Managing soil pH is essential for a healthy lawn. When pH falls outside the ideal range of 6.0 to 7.0, your grass can’t absorb nutrients properly, leading to thin, yellowing turf and poor growth. Fortunately, the right amendments can correct it.
The best way to change acidic soil (low pH) is by adding lime, wood ash, or oyster shells to raise the pH. Make alkaline soil (high pH) more acidic by adding sulfur, aluminum sulfate, or iron sulfate.
As a soil scientist who’s tested thousands of samples, I know soil pH inside and out. Living with alkaline soil (pH 8.2-8.4) in Idaho, I’ve put that knowledge into practice in my own lawn and garden. Below, I’ll show you exactly how to adjust your soil pH.
Ready to transform your lawn? Once you know your soil pH, let our local lawn treatment pros apply the right treatments and fertilization to get your grass thriving. We handle everything from amendments to lawn pest control — all you do is enjoy the results.
| Key Takeaways |
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| ● Ideal soil pH for lawns is 6.0 to 7.0. ● Professional soil testing provides best amendment recommendations. ● Add lime or wood ash to raise pH. ● Add sulfur products to lower pH safely and economically. ● Clay soils need more amendments than sandy soils. |
How to Raise Soil pH (Make Soil Less Acidic)
Infographic by Juan Rodriguez
To make soil less acidic, you need to add amendments that contain cations — positively charged ions — to replace the hydrogen ions. There are different products you can use to raise a soil’s pH level, but lime, a calcium-based compound, is the most common and effective method for lawns.
Agricultural Lime (Calcitic Lime)
Calcitic lime primarily contains calcium compounds: calcium carbonate, calcium hydroxide, and calcium oxide. This pure calcium formulation makes it ideal for soils with balanced magnesium levels that simply need pH adjustment.
Acidic soils that need their pH bumped up only slightly typically require 20 to 50 pounds of calcium carbonate per 1,000 square feet. Heavy clay soils need more material than sandy soils to achieve the same pH change.
Note: When applying more than 50 pounds per 1,000 square feet, split into multiple applications.
Pro Tip: Particle size significantly impacts how quickly lime works. Limestone doesn’t readily dissolve in water, so a finer grind creates more surface area for soil interaction, speeding up the process. Add a mix of lime particle sizes to your soil — you’ll see faster results from the small, fine particles, and the larger particles help stabilize soil acidity over time.
Dolomitic Lime
Dolomitic lime offers dual benefits because it contains calcium compounds along with significant amounts of magnesium carbonate. This makes it the perfect choice for acidic soils suffering from magnesium deficiencies, addressing two problems with one application.
Expect lime to take up to 6 months before seeing significant pH changes. The full effect of liming typically takes 2 to 3 years.
Note: Don’t use anything labeled as “hydrated” limestone. These products work quickly to correct soil pH, but their caustic properties pose safety concerns, making them very dangerous.
Pro Tip: If your soil is too acidic, I highly recommend you never guess and throw lime down. Go outside, take a soil sample, and send it off for analysis. The lab will test your soil, determine the pH and buffering capacity, and tell you exactly how much lime to add per 1,000 square feet to hit your target pH.
Related:
- Lime for Lawns: Why, When, and How to Lime a Lawn
- How to Tell If Your Lawn Needs Lime (6 Signs)
- How to Amend Sandy Soil
- How to Read a Soil Test Report
Wood Ash
The ash left by burning wood is high in the base cations calcium and potassium, and has been used to adjust soil pH since the 1700s. The carbonates that form react with hydrogen ions, neutralizing the acidity and raising the soil pH.
It can take 2 to 4 times as much wood ash to raise soil pH as lime does, but it works faster because it’s more water-soluble.
Oyster Shell Meal
Finely ground oyster shells offer a natural and sustainable alternative to traditional agricultural lime. This organic soil amendment primarily contains calcium carbonate, providing a long-lasting, slow-release calcium source that benefits your soil for several years.
Oyster shell meal works more gradually than standard lime. Noticeable improvements may appear within weeks of application, but it will take several months to see significant benefits.
How to Lower Soil pH (Make Soil More Acidic)
Lowering pH in alkaline soil takes patience, especially if you’re working with clay. But it’s absolutely doable with the right approach. The three most effective amendments are elemental sulfur, aluminum sulfate, and iron sulfate. Each has distinct advantages depending on your timeline and soil type.
