How to Change Your Soil pH

Like Goldilocks choosing her bed, plants look for particular qualities in their soil. One essential quality is soil pH, the measure of how acidic or alkaline the soil is. We’ll walk you through how to change your soil pH so it’s just right for a lush landscape.

What is soil pH?

The unit pH measures the acidity or alkalinity of a substance, such as soil. The pH scale goes from 0 to 14, with 7 being neutral. The lower the number, the more acidic the substance. The higher the number, the more alkaline. Each increase of 1 on the scale is equal to a tenfold change. For example, a pH of 7 is 10 times more alkaline than a pH of 6.

Many factors affect soil pH, including:

• Mineral content: The minerals in your soil come from the parent materials, such as rocks or organic materials.

• Climate: Areas with more rainfall tend to have higher soil acidity because the water leaches nutrients like calcium and magnesium, which are then replaced by acidic elements like aluminum and iron. Soils in drier climates, on the other hand, are usually neutral or alkaline.

• Irrigation water: Water, just like everything else, has its own pH level. If your water’s pH or alkalinity levels are significantly different from your soil pH, it may shift soil pH over time. Get an irrigation water test to find out your water’s pH.

• Fertilizer: Some fertilizers affect soil pH. For example, nitrogen fertilizers can gradually lower pH, while animal manures gradually increase pH.

• Vegetation: Plant litter and decomposing vegetation can shift soil pH over time. Forested areas tend to have acidic soil due to the organic matter that breaks down there, such as pine needles.

The pH of your property’s soil probably falls within 3 to 10. Between 6 and 7.5 is the ideal pH range for most plants since nutrients are most available. However, some plants prefer a lower or higher pH.

Soil pH can impact the plants in your yard in many ways, including:

• Availability of nutrients to plants
• Plant poisoning from toxic levels of manganese
• The well-being of microorganisms in the soil, which impacts plant health

How to increase your soil pH 

If your soil is too acidic, this is the section for you. Raising your soil’s pH will make it more alkaline. Overly acidic soil decreases the availability of nutrients, affects the process of nitrogen fixation, reduces water absorption, and decreases microorganism activity. It also indirectly causes soil erosion due to decreased plant growth.

There are several alkaline soil amendments, but we’ll cover the most popular options.

Lime

Limestone is an inorganic soil amendment and the most popular way to increase pH levels. You’ll start to see benefits in a few months, but full results can take as long as two years.

There are two primary varieties of limestone soil amendments:

• Calcitic lime: Also known as calcium carbonate, this type of lime neutralizes acid and provides calcium. Use in soils that already have sufficient magnesium.

• Dolomitic limestone: This amendment contains carbonite and magnesium, which makes it suitable for soils with deficiencies in those nutrients. It’s commonly used for gardens.

The best time to apply lime is in the fall, so it has time to incorporate into the soil before the spring planting and growing season.

Lime soil amendments come in many forms, such as pelletized, powdered, and liquid lime. Though liquid lime works quickly, pelletized lime is more affordable and accessible. It also is easier to apply evenly than powdered lime. Because of this, our application instructions are for pelletized lime.

How to apply lime to your lawn:

1. When you apply lime to a lawn, it shouldn’t be wet, wilted, or dormant.
2. Remove any debris.
3. Aerate lawns with a core aerator so there’s space for the lime to make its way into the soil.
4. Spread the pelletized lime with a drop or rotary spreader, walking straight over your lawn, then again in a direction perpendicular to the first.

How to apply lime to your garden:

1. Start with an empty garden bed if possible. Only apply lime to dry soil.
2. Remove any debris.
3. Apply evenly over the soil with a spreader or by hand.
4. Till into the soil.

How much lime should you apply?

Your soil test results will give you an exact limestone application rate. You can apply it all at once if it’s less than 50 pounds of lime per 1,000 square feet. If it’s more, you’ll need to split it up over two applications in the spring and fall to avoid shocking your plants or lawn.

The soil test you get should provide the amount of lime needed based on the buffer pH. However, you can use this table from Iowa State University Extension and Outreach in case you need to calculate it yourself.

Pounds of lime required to increase soil pH to a depth of 6 inches per 1,000 square feet:

	Target soil pH
Buffer pH	6.5	6.9
7.0	0	25
6.9	0	44
6.8	14	62
6.7	30	80
6.6	48	101
6.5	64	119
6.4	80	138
6.3	96	16
6.2	115	177
6.1	131	195
6.0	147	213
5.9	163	232
5.8	181	253
5.7	197	271

Wood ash

Wood ash is the go-to organic choice for making the soil more alkaline. It comes from burning hard and softwood with other organic materials and contains calcium, potassium, and magnesium. Not only do these elements raise soil pH, they’re also great for plant growth.

