How to Conduct a Soil pH Test

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As a home gardener, it's important to test your soil's pH bi- or tri-annually, especially if you're growing vegetables. Certain plants can only access the soil's nutrients if the pH is within a certain range. If your soil lies outside of the range for a given plant, adding fertilizer won't remedy the situation.

Technically speaking, a soil pH (potential hydrogen) test measures how many hydrogen ions are in the soil, indicating its acidity or alkalinity. Anything with a pH less than 7 is acidic, 7 is neutral, and anything higher than 7 is alkaline. Being acidic or alkaline isn't necessarily bad; it all depends on what you're growing. Most plants can adapt to soil pH that ranges from 6.0 to 7.5, but some plants have distinct preferences. Blueberries, for instance, prefer acidic soil, and asparagus tends to do best in alkaline conditions.

When to Do a Soil pH Test

Testing your soil's pH should be a fall garden checklist item. After you pull the last of your plants from the garden, it's good to take inventory of where you're at. That way, you can amend the soil before winter or first thing in the spring before you plant. It's also a good time to inventory your weeds, giving you a good idea of various conditions. Dandelions, wild strawberries, and plantain proliferate in acidic soil. Chickweed, Queen Anne's Lace, and chicory favor alkaline soil.

Depending on the outcome of your pH test, performing it in the fall gives you plenty of time to plant a nitrogen-fixing cover crop (for mild winter climates) or tweak next year's planting to suit your reading. In the case of alkaline soil, adding organic materials like pine needles, peat moss, and composted leaves, and allowing the compost to overwinter, will raise your pH to a suitable number. Acidic soil can be made neutral by adding lime. How much you add depends on the actual correction you need, so the more accurate the test the better.

If you wait for spring to test, keep in mind that pH readings will be highest at this time before any amendments are made to the soil.

What You'll Need

Equipment/Tools

  • Shovel
  • Paper or plastic cup
  • Vinegar
  • Baking soda

Materials

  • pH testing kit
  • Distilled water
  • Coffee filter

Instructions

Testing pH Using Kitchen Supplies

An acidic solution generally reacts when it's added to something basic, and that's where common items like vinegar and baking soda can give you a quick read. This test uncovers the general composition of your soil and is recommended for those who have healthy gardens that may benefit from just a little pep.

Project Metrics

  • Working Time: 10 minutes
  • Total Time: 15 minutes
  • Materials Cost: Under $10
  1. Using a hand shovel, dig 4 to 6 inches below the surface of your garden to obtain a soil sample.
  2. Remove stones, sticks, and other foreign debris from the soil. Break up any large clumps.
  3. Place approximately 1 cup of soil into a clean glass container and add enough water to turn the soil to mud.
  4. Next, add 1/2 a cup of vinegar and stir slightly. If the soil fizzes, foams, or bubbles, your soil is alkaline.
  5. If no bubbling occurs, repeat the process: Take a soil sample, clean it of debris, place it into a clean container, and turn it to mud.
  6. This time, add 1/2 a cup of baking soda and stir. If the soil fizzes, foams, or bubbles, your soil is acidic.

Testing pH Using Soil pH Strips

Testing your soil with basic kitchen items can tell you on which end of the pH scale your soil is leaning. But for an exact measurement, a pH soil testing kit is the way to go. You can purchase home testing kits at most garden centers and through local cooperative extension offices.

Project Metrics

  • Working Time: Half an hour
  • Total Time: Under one hour
  • Materials Cost: Under $10
  1. Using a hand shovel, dig 4 to 6 inches below the surface of your garden to obtain a soil sample.
  2. Place 1 to 3 teaspoons of soil in a clean plastic cup and remove sticks, stones, and debris.
  3. Fill the cup with distilled water to match the same level as the soil sample.
  4. Agitate the soil vigorously, by stirring or swirling, and then let the solution rest for 30 minutes.
  5. Pour the soil sample through a coffee filter and into another clean cup, capturing the solids and allowing the liquid to pass through.
  6. Dip the pH strip into the liquid and compare the color to the chart on the manufacturer's packaging to determine the pH.
  7. Repeat the process several times with samples from different parts of your garden to determine the overall average pH.

Soil pH Testing Tips

If you test your soil using kitchen ingredients and neither test produces much of an effect, your soil is probably in the neutral range. No further testing is needed.

If you have a small garden, you can mix soil from three or four different samples for the kitchen test. But, if you have a large garden, it is better to test several samples separately.

For extremely dire garden soil that won't grow anything, it's best to send a soil sample to a lab for testing. Most extensions offices offer soil testing for a nominal fee. Then, based on the results, they can make recommendations to get you back on track.