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How to Adjust pH in Soil

When your plants are not growing well even if you provide enough sunlight, fertilizer, and water, the problem might be the soil. If the soil pH is too acidic or too alkaline, plant growth can be negatively affected.

Thankfully, you don’t have to spend money and replace all of the soil. Here, we’ll teach you how to adjust pH in soil.


What is Soil pH?

What is Soil pH?

Soil pH basically refers to the acidity or alkalinity of the soil. The pH result can range from 0 up to 14. If the pH is between 0 and 7, your soil is acidic.

If you have a soil with a pH exceeding 7, it is noted as having more alkalinity. Too much of either can be detrimental to your plants. 

For one, most lawn grasses and vegetables will thrive if the soil pH hovers between a slightly acidic level of 6.5 and the neutral pH of 7. To know the exact soil pH in your lawn, you can get a soil test kit and do your own accurate soil test and examine it yourself.

To get a more comprehensive result along with recommendations, you can seek the assistance of a local county extension or a private laboratory.

Both of these options cost a little more than doing a soil test by yourself, but the analysis will help you a lot. When you do send a soil sample to them, you must get the soil from different sections in your lawn to get a more accurate representation.

How to Adjust pH in Soil

How to Adjust pH in Soil

1. Raise the pH of Acidic Soil

If the pH of your soil is between 0 and 7, you can increase the pH by applying lime. There are two common types of limestone to use. The first one, calcitic limestone is mostly comprised of calcium carbonate.

The second type is dolomitic limestone, which has the added benefit of increasing the magnesium content in the soil. No matter which limestone you prefer, both of them will effectively raise the pH of acidic soil.

Furthermore, lime products come in a variety of forms: granular, hydrated, pulverized, or in pellets. A pulverized type of lime works fast, but the fine particles could clog your lawn spreader. 

If you want the fastest results, you can use hydrated lime. However, the problem is that you can apply too much lime products than necessary. On the other hand, both pulverized limestone and pelletized limestone are slow-acting but they spread to the soil quickly. 

Regardless of the lime product, all of them are better applied to the soil rather than just at the soil surface. Thus, we recommend liming the soil after aerating it and giving watering it well in fall.

Here is a video on why we add lime to soil:

Apart from limestone, you can use wood ash to lower the soil acidity. This is an excellent way to recycle the ashes in your fireplace. First, you need to get a layer of wood ash at least 0.5 inches thick.

Next, mix the wood ash with the acidic soil at a depth of 12 inches. One issue with this organic method is that it requires several applications for many years. Still, the long-term results prove that it is an effective solution.

2. Lower the pH of Alkaline Soil

On the other hand, you should lower the pH if it exceeds 7. There are many options that help adjust the soil pH of alkaline soil: sphagnum peat, sulfate products, sulfur, fertilizers, mulching, and composting.

First, you can get a two-inch layer of sphagnum peat to mix into the soil at a depth of 12 inches. Apart from lowering the alkalinity, sphagnum peat can improve water retention of your soil while providing organic matter.

Sphagnum peat moss can help adjust the soil pH of alkaline soil

Second, you can apply sulfate products. In particular, you can choose between aluminum sulfate and iron sulfate. Both of them work quickly to adjust the soil pH, but you should be extra careful.

These products can damage your lawn in the long run since they also result in the buildup of salt. Thus, no more than five pounds of this product should be used for every 100 square feet of soil.

Third, you can acquire fertilizers to increase the acidity in your soil. Specifically, fertilizers that have urea, amino acids, and ammonium nitrate will lower the soil pH in the long run.

Finally, organic methods such as composting and mulching will help your soil get a more neutral pH with regular application. Even better, composting allows you to recycle kitchen scraps while mulching ensures that your lawn has enough moisture.

Do you have clay soil? Refer to our in-depth guide on how to improve clay soil

Frequently Asked Questions on Adjusting Soil pH

What is the fastest way to increase soil pH?

Lime and baking soda work quickly to increase soil pH if your soil is overly acidic, or you plan on growing alkaline soil-loving plants. Lime can easily be over-applied, so be careful when checking the existing pH and calculating how much you need.

Baking soda is gentle on soil and won't harm plants unless applied in excess.

What is the best way to lower soil pH?

Elemental sulfur is a natural material, but not naturally present or accessible in most gardens. It will quickly lower the soil pH by shifting sulfurous compounds to sulphuric acid.

Most plants like soil to be around 6-7 pH (slightly acidic to neutral) but will cope with soils of 5.5.

How can I adjust soil pH naturally?

Lime is a natural soil additive, which can be damaging to some plants in excess, but when used correctly it is a great natural material to use in your garden.

Other natural and eco-friendly options include coffee grounds, which will add very light acidity to pots and containers.

Does compost lower soil pH?

Compost, especially homemade compost, is a natural and variable material, and its pH will vary depending on its composition and age. However, an annual mulch or 1-2 inches of compost will generally achieve a soil pH of about 6.5 over three years, as well as feeding the soil.

Wrapping Up Our Guide on How to Adjust pH in Soil

In conclusion, adjusting the pH in your soil isn’t too difficult. You need to know the actual soil pH to assess whether you need to increase the acidity or alkalinity. Furthermore, there are organic methods to choose from in either case.

We hope that you will get to improve the soil pH of your lawn to have robust plant growth. If you have any questions, feel free to send us a comment.

How to adjust ph in soil

About the Author Ann Katelyn

I'm Ann Katelyn, Creator and Chief Author of Sumo Gardener. Since I was a child I've always been fascinated with plants and gardens, and as an adult this has developed into my most loved hobby. I have dedicated most of my life to gardening and started Sumo Gardener as a way to express my knowledge about gardening with the hope of helping other people's gardens thrive.

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Leave a Comment:

Jeffery says August 5, 2020

Love to know how rain water affects the Ph of soil?

    Ann Katelyn says August 11, 2020

    Hey Jeffery,

    Thanks for your question!
    Rain water causes trace elements like calcium, magnesium and potassium (which contribute to soil pH) to leech out of the soil into rivers and waterways.

    Generally, soil pH tends to decrease slowly in warm and humid climates where there’s a lot of rainfall, as this slowly washes these more alkaline elements out of the soil.

    Rain water is not the only factor impacting pH, however. Other factors include the pH of the materials breaking down to form the soil itself (rocks, plant matter, etc.) and fertilizer use in your area, as this gets into the ground water.

    I hope that answered your question!

    Thanks Ann

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