The shocking truth about topsoil
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EmailWhat every gardener should know when purchasing topsoil.
Almost every gardener has said at some time, "We need to buy some topsoil." Whether it is to fill flower beds, build a vegetable garden, or help establish lawns in sandy or clay soils, you may have needed to purchase either bulk or bagged topsoil. But do you really know what you are getting?
Myth #1: Topsoil means that it will be good, dark and rich soil.
Reality: There is no regulated definition for the word topsoil. Technically, it is whatever soil is on the surface; it is presumed to be fertile. It’s important to always look at what you are buying, especially if you are unfamiliar with the seller. Purchasing bagged soil can complicate this issue because you can't easily see and feel the soil. Before committing to a large purchase, buy one bag and inspect its contents. If you are buying in bulk from a landscape supplier, visit the facility and inspect the product before you purchase it. You want to be sure there are no large clumps or rocks.
Myth #2: Good topsoil is very black.
Reality: Very black soil is not always the best soil. Dark coloration can indicate a high level of organic matter, or it can suggest the soil was dredged from a wetland or water-saturated area. These soils may have poor structure and an undesirable pH. Soils that are good for agricultural purposes, i.e., plant growth, often have a loamy texture containing clay, silt and sand in balanced proportions. Excessive levels of any one component can cause problems.
Myth #3: There are no weed seeds in good topsoil.
Reality: All topsoil will contain some weed seeds. There is no way for even the most diligent seller to remove these. Soil equals seeds, and when plants appear, they are often plants that you will notice because they are not currently growing on your property.
Myth #4: All I must do is spread it over my existing soil, jump back, and watch great things happen.
Reality: Topsoil sitting as a separate layer on top of the existing soil will create drainage and growing problems. When adding topsoil, it is almost guaranteed to be different from the existing soil. This can create problems for roots growing downward. Roots may stop at the original soil layer, especially if that layer is dense. It is essential to mix the soils together. When amending existing soil, add 2 to 3 inches of topsoil, then till or broad fork the soil to combine the existing and new soil. Then, more can be added because you have just created that transitional layer. This step will be well worth the additional effort.
Myth #5: I don't have to fertilize when I use topsoil.
Reality: The seller is providing soil, not fertilizer. What you have just purchased may be lower in nutrients than what you already have in your garden. Topsoils can have significant variations in nutrient composition. You should still test your soil to see which, if any, nutrients are needed. More information about fertilizer basics can be found in Smart Gardening: Fertilizer Basics for the Smart Gardener.
Myth #6: I won't need to fertilize if I use compost instead of topsoil.
Reality: Compost is organic matter used to amend soil. It isn't the same thing as topsoil. Topsoil is mostly inorganic matter and minerals. Believe it or not, you can overapply compost. Excess nutrients, especially phosphorus from animal compost sources, due to overapplication can run off into our waterways and cause pollution. It can also cause nutrient imbalances in your garden. Michigan State University Extension suggests getting a soil test to test these levels before applying any amendments or fertilizers. For more information on compost, visit Gardening in Michigan – Soils & Composting.
Myth #7: Topsoil is pristine and pure.
Reality: The topsoil you can purchase in bags or from your local landscape company can come from various sources. One of these sources is construction sites. You may find construction debris in your topsoil. This can include plastics, wire, cans, concrete, wood chips or even brick. Most suppliers do their best to remove these materials before selling the product, but it isn't uncommon to find stragglers.
Myth #7: I can save money by purchasing topsoil instead of garden soil.
Reality: Garden soil and topsoil are different products. Landscape suppliers often blend compost or other organic matter with topsoil and sell it as garden soil. Using garden soil can be a great way to save labor when constructing garden beds.
You should get a soil test before amending your soil or purchasing topsoil. This will help you make sound and environmentally friendly decisions and potentially save some of your hard-earned cash.
For information on soil testing and to purchase a soil test kit from Michigan State University, go to https://homesoiltest.msu.edu/.
