Lowering Soil pH: A Guide to Adjusting the Acidity of Your Soil for Optimal Plant Growth

Is your soil pH too high? If you want to reduce soil pH, you’re probably trying to grow blueberries, blue hydrangea, silver maple, or azaleas. To help these grow, you have to make soil acidic, solely lowering the soil pH.

What is pH?

pH (Potential Hydrogen)  is the acidity or alkalinity of a substance measured in pH units. It is one environmental condition that affects the quality of plant growth and directly affects nutrient availability. Furthermore, most soils have pH values between 3.5 and 10. In areas with higher rainfall, the natural pH of soil ranges from 5 to 7, while in dry areas, it ranges from 6.5 to 9.

In addition, soils can be classified according to their pH values;

  • Below 3.5pH – Ultra-Acidic
  • 2.5 – 4.4pH – Extremely Acidic
  • 4.5 – 5pH – Very Strongly Acidic
  • 5.1 – 5.5pH – Strongly Acidic
  • 5.6 – 6pH – Moderately Acidic
  • 6.1 – 6.5pH – Slightly Acidic
  • 6.6 -7.3pH – Neutral
  • 7.4 – 7.8pH – Slightly Alkaline
  • 7.9 – 8.4pH – Moderately Alkaline
  • 8.5 – 9pH – Strongly Alkaline
  • Above nine pH – Extremely Alkaline

Factors That Affect Soil pH

Soil is affected by the materials from which the soil was formed. Also, soils developed from bare rocks generally have higher pH values than those formed from acid rocks.

Temperature and rainfall are one of the primary factors that affect soil pH. When water passes through the soil, it leaches essential nutrients such as calcium and magnesium from acidic elements and is replaced by aluminum and iron. As a result, soils formed under high rainfall conditions are more acidic than when in dry conditions.

Although clay content in the soil cannot be altered, the reverse is the case for organic matter content. Sandy soil tends to have a low content of organic matter, which results in a lower capacity. They have higher water infiltration and percolation n, which means they are prone to acidification.

Effect of Soil pH

Soil pH has a wide range of indirect effects on plants. For instance, it can affect plant nutrient availability, crop yields, crop suitability, and soil microorganisms activity. Insufficient soil acidity can trigger the yellowing of young leaves resulting in iron deficiency.

Furthermore, Soil pH can also affect organisms like Fungi, Protozoa, Bacteria, Earthworms, and Nematodes.

How To Test Soil pH

Before attempting to Lower Soil pH, it is advisable to start with a Soil Test. The Soil test helps to determine the current pH of the soil. For instance, if a soil pH is less than 7.5, a form of Sulphur should be added as a soil amendment, but it shouldn’t be done if it is above 7.5. This is because it will not reduce the pH because of the free calcium carbonate or marl present in these soils.

However, there are various steps to analyze the pH level of the Soil;

  • The first step is to dig 4 to 6 inches around the surface of your garden to get a sample.
  • Check out the stones, large 
  • Create a muddy mixture by adding distilled water.
  • Pour the sample into a clean glass using a coffee filter.
  • Dip the pH test strip into the liquid.
  • Repeat the process a few times with different samples to get an average pH level.

How To Lower Soil pH

After getting the soil test results, and the acidity of your soil is lesser than the recommended acidity for the plants you are trying to raise, you can go ahead to lower the soil pH. 

 Soil pH means making it less alkaline and more neutral and acidic. However, there are many ways to lower Soil pH naturally, organically, and eco-friendly.

  1. Compost Tea

Watering your plants with Compost Tea is an organic way to lower the Soil pH level. It also feeds your plants, offering fast absorbing nutrients to help protect them against diseases and pests.

  1. Well-Decomposed Compost

Well-Decomposed Compost will help lower the soil pH over time. It also offers a wide range of benefits that improves the soil texture and adds microorganisms to the soil. Make sure you do well to add plenty of well-decomposed compost the next time you plant.

  1. Elemental Garden Sulphur

Sulfur is an essential nutrient that helps plants resist disease. It is one of the best ways to reduce your soil significantly, but it is advisable to use it in moderation.

  1. Coffee Grounds

Coffee Grounds are also another effective way of lowering your soil pH. Sprinkle them around your garden or add them to the compost pile. The more the grounds break down, the more they make your soil acidic. 

Your Soil will also be enriched with ingredients that benefit from water, retention, drainage, and aeration.

  1. Mulch

Mulch is another effective way to lower your soil pH naturally. It gives the soil an acidic boost and helps decrease soil erosion, regulates temperature, and releases valuable nutrients.

  1. Organic Matter; Peat, Manure- Mulch

Organic matter is reasonably practical but won’t give instant results. Instead, it lowers soil pH gradually.

  1. Sulfur

Sulfur is also effective in lowering soil pH. It is cheaper and more robust than aluminum sulfate, and it requires less amount for a significant effect. For instance, it is required that you use only 0.2 pounds for 10 square feet of soil.

  1. Aluminum Sulphate

Just in case you need quicker results, Aluminum is the best. The more it dissolves in the soil, the more acid it makes right away. 1-1 or 2 pounds of aluminum sulfate is required for 10 square feet of soil. However, be careful not to use it in excess.

  1. Vinegar

Like coffee, Vinegar is regarded as harmless, effective, and one of the cheapest ways to lower your soil pH. It is advised to use it in moderation because it is very acidic and can be added directly to the soil or into the irrigation system.

The application of Vinegar is relatively easy. You need to mix one cup of vinegar into a gallon of water daily until the desired effect. After this, go ahead to pour the solution into the soil.

10. Ammonium Based Fertilizers

Ammonium Based Fertilizers is another way to lower soil pH and it is of two options; Ammonium Nitrate and Ammonium Sulphate. Ammonium Nitrate contains plenty of nitrogen and it is advisable to not use too much.

Adding too much Ammonium can burn your plants and can lead to excessive nitrogen in your soil.

 Frequently Asked Questions

What Is A Good Soil Acidifier?

Soil becomes acidified when it goes through the process of becoming more acidic. However, the most common substances used for soil acidification are sulphuric acid and nitric acid.

What Is The Fastest Way To Lower Soil pH?

Reports have proven that elemental sulfur, aluminum sulfate, or sulphuric acid effectively lowers soil pH.

How Long Does It Take To Lower Soil pH?

In three to four weeks, Iron sulfate and aluminum sulfate can lower soil pH. They act faster than elemental sulfur.

What Are The Signs Of Highly Acidic Soil On Plants?

Here are a few signs that show your plants have high pH;

  • Death of new leaves
  • Spots of leaf necrosis
  • Brown spots on leaves
  • Stunted leaves
  • Dark green leaves with red bronze or purple.

What Causes High pH?

  • High accumulation of soluble plants
  • Soil carbonates
  • Climate and organisms
  • Imbalanced fertilizers

Does Lime Lower Soil pH?

No, it doesn’t. Lime is an alkaline substance. Therefore adding it to the soil increases its pH, making it more alkaline and less acidic.

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