How can I naturally lower high soil pH?
Written by
Olivia Mitchell
Reviewed by
Prof. Charles Hartman, Ph.D.Reducing elevated soil pH levels naturally requires patience, but the results are enduring. If the soil pH rises above 7.5, plants that prefer acidic conditions, such as blueberries, suffer. The natural methods, used gradually, do not shock the plants. I have converted alkaline beds into soil suitable for the plants above using this method.
Elemental sulfur is the best natural acidifier. The bacteria in the soil change it to sulfuric acid in a matter of months. Apply it at the rate of 1 to 2 pounds per 100 square feet (0.45 to 0.9 kg per 10 square meters) per year. Do not over-apply since its bacteria-destroying properties are harmful to soil biology. Be sure to incorporate it into the soil before planting season.
Elemental Sulfur
- Converts to sulfuric acid via bacterial action
- Apply 1-2 lbs/100 sq ft annually
- Works in 3-6 months depending on soil temperature
Peat Moss
- Contains tannic and gallic acids
- Mix 2-inch layer into topsoil before planting
- Effect lasts 1-2 years before reapplication
Pine Needles
- Release weak acids as they decompose
- Apply 3-inch mulch layer around plants
- Acidifies surface soil over 6-12 months
Organic Compost
- Buffers pH while improving soil structure
- Apply 1-2 inch layer quarterly
- Microbes produce mild acids during decomposition
Peat moss will acidify while increasing water retention. Mix a two-inch layer into the topsoil before planting acid-loving species. Pine needle mulch is satisfactory for established plants. I use oak leaf mold for added acidification. These organic materials release acids slowly.
Avoid wasting time on misconceptions, such as using vinegar as a substitute for bleach. It causes an almost instantaneous pH drop, but this is detrimental to soil microorganisms. Coffee grounds provide very little acidification (though this myth is common). Concentrate on sulphur and organic matter instead. Check the soil every three months during the treatment period. This prevents excess acidification.
Water management helps correct the pH. Water from an alkaline source will neutralize acids. Use rainwater as much as possible. I use distilled water for watering my pot plants. This keeps the pH low. Patience will yield acid-loving plants that thrive well.
Read the full article: Soil pH Testing: The Complete How-To Guide
