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Is Clay Soil Acidic?

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Your soil is the most important factor for growing healthy and thriving plants. Clay soil contains at least 50% of clay particles, and this soil type can be difficult to dig. It’s so firmly packed into small grains that you might not even notice any dirt moving around back there.

However, 50% of clay particles in clay soil make it one of the most fertile types in a garden. If we want to know “Is clay soil acidic?” the soil pH level will give us the answer. Let’s find the answer to this question and know about soil pH in detail.

Is Clay Soil Acidic

Soil pH

The pH of the soil is a measure of how acidic or alkaline water is held in its pores. It affects whether minerals and nutrients are easily available to plants.

Therefore, understanding the pH scale is key to having healthy soil. The letters “pH” refers to potential Hydrogen concentrations in an item or substance, and the higher your hydrogen concentration, the better!

Soil pH can range from 0 to 14, with lower numbers representing more acidic substances and higher numbers indicating alkaline solutions. The spot in the middle, i.e., pH 7, is the neutral point where your soil is at its most fertile and balanced state.

  • pH between 0 and 7 – Acidic or ‘ericaceous’ soils
  • pH 7 – Neutral soils
  • pH between 7 and 14 – Alkaline or ‘limey’ soils

Reasons for Soil Acidity

The soil can be inherently acidic, or it tends to be acidic due to various factors. In general, the reasons of soil to be acidic are:

  • Rainwater that leaches away basic ions (magnesium, potassium, calcium, etc.)
  • Production of carbon dioxide from decomposing organic matter
  • Production of inorganic and organic acids, i.e., nitric and sulfuric acid

To combat these effects, scientists have come up with methods including applying lime rocks, specifically calcium oxide (limestone), at different rates depending upon the types of cultivated crops.

Difference Between Acidic and Alkaline Soil

Here is the difference between acidic and alkaline soils that helps you understand them better.

Alkaline Soil

Alkaline soil is usually found in areas that lack adequate rainfall or receive a lot of hard water. This type of soil has excessive amounts of sodium, calcium, and magnesium, which causes it to become less soluble and limits the nutrients from absorbing into plants’ roots.

Acidic Soil

Acidic soil can occur when the moisture stability of your lawn is compromised by heavy waters, which wash away calcium and magnesium from the base.

Extra minerals/chemicals in organic matter cause acid levels to rise. Toxic “sour” ground becomes home to an excess of elements like carbon dioxide or nitric acid that may shock certain plants; this could even kill them if left unchecked!

Acidic SoilAlkaline Soil
• 0 – 7 pH
• Lacks calcium and magnesium
• Carbon dioxide, nitric acid, sulfuric acid is present in a larger amount
• Common in moisture-rich climates
• 8 – 14 pH
• Loaded with calcium, sodium, and magnesium
• Has trouble absorbing nutrients
• Common in arid climates

Clay Soil Properties

Soil rich in fine clay particles is called ‘heavy soil’ or clay soil. Although it may be hard to manage, this soil type can yield a very fertile crop when treated with the right techniques. It has the following properties:

  • Feel very sticky
  • Hold more water than most other soil types
  • Swell when wetted and shrink when dried
  • Lie wet in winter
  • Clay soils are slow draining
  • Rich in potash
  • Deficient in phosphates
  • Usually need large, infrequent input of lime


Clay soil has many drawbacks, but it has got some good qualities too. The following are the advantages of clay soil:

  • It is negatively charged. It means clay particles capture and holds onto positively charged nutrients like calcium
  • Don’t need as much maintenance because their clay particles retain most water during dry periods, saving your time watering your plants
  • Nutrient-rich
  • Make your plant stronger against pests


Clay soil has many drawbacks as well, which are as follows:

  • Its slow drainage and tendency to compact easily make it difficult for plant roots to grow
  • Take a long time to warm up in spring
  • It tends to heave in winter due to the alkaline pH

Adjusting Clay Soil pH

The best clay type to promote plant growth, ensuring an evergreen garden, is a neutral clay with pH 7. Therefore, the lawn care professionals recommend lowering the pH if the soil is more alkaline and increasing the pH if it is acidic.

Increase Acidic Soil pH

Lime or dolomite are used to increase the pH or “sweeten” the soil. It contains calcium carbonate, which helps with nutrient absorption by plants.

If the soil is acidic, the best way to restore clay soil is by adding organic matter. It will lower the pH and break up existing waste, giving your plants what they need for growth.

Decrease Alkaline Soil pH

It can be difficult, if not impossible, to change the pH level appreciably in naturally alkaline soils with acid materials like ammonium sulfate and sulfur. However, you may want to consider applying them anyways because they are fewer damaging plants than other methods.

Choose Soil Favored Crops

One way to ensure your plants thrive in a home with either clay soil type is by choosing the right crops. Some plants prefer acidic soils, some alkaline while other neutral soils.

You can improve on this further by growing specific types of vegetation depending upon the soil type and plant needs. Here is a list of plant types with their pH preferences to grow well.

• Crabapple – 5.0-6.0
• Hawthorn – 6.0-7.0
• Holly – 4.5-5.5
• Strawberry – 5.5-6.5
• Apple – 5.5-6.5
• Broccoli – 6.0-7.0
• Cabbage – 6.0-7.5
• Carrots – 5.5-7.0
• Eggplant – 5.5-6.5
• Lettuce – 6.0-7.0
• Onions – 6.0-7.0


The answer to the question “is clay soil acidic” contains several sentences describing what causes acidic soil but then says how it’s remedied.

  • Reduce clay soil’s acidity by adding more lime-based products/organic matter to increase its pH
  • Decrease soil’s pH by adding acid materials like ammonium sulfate and sulfur.

Neutral soil is best for most plants’ smooth growth, and you can adjust the soil pH to neutral. If not, you can select the right crops that suit your soil type, i.e., acid or alkaline. If you have any questions, please don’t hesitate and ask in the comment section below.