Testing Your Soil by MGV Ann Marie Ott


soilBefore adding fertilizer to your garden shopping list, consider collecting a soil sample and sending it to the University of Wisconsin soil testing laboratory for analysis to determine your fertilizer needs.  As the University’s website indicates, many publications offer general recommendations for fertilization of lawns, plants and gardens, however using the analysis provided by the lab you will be able to tailor your application plan and potentially save money.


Obtain a soil sample bag from your UW-Extension office. If travel to the office is inconvenient, choose a clean plastic bag to hold the soil. Next, collect a representative soil sample from your garden.  If you don’t have a soil probe in your toolshed and don’t want to purchase one, you can use a trowel to dig “cores” of soil from your garden.  Dig soil 5 to 7 inches deep from at least five places in your garden area and mix them together.  From this mix, place two cups of the dirt into the bag or fill it to the line indicated on the UW-Extension bag.


If your garden is large or your plantings in the spaces vary, you may wish to collect more than one sample.  After you have prepared the sample, complete the submission form which can be downloaded from the webpage listed below. On the form you will record the location of the sample and indicate the landscape category of plants that you intend to grow or are growing using the lab’s codes that appear on the form.


You may pay the $15 per sample fee through several options.  Additional fees are required for special testing for lead, soluble salts or if you want a physical analysis. Test for other nutrients are also available.  Mail your samples or deliver them in person to:University of Wisconsin Soil and Forage Analysis Lab 2611 Yellowstone Dr. Marshfield, WI 54449. See the Soil and Lab Brochure for how to correctly sample for different test. 

See full list of fees: https://uwlab.soils.wisc.edu/fees/

In about two weeks you will receive a report from the analysis of your soil. Information about the pH, organic matter, the available phosphorus (P) and potassium (K) will be included in the report. The report will provide advice for adding nitrogen (N), P or K based on the types of plants you indicated on the submission form and will also tell you whether you should add lime to your soil, too.


Testing is recommended about every three years so this small investment of time and money will put you on a path to superior results!


For complete information and to obtain the necessary instructions and submission form as well as a variety of other resources related to fertilization, visit this webpage:  http://uwlab.soils.wisc.edu/lawn-garden/