How to Raise Soil pH

Successful gardens have the proper soil pH.

The term pH stands for the potential (p) of the hydrogen ion (H+) in water. There are simple ways to measure the pH of almost anything, and soil is one of the easiest. Knowing your soil's pH is key to understanding why plants aren't doing well and what to do to resolve the issue. The range for pH measurement is 1 to 14, with the highest acidity having a pH of 1, and the highest alkalinity having a pH of 14. A pH of 7 is neutral. Adding lime to your soil will raise the pH in a short time.

Things You'll Need

• Lime
• Optional:
• Hardwood ash
• Manure
• Potassium carbonate

Instructions

1. Visit your local nursery or garden center and purchase a soil testing kit. These cost about $10, as of July 2011, and are simple to use. Take it home and test your garden's soils. You can check more than one area, but the results will probably be similar. Log your test results in your garden journal or a notepad to track how the soil improves over time.

2. Purchase enough lime to treat your soil if the pH is too low. Ground lime is considered too fine, difficult to work with and messy. A better option is pelletized limestone which is much easier to apply, and you'll get faster results.

3. Read the application guidelines on the package of lime you purchase. Always use a lighter application when uncertain of the amounts. You can always add more later. An excellent way to ensure the proper amount is to contact your local county extension office for recommendations for applying lime to soil in your area.

4. Add the lime to your soil, digging it in to a depth of 6 to 12 inches. Though you can add lime any time during the year if indicated by poor plant growth or other symptoms, it's ideal to apply it three to six weeks before planting begins. Your pH should ideally be between 6.0 and 6.9 for normal growing of vegetables, shrubs, annuals and perennials. A pH reading of 7.3 is the highest it should get.

5. Test your soil again a couple of months later, and adjust the soil as indicated by your test results.

Tips & Warnings

• Other ways to increase soil pH are to add hardwood ashes to the soil -- direct from your fireplace. But there are some important factors to know and it's advisable to research the information. Typically you'll add two times as much ash as lime since it is half as potent.

• Manure can help increase pH, too. Opinions differ regarding fresh manure versus decomposed, when to apply and so forth. Consult your local master gardeners on this. You can find them at quality nurseries as well as through agricultural extension programs.

• Areas of heavy rain will leach soils of nutrients faster than dryer areas. Pay attention to your soil condition after a major rainy season, as well as during a drought.

• If you are growing azaleas, rhododendrons, blueberries, camellias, conifers, huckleberries and other acid-loving plants, you'll want an acidic pH. However, if you want to grow apples, pears, annuals, bulbs, lilacs and many vegetables, you'll want to raise the pH level.

• Avoid using hydrated lime. This is known to be far too fast-acting and can harm your plants.

• If you choose to use the fine, ground limestone, wear gloves and a face mask and use caution, such as don't apply it on a windy day.

References

• Iowa State University Extension; How To Change Your Soil's pH; Eldon Everhart; April 1994
• Oregon Live; Wood ash can fertilize plants and raise soil pH; Vern Nelson; December 2008
• Smart Fertilizer Management: Low Soil pH
• Oklahoma State Cooperative Extension Service; Animal Manure Can Raise Soil pH; Hailin Zhang; February 1998
• National Gardening Association: It's Time to Lime; Suzanne DeJohn; December 2006
• Clemson University; Soil Acidity and Liming (Overview); Charles C. Mitchell