Proper Soil Testing

A beautiful and fruitful garden starts with healthy and productive soil. Whether you are growing in a small raised bed or have several acres of commercial farm, the only accurate way to get information about your soil is to take a soil test.  Soil testing is an inexpensive way to manage nutrients effectively and optimize crop yields. 

A soil test is a chemical analysis that estimates a soil’s ability to supply nutrients. 

The results provide valuable information about your soil profile, including soil pH, texture, percent of organic matter, nutrients, and cation exchange capacity (CEC).  Information about the macro- and micronutrients available in your soil saves growers time and money by allowing them to tailor fertilizer applications for the plants growing.  It is essential the soil’s nutrient profile is in the right balance to amplify the natural relationship nutrients have with each other.  If some nutrients are too high or too low, the accessibility and availability of other nutrients to the plant will be hindered.  The key to maximizing soil health is to ensure each nutrient is in proper balance.


How to Take a Sample [1]

You will need:

  • A clean shovel, hand trowel, or soil probe.
  • A clean plastic container, such as a 5-gallon bucket.
  • Sampling bags (gallon-size plastic zipper-style bags will work).

Steps:

  1. Designate sample areas based on what is growing there. For example, one sample area could be a garden of mixed vegetables; however, if you have a pasture and a garden, take separate samples of each area and submit two tests instead of one.  If an area has varied characteristics, such as topography, soil moisture, soil type (sandy or clay), or if one area grows poorly, designate separate sample areas for each characteristic.
  2. For each sample, take 10 to 15 sub-samples across the entire sample area. To ensure even coverage, a zig-zag pattern works well.
  3. Sampling depth should be between three and twelve inches of soil, depending on the crop and time of year. I recommend using a soil probe for ease and consistency of sampling. To use a shovel or trowel, begin by pushing the blade into the soil at an angle to the desired depth and remove a full blade of soil. Then, remove a thin slice (about ½”) from the face left behind in the soil. Place the thin slice in your clean bucket.
  4. Repeat step 3 until 10 to 15 sub-samples have been collected in the sample area.
  5. Thoroughly mix the 10 to 15 sub-samples, removing rocks or other debris.  If the soil is overly saturated, lay the soil out on a table until it has dried.
  6. Prepare and submit the sample according to the lab’s instructions. Plastic zipper bags work best; do not use a paper bag unless the lab provides one lined with plastic. Most laboratories ask you to label the sample bag with identifying information and to include their information sheet with the sample. 
  7. Keep the sample cool and send it to the lab immediately. Avoid shipping in the middle of the week, as the sample may arrive over the weekend and may not be processed until the following week.

Sampling Tips:

  • Use clean sampling tools to avoid contaminating the sample. A small amount of fertilizer residue on tools can cause serious contamination, altering the results of your true soil profile.

 

  • Do not include mulch, medium to large rocks, or vegetation in the sample.

 

  • Do not use galvanized metal, brass, or bronze tools to collect samples that will be tested for micronutrients, such as zinc.

 

  • Avoid sampling when soils are saturated (after heavy rain) or within a few weeks after applying lime, fertilizer, compost, or aged manure.

 

  • Avoid sampling any unusual areas, such as the site of an old trash dump, burn pile, rabbit hutch, or fence lines. You often can spot these places by looking for plants growing especially well or particularly poorly.

To find a testing center, you can contact your local University County Extension Office or a certified agricultural laboratory.  Many state extension offices provide soil testing services for a very low fee or even free, depending on your location.  Complete the submission form for the testing location you choose, detailing what you plan to grow in that area.  Most laboratories will provide tailored recommendations based on your results and what you intend to grow.  

When the soil test results arrive, review and apply the recommended amendments before planting.  The ideal timing of applying soil amendments depends on the type.  Some require months to start breaking down and react, while others can be mixed the same day you plant.  Amending in the fall allows enough time for the amendments to break down or alter the chemical composition for spring planting.  Feel free to email me your soil test results! I am happy to help you decipher the results and make amendment recommendations based on your soil’s profile. Reach me at brooke@landogiants.com. Recommendations based on soil test results save you time and money, and help protect our environment by discouraging the overapplication of fertilizers.

References:

  1. King Conservation District Soil Nutrient Testing Program. (2025). https://kingcd.org/programs/better-soils/healthy-soil/



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