Wood ash works quicker than limestone. However, you must apply more of it to get the same pH change because it’s less concentrated.

You can purchase wood ash, but some homeowners make their own. Don’t use treated or painted wood, charcoal, or ashes from garbage fires – you could inadvertently harm your plants.

Apply wood ash soil amendments in spring or fall, but not when seeds germinate.

How to apply wood ash to your yard:

1. Remove any debris.
2. Water your lawn the day before applying.
3. Apply the wood ash by raking the ash over the surface of your lawn with a leaf rake or regular garden rake.
4. Use a shovel or garden hoe to work the ash into the top inch of the soil.
5. Water your lawn after spreading it to help the ash sink in.

How to apply wood ash to your garden:

1. Remove any debris.
2. Water your garden the day before applying.
3. Sprinkle wood ash over the soil evenly. Mix it into the soil if there are no plants, but you also can topdress existing gardens.
4. Water your garden to help the ash sink in.

How much wood ash should you apply?

If you get a soil test recommending lime, you can use that to determine how much wood ash to spread. Use two to four times as much ash as lime. Generally, 10 to 15 pounds of wood ash per 1,000 square feet is safe for lawns, while up to 20 pounds per 1,000 square feet is recommended for gardens.

How to decrease your soil pH

If your soil is too alkaline, this is the section for you. Lowering your soil pH will make it more acidic. Alkaline soil contains a lot of sodium, magnesium, and calcium. This makes the soil less soluble, which causes plants to have difficulty absorbing nutrients. Alkaline soil is one possible cause of iron chlorosis in lawns and other plants.

The following soil amendments are the most common for lowering soil pH.

Elemental sulfur

Elemental sulfur is the top dog when it comes to acidifying your lawn. It produces two hydrogen reactions when mixed with soil, which causes the pH to decrease. However, it can harm your grass in high amounts. That means it may take years to achieve your desired soil pH safely.

Be aware that sulfur takes three to six months of warm soil temperatures (when the soil microbes are active) to lower soil pH. The best time to apply elemental sulfur is in spring.

How to apply elemental sulfur to your lawn:

1. Core aerate your lawn so the amendment can penetrate the soil.
2. Use a spreader to distribute the elemental sulfur evenly over your lawn in straight lines, then go over it again in a perpendicular path.
3. Water your lawn thoroughly.

How to apply elemental sulfur to your garden:

1. Spread sulfur using a drop spreader or by hand (while wearing gloves).
2. Work it into the top 4-6 inches of the soil with a shovel or garden spade.
3. Water the soil well.

How much elemental sulfur should you apply?

This table from Iowa State University Horticulture and Home Pest News demonstrates the pounds of elemental sulfur to apply to your lawn depending on your soil type (sandy loam, loam, or clay loam).

Pounds of elemental sulfur required to decrease soil pH to a depth of 6 inches over 1,000 square feet:

Current pH	Target pH	Sandy loam	Loam	Clay loam
5.0	4.5	4 lbs.	13 lbs.	18 lbs.
6.0	4.5	12 lbs.	38 lbs.	53 lbs.
7.0	4.5	19 lbs.	65 lbs.	88 lbs.
8.0	6.0	31 lbs.	44 lbs.	53 lbs.
7.0	6.5	2 lbs.	4 lbs.	74 lbs.
8.0	6.5	28 lbs.	27 lbs.	46 lbs.

Elemental sulfur is a strong chemical that can burn grass in excess. Only apply up to 5 pounds per 1,000 square feet at a time. If you need to use more, divide it into two applications, one in spring and one in fall, so you don’t exceed 10 pounds in a single year.

Aluminum sulfate

Aluminum sulfate is a good option if you don’t have months to wait. It reacts fast because it’s soluble and can change pH in days. However, it requires more material to get the same pH change, and you can’t apply too much at once because of aluminum toxicity. Aluminum sulfate is commonly used to improve the color of hydrangeas.

The best time to use this soil amendment is in spring. Some types of aluminum sulfate are water-soluble, in which case you should follow the package instructions for mixing and application. The directions below are for the granular variety.

