Soil testing

Soil testing is a quick and easy task that has many benefits for anyone growing plants outdoors.  By conducting a soil test, it will allow you to see what the pH of your soil is, as well as what the nutrient levels in your soils are like.  

Conducting a soil test is good for both your wallet and the environment.  By knowing what the nutrient and pH levels are like in your soil, you can amend your soils to optimize the growing conditions for your plants.  Knowing the nutrients levels in your soils may lead to you using fewer fertilizers which will save you money and is better for the environment.  Adding to much fertilizer to the soil can lead to the fertilizer leaching or run-off into bodies of water and polluting them.

Most flowers, shrubs, grasses, fruits and vegetables grow best in soils that have a pH of 6.1 to 6.9 (slightly acidic).  It’s no coincidence that most nutrients that are used by plants are readily available for plant uptake in this range.  Other plants, such as rhododendron, azalea and blueberries, grow best in more acidic soils.  By conducting a soil test, you can determine if any adjustments need to be made to the soil pH.  Improper soil pH is one of the main reasons plants that like acidic soil don’t do well for people.  

Soil tests can be conducted at any time (as long as the soil isn’t frozen).  Fall is a good time to test soils because any fertilizers and organic matter that have been added have had time to react with the soil.     

When conducting a soil test you want to make sure you are getting a representative sample.  According to University of Illinois Extension horticulture educator Rhonda Ferree, “before sampling the area, size it up for differences in soil characteristics, such as color, texture and drainage.”  She adds “if these features are uniform throughout the area to be treated, a single composite sample of the topsoil is adequate. If there is great variation in these features, take a composite sample from each predetermined area.”

When taking a sample, dig a hole 6-8 inches deep for gardens, flowerbeds, trees and shrubs, and 3 inches deep for samples being taken from the lawn.  Next, take a thin slice of soil down one side of the hole and collect the soil.  Make sure to remove any roots or other debris from the sample.  You want to take at least eight random samples from the area you are sampling.  Combine all of the samples together and break up any soil clumps.  You will need about one pint of soil for the test.  

After you have obtained your sample it can be sent off to a soil testing lab.  University of Illinois Extension has a list of soil testing labs at

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