How to Test and Adjust Soil pH

If you’ve ever wondered what the letters pH stand for, it is “potential Hydrogen” and refers to the level of acidity in the soil. The measurement of potential Hydrogen forms a spectrum from 0 to 14, and soils that test 7.0 pH and below are considered to be acidic, and those above that level are called alkaline. Moist climates tend to produce acidic soils, while dry climates generally produce alkaline soils.

The measurement is crucial for gardening because each plant does best within a range on the alkaline/acidic spectrum. For example, Clematis thrives in more alkaline soil, while rhododendrons prosper when more acid is found in the soil. When you purchase plants, the packaging will often tell you what pH level they prefer. If that information is not present, it is likely that pH is not a major factor in their ability to thrive – that is, they’ll do well in most soils.

The key soil element related to pH is calcium, often in the form of lime. Calcium neutralizes acid, so the higher the levels of calcium the more alkaline the soil will be. Many plants will do well in most soil conditions, but for the sensitive types you want to grow in your garden, it is essential that you be able to test the soil’s pH.

Most nurseries or garden centers will test the soil for you if you take in a sample. However, most experienced gardeners like to have the necessary means of testing the soil themselves. A variety of testing kit styles and brands are available that allow you to quickly and accurately measure the pH balance of the soil in your garden. Here’s how it works: The kit contains a tube that you fill with a small amount of soil from your garden. To the soil you add a few drops of the test solution, and then you cap and shake the tube vigorously to mix the contents, before leaving it to settle for an hour. The solution will turn color, and you match that color to the chart that comes with the test kit, showing you your soil’s place on the spectrum. It is a good idea to test soils from 2-4 locations in your garden when evaluating a new garden plot, one in which agents have not been added to adjust soil pH.

Adjusting soil pH to produce a level that best suits what you are planting is fairly easy. The best way to bring soil into natural balance is to add large doses of quality compost. This compost can be easily made at home in your yard. Our guide “Understanding the Basics of Composting” is a great place to begin. Beyond composting, if you need a more alkaline soil, add hydrated lime to the soil at a rate of 4 ounces per square yard of ground. Mix it in very well and wait one to two days before measuring again. Add hydrated lime until the soil tests show the level you desire. Sandy and loam soils will respond more quickly to lime, while clay or peaty soils will require more, since they absorb it more readily. Hardwood ash and bone meal are also good sources for reducing acid levels to make soil more alkaline.

A more acidic soil is produced by adding ground rock sulfur according to manufacturer’s directions. Other, more natural, sources include peat moss, wood chips, and composted leaves. Whether you are raising or lowering pH, it is best to do so gradually, over the course of one to two seasons. This will prevent rapid changes from damaging existing plant root structures.

Once again, while most plants and vegetables will do well in diverse soils, when you have a plant favorite that is particular about its pH level, it makes sense to have a testing kit available. You will be able to give your plant the soil it wants in a few easy steps, and it will show its appreciation with vigorous, healthy growth and blooms.

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