How to lower soil pH in potted plants?

If you want to lower soil pH in potted plants, you should add sulfur or aluminum sulfate to the soil. Moreover, the amount of sulfur or aluminum sulfate should be measured carefully before adding. The amount of sulfur and aluminum required according to the size of the plant. If the soil pH is right according to the plant’s needs it will boost the plant growth. Keep reading the article to know about how to lower soil pH in potted plants.

How to lower soil pH in potted plants?How to lower soil pH in potted plants?

pH is so important to plant growth because it determines the availability of almost all essential plant nutrients. Before discussing the methods for lowering the soil pH in potted plants we should know what is soil pH?

What is soil pH?

Soil pH is the measure of the sourness (Acidity) or sweetness (alkalinity) of soil. A simple numerical scale is used to understand pH levels. The scale goes from 0 To 14 with 0.0 being most acid, and 14.0 being most alkaline. The value, 7.0 is neutral i.e., neither acid nor alkaline.

Is soil pH important for plants?

Soil pH is so important because it is responsible for several soil factors that primarily affect plant growth, such as

  •         Soil bacteria
  •         Nutrients availability
  •         Nutrients leaching
  •         Soil structure
  •         Toxic elements

Bacterial activity that releases certain fertilizers and nitrogen from organic matter is particularly affected by soil pH because bacteria operate best at the pH level of 5.5 to 7.0.

A lower pH level allows certain plants to more effectively absorb nutrients from the soil so they can grow. When soil pH is too high, it can create a lot of problems for plant growth and health. For many plants, soil that is high in alkalinity makes it harder for plants to absorb nutrients from the soil, which can limit their optimal growth.

Alkaline soils slow the availability of nutrients such as zinc, copper, manganese, iron, and also phosphorus. Therefore, it is necessary to lower the pH level for the best growth of plants.

Soil test

It is essential to analyze soil for understanding the pH level.lower soil pH

Portable pH meters can be used to test soil pH. We can obtain a simple test kit at our local garden center. This result will help guide us on the next steps to adjust the soil accordingly.

Methods for lowering the soil pH

Two methods for lowering the soil pH level according to the plant’s needs are the biological method and the chemical method.

Biological reactions can be slower than chemical reactions since soil microbe activity drops if the soil is not warm, moist, and well aerated. When selecting the best method of acidifying the soil, then consider the following questions

  • a)   How much do you want to lower the pH
  • b)   Whether the soil amendment you select will also provide beneficial nutrients
  • c)   Your time frame (how quickly do you need to change the soil pH)
  • d)   Budget

Organic Matter (manure, mulch, peat)

Incorporating any organic matter will make the soil more acidic. Enormous amounts of organic matter must be turned into the soil to have a significant effect on pH. Because of the cost and effort, this method is generally limited to small garden plots. Organic material has many other benefits such as; added nutrients and improving the aeration and drainage of the soil. This won’t help too much if the soil is mostly clay.

Chemical methods to lower soil pH

Lower soil pH with vinegarvinegar to lower soil pH

Vinegar is acetic acid with a low pH of 2 -3 and can be used to lower soil pH in house plants. A good way to use vinegar for lowering soil pH is to apply it with irrigation. The solution should be kept dilute and a mix of 1 cup vinegar in 4 liters should be used as a solution ratio. Furthermore, it should be applied gradually with normal irrigation intervals.

Ammonium Fertilizers: –

This includes ammonium sulfate, urea, and ammonium nitrate. Bacteria in the soil convert the ammonium into acidic compounds. Ammonium fertilizers are convenient because they simultaneously fertilize your plants and acidify the soil. However, to avoid applying too much nitrogen, use these products only to make gradual changes to the soil pH. Still, there is less risk of lowering pH too much when using ammonium fertilizers than there is when using elemental sulfur. Ammonium fertilizers also can be used with acid-loving plants to maintain an already low soil pH.

Sulfur Compounds: –

Elemental sulfur, iron sulfate, and aluminum sulfate are products that are often used to dramatically acidify the soil. Soil bacteria combine elemental sulfur with water and oxygen from the soil to form sulfuric acid. These bacteria require moist, aerated, and warm soil.

Acidification occurs faster when the application is incorporated into the soil than when the application is left on the soil surface. Sulfur compounds may take up to a year before they have their full effect on soil pH. Too much sulfur can reduce the soil pH below the optimum range for your plants.


Soil pH can be reduced most effectively by adding elemental sulfur, aluminum sulfate, or sulfuric acid.  The choice of which material to use depends on how fast you hope the pH will change and the type/size of the plant experiencing the deficiency. 

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