Garden not doing well? Consider testing your soil

Every spring, gardeners across Minneapolis plant their seeds and hope for a productive growing season. Some gardens thrive, but others limp along despite careful watering and fertilizing. If you’ve ever wondered why your lovingly tended plants aren’t doing as well as you would like, consider testing your soil! Read on for more information on why soil testing is important and how to request a soil test through the University of Minnesota Soil Testing Lab.
Most garden fertilizers have three numbers on the front. These are the percentages of nitrogen, phosphorus, and potassium – three of the main nutrients used by plants. Having a soil test done is the best way to know what fertilizer to use, since it will tell you which nutrients are plentiful in your soil and which are lacking.
The U of M offers a number of different soil test options, but most home gardeners will want to choose the “lawn and garden” version. This test measures several key factors, including soil pH, phosphorus, potassium, organic matter content, and the texture of your soil. You can also choose to add tests for lead or soluble salts. A lead test can be helpful if you are concerned about lead paint that may have flaked into the soil near your house or garage. Testing for soluble salts will help determine if excess road salt, sidewalk salt, or fertilizer is impacting your plants.
Soil test results from the U of M Soil Testing Lab come back not just as numbers, but as specific recommendations. The soil test report explains what type of fertilizer would be best for your yard, whether to add lime to modify the soil’s pH, and other important information. Getting specific science-based recommendations helps save money by telling you exactly what soil amendments you need, and it prevents the environmental harm of applying unnecessary nutrients that can run off into our lakes and rivers.
To get started, visit the Soil Testing Lab’s website at soiltest.cfans.umn.edu. Print and fill out the form from the website, collect your soil samples, and mail or drop off the samples to the Soil Testing Lab in St. Paul.
You can include up to three soil samples on each request form, and each sample should include 2-3 cups of soil. It’s a good idea to sample several locations in your yard since soil conditions can vary. For example, the soil in your yard, flower beds, raised beds, and near the street may all have different levels of nutrients and salts and need different amendments.
Collecting the sample correctly is important. For each area you want to sample, scrape away surface litter, grass, or leaves. Collect 4-6 samples in the area using a garden trowel or shovel. Typically, a sample from 3-5 inches deep will work well. Thoroughly mix together the samples from one area, remove rocks, and break apart clumps. The mixed soil from each area can be submitted in a Ziploc bag or plastic container. Remember to label clearly with your name and the area the sample is from! Results are typically available within two weeks.
If you've never tested your soil, start now! For established gardens, retesting every three to four years can be helpful as soil chemistry shifts when you plant, harvest, and amend the soil each year. It’s also a good idea to test the soil when you build a new raised bed, and, of course, when you move into a new house or start gardening in a new community garden plot.
Soil is critical to gardening success – it’s the foundation on which everything else is built. Send in a container of dirt and learn what your garden needs to thrive!
For more information, check out the University of Minnesota Extension Yard and Garden website. Extension resources are written by experts and contain the latest and most reliable research-based information. Happy gardening!