What is Acidic Soil?

Acidic soil, also known as sour soil, is soil that has a pH level below 7.0. The pH scale ranges from 0 to 14, with 7 being neutral. Soils with a pH level above 7 are considered alkaline, while those below 7 are acidic. Acidic soil is characterized by its high concentration of hydrogen ions (H+), which makes it more acidic and less suitable for certain plants.

Causes of Acidic Soil

There are several factors that can contribute to the development of acidic soil. One of the main causes is the leaching of basic nutrients such as calcium, magnesium, and potassium. This leaching occurs when excessive rainfall or irrigation water washes away these nutrients from the soil, leaving behind acidic elements like aluminum and iron.

Another common cause of acidic soil is the decomposition of organic matter. When organic materials such as leaves, twigs, and dead plants break down, they release acids into the soil. This process is known as organic acidification and can gradually lower the pH level of the soil over time.

Effects of Acidic Soil on Plants

Acidic soil can have a significant impact on plant growth and health. One of the main effects is the reduced availability of essential nutrients. Many plants require a slightly acidic to neutral pH level in order to absorb nutrients effectively. In acidic soil, these nutrients become less soluble and therefore less accessible to plants. This can lead to nutrient deficiencies and stunted growth.

In addition to nutrient deficiencies, acidic soil can also affect the activity of soil microorganisms. Many beneficial bacteria and fungi that help break down organic matter and release nutrients thrive in neutral or slightly acidic conditions. When the soil becomes too acidic, these microorganisms may become less active, further limiting nutrient availability for plants.

Measuring Soil pH

The pH level of soil can be measured using a soil pH test kit or by sending a soil sample to a laboratory for analysis. The test results will provide a numerical value that indicates the acidity or alkalinity of the soil. This information is crucial for determining the appropriate amendments and treatments needed to adjust the pH level and improve soil fertility.

Amending Acidic Soil

If a soil test reveals that the soil is too acidic, there are several methods for amending it. One common approach is to add agricultural lime, also known as limestone, to the soil. Lime is a natural substance that contains calcium carbonate, which helps neutralize the acidity and raise the pH level. The amount of lime needed will depend on the current pH level and the desired pH level for the specific plants being grown.

Another method for amending acidic soil is to incorporate organic matter such as compost, manure, or peat moss. Organic matter helps improve soil structure and fertility, while also buffering the pH level. It can help raise the pH of acidic soil and make it more suitable for a wider range of plants.

Plants Tolerant to Acidic Soil

While many plants prefer neutral or slightly acidic soil, there are some that are adapted to thrive in acidic conditions. These plants are often referred to as acid-loving or ericaceous plants. Some examples include azaleas, rhododendrons, blueberries, and hydrangeas. These plants have specific nutrient requirements and are better suited for acidic soil environments.

Preventing Acidic Soil

Preventing the development of acidic soil is often easier than trying to amend it later. One way to prevent soil acidity is to regularly test the pH level of the soil and make adjustments as needed. This can be done by adding lime or other amendments to maintain a slightly acidic to neutral pH range.

Another preventive measure is to avoid over-fertilizing with acidic fertilizers. Some fertilizers, such as those high in ammonium or sulfur, can contribute to soil acidity over time. Using balanced fertilizers and following recommended application rates can help prevent excessive soil acidity.


In conclusion, acidic soil is soil with a pH level below 7.0. It can be caused by leaching of basic nutrients, decomposition of organic matter, or other factors. Acidic soil can have negative effects on plant growth and nutrient availability. However, it can be amended by adding lime or organic matter. Some plants are adapted to thrive in acidic soil, while others prefer neutral or alkaline conditions. Regular soil testing and preventive measures can help maintain optimal soil pH levels for healthy plant growth.