Soil Testing and Soil Testing Labs

Why is soil testing important?

Soil's importance for plant growth can be summed up in the aphorism "it's better to plant a $2 tree in a $25 hole, than a $25 tree in a $2 hole."

• Have your soil tested before planting a vegetable or flower garden, trees, and shrubs, or starting or renovating a lawn.
• Soil testing labs provide more complete and accurate results than do-it-yourself soil test kits.
• Soil test results give you baseline information on soil pH, nutrient levels, and organic matter content and recommendations for fertilizing and adjusting soil pH. Soil testing is an essential tool for improving soil health.
• Soil testing helps reduce overfertilizing, keeping excess nutrients (nitrogen and phosphorus) out of Maryland's groundwater and surface waters.
• Vegetable gardens, regardless of location, should be tested for lead (Pb).
• Need help understanding the report and recommendations from a soil testing lab? Send us your questions and the report through our Ask Extension service.

Selecting a lab

• The University of Maryland no longer has a soil testing lab but HGIC maintains a list of recommended soil testing labs for you to choose from. The University of Maryland does not endorse particular businesses and the inclusion or exclusion of specific labs does not reflect a bias. All of the listed labs competently test soils and provide reports that include liming and fertilizing recommendations.
• The labs listed below offer lawn/garden and commercial soil testing. Select the appropriate category.
• Test results are usually available online for fast, efficient reporting.

Select the "Basic Test"

• Select the basic test offered by the lab that you choose. This typically includes pH (a measure of the alkalinity or acidity of your soil), phosphorus, potassium, calcium, and magnesium. The chemical symbols for these four nutrients are P, K, Ca, and Mg, respectively. These are important nutrients required by plants in large quantities.
• The basic soil test may also include other nutrients like sulfur (S), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), and boron (B), as well as % of organic matter (OM), and cation exchange capacity (CEC). A couple of the labs also include lead testing (Pb) as part of a basic test.
• Soil pH is one of the most important measurements. It plays a big role in the availability of nutrients to plant roots, nutrient run-off and leaching, and microbial efficiency.
• Nitrogen is needed in relatively large quantities but it is not measured because it continuously moves between organic forms (not available for plant uptake) and inorganic forms (available for plant uptake). This is affected by temperature, rainfall, soil texture and structure, biological activity, and many other factors. Nitrogen recommendations are provided, but they are based on the need of the particular plant you are growing for the upcoming season, not the amount in your soil.
• Boron, zinc, and manganese are trace elements that can sometimes be deficient in Maryland, especially in Coastal Plain soils. If a soil test report shows a low Boron level dissolve 1 tablespoon of Borax in 1 gallon of water and apply the solution evenly from a sprinkling can over 100 sq. ft. 
• Don't pay for extra tests, such as soluble salts, or specific micronutrients unless you have a very good reason.
• In addition to testing for lead (Pb), some labs also test for arsenic (As), cadmium (Cd), and chromium (Cr). Soils on old industrial sites are sometimes contaminated with these heavy metals. Soil testing labs do not generally test for other types of soil contaminants, such as human pathogens and pesticides.
• Some labs offer a textural analysis for an additional fee. Your soil's texture is the relative percentages of sand, silt, and clay particles that make up the mineral portion of the soil.
• Perform a soil test every 3 years for lawns and vegetable gardens. Problem sites can be tested more frequently. Fall is a good time to test soil because any soil amendments that you add, like lime and compost, will have time to improve the soil before spring in time for planting.
• Use the same lab each time you have your soil tested. Labs can use different chemical extractants to determine nutrient levels which leads to different test results, and they use different units (e.g., lbs./acre vs. ppm) and bases (e.g., P-phosphorus vs. P2O5,-phosphate) for expressing those results.

Table of soil testing laboratories

Basic soil tests typically cost $11 - $20, plus mailing costs. Any additional testing will increase the cost. Please contact the lab for current pricing before submitting your sample. Include payment with your sample.

Getting your soil tested

• Follow the specific instructions provided by the soil testing lab you select.
• General guidelines
  • Separate samples should be taken for distinct areas like the front yard, back yard, vegetable garden, etc. The sample should represent the soil in which the plants are or will be growing in.
  • Use a spade or trowel to take 10-12 random sub-samples per sampling area. The samples are thin slices taken to a depth that contains or will contain the bulk of the plant's roots- 4 inches for turf; 6-8 inches for garden and landscape beds.
  • Mix together all of the slices in a clean bucket removing all rocks, debris, and plant parts.
  • Labs typically require 1 cup of soil per sample. Mail the soil in a zipper-sealed bag or a clean plastic bag.
  • Don't mail wet soil; you should not be able to squeeze water from the sample.
  • Download the soil test submission forms from the lab's websites. Fill out the form including your contact information and answers to the questions about the soil you are testing. Mail the completed form back to the lab in a small box or padded envelope with the sample and payment for the correct amount.