Testing Soil pH

Updated on September 1, 2017
Jeanne Grunert profile image

Jeanne Grunert is a Virginia Master Gardener, gardening magazine columnist, and book author. She is a full-time freelance writer.


Importance of Testing Soil pH

Testing soil pH is critical for healthy plant growth and development. Soil pH affects overall plant health as well as the plant's ability to grow and reproduce. And it's plant reproduction, in the form of flowers, fruits or vegetables, that most gardeners are after when they grow a vegetable garden or flower garden! Proper soil pH is essential to healthy, vigorous plants.

What Is pH?

The pH scale is a logarithmic scale ranging from 0 (pure acid) to 14 (pure alkaline). The midpoint or neutral point is 7. Most plants thrive in a range near neutral or slightly acidic. Any soil readings to either end of the scale can negative impact a plant's ability to absorb various nutrients. For example, a too-acidic soil can prevent the absorption of calcium. Often, tomatoes exhibiting blossom-end rot disease are suffering from calcium deficiency. There may be plenty of calcium in the soil, but if the pH is too acidic, the calcium remains bound in the soil and the plant cannot absorb it. Adjusting soil pH through the addition of various soil amendments makes the calcium available to the plant, and blossom end-rot can be avoided. (There are other causes of blossom end-rot; this is just an example.)

The pH scale is not a direct, progressive scale but what is known as a logarithmic scale; the Richter scale is another logarithmic scale you may be familiar with. Increases in pH are to a factor of 10, which means that the leap from a pH of 6.5 to 7.5 is not a factor of one, but 10x more alkaline. Adjusting soil PH must be done with care, and only after a thorough soil test is completed.

Soil pH Requirements for Most Plants

Most plants thrive with a soil pH of between 5.5 to 6.5 - slightly acidic. Of course, there is some variation in that. Plants evolved around the world in different climates and habitats. Blueberry bushes are a famous example of plants needing a more acidic soil.

Testing Soil pH

There are several methods for testing soil pHin the home garden. Home owners can avail themselves of testing kits found at the local home and garden store. These range from devices that include a battery inside and a digital reading; you simply push the end with the metal prongs into the soil, and voila - the digital reading tells you the pH and other factors, depending upon the complexity of the equipment.

Older soil testing kits included liquids and litmus paper, which turns colors depending on the pH of the liquid placed upon the paper. These can be messy and imprecise.

The best way to test soil pH is to work with your local County Cooperative Extension office if you live in the United States. These offices are staffed by employees and Master Gardener volunteers who can instruct you on the proper method of obtaining a soil sample from the garden. For a small fee, which varies according to the location and facility used, the samples are sent to a professional laboratory and analyzed not just for soil pH but for macro and micro nutrients. The resulting information on soil structure, nutrient content, pH and more can be a huge asset to gardeners, but especially to organic gardeners seeking to use natural amendments such as wood ashto improve soils and alter pH values. Most soil testing results also include recommendations, and there again, using a professional laboratory is very helpful. The local County Cooperative Extension agents or Master Gardener volunteers can help you interpret and understand the soil test results and provide recommendations to adjust soil pH or improve drainage, nutrient quality and aeration within the soil. And, because they are local experts, they can tailor their recommendations to the soils found in your part of the country. Spring is the best time to have soil tested, usually before you plant your first crops or flowers. This gives you enough time to have the soil tested and add any amendments recommended from the test results.

Never Underestimate the Importance of Soil pH

I used to scoff at the experienced gardeners of my acquaintance who fussed and fussed each spring with soil testing. Then I moved to a small farm in south central Virginia. I was not used to Virginia red clay soils, and the farm had been used to raise loblolly pine, a timber crop that can leave the soil acidic. I also learned that prior to my farm being used to raise timber, it was used for hay and cattle production and growing tobacco - and tobacco really depletes the soil. I was left with highly acidic, heavy clay soil nearly devoid of organic matter. That's a big challenge for any gardener but especially an organic gardener!

After an initial soil test, I patiently worked the recommended amendments, including lime, as well as plenty of organic, well-rotted manures into the flower garden soil. For the vegetable garden, creating raised beds and starting with the right soil gave us higher harvests almost immediately.

Testing soil pH really helped my garden. Because I knew what I was working with right from the start, I could add the right amendments to the soil quickly and thus increase my plants' chances of success. Over time, as the garden grew, the natural progression of organic breakdown of wood mulch, manures and compost have helped the soil, and the soil pH has gradually risen from very acidic to merely acidic. And my garden thrives.

Have your soil tested this spring and talk to a professional about the results. Testing soil pH is an important step to growing a great garden, and worth the time and investment.

Healthy soils build healthy gardens.
Healthy soils build healthy gardens. | Source
Good soil encourages higher production.
Good soil encourages higher production. | Source

© 2013 Jeanne Grunert


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      kuenzang 4 years ago

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