What Is Soil PH? Factors, Methods, and Effects On Plants

Soil pH is the level of acidity or alkalinity in the ground. A simple pH test can determine the pH level in relation to the pH scale, and the results of that test will act as a guide for adjustments that need to take place within the soil. Home gardeners looking for the best soil for gardening and even farmers can use the information gained from a ground pH test to help their plants and crops grow stronger and healthier.

What is ground pH, and how does it affect your plants? This article will provide you with everything you need to know. If you want to learn specifically about test methods click here: pH test methods: the definitive guide 2020.

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What Is PH? Terms and Definitions

PHThe measure of the acidity or basicity of aqueous or other liquid solutions (see full definition).
AcidicA substance that is acidic will have a pH that is below 7.0 on the pH scale.
Basic When a substance is basic, it can neutralize an acid when combined, to raise the pH.
AlkalineA substance that has a pH greater than 7.0 on the pH scale.
NeutralWhen a substance is neutral, its pH level sits in the very middle of the pH scale. Neutral pH is neither an acid nor an alkaline.

Factors Affecting the PH of Soil

There are at least six factors that can affect pH of soils. These factors have a direct impact on the soil and the health of plants that grow in it. Awareness of these factors affecting ground pH will ensure that your plants get everything they need.

Soil Physical Properties Effect on PH

Physical properties from the soil formation process can affect the ground pH. During soil formation, many minerals, nutrients, and plant materials are introduced to the soil, which all contribute to the final result.

An excess of hydrogen in the soil can lower the pH, and other minerals such as calcium, magnesium, potassium, and sodium can raise the pH.


Temperature is one of the environmental factors that can help control leaching intensity in the soil. Leaching is the loss of soil nutrients due to excess rain and irrigation.

The pH of soils decreases from warm temperatures, especially in a humid climate. Dry, hot climates do not have as much of a problem with a change in the ground pH level.

According to NCRS (United States Department of Agriculture), “In dry climates, soil weathering and leaching are less intense, and pH can be neutral or alkaline.”


Humidity causes ground pH to become acidic faster compared to dry climates.


The relationship between the resistivity and pH of soil actually has a reversed effect. Soil alkalinity lowers the resistivity in a soil.


The soil texture, as in the clay, sand, and silt content, can affect the ground pH as well.

For instance, soils that are high in clay have a greater buffering capacity and can resist a drop or rise in pH. Sandy soils (soils with a high percentage of sand compared to silt and clay), on the other hand, cannot resist a change in pH as easily and are more susceptible to it.

A way to enhance sandy soils so that they can better resist dramatic changes in pH is to add more organic matter to the soil. Add compost, leaves, and other organic matter, and take care of the soil until the items decompose and fully mix with the soil. The excess organic matter will increase the soil’s buffering capacity. Desert soils, that are 90-95% sand, tend to have slightly to highly basic pH levels.


The layers in the soil, otherwise known as soil horizons, can also affect the ground pH because of each layer’s composition. Some layers in soil have higher concentrations of organic matter, which helps to prevent changes in pH. However, some soil horizons can have a negative effect on the pH of soils.

The topsoil, which is the uppermost soil horizon, should be the greatest concern since that is the pH that will matter the most for crops. Most soil horizons will have varying pH levels since they are not all the same in composition or texture.

Importance of soil PH

Gardening and farming are the most known uses of soil but hey are not the only uses. Soil is used for creating energy, building houses, and even medicine. pH level plays a vital roll in all of these uses.

For a gardner, pH is a vital aspect to check when tending to soil because it can prevent a plant from thriving. Certain types of plants grow best in certain types of soils due to their preferred pH level, and some will not grow properly without it.

As a gardener trying to provide the best soil for his herbs or vegetables, the pH level of your soil should be the number one priority. Before planting your vegetables and flowers for the year, use a pH tester kit to determine if any changes need to happen. Compare the results of the testing kit to the optimum pH range for that specific plant. Many pH charts for soils are available online. A great resource for information on plants is The Old Farmer’s Almanac.

Optimum PH Ranges

Here are some helpful pH ranges for common garden plants:

Azalea – 4.5 to 6.0

Blueberry – 4.0 to 6.0

Lilac – 6.0 to 7.5

Cabbage – 6.0 to 7.0

Carrot – 5.5 to 7.0

Chive – 6.0 to 7.0

Pumpkin – 5.5 to 7.5

Methods to Measure Ph of Soils

The easiest way to measure pH of soils is by using a pH test kit. These are widely available online and we have a guide covering this topic exactly: 3 Methods to measure soil’s pH.

Here are some of the best pH test kits:

How to Lower Soil PH

To lower the pH in soil, apply a soil acidifier to the soil before planting.

Espoma Organic Soil Acidifier

How to Raise Soil PH

Raising pH takes a different kind of product. Lime is the material you will need to make the right adjustments.

Pennington Fast Acting Lime Soil Amendment

Taking Care of Your Plants

The pH level is not the only aspect that has a significant impact on plants. The soil temperature, moisture, and nutrient content are also very important. But before changing the soil to meet the requirements of your plant, make sure that you have a full understanding of your plant’s preferences.

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