soil testing resources

Commercial Laboratory Soil Tests          

• Commercial lab tests often check for plant nutrients in 3 categories:
  • Major nutrients: nitrogen (N), phosphorus (P) and potassium (K)
  • Secondary nutrients: sulphur, calcium, magnesium
  • Minor nutrients: iron, manganese, copper, zinc, boron, molybdenum, aluminum
• Lab tests are more accurate than DIY tests, though both types are useful
• Lab tests frequently include professional interpretation of results and recommendations
• Soil testing is often performed by commercial labs that offer a variety of tests targeting groups of compounds and minerals
• There may be some advantage to using a local lab that is familiar with the chemistry of the soil in the area where the sample was taken
• Searching online for soil testing will produce many results including national and local groups and organizations that offer testing and reporting
• Here is an example soil sample report from one laboratory
• Most labs will offer a guide on how to decipher the report

Do-It-Yourself Kits

• Usually only test for the three "major nutrients" and for soil acidity or pH level
• Do-it-yourself kits are often sold at farming cooperatives, university labs, private labs, and some hardware and gardening stores
• Electrical meters that measure pH, water content, and sometimes nutrient content of the soil are also available at many hardware stores

At Home, Individual Tests

Soil Test #1: The Squeeze Test

• One of the most basic characteristics of soil is its composition
• In general, soils are classified as clay soils, sandy soils, or loamy soils
• Clay is nutrient rich, but slow draining
• Sand is quick draining, but has trouble retaining nutrients and moisture
• Loam is generally considered to be the ideal soil because it retains moisture and nutrients but doesn’t stay soggy
• To determine your soil type, take a handful of moist (but not wet) soil from your farm/garden, and give it a firm squeeze then, open your hand -- One of three things will happen:

              1) It will hold its shape and when you give it a light poke, it crumbles -- this means you have loam

              2) It will hold its shape and, when poked, sits stubbornly in your hand -- this means you have clay soil

              3) It will fall apart as soon as you open your hand -- this means you have sandy soil

Soil Test #2: The Percolation Test

• It is also important to determine whether you have drainage problems or not
• Some plants, such as certain culinary herbs, will eventually die if their roots stay too wet
• To test your soil’s drainage:

              1) Dig a hole about six inches wide and one foot deep

              2) Fill the hole with water and let it drain completely

              3) Fill it with water again

              4) Keep track of how long it takes for the water to drain

              5) If the water takes more than four hours to drain, you have poor drainage

Soil Test #3: The Worm Test

• Worms are great indicators of the overall health of your soil, especially in terms of biological activity
• If you have earthworms, chances are that you also have all of the beneficial microbes and bacteria that make for healthy soil and strong plants
• To do the worm test:

              1) Be sure the soil has warmed to at least 55 degrees and that it is at least somewhat moist, not soaking wet

              2) Dig a hole one foot across and one foot deep and place the soil on a tarp or piece of cardboard

              3) Sift through the soil with your hands as you place it back into the hole, counting the earthworms as you go

              4) If you find at least ten worms, your soil is in pretty good shape

              5) Less than that indicates that there may not be enough organic matter to support a healthy worm                                                        population, or that your soil is too acidic or alkaline

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