If you're planning a garden, you can plant blindly and hope your garden's soil is fertile enough to support plant growth. Or, you can collect a sample of garden soil, have it tested and then adjust the needs of your soil and future garden based on the results of the soil test.
Purpose of Soil Testing
The process of soil testing is more than just mineral analysis. Information from a test can provide insightful information into the acidity, temperature, the health of your top soil and the soil's potential to support growth. Soil testing labs typically analyze soil samples for major nutrients like phosphorous, potassium, calcium, magnesium and sulfur. They also test for micronutrients. like copper, manganese and zinc. Testing also checks sodium levels, pH, base saturation, humus concentrations and the soil's permeability. A good soil test will be able to project future plant problems based on quality soil samples.
If you're planning to plant a garden in a certain area of your yard, you need to provide a representative core sampling of the soil in that region. The first step in collecting samples is to use non-reaction stainless steel which doesn't react or leave metallic residue in the sample. Secondly, collect a sample at least 6 inches below the surface of the soil. Finally, in each gardening region, you should take an average of 10 core samples, mix them together and store them in a bag provided by the testing lab. Each garden region should have a representative sample with identification, so the lab can reference the garden in the report.
Many private testing labs or university extension programs, like Cornell Extension, offer soil testing for a fee with a representative sample of soil. A sample should represent an average of core samples taken from a variety of locations in the garden. Results usually take a week and can be provided online or as a printout. Reports should show an analysis by category including: macro- and micronutrients, a a regional and national comparison, soil acidity and soil permeability. Finally, the report should make recommendations in terms of how to improve soil condition based on the plant types and individual plant nutritional needs.
Using the Results
After you receive the soil test report, note any nutrient or fertilizer recommendations. For each grass, flower, fruit or shrub you wish to plant, the lab will provide ranges for each soil sample and the nutrients recommended. It will also provide a ratio you can use when purchasing and adding nutrients. Many gardening centers can help you with fertilizer and nutrient recommendations based on the report.
Do-It-Yourself Soil Testing Kits
If you'd rather not use a lab for soil testing, you can use a do-it-yourself soil testing kits. Heirloom, makers of Heirloom seeds and tomatoes, offers a RapiTest kit that tests 10 different gardening components. The company claims results are easy to read and provides guidelines for interpreting the results. In addition, you can do some simple tests like the soil sedimentation test. To do, mix a sample of soil in a glass and let everything settle for several hours. The beauty of this test is that by density, each main component (sand, silt, clay and organic matter) will settle in layers. By measuring each layer of sedimentation and dividing it as a percentage of the total, you can assess your garden's soil type. Your garden center carries gardening books that show you typical soil types.