How to Lower Soil pH in 4 Easy Steps

Updated on 04/27/23

Reviewed by

Overhead view of a gardener holding a handful of soil in the garden — The Spruce / Jayme Burrows

Project Overview

Working Time: 1 hr, 30 mins - 3 hrs
Total Time: 1 hr, 30 mins - 3 hrs

Skill Level: Beginner
Estimated Cost: $25 to 50

While many vegetables, fruits, and ornamentals grow well in a fairly wide range of neutral soils (6.5 to 7.5), some plants, like blueberries, azaleas, and hydrangeas, won't tolerate alkaline soils. To grow them, the soil pH must first be lowered, by amending the soil with elemental sulfur.

To find out your soil type, first you have to test the pH levels of the soil. A general, scientific classification for soil type is based on pH, which measures the levels of acid and alkali present. The pH scale uses numbers 1 to 14 with soil testing below 7 as acidic. Test results above 7 indicate an alkaline soil.

Lowering your soil pH is often a long-term project. When the alkalinity is at 8.5 or higher, it may take several years and repeated applications to achieve the ideal pH for most plants. Sulfur levels can also be depleted so it's a good idea to test your soil pH every few years and adjust if needed.

How to Test Your Soil

Your cooperative extension office can perform a basic analysis with a soil sample from your garden for a minimal fee. Results include pH as well as primary and secondary nutrients and micronutrients that your sample may be lacking.

You can also purchase a test kit at retail outlets, garden centers, and online, or you can perform a basic test using ingredients from your kitchen cupboard.

Testing soil pH in a glass bowl with water — The Spruce / Jayme Burrows

When to Lower Soil pH

If you are planning a new garden bed, it's helpful to have the soil tested as early as possible. Sulfur reacts with soil bacteria to lower pH, but soil temperatures must be above 55 degrees Fahrenheit for it to be effective. You should allow about a month before planting following a sulfur application. Adding sulfur in fall or winter will not give the desired result.

Making adjustments to soil composition also is the easiest and most effective before you plant. This isn't always practical but take care to use the best methods and materials to avoid root damage.

Warning

Always take precautions when working with chemical substances. Gloves, safety glasses, and protective clothing can prevent unintended burns and other skin and eye irritations.

Equipment / Tools

Hand or wheeled spreader
Rototiller, shovel, or hoe
Hose
Hard rake

Materials

Sulfur
Water
Gloves
Protective glasses

Lower Soil pH With Sulfur

Sulfur for amending soil is sold at retail centers and gardening outlets. It is often labeled as sulfur but may also be called soil acidifier. It's usually sold by the pound in five to 50-pound bags as dust or small particles. Your extension agent can help you calculate how much you need based on the size of the planting area, how much the pH should be lowered, and your soil type.

A general rule of thumb for lowering the pH by 1 point is as follows:

Clay soil-1/2 lb of sulfur per square yard
Sandy soil-1/4 pound of sulfur per square yard
Loamy soil-6 ounces of sulfur per square yard

Apply Sulfur

Use the hand or wheeled spreader to distribute sulfur over the planting area in the correct amount determined by the results of your soil test.

The Spruce / Jayme Burrows
Work Sulfur Into the Soil

Use the shovel, hoe, or a rototiller to work sulfur into the soil to a depth of 6 inches.

The Spruce / Jayme Burrows
Water the Treated Planting Bed

Tilling and watering in the sulfur gives faster results. Wet the soil but avoid drenching. Too much water dilutes the application with less benefit.

The Spruce / Jayme Burrows
Wait to Plant

Give the sulfur application about a month to work before planting. This insures more even soil distribution and prevents plantings from exposure to concentrated acidity.

The Spruce / Jayme Burrows

What Can Affect Soil pH?

The natural pH of soil is determined by the type of rock from which it formed. It also is affected by dry or wet climates, vegetation, topography, and time. Fertilizers with ammonium sulfate and nitrogen fertilizers with ammonium reduce pH over time. Some organic fertilizers can also reduce pH, slowly. Minerals and salts in hard water and large amounts of wood ash raise the pH of soil.

How to Lower pH Naturally

Lowering pH with natural materials takes time and repeated applications but is one of the easier methods for existing flowerbeds and gardens. You can add organic materials like compost and manure to vegetable gardens before planting, or as side dressings raked or hoed in once crops are established. Chicken manure works best for acidifying soil but all types should be aged before being added to garden soil. Pine products including mulches, barks, and needles lower pH but break down very slowly.

How to Lower pH After Planting

Soil acidity is depleted over time which causes the pH level to rise. This makes maintaining the best balance for plants an ongoing process. Ammonium nitrate works quickly but is also depleted quickly, creating a need for repeat applications. It has to be worked into the soil around the plants and adding too much can damage roots and nutrient uptake. The best way to maintain a neutral pH for your flowers, fruits, and vegetables is to add well-composted material and organic mulches annually.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Soil pH. Queensland Government.
Understanding Soil PH. Penn State Extension.