Buzz
Finding the right soil pH is a crucial step in ensuring healthy plant growth. The pH level determines how effectively plants can absorb nutrients. To adjust the soil pH, you first need to identify materials that can alter the pH level. If you need to increase acidity or lower the pH, there are several common compounds you can add to the soil to achieve the desired results. You can also raise the pH in overly acidic soil by adding agricultural lime or other alkaline-based compounds. By properly assessing the soil and adding the right materials, you can cultivate a thriving and high-yielding garden.
Steps
Assess the Soil
Determine the soil type. Before testing the pH or adding anything to the soil, you need to identify the soil type. Determine whether your soil is clumpy, dry, loose, or wet to understand how to adjust it. Therefore, it’s essential to research the type of soil you plan to cultivate.
- Loose or well-draining soil is the easiest to adjust. In contrast, compacted clay-rich soil is more challenging to modify.
- Identifying the soil type will help you find the best method to amend it.
Understand soil pH. To adjust soil pH, you need to know what pH means. Soil pH indicates the acidity or alkalinity of the soil and is measured on a scale from 0 to 14, with 7 being neutral—neither acidic nor alkaline. Soil with a pH above 7 is alkaline, while below 7 is acidic. Most plants prefer a pH between 6 and 7.5, which is also the preferred range for earthworms and beneficial soil microorganisms.
Consider the type of plants you want to grow. The plants you intend to cultivate will determine the required soil pH. Many plants prefer more acidic soil, especially flowering plants and certain fruits like blueberries. Research the ideal pH for the specific plants you plan to grow.
- Azaleas, blueberries, and conifers thrive in acidic soil (pH 5.0 to 5.5).
- Vegetables, grasses, and most ornamental plants prefer slightly acidic soil (pH 5.8 to 6.5).
Test the soil pH. Once you understand pH and the type of soil for your plants, you can proceed to test the soil pH. You can purchase a pH testing kit from a gardening supply store or send a sample to a soil testing service. The easiest way to test pH is to dig a hole, pour water into it, and insert the testing device into the muddy water. However, sending a soil sample for testing will provide more accurate results.
- There are also some DIY soil testing methods, including using homemade pH test strips.
Test the water. Check the water to determine its impact on the soil. Groundwater, household water, and garden irrigation water often have higher alkalinity. In contrast, rainwater tends to be more acidic. If you live in a rainy area, the soil there might be slightly more acidic. If you frequently water your garden with tap water, the soil may be more alkaline.
- You can use pH test strips or commercially available electronic pH meters.
Increase pH
Select an agricultural lime. If your soil test reveals excessive acidity, you can raise the pH by adding alkaline materials. The most common substance used to increase soil pH is powdered lime, available at gardening supply stores. Standard lime comes in four forms: powdered, hydrated, granular, and pelletized. Depending on your soil type and moisture levels, one of these options will suit your needs.
- Powdered lime is finely ground and absorbs more easily into the soil. However, it can be harder to spread due to clogging equipment.
- Granular and pelletized lime is easier to spread but less effective at altering soil pH.
- Hydrated lime should only be used for extremely acidic soils, as it dissolves quickly in water and can rapidly increase soil pH.
- Some lime products contain micronutrients, such as dolomite, a mix of calcium and magnesium carbonate. Use dolomitic lime only if your soil lacks magnesium, and avoid it if magnesium levels are already high.
Consider using wood ash. Wood ash from burned firewood is also highly alkaline and contains micronutrients like calcium, potassium, phosphate, and boron. While not as effective as lime, wood ash can significantly raise soil pH over time. Monitor your soil carefully when applying wood ash.
- Avoid letting wood ash come into contact with plant roots or seedlings, as it can damage them.
- Wood ash works best in sandy soils.
Apply lime. For optimal results, apply lime to the soil 2-3 months before planting (typically in fall or winter) to allow sufficient time for pH adjustment. Spread lime in the root zone or the top 18 cm of soil.
- Use your hands for small areas and a spreader for larger gardens.
- Use a rake or tiller to mix the lime into the soil.
- Lime doesn’t dissolve easily in water, so tilling ensures maximum effectiveness.
Water regularly. Lime is less effective in dry soil, so consistent watering is essential. Water activates the lime and helps it penetrate the soil. Use a garden hose or sprinkler for even distribution.
- Watering frequency depends on soil area and existing moisture levels. Overwatering can wash away other soil minerals.
Lower pH
Use organic materials. Over time, organic matter such as leaves, compost, or manure can lower soil pH. However, this process may take several years and is best suited for long-term goals. This is an excellent option for organic gardening methods.
- Organic matter also improves soil drainage and aeration.
- Due to factors like the volume of organic material and the time required for decomposition, this method is most effective for small garden areas.
Consider adding sulfur. Another way to increase soil acidity is by gradually applying sulfur. The effectiveness of sulfur depends on factors like moisture, temperature, and bacteria, which are unpredictable. Therefore, it may take months for sulfur to lower soil pH significantly.
- Sulfur is available at most gardening supply stores. Avoid powdered sulfur as it is too light for soil acidification purposes.
- Soil acidity increases due to a biological reaction involving bacteria.
Consider using aluminum sulfate. This compound rapidly increases soil acidity through a chemical reaction with aluminum. For this reason, many small-scale and amateur gardeners prefer aluminum sulfate over organic compounds or sulfur. However, due to its fast-acting nature, controlling soil acidity can be more challenging when using this method.
- Aluminum sulfate is available at most gardening supply stores.
- Since aluminum sulfate creates a chemical reaction in the soil rather than a biological one, some farmers and gardeners prefer materials that produce acidity through biological processes.
Mix materials into the soil. Organic compounds, sulfur, and aluminum sulfate must be thoroughly mixed into the soil to be effective. Organic materials may require multiple applications, depending on soil pH. Always test the pH before reapplying.
- Avoid overusing sulfur or aluminum sulfate.
Rinse plants after applying soil amendments. If sulfur or aluminum sulfate comes into contact with plant leaves, rinse them off with a hose. If not washed away, these compounds can burn leaves and damage plants. Watering also helps the amendments penetrate the soil.
