UW-Extension Cooperative Extension
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Contact: Michael Maddox, 608 752-3885
Entry Date: April, 2003
File Under: Horticulture
Getting a soil test will improve lawns, shrubs and gardens.
Madison - Wisconsin home gardeners look forward to the warmer days in April as a long anticipated chance to prepare for the coming growing season. One important early gardening task is getting a soil test.
"It doesn't matter if you are growing vegetables, perennials or woody ornamentals," said UW-Extension commercial horticulture educator Michael Maddox. "A soil test will show any deficiencies or abundance of nutrients you have in your soil and will give appropriate recommendations."
Getting soil tested and following the recommendations about fertilization has many benefits - healthier plants, a healthier environment and a healthier garden budget. A soil test is the only way to know what nutrients your plants need. The test also tells you if your soil is acidic or alkaline and if it contains micronutrients or lead.
"Over fertilizing does more harm than good, and it takes a long time to correct the consequences." Maddox said, explaining that adding too much fertilizer may injure plants and pollute water supplies.
An accurate soil sample should reflect the overall condition of the lawn or garden. UW-Extension recommends collecting small amounts of soil from scattered spots. For a garden or lawn of less than 500 square feet, you will need to take soil from at least five places. For areas between 500 and 1,000 square feet, take at least 10 different samples. Use a clean soil probe, shovel or garden trowel to take thin slices or cores of soil four to six inches deep. Break up these individual soil samples and mix them together. You should have about one to two cups of soil for each sample.
Take representative samples for each area you want analyzed. The plants in each area have different nutrient needs so don't mix lawn and garden soils into one sample. Take separate samples for your shrub bed, lawn, vegetable gardens, flower gardens and any specific problem areas. You may want to take separate tests for the front and back yard, or shady and sunny areas. More representative and specific samples mean you will get more accurate recommendations.
After collecting your samples, place each one in a clean plastic bag and label it with your name and address and the sample location. Keep a record of the area of the lawn and garden where you collected each sample. Remember to enclose a completed information sheet, which you can get from your county UW-Extension office.
You can have your soil samples tested by the University of Wisconsin Soil and Plant Analysis Laboratory or any state-certified soil testing facility. Homeowners may receive recommendations specifying "winterizer" blends, "maintenance" blends or "starting" blends. Maintenance blends are high in nitrogen, low in phosphorus and potassium. Winterizer blends are high in nitrogen and potassium, low in phosphorus. This type is often recommended for soils that are high in phosphorus. Starting blends include phosphorus and are good for germinating seeds.
Your county University of Wisconsin-Extension Office has more information about submitting a soil sample. You can also get more information on this topic by requesting UW-Extension bulletin A2166-Sampling Soil for Testing.