How to apply aluminum sulfate to your lawn:

1. Core aerate your lawn so the amendment can penetrate the soil.
2. Use a spreader to distribute the aluminum sulfate evenly over your lawn in straight lines, then go over it again in a perpendicular path.
3. Water your lawn thoroughly.

How to apply aluminum sulfate to your garden:

1. Measure out your aluminum sulfate.
2. Distribute it over your soil by hand, wearing gloves. 
3. Dig it into the top 6 inches of the soil with a shovel.
4. Water thoroughly. Rinse the product off of any leaves to prevent damage.

How much aluminum sulfate should I apply?

Although this solution is quicker than sulfur, aluminum can be toxic to plants. Don’t use more than 5 pounds over 100 square feet at a time.

This chart from Clemson University’s Home & Garden Information Center details how much aluminum sulfate to use based on your desired pH. This table is specific to loam – decrease by ⅓ for sandy soils and increase by ½ for clay soils.

Pounds of aluminum sulfate per 10 square feet needed to reach your target pH:

	Target pH
Current pH	6.5	6.0	5.5	5.0	4.5
8.0	1.8 lbs.	2.4 lbs.	3.3 lbs.	4.2 lbs.	4.8 lbs.
7.5	1.2 lbs.	2.1 lbs.	2.7 lbs.	3.6 lbs.	4.2 lbs.
7.0	0.6 lbs.	1.2 lbs.	2.1 lbs.	3.0 lbs.	3.6 lbs.
6.5	N/A	0.6 lbs.	1.5 lbs.	2.4 lbs.	2.7 lbs.
6.0	N/A	N/A	0.6 lbs.	1.5 lbs.	2.1 lbs.

Sphagnum peat moss

You might hear that peat moss is a great way to acidify your ground naturally, but most peat moss in garden centers isn’t acidic enough to make an impact. Only Canadian sphagnum peat moss, which you can order online, has a low enough pH to affect soil conditions. This soil amendment is a better option for container gardens than whole lawns.

Though peat moss has several advantages, it’s expensive and not environmentally sustainable. If you decide to use it, apply in the spring or fall.

How to apply sphagnum peat moss to your lawn:

1. Put the peat moss into a compost spreader and walk all over your yard with it.
2. Use a rake to distribute the peat moss evenly throughout your turf.
3. Water your lawn so the peat moss is moist.

How to apply sphagnum peat moss to your garden:

1. Place the peat moss in a big container and add enough water to moisten it thoroughly.
2. Wait a few minutes for the water to sink in before adding more as needed.
3. Spread a 2-3 inch layer of wet peat moss with a garden fork, incorporating it with a shovel into the top foot of the soil.

How much peat moss should I apply?

Peat moss isn’t an exact science. Follow the instructions on your bag, which will be specific to the pH of that particular peat moss.

How to test your soil pH

Before you haul out bags of soil amendments, you must know your soil’s starting pH. There are two ways to do this: Send a soil sample to a lab or test the soil yourself.

Testing soil yourself is cost-effective and quick (you’ll get the results in 30 minutes). Sending a sample to a lab takes about two weeks. However, you’ll get a thorough soil test report on other soil qualities, including any nutrient deficiencies and recommendations for amendments.

To send a soil sample to a lab:

There are lots of labs that will give a full soil report. We recommend looking up the closest cooperative extension office for affordable and reliable services, but you also can choose a commercial soil testing lab.

1. Order a testing kit from the lab of your choice.
2. Use a trowel or shovel to take a 6-inch deep slice of soil.
3. Moving in a zigzag fashion, collect at least eight samples spread evenly across your lawn.
4. In a large container, mix the soil samples thoroughly.
5. Place two cups of the mixture into the resealable bag from your kit, fill out the form (also in the kit), and send it off for testing. 

To test your soil pH yourself:

You’ll need pH strips for this. You can get those at most big box stores or online.

1. Follow steps 1 through 3 for sending a soil sample to a lab.
2. Put 4 ounces of the mixture into an 8-ounce plastic cup.
3. Add 4 ounces of distilled water and mix with a plastic spoon.
4. Let the sample sit for 30 minutes.
5. Dip a wide range pH strip into the soil solution.
6. Use the color reference chart that comes with the test to determine where your soil pH falls on the scale. 

How soil type affects pH

Soil type refers to the material makeup of your soil. There are three main types of soil: loam, sand, and clay.

