Does Lime Lower the pH in Your Soil?

Soil and pH

• The pH of soil is a common way to measure its acidity or alkalinity. A pH of around 7.0 is considered neutral, while anything lower is acidic and anything higher is alkaline. Most lawn and garden plants, including turf grasses and vegetables, grow best in soil that is neutral to slightly acidic, although each plant has its own specific requirements.

Lime

• Acidic soil can cause a number of problems for plants, including mineral deficiency, poor growth of beneficial bacteria and toxicity. If your soil is acidic, adding lime is the most common way to raise the pH. "Lime" is actually a somewhat generic term that refers to several materials used to raise pH. These include crushed limestone, dolomite and alternative materials like wood ash or ground egg or oyster shells. What these materials have in common is that they are composed of, or contain high levels of, calcium carbonate, which neutralizes acid to raise pH.

Considerations

• If you are unsure of your soil's acidity levels, a soil test from your local University Extension will tell you the pH, as well as nutrient levels. Most test results will also include a lime application recommendation, measured in pounds of pure calcium carbonate per 1,000 square feet, or per acre. The amount of lime you will need to add depends on a variety of factors, including the type and quality of liming material you use and the starting pH of the soil.

Alkaline Soil

• While lime is a common soil amendment, it is not a catch-all solution, nor should it be applied unless you need it. Applying lime annually without a soil test can cause your soil to become alkaline over time. Alkaline soil can cause just as many problems as acidic soil, and is not as easy to fix. If you have alkaline soil, adding elemental sulfur can help lower the pH. It is slow-acting, however, and should be applied a full year before you intend to grow anything.