Garden Soil pH Testing and Amending

pH stands for potential hydrogen, and it can tell you a lot about your soil. For your purposes think of it as potential nutrients—pH determines which nutrients are available to plants. In fact, pH affects the microorganism activity in your soil. Soil pH determines its acidity (sourness) or alkalinity (sweetness). The lower the pH, the more acidic your soil is; the higher the pH the more alkaline it is. A pH of 7 is neutral (neither acidic or alkaline). For gardening, most plants prefer a soil pH between 6 and 7 with 6.5 being your target soil pH. Some plants prefer more acidic (below a pH of 6) or alkaline soils (above a pH of 8), but for general gardening, all that matters is that your soil not be too acidic or alkaline unless the plants you select can tolerate these conditions. Plants are very flexible with respect to pH, so long as your site isn’t near the extremes of acidity or alkalinity for the particular plants.

If your soil pH is too extreme for your plants, it creates an unhealthy environment by limiting the nourishment that is available to the plants and by weakening their natural defenses against pestilence and disease.

The pH test is a simple indicator test requiring some soil, water (use distilled water for best results), a clean cup or jar, and a Garden Tutor pH test strip. The Garden Tutor pH test strips cover a pH range of 3.5 to 9.0 in .5 increments. Each pH test strip has three pads that change color depending on the pH of the test material. Each pad on the pH test strip covers a specific segment of the pH range. Having three pads helps with accuracy since a pH range of 3.5-9 is broad and the color changes can be subtle and difficult to determine.

Garden Tutor pH test

Vegetables

Non-Woody Perennials

Non-Woody Annuals

Before you can adjust your soil pH you should know your soil type (Sand, Silt, Clay or Loam). Your soil type can affect the quantity of pH amendment (lime or sulfur) you use. This due to the “buffer capacity” of the soil which is a measure of how well soil can resist changes in pH. For example, clay soils have a high buffer capacity and require more lime than other soil types to alter pH. Clay soils require more work to alter pH but once you change them the effects will last longer so you don’t need to add lime as frequently. You should also be aware that it takes a lot of amendments to change pH. If you need a more acidic soil you can use sulfur or naturally acidic organic materials (peat moss, leaves or needles from acidic plants). If you use organic material the pH change will be very gradual; if you are in a hurry you may opt for sulfur. It is best not to use commercial plant acidifiers containing aluminum sulfates or fertilizers containing ammonia to alter soil pH; they are best used only to maintain plants already growing in acidic soil, and misuse can ruin your soil.

The best way to raise soil pH is to add lime. Lime is readily available and easy to apply. You may have a few types of lime to choose from depending on what retailers in your area carry. Pulverized or pelletized limestone is usually a good choice (pelletized lime can be used in a broadcast spreader). Dolomitic limestone is limestone which contains magnesium and a few other trace nutrients. You can use ground limestone, just be aware that it is a powder, and powders are harder to apply with a broadcast spreader. Hydrated limes are also available; they work quickly but can burn plants and flesh if used incorrectly. In any case, be sure to follow the application rates and package instructions strictly. If you add too much at one time you can harm your plants and your soil.

Below is a handy soil pH adjustment calculator that you can use to determine how much lime or sulfur is needed to raise or lower your soil pH. Just note if the amounts of lime or sulfur from our calculator disagrees with the label on the product you buy, always go with the manufacturer guidelines. Adjusting soil pH with lime and sulfur is not permanent so you’ll need to recheck soil pH every year or two and make adjustments as necessary. The degree and duration of the change depends on how finely ground the amendments are (lime and sulfur). The more finely ground (e.g. pulverized) the faster they alter pH but shorter their effects last (generally 1-2 years depending on your climate). Note that pelletized lime is finely ground but aggregated with a binding agent to form easy to spread pellets. It is best to apply lime and sulfur in the fall or early spring, so they can start working on your soil before you plant.

How to Get Accurate Results with Your Garden Tutor Soil pH Test Kit
Welcome to Garden Tutor! As fellow gardeners, we’ve spent thousands of hours perfecting this tool to ensure accurate results. Below, you’ll find some quick tips to help you get the most out of your pH test kit and avoid common issues.

Key Tips for Success

1. Soil-to-Water Ratio
For the most accurate results, use a 1:1 ratio of soil to water (e.g., ½ cup of soil to ½ cup of water) to create the ideal slurry for testing.

2. Mix Thoroughly
After adding water to your soil sample, stir or shake the slurry for 30 seconds. This helps break up clumps and fully incorporate the soil for accurate pH readings.

3. Why Wait Time Matters
Let the slurry sit for at least 30 minutes to allow the pH to stabilize. For soils like desert or clay soils, waiting up to 4 hours (or even overnight, if needed) ensures the water fully interacts with the soil particles, giving you the true pH. This also allows soil particles to settle, reducing the chance of staining the test strip pads, which can obscure results.

4. Water Quality
Tap water usually works well, but if you have hard or soft water—or if you use a well system—it’s best to use distilled water for more accurate results.

5. Clear Readings on Your Test Strip
After dipping the strip into the slurry, be sure to shake off excess solution to prevent soil and water buildup on the test pads. If the pads are stained, a quick rinse in clean water can help. For clay soils, you can filter the slurry using a coffee filter or 1-2 layers of paper towels. You only need enough filtered water to saturate the test pads for a few seconds. See Paper Towel Filter for Fine Soil and Clay Soil Filtering with a paper coffee filter Documents

6. Lighting Matters
For the best results, compare your test strip to the color chart in a well-lit area, preferably by natural sunlight, to get the best color match.

Understanding the Results
Sometimes, the colors may not match the chart exactly. This is normal, as the test is qualitative and requires some interpretation. Here’s how to approach it:

First, find the column with the best overall match.
If the result falls between two columns, you can split the difference. For example, if it’s between 6 and 6.5, you can assume the result is about 6.25.
Troubleshooting Tips
If you encounter issues with color pads or soil staining, consider using the Coffee Filter Technique described above to clarify the solution. This will help you get a clearer reading.
If you’re still having trouble, feel free to email a picture of your results to us at info@gardentutor.com for additional assistance.

By using these simple tips, you’ll be able to get accurate results from your Garden Tutor Soil pH Test Kit. For more detailed guidance, explore our Soil pH Testing Handbook or reach out with any questions!