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Sometimes you can do everything right for your lawn and still find your plants aren’t happy. 

If you’re watering the lawn correctly and mowing regularly, the problem might be soil-deep. That means checking your soil pH.

And if the pH of your soil is too high, that could be bad for your grass and plants!

How to lower ph in soil? There are several tactics for you to use, such as:

  • Elemental sulphur
  • Aluminium sulphate
  • Organic materials
  • Ammonium sulphate

Soil too acidic? Learn to manage your soil pH levels – just be safe while you’re at it.


What is Soil pH?

The pH scale ranges from 1.0 (highly acidic) to 14.0 (highly basic or alkaline). 

pH measures the “potential of hydrogen,” or the free hydrogen ions in a substance. 

More hydrogen ions lower the pH level and indicate an acidic substance. For example, lemon juice has a pH level of 2.0, water has a pH of 7.0, and soapy water has a pH of 12.0.

Many factors affect the soil’s natural pH.

The primary factor is the rock from which it formed (limestone, slate, etc). Other elements are climate (more rain means more acidity), local vegetation, and topography. Minerals and salts in water can also make soil more alkaline.


Why Soil pH Value is Important

A fertile loam in the hands of a farmer man and a soil measurement in place.

Plants have different tolerances for soil pH. Some plants thrive in alkaline soil, while others prefer acidic soils. 

Most plants will do best at a neutral pH of 6.5–7.5, but your garden soil might not fall within that pH scale.

Variations in soil pH will affect plant health and growth. Some acid-loving plants include azaleas, blueberries, English holly, magnolias, and roses.

High alkaline levels may also lead to nutrient deficiencies in soil. This means your plants will be very unhappy, and can lead to diseases. Some symptoms of too-high pH include yellowing leaves, brown spots, and stunted growth.

On the other hand, if the pH of your soil is too acidic (4.5 or lower), then you risk aluminum toxicity. Metal elements leach into the soil and affect the health of your garden. 

For soils with a pH of 4.5–5.0, you can plant acid-loving plants. Otherwise, you’ll need to increase the pH levels.


How to Do a Soil Test

The easiest way to conduct a soil test is to consult a professional gardening service or your local council. They can conduct soil testing to determine the pH value of your garden soil, and will determine the most accurate results.

Alternatively, you can purchase a soil testing kit and follow the instructions.

You can also use a soil pH meter – a skewer-like metal probe that you insert into the ground or a cup of soil.

If you want to go full DIY, you can test your soil with some kitchen supplies. 

It won’t accurately identify soil composition and pH values, but it’ll give you an idea if you have more acidic or alkaline soil.

To do a homemade test on your soil’s current ph level:

  • Dig up a soil sample about 10–15cm below the surface. Try to get samples from several spots to get a more representative result.
  • Remove any debris such as rocks and twigs. Break up any large clumps.
  • Mix a cup of soil with enough water to make it muddy, in two different containers.
  • In one container, add half a cup of vinegar. Fizzing indicates alkaline soils.
  • In the other container, add half a cup of baking soda. Fizzing indicates acidic soils.
  • If you do not get a reaction, then you have a fairly neutral pH.


Important Factors for Garden Soil pH

The vegetables are growing in a raised bed.

Your soil structure and type are some of the most important considerations if you’re planning to lower pH value. 

Having sandy soil or clay-like soil will necessitate different amounts of soil amendment. Some substances may also be more effective on different types of soil.

Time is also an important factor. Lowering soil pH is a long-term effort – it will take months (if not years) and repeat applications before you reduce pH to an ideal level. This is especially true for a soil pH of 8.5 or higher.

The types of plants you wish to grow will determine how far you’ll need to lower pH. Most plants will prefer a neutral level, but some plants will require more acidity.

And of course, you’ll need to understand your soil’s “buffering capacity.” This is the soil’s ability to resist pH changes. 

Clay soils are more resistant, while sandy soils are easier – although you’ll need to be careful of lowering the pH too far.


How to Lower pH in Soil

There are several strategies you can take to lower soil pH, using organic acids or organically acidic material. These four methods are great ways to lower pH in soil naturally.

Always make sure to wear protective equipment such as gloves, eye goggles, and a mask. 

Since many of these substances come in powder form, you want to limit the risk of exposure and health hazards.


1. Lower soil pH using elemental sulphur

Elemental sulphur

Elemental sulphur (or soil acidifier) is an economical way of lowering soil pH levels. It’s best for dense, clay soils and large garden areas. However, it takes time to break down.

