Tales from the Help Desk, Soil Test Unwrapped!
Written by Patsy McGrady, Master Gardener, Class of 2010
Q. Why should I get a soil test and how do I get one?
A. Gardening without a soil test is like cooking without a recipe. Sometimes the results are good, and other times, not so good. A soil test identifies the pH of the soil and states whether the soil needs to have lime added. The report provides the level of various nutrients in the soil, such as phosphorus, potash, calcium, etc., and includes recommendations for fertilizer. Ranging from 1 to 14, pH is a measure of the acidity of the soil.
A pH value of 7 is considered neutral. Values below 7 are acidic, and above 7 are alkaline, also known as “base.” From a scientific perspective, pH is a term that measures the hydrogen ion (H+) activity in the soil, and therefore the acidity or alkalinity of the soil. Acidic soils contain a high level of hydrogen ions while alkaline soil has a low level. pH is important because it determines how well various nutrients can be absorbed by plants. For example, iron is more available to plants when the soil is acidic, phosphorus is more available at high alkaline levels, and nitrogen decreases in availability when the pH is less than 6 or more than 8.
Some plants such as azaleas, camellias, and ferns prefer acid soil while other plants such as buddleia, lilac, and lily of the valley like alkaline soil. Fertilizer is labeled by its relative content of nitrogen (N), phosphate (P), and potash (K). The soil test report recommends an appropriate fertilizer and an appropriate amount.
A homeowner recently shared his soil test results with the Help Desk. His pH level was 7. The phosphate level was very high, potash was medium. Zinc, magnesium, and calcium levels were sufficient. The report recommended using a nitrogen-only fertilizer, suggested four types of nitrogen-only fertilizer, and gave appropriate amounts (pounds and cups) for each.
Soil test kits (a box with an application and instructions) are available on a rack outside the VCE office at 3127 Forge Rd, Toano. The homeowner takes soil samples at several locations and mails the sample to the VT/VCE address provided. Results are provided by email. The cost per kit for the soil analysis is generally $10 (see https://www.soiltest.vt.edu/fees-and-forms.html).
Depending on the size of your planting area you may want more than one test. Here’s some additional information on soil testing from our Master Gardener friends in the area.
Henrico Master Gardeners have a highly recommended video: https://youtu.be/oNaL07uqka4.
The Northern Virginia Master Gardeners offered up this link to the Northern Virginia Soil and Water Conservation District – https://www.fairfaxcounty.gov/soil-water-conservation/test-your-soil.
Piedmont Master Gardeners offer this great information: https://piedmontmastergardeners.org/article/soil-testing-2/.
There’s good information on the VCE soil sample kit as well, like directions on what to do and where to mail it.
Got questions? Call our Help Desk at 757-564-2175! 