Too much lime leads to high pH

Q. The pH of my soil sample is 8.5. What can I do to lower this pH by spring planting?

Gary from Austintown

A. Higher than normal pH levels are being found in many soil samples brought to the OSU Extension office. There can be many reasons for these higher pH levels, but the main reason may be the over-application of lime.

To keep the pH from getting higher, stop applying so much lime or wood ash to the garden area.

Back when we had a great number of steel plants and related factories in the Mahoning Valley, we had acid rain due to the emissions from burning coal. In the late 1990s, a bill was signed into law that eventually reduced acid rain. It is commonly referred to as cap and trade.

Because it was so successful, acid rain isn’t even a common term you hear on a regular basis.

Basically, acid rain is just rain that has a more acidic pH than normal rainwater. Over time, most soils can withstand slightly acidic rain without affecting pH.

The Mahoning Valley very likely had acid rain that was affecting soil pH over time, back when emissions were high. Thus, many home gardeners got used to applying small amounts of lime to the soil every couple of years.

Unfortunately, the practice of adding lime has continued after acid rain issues have gone away.

The only way to tell if your soil needs lime is by doing a proper soil test and looking at the current pH of the soil.

With Gary’s soil pH being higher than what is needed for most garden/landscape plants (5.5-7.0), his soil test results suggest reducing the pH.

Optimal pH helps plants take up the nutrients they need to be healthy and productive.

Changing soil pH is a not a rapid process, and you should act as soon as possible to improve your soil for spring.

Sulfur is one way to reduce soil pH, but it should be incorporated (tilled) for the best results. So, if your soil is frozen or saturated, you may need to wait until spring.

Soil bacteria are required to metabolize the sulfur to reduce the pH, and they won’t be very active in these lower temperatures. If you have to wait until spring to apply, you won’t be too far behind.

Another option is peat moss, which will probably lower pH quicker, but requires lots of work to incorporate into the soil profile.

To learn about more options to lower the soil pH, visit http://go.osu.edu/lowerph.

To learn about acid rain, visit http://go.osu.edu/acidrain.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Winter hours for the Plant and Pest Diagnostic Clinic vary. Submit questions to the clinic at 330-533-5538 or drop samples off to the OSU Extension Office in Canfield.