2 Ways to Amend Your Soil's pH - Backyard Boss
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2 Ways to Amend Your Soil’s pH

Soil is the basis for all plant life and has many characteristics that dictate its health and ability to sustain plants. One of these characteristics is the soil pH which refers to measuring whether the soil is acidic, neutral, or alkaline.

Since soil pH isn’t as tangible as feeling the soil for drainage or structural makeup, it is measured with a professional pH testing kit or using basic household items. The pH can read anywhere between zero and 14, with zero meaning extremely acidic, seven meaning neutral, and 14 meaning intensely alkaline.

So, how should you go about amending your soil’s pH? Is there anything you should keep in mind? More dirt below!

Understanding Soil pH

pots and seedling
Image credits: Ylanite via Pixabay

Soil pH refers to the chemical processes in the soil that affect the availability and solubility of essential nutrients and water for healthy plant growth. These nutrients exist as cations and include:

Nutrient Process
  • Synthesizes energy compounds
  • It’s needed to convert carbohydrates within the plants
  • Controls gas exchange and water during transpiration
  • A crucial nutrient in the plant cell wall that influences absorption
  • Important to cell growth
  • Associated with transporting carbohydrates and nutrients within the plant
  • A component of chlorophyll that plays a role in photosynthesis
  • Involved in generating proteins and energy transfer in the plant

To demonstrate the relationship between pH, soil nutrients, and water, take an example of pin oaks that grow in the U.S. Midwest. Many pin oaks are afflicted by iron chlorosis, an iron deficiency, whereby their leaves turn yellow-green.

The irony is that soils across the Midwest have ample amounts of iron, a nutrient that’s beneficial for plant development and leaf pigmentation. So, what gives?

The answer, or problem, lies in soil pH. When the soil pH is above 7, plants can’t absorb the soil’s iron content because it becomes insoluble at that pH level. Iron is soluble when pH ranges between 5 and 6.5, which is slightly acidic.

Coming back to the pin oaks, the best solution to combat leaf discoloration would be to lower the soil pH to meet this plant’s particular development.

Test Your Soil First

pH strips test
Image credits: Garden Tutor Store via Amazon

It’s essential to test your soil pH first before you start amending it. A soil test will give you the exact pH measurements to help you decide how and what to amend it with. Most nurseries and gardening centers have a pH testing kit that you can purchase.

If you’d rather order soil pH test kits from Amazon, check out the Garden Tutor Soil pH Test Strips Kit or the BlueLab Soil Tester Pen.

After testing your soil, use the number to understand your soil’s current pH using the table below:

Classification pH range
Extremely acidic Less than 3.5
Intensely acidic 3.5 to 4.4
Strongly acidic 4.5 to 5.5
Moderately acidic 5.6 to 6.0
Slightly acidic 6.1 to 6.5
Neutral 6.6 to 7.3
Slightly alkaline 7.4 to 7.8
Moderately alkaline 7.9 to 8.4
Strongly alkaline 8.5 to 9.0
Intensely alkaline More than 9.0

Understanding Soil Profiles

Now that you know the kind of soil you’re dealing with, it’s essential to understand its profile to make necessary amendments.

1. Acidic Soil

Image Credit: Lakeisha Ethans for Backyard Boss

Acidic or “sour” soil lies between the pH ranges of 0 to 6.5. Acidic soils display poor incorporation of the organic surface layers of soil and the mineral layers beneath. Elements and factors that cause soil to be acidic include:

Elements and Factors How it Happens
Rainfall Rainwater has an average pH of 5.6. When it pours and is absorbed into the soil, it leaches the basic cations (potassium, calcium, and magnesium) out of the soil, making it more acidic.
Decomposition and Root Respiration


When microorganisms decompose organic matter, they release carbon dioxide, increasing carbonic acid and leeching and acidifying the soil.
Using Certain Fertilizers


Ammonium fertilizers react with soil to make nitrate. The nitrification process releases hydrogen ions, which decreases the soil’s pH, making it more acidic.

Acidic soil caters to a handful of plants like blueberries, pineapples, and cashews but can harm many other plants due to the high quantity of minerals in the soil. These minerals include manganese, hydrogen, and aluminum, which don’t wash away, unlike valuable nutrients like potassium, calcium, and magnesium.

Aluminum doesn’t nourish the plant but hinders root growth and is most soluble at a pH of 5 and lower.

