You can change the pH of soil by adding specific amendments that either raise (increase alkalinity) or lower (increase acidity) the pH level, creating a more suitable environment for plant growth.
Lowering Soil pH (Making it More Acidic)
To lower the soil pH, you'll typically add materials that introduce acidity. The most common and effective options include:
- Elemental Sulfur: This is often considered the safest and most cost-effective method. Soil bacteria slowly convert the sulfur into sulfuric acid, which lowers the pH over time. The amount needed depends on the existing pH, soil type, and desired pH. It's widely available at agricultural suppliers and garden centers.
- Aluminum Sulfate: This amendment works more quickly than elemental sulfur because it directly produces acidity when it dissolves in the soil. However, it can potentially lead to aluminum toxicity in certain soil conditions, so use it with caution and follow recommended application rates.
Why Lower Soil pH?
Some plants, like blueberries, azaleas, and rhododendrons, thrive in acidic soils. Lowering the pH makes essential nutrients more available to these acid-loving plants.
Raising Soil pH (Making it More Alkaline)
To raise the soil pH, you need to add alkaline materials. The most common choices are:
- Lime (Calcium Carbonate or Dolomitic Lime): This is the most widely used amendment for raising soil pH. Dolomitic lime also provides magnesium, an essential nutrient. The amount of lime needed depends on the soil type, current pH, and desired pH level. A soil test is crucial to determine the appropriate amount.
- Wood Ash: Wood ash is a good source of potassium and can raise the pH. However, it should be used cautiously, as it can also contain high levels of salts.
Why Raise Soil pH?
Many common garden vegetables and ornamentals prefer slightly alkaline to neutral soil. Raising the pH can improve nutrient availability for these plants.
Important Considerations
- Soil Testing: Before making any changes to the soil pH, conduct a soil test. This will provide valuable information about the current pH level, nutrient content, and soil type. Soil test kits are available at garden centers or through local agricultural extension offices. The results will guide you in selecting the appropriate amendment and application rate.
- Gradual Changes: It's generally better to make gradual changes to the soil pH over time rather than attempting to drastically alter it all at once. This minimizes the risk of shocking plants or creating nutrient imbalances.
- Soil Type: The amount of amendment needed to change the pH varies depending on the soil type. Sandy soils require less amendment than clay soils.
- Incorporation: Thoroughly incorporate the amendments into the soil for even distribution. This can be done by tilling or digging.
In summary, changing soil pH involves adding specific amendments like elemental sulfur or aluminum sulfate to lower pH (increase acidity) or lime or wood ash to raise pH (increase alkalinity), tailoring the soil environment to meet the needs of the plants you wish to grow. Always start with a soil test for informed decision-making.
