ABCs of pH: Why, How and When to Soil-Test Your Lawn

soil test

Have you heard of soil pH? It’s critical for proper nutrient uptake in your lawn, but you’ll need to test your soil to get an accurate pH reading. Every homeowner wants a beautiful, healthy turf, so we’ll show you why, how, and when you should soil-test your lawn. 

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How to Take a Soil Sample

Jim Friedericks
Jim Friedericks

Every lawn needs nutrients to thrive, but before you start adding fertilizer, lime, or other soil amendments, dig in and send a soil sample for a pH soil test.

“Soil testing provides information about the soil that is necessary to manage the soil for good plant growth,” says Jim Friedericks, Director of Outreach and Education at AgSource Laboratories. 

“It’s like the sensor code reader used by a car mechanic. The warning light may or may not be flashing, but if you plug in the sensor code reader you will find out what is going on with the car and can plan to fix it.”

If you plan to send the soil sample to a lab, check the lab for specific instructions as they may vary from lab to lab. The same goes for an at-home test. Read instructions carefully to be sure that your collection follows the at-home pH test kit of your choice.

That being said, most lawn soil sample collections will be about the same.

What you’ll need:

  • Plastic bucket: Galvanized buckets can contaminate the soil sample.
  • Shovel: Make sure it’s clean and has no rust.
  • Hand Trowel: Make sure it’s clean and has no rust

Here’s what to do:

  • Make a map: Consider collecting a few samples to get an accurate view of all your soil, especially if your lawn is large. In addition, if your soil is visibly different in some areas, you should take more than one sample.
  • Choose an untainted area: Do your best to take your samples from areas without fertilization or chemicals.
  • Clear organic matter: Remove or set aside any thatch and growing or dead plants from your dig area.
  • Dig: Using your shovel, dig a hole about 6 inches deep if you’re sampling for a lawn. Mix up the dirt at the bottom and take about one cup of dirt and put it in the bucket.
  • Take more samples: Going in a zigzag pattern, take a total of 10 1-cup samples and put them in the bucket.
  • Gather the final sample: Mix up the dirt in the bucket, removing any rocks and crushing clumps until you have relatively smooth soil. Make sure the sample is completely dry. Add 1-2 cups in a plastic bag, and label it based on where you took your sample. 
  • Gather other samples: If needed, follow the same procedure and gather more samples throughout your lawn.
  • Next Steps: If you’re sending in your sample to a lab, follow the lab’s instructions to mail them in. If you’re using an at-home kit, follow the instructions on the kit.
*It’s sufficient to dig only 6 inches deep if you’re sampling a lawn.

How to Test the Soil pH

At-home test kits vary hugely, so it’s absolutely critical to follow your chosen test’s instructions. The test kits can be as simple as a pH test you used in high school all the way to multiple tests with various chemicals. Be sure to pick up some distilled water because most soil test kits require it. 

Here is how to test your soil’s pH using a La Motte soil test kit:

  • Collect your sample: Collect a soil sample as explained in the previous section or according to the test kit instructions.
  • Read instructions: Read the instructions carefully and wear protective gloves and eyewear as some chemicals can cause irritation.
  • Fill: Fill a test tube to the fourth line with the pH indicator solution and add in 1.5 grams of soil. 
  • Shake: Put the cap on the tube and shake gently for one minute. 
  • Settle: Let the solution settle for 12 minutes.
  • Results: Compare the color of the solution to the pH color card to determine your soil’s pH. Although this test doesn’t use a pH tester, there are several that do.
  • Other data: If