How to Control Soil pH?


Soil pH is simply the measure of its level of alkalinity or acidity. The soil pH scale ranges from 1 to highly acidic to 14 for strongly alkaline, whereas 7 is typically the neutral point.

Extreme soil pH levels can significantly affect the overall health and development of some of your plants.  For instance, strongly alkaline soils with pH levels of 7.5 and highly acidic soils with pH levels below 5.0 usually inhibit proper plant growth.

This is mainly because plants cannot absorb nutrients effectively within such extreme pH levels. Highly acidic soils tend to leach off plant nutrients whereas highly alkaline soils confine nutrients that are present in the soil. The good thing is that most home gardens have soil pH levels that range between 4.0 and 8.0, and most plant varieties do well within the 5.5 to 7.5 pH range. Thus, doing slight adjustments to the soil’s pH would lead to improved soil quality.

How to Control Soil pH That Affects your Plants Growth?

The soil pH level is one of the major factors that affect the quality of plant growth.  The level of soil’s pH mainly affects nutrient availability for the plants.  Plants thrive best in different soil pH ranges and altering these ranges can lead to less vigorous growth and nutrient deficiencies.

Plants Growth

Most mineral nutrients such as iron and nitrogen are available to plants once they are dissolved in water. Highly acidic or alkaline soils may prevent some nutrients from getting dissolved, making them not available for plants to absorb. Most nutrients are more available to plants when the soil pH solution is between 5.9 and 7.5. In highly acidic soils, however, some nutrients such as potassium and nitrogen can become less available.

In highly alkaline soils of above 7.5 pH value, phosphorous and manganese become less available. Apart from the affecting nutrient availability, the soil’s pH can as well affect the presence of beneficial micro-organisms. Most of these creatures prefer soil’s pH of 6.5 and increase, or reduction in these levels may create an environment not conducive to micro-organisms. With that being said, maintaining the correct soil pH is crucial for healthy plant growth.

Testing for Soil pH

Plants thrive in varying soil pH levels. Thus, before planting it’s important to determine your soil’s pH level and the best way to do this is by testing the soil. You can achieve this in two ways:

Testing for Soil pH

  • Using a soil test kit
  • Sending soil samples to a laboratory for a soil analysis.

If you choose to perform the test yourself using a soil test kit, ensure that you use collect soil samples from different spots in your garden and a depth of at least 4 inches. Carefully mix the soil sample a reagent in a test tube and wait for the color to change. You can then determine your soil’s pH from the chart that’s included in the kit.

Improving Acidic Soils

If you find your soil highly acidic, then you need to increase the pH levels to the optimum pH range.  You can achieve this is by liming, which is the addition of alkaline material. Some of the most common liming material includes Ground limestone or dolomite- Add it to the garden soil during autumn to give it ample time to act on soil pH before the next growing season. The amount to apply will be determined by the type of soil in your garden; Sandy soils, for instance, will demand lesser limestone to change the pH levels compared to clay soils.

Acidic soil

However, the safest approach is to have your soil tested and apply as recommended by the lab results. Wood ash- You can effectively raise your soil’s pH by adding wood ash as it is fast acting due to its fine particle size. Lightly sprinkle the wood ash over the soil and ensure that you mix it properly into the soil. To get the best results, limit your applications to 25 pounds for every 1,000 square feet.

Improving Alkaline Soil

For alkaline soils, you should add some acidic material to lower the soil’s pH levels.  Some of the most common acidic material to add includes:

Alkaline soil


The good thing about using sulfur to reduce pH value is that it’s cheap, relatively safe to be sprinkled over the garden soil.  Try not to apply more than two pounds of sulfur per a hundred square feet each time as it’s known to be slow-acting.

Sphagnum Peat

A great organic approach to lower soil pH is by adding sphagnum as it adds organic matter and improves your soil’s water retention.  All you need to do is to mix sphagnum peat into your soil at least one foot deep.

Acidifying Fertilizer

You may as well add fertilizers that contain amino acids, ammonia, or urea and it will eventually produce an acidifying effect on your garden soil.

Mulches and Compost

Addition of organic matter tends to lower the soil’s pH as it breaks down. If you apply organic matter regularly, with time, this will improve the soil pH to the desired neutral or rather slightly acidic levels.

The Bottom Line

In conclusion, you can improve the soil’s quality by making small adjustments to the soil pH in your garden. Applying organic matter to the soil will buffer the pH as it tends to bring the pH within the required or optimum range. Before you make any changes to your soil pH levels, ensure that you first have your soil analyzed by the laboratory or by testing it yourself using the best soil test kit.

Always keep in mind that the amount of liming or acidifying material required to change soil pH varies depending on some factors.  These include the current pH, the type of material, and the soil texture. A soil lab report includes some recommendations on the different types and quantities that you can use for the best results. On the other hand, you can choose to grow plants that are suited to your soil pH and other soil conditions.

You May Also Read: 5 Quick Tips to Know Before Growing Potatoes in Container


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