Making soil more acidic - Ask Extension
1. Garden. Our garden has clayey soil and is doing ok. It is 29 feet long and 21 feet wide (609 sq. feet). Based on the recommendation of adding 3....
Knowledgebase
Making soil more acidic #924672
Asked February 16, 2026, 10:26 PM EST
1. Garden. Our garden has clayey soil and is doing ok. It is 29 feet long and 21 feet wide (609 sq. feet). Based on the recommendation of adding 3.4 cups per 100 sq. feet, I plan to add 20.4 cups of sulfur across the garden and then spade it into the soil in the spring. Does that make sense?
2. Blueberries. We have seven blueberry plants. They are on a mound that was built with topsoil from a local nursery. They have been in the ground for two years and are 2 to 3 feet tall. The soil around the plants is covered with mulch. In the past two years, I have pulled the mulch away from the plants and then mixed half a cup of Espoma Soil Acidifier into the soil by mixing the top two inches or so of soil by hand around the plant. I have encountered and damaged some roots and they may have been blueberry roots. I would like to add sulfur to the blueberries in the spring, but I want to do it correctly. Questions:
Should the mulch be pulled back and the sulfur placed directly on the ground?
Should the sulfur be mixed into the soil? Does that damage the blueberry roots?
Is mulch good for the blueberries? How much mulch - 3 inches? Should the mulch not be disturbed? Can sulfur be added on top of mulch?
How much sulfur should be used for each plant? Is one cup of sulfur per plant a good start? Should it be placed on the soil a minimum of 3 inches from the plant and out to the drip line (approx 12 inch radius)
Any other recommendations?
Butler County Ohio
Expert Response
Hi Anthony.
You are off to a good start with getting a soil test!
For question #1.
The soil test for "Garden" says you have high to very high levels of nutrients. This is consistent with your comment about your soil is clayey. Before adding the sulfur to reduce the pH as recommended, would you consider what will you be growing in the garden this year? You might not have to add sulfur and save yourself a lot of time, money, and back breaking work spading it in.
Here is a link to an article with a list.
What Plants Like High Ph Soil? - Thrive In Alkaline - GardenerBible
It may be more beneficial to add organics materials (such as compost) to improve the soil tilth
Soil improvements and preparation | UC Master Gardener Program
For question #2a
How should the sulfur be added?
Pull back mulch to mixed sulfur into the soil?
or can sulfur be added on top of the mulch?
or directly on the ground?
Answer: You must mix the sulfur in to get the best result. You can apply it directly on top but it will take longer. Here isa link to a good article:
Lowering_Soil_pH_with_Sulfur.pdf
Question #2b. Is mulch good for blueberries?
Answer: Yes. Blueberries have shallow roots; mulching is recommended in addition to irrigation.
Blueberry Mulching and Water Management | Cornell Fruit Resources: Berries
Question #2c. How much mulch? 3inches?
Answer: The recommendation is 2-4 inches so 3 inches works!
Growing and Caring for Blueberries | Small Fruits for Home Gardens | Illinois Extension | UIUC
Question #2d. How much sulfur for each plant? is 1 cup a good start?
Answer: the amount of sulfur you add will depend on the clay content of your soil. See page 5 of this article to determine clay content and how much sulfur to add:
Acidifying Soil for Blueberries and Ornamental Plants in the Yard and Garden: West of the Cascade Mountain Range in Oregon and Washington
Finally, please keep in mind that changing soil natural pH is not a quick process. You will need to keep testing the soil about every two years and keep adding amendments to keep your blueberries happy and productive.
I hope you have bumper crop!
You are off to a good start with getting a soil test!
For question #1.
The soil test for "Garden" says you have high to very high levels of nutrients. This is consistent with your comment about your soil is clayey. Before adding the sulfur to reduce the pH as recommended, would you consider what will you be growing in the garden this year? You might not have to add sulfur and save yourself a lot of time, money, and back breaking work spading it in.
Here is a link to an article with a list.
What Plants Like High Ph Soil? - Thrive In Alkaline - GardenerBible
It may be more beneficial to add organics materials (such as compost) to improve the soil tilth
Soil improvements and preparation | UC Master Gardener Program
For question #2a
How should the sulfur be added?
Pull back mulch to mixed sulfur into the soil?
or can sulfur be added on top of the mulch?
or directly on the ground?
Answer: You must mix the sulfur in to get the best result. You can apply it directly on top but it will take longer. Here isa link to a good article:
Lowering_Soil_pH_with_Sulfur.pdf
Question #2b. Is mulch good for blueberries?
Answer: Yes. Blueberries have shallow roots; mulching is recommended in addition to irrigation.
Blueberry Mulching and Water Management | Cornell Fruit Resources: Berries
Question #2c. How much mulch? 3inches?
Answer: The recommendation is 2-4 inches so 3 inches works!
Growing and Caring for Blueberries | Small Fruits for Home Gardens | Illinois Extension | UIUC
Question #2d. How much sulfur for each plant? is 1 cup a good start?
Answer: the amount of sulfur you add will depend on the clay content of your soil. See page 5 of this article to determine clay content and how much sulfur to add:
Acidifying Soil for Blueberries and Ornamental Plants in the Yard and Garden: West of the Cascade Mountain Range in Oregon and Washington
Finally, please keep in mind that changing soil natural pH is not a quick process. You will need to keep testing the soil about every two years and keep adding amendments to keep your blueberries happy and productive.
I hope you have bumper crop!