Each material responds to soil amendments differently. How easily soil will respond to pH changes is called its “buffering capacity.” Materials with a high buffering capacity can absorb a lot of acidic or basic solutions before their pH changes. In contrast, materials with a low buffering capacity require only a little amendment solution to change.

Clay soil has a higher buffering capacity than loam, which, in turn, has a higher buffering capacity than sandy soil. That means you need more material to affect clay soil, a medium amount for loam, and a low amount to amend sand.

How to test your soil type 

There are two standard methods for determining what kind of soil you have. Go for the squeeze test if you want a quick, rough estimate. If you want more precise results and are willing to wait a few days and flex your algebra skills, go for the jar test.

Squeeze test:

Grab a handful of moist (not wet) soil and squeeze it in your hand:

• Clay soil feels sticky and will hold its shape.
• Sandy soil feels gritty and will fall apart. 
• Loamy soil is somewhere in between – it will hold its shape but crumble if prodded. 

Jar test:

1. Collect about 1 cup of soil from your yard. 
2. Sift it with a sieve or colander to remove any rocks or debris.
3. Fill a jar with your sifted soil so the jar is ⅓ full, then fill the rest with water. 
4. Add one tablespoon of powdered dishwashing detergent, then shake the contents until everything is mixed.
5. Place the jar on a flat surface and set a timer for one minute, then put a mark on the jar measuring the layer of coarse sand that’s settled at the bottom.
6. Set a timer for two hours, then put a mark on the jar at the top of the next settled layer, which is silt.
7. Leave the jar for two days, then mark the top of the next settled layer: This is clay. 
8. Measure the height of each layer and the total height of all three layers, then calculate the ratio of layers using the formula below.
   1. % sand = sand height ÷ total height x 100
   2. % silt = silt height ÷ total height x 100
   3. % clay = clay height ÷ total height x 100
9. Use the soil texture graphic to find what category your soil falls into.

FAQ about soil pH

What plants prefer acidic soil?

Most cultivated plants enjoy slightly acidic soil (a pH of 6.5). A few (like rhododendrons and blueberries) prefer a lower range of 4.5 to 5.5. Check your plant’s label when you buy it or check online to ensure you have the correct range.

Flowers for acidic soils:

• Bleeding hearts
• Flossflower
• Daffodils
• Marigold

Vines for acidic soils:

• Trumpet vine
• Persian ivy

Shrubs for acidic soils:

• Azalea
• Rhododendron
• Oakleaf hydrangea
• Gardenia

Trees for acidic soils:

• Colorado blue spruce
• Dogwood
• Magnolia

What plants prefer alkaline soil?

Though most plants prefer neutral or slightly acidic soil, you have plenty of options if your soil is alkaline. Below are some popular options.

Flowers for alkaline soils:

• Bearded iris
• Black-eyed Susans
• Columbine
• Goldenrod
• Woodland phlox

Vines for alkaline soils:

• Clematis
• Kiwi
• Virginia creeper

Shrubs for alkaline soils:

• Forsythia
• Smooth sumac
• Viburnum
• Yucca

Trees for alkaline soils:

• Common beech
• Ginkgo biloba
• Ornamental cherry

What do I do if my soil is resistant to pH changes?

If you have clay-heavy soil with a high buffering capacity, it might be hard to make a lasting change to your soil pH. The soil in Utah, for example, is highly resistant to acidification.

If you’re willing to wait a few months to make your pH changes, you can topdress your landscape with compost to make it more amenable and then add your pH-altering substances.

If you want to start your garden immediately, consider a raised garden bed or container planting. That way, you have total control over the soil conditions.

What other soil amendments might I need to make?

If you want to secure your soil’s position as a prime spot for plants, you might need to make other changes. These include soil amendments to:

• Change your soil texture
• Add nutrients
• Alter salinity

Read here for a complete guide to different types of soil amendments. 

How often should I test my soil after I’ve applied amendments to alter the pH?

To track the efficacy of your amendments, test your soil’s pH every six months until the desired pH is reached. After that, test it once every three years.

Get help from a lawn care pro

Correcting your soil pH is only the beginning of the work to keep your lawn healthy. Once the soil is healthy and the grass grows, you must mow the lawn regularly, keep weeds in check, and kick pests to the curb.

If this seems like too much work for a weekend, Lawn Love’s local lawn care professionals can help with everything from lawn mowing to seasonal yard cleanup.

Main Photo Credit: Binyamin Mellish | Pexels