Note: Sulfuric acid is sometimes used in agriculture to lower soil pH, but homeowners should avoid using it. It is incredibly caustic and corrosive, making it dangerous even for trained professionals.
Elemental Sulfur
Elemental sulfur is the safest and most economical option for most homeowners, though it’s also the slowest. Soil bacteria convert sulfur into sulfuric acid, gradually lowering your pH over 3-6 months.
To drop your soil’s pH by about half a point, you typically apply 0.5-1.0 pound of elemental sulfur per 1,000 square feet.
Like lime for acidic soils, smaller particles work faster than larger ones, and sandy soils need less material than clays to achieve the same pH change.
Pro Tip: A professional soil test is really the best move to determine how much sulfur to apply. The lab will analyze your specific soil texture and buffering capacity, then tell you recommended application rates, taking all the guesswork out of it.
Aluminum Sulfate
If you need to lower the pH of alkaline soil in a hurry, aluminum sulfate is your best bet for quick results. It rapidly changes soil pH, often within days to a few weeks, because it doesn’t need soil bacteria; it only needs water to form sulfuric acid.
The downside? Aluminum can be toxic at high levels, so use it cautiously around your lawn or vegetable garden.
Iron Sulfate
Iron sulfate works more slowly than aluminum sulfate but faster than elemental sulfur, making it a good middle-ground option. It adds essential iron while lowering pH, helping with plant growth.
The catch is you’ll need about 8 times more iron sulfate than elemental sulfur to significantly reduce pH.
Personal Experience: My soil typically has an unamended pH of 8.2 to 8.4. I haven’t seen enough issues to warrant the work needed to adjust it for my lawn, but I do use a mix of elemental sulfur and iron sulfate in my garden.
I use elemental sulfur in areas I can rototill in the spring, working it into the ground before planting. I scatter iron sulfate in my raspberry patch where I don’t till. I water it in well so it goes to work quicker than the elemental, and it gives an extra boost of iron to my deficient soil.
Peat Moss
Not all peat moss can help acidify soil, but Canadian sphagnum peat moss has a significantly acidic pH (around 3.0 to 4.5), making it effective for lowering soil pH when mixed into the top 6-12 inches before planting.
FAQ About Changing Soil pH
Apply lime in fall or early spring when your lawn isn’t stressed by heat or drought. The fall application is ideal because it gives lime time to work over the winter. Apply sulfur in spring or fall when temperatures are moderate, and soil moisture is adequate for activation.
Coffee grounds won’t lower your soil pH in the long run. Their pH is 6.5 to 6.8, putting them only slightly below neutral. You might see a slight decrease in pH when you add them to alkaline soils, but the effect doesn’t last. If you’re serious about lowering pH, stick with elemental sulfur or iron sulfate.
Take soil samples from 4-6 inches deep at multiple locations across your lawn. Mix the samples together, removing roots and rocks, and send them to a soil testing lab. Home test kits are available, but professional labs provide the most accurate results along with specific amendment recommendations tailored to your soil.
Related: How to Test the Soil pH of Your Lawn
Get Professional Help with Your Lawn
Changing your soil pH is an essential step towards having a thriving lawn and garden, but it’s just one piece of the bigger puzzle. Even after you achieve the optimal pH, regular maintenance like mowing, fertilizing, and aerating is key to keeping your landscaping healthy and vibrant.
If you need a hand with your lawn care, reach out to a pro in your area. LawnStarter’s local lawn care professionals can handle everything from weed control to fertilization so you can sit back and enjoy a lush, green yard without the hassle.
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Sources:
“Fertilizers and Soil pH.” University of California Division of Agriculture and Natural Resources.
“How To Change Your Soil’s pH.” By Joe Hannan, field specialist. Iowa State University.
“Keeping pH in the Right Range is Essential.” By Kym Pokorny, master gardener. Oregon State University.
“Soil Health – pH.” Natural Resources Conservation Service.
“Soil pH and the Home Landscape or Garden.” By Amy L. Shober, Extension specialist; Christine Wiese, assistant editor; Geoffrey C. Denny, former assistant professor; and Rao Mylavarapu, soil and nutrient management specialist. University of Florida.
“Understanding Soil pH.” By Mary Jo Gibson, master gardener. Penn State Extension.
Main Image: Hand spreading wood ash on soil. Image Credit: tonifrito / Adobe Stock