Ideally, you should amend soil with elemental sulphur 6–12 months before planting.

For acidifying soil, consult the instructions or a professional on:

  • How much elemental sulphur is necessary
  • How far you should lower soil pH

Use either a hand spreader or wheeled spreader to distribute the elemental sulphur over the soil. 

Do not apply the full amount at one time – you’ll need to do this gradually. Distribute a small amount or work in small areas.

Work the sulphur into the soil with a shovel or rototiller, to a depth of 15cm.

Water the soil afterward, but avoid drenching or soaking the ground as this dilutes the effectiveness.


2. Lower soil pH using aluminium sulphate

Aluminium sulphate acts faster than elemental sulfur since it’s water-soluble and dissolves instantly when there is water present. 

The substance is user-friendly but pricier, so it’s less suitable for large gardens.

Follow the instructions regarding the amount to use. Generally, you need 200g of aluminium sulphate per 1.0 sqm to lower pH by 0.5 levels in loamy soils.

Distribute the aluminium sulphate powder evenly over the ground by hand or by spreader. Wash off any powder on plant foliage.

Till the soil about 15 cm to work the powder into the soil.

Water the soil well without soaking it through to activate the substance.


3. Lower soil pH using organic materials

sphagnum moss in female hands close up

You can use organic soil amendments for reducing soil pH, although it will take a much longer time. 

These materials break down very slowly, usually needing several weeks or months.

Organic materials you can use to lower the pH of your soil include:

  • Aged or composted chicken manure
  • Pine needles and bark
  • Sphagnum peat moss


4. Lower soil pH using ammonium sulphate

This substance is generally safe for home gardeners to use when they need to lower pH value. You can use it when top dressing your lawn, then water it in. 

Naturally-occurring microbes decompose ammonium and sulphate when soil is moist.

There’s also less risk of over-application of sulphate versus sulphur or aluminium.

You can apply ammonium sulphate through a fertiliser blend or as granular crystals on your lawn. Use a spreader to distribute the crystals, then till the soil to 15 cm so the substance incorporates into the ground.

Water well, but don’t soak the soil through.


How to Lower Soil pH in Potted Plants?

Most commercial potting mixes will already have a balanced pH, so it’s not necessary to change it. 

If it’s necessary to lower the pH, you can add some white vinegar or peat moss to make the soil more acidic.


When to Lower Soil pH

Soil pH meter is used on loam for planting

It’s best to check your soil’s pH if you’re planning to create a new garden bed or vegetable garden, or if you’re just starting out with your gardening. Then you can decide whether you need to increase soil acidity.

When using products such as sulfur, you should only work during summer, when there is no rain. 

Sulphur reacts with soil bacteria to lower the pH level, but the soil temperature should be above 12ºC.

Aim for an early morning with mild weather and no wind.

Avoid planting anything for a month after amending soil.


Can I Use Sulfuric Acid for Lowering Soil pH?

Short answer: No. 

If you’re looking to lower soil pH levels naturally, some websites will recommend sulfuric acid. It’s fast-acting, but incredibly dangerous.

Sulfuric acid is a corrosive substance that can damage your skin, eyes, and lungs. In some cases, severe exposure can result in fatality.

Industry professionals such as experienced landscapers can use the substance to reduce pH around mature trees. However, home gardeners should not attempt to use it for safety reasons.


Tips for Maintaining Soil pH Level

When you have a more neutral pH or acidic soil (depending on your garden needs), maintain your soil’s pH with a well-balanced fertiliser. 

You can use ammonium-containing nitrogen fertilisers to help maintain soil acidity, but they shouldn’t be your sole method.

Organic matter is one of your best friends for balancing the soil’s pH level. 

Acidic plant materials such as peat moss or pine needles will drop soil pH over time. Meanwhile, manure can gradually lower the pH while also adding essential plant nutrients.

Some people will suggest using coffee grounds for more acidic soil, but that’s not really effective. Most of the acidic components of coffee are water-soluble and are removed in the brewing process.

Substances like hydrated lime and wood ash raise soil pH – they won’t make your soil acidic. Don’t get things mixed up!

Regularly test your soil’s pH so you can track its composition. 

Knowing how to lower pH in soil is valuable, but it’s better to catch things earlier or prevent a rise in soil pH value. 

Then your lawn or garden will be much happier and your plants will thrive – so long as you remember to water and fertilise them, too!

About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.


About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.