, peat moss and manure, also commonly is needed. Add amendments based on what you plan to grow. Not all composts are good for vegetables and peat moss may not be right for your flower bed.
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