2. Neutral Soil

Hands holding soil
Image credits: Gabriel Jimenez via Unsplash

Soil pH that measures between 6.6 and 7.0 is considered neutral. The Journal of Nature published a map highlighting different soil pH levels in different regions worldwide. They are usually either more acidic or alkaline, with neutral soil barely being highlighted.

This is due to climate differences around the world. For example, wet climates foster acidic soil, while dry climates have alkaline soil. Neutral soil only shows up in intensely cultivated land like Ukraine or Iowa, which boast fertile farmland growing many crops.

Rich, neutral soil is ideal for growing both acid-loving and alkaline-loving plants like asparagus, hellebores, and candytuft. Achieving neutral soil is a matter of knowing your soil’s current pH and adjusting it accordingly, whether increasing or decreasing it.

3. Alkaline Soil

Spinach plants
Image credits: ha11ok via Pixabay

Alkali, or “sweet” soil, has a pH between 7 and 14. Highly alkaline soil displays a caliche layer, which is a cemented deposit of magnesium and calcium carbonates. This chalky layer is likely found in arid conditions and can be soft or hard; the latter makes it challenging to grow plants.

Alkaline soils have poor infiltration, which makes it difficult for water to flow to soluble calcium, potassium, and magnesium minerals. This, in turn, makes it difficult for plants to establish themselves. Elements and factors that cause soil to be alkaline include:

Elements and Factors How it Happens
Irrigating With Water That Contains Bicarbonates


When irrigation water contains dissolved bicarbonates and mixes with calcium, magnesium carbonates present themselves in the soil thus increasing soil pH. This raises the alkalinity levels in the soil.
Build Up of Basic Elements


Since alkaline soils have poor water infiltration, minerals like bicarbonates and carbonates are hardly absorbed by the plant. Instead, they accumulate over time.
Erosion of Basic Elements


Over time, large accumulations of basic minerals like silicates and carbonates in the soil increase alkalinity.

Alkaline soil nourishes many plants and edible crops, including asparagus, spinach, and candytuft. The problem with slightly alkaline soils is the lack of nutrients like zinc, boron, copper, and manganese, which cause nutritional deficiencies in plants. These deficiencies are caused by the soil’s high sodium, sulfate, and chloride levels.

2 Ways to Amend Your Soil’s pH

After testing your soil and understanding its pH and profile, you can start amending it to suit the requirements of the plants you want to grow in your garden.

Increasing Soil pH

Lime for soil
Image credits: FotoHelinvia Shutterstock

To increase soil pH, add minerals that contain lime. This includes limestone, which contains calcium carbonate, and dolomite limestone, which includes calcium carbonate and some magnesium carbonate.

Depending on the soil pH level you want to achieve, you’ll need 4 tablespoons of lime per square foot of soil to increase the pH by two points. Apply lime in the fall, and based on how much lime you want to use, add half and then till the top 6 inches. Then add the remaining half and till again.

Remember, the finer the liming material, like Thermocal’s Limestone Powder, the faster it will react with the soil to increase the pH. Remember to note down your soil’s pH before adding lime and after adding it for future reference.

Besides lime, you can use baking soda, wood ash, eggshells, and compost to increase your soil’s pH.

Decreasing Soil pH

working with the soil
Image credits: CDC via Unsplash

Add elemental sulfur to your soil to decrease soil pH before planting your crops in spring. The amount of sulfur your soil requires depends on your target pH level and the soil’s texture. That said, you’ll need to apply sulfur to your soil a year before planting your acid-loving plants.

For example, if the current pH is 5 and your target pH is 4.5,

  • Sandy soil will require 175 pounds of sulfur per acre,
  • Loamy soils need 530 pounds per acre, and,
  • Clay soils will need 800 pounds per acre.

Besides using elemental sulfur, you can use aluminum sulfate to decrease soil pH. You’ll need about 4 to 6 pounds of aluminum sulfate per plant to lower the soil pH by one point.

Let’s Talk Dirt!

Soil is the universal medium for plant life and is incredibly diverse. Measuring the soil pH helps make sense of the various soil profiles and can inform you of the details beyond what the eye can see.

From nutrient makeup and deficiencies to surplus and infiltration, addressing your soil pH is the first step to healthy soil and thriving plants. However, remember to test your soil before and after amending it, and maintain a soil journal to record your results for future reference.

Leave your experiences, thoughts, and questions in the comment section! And share with friends and family who might find this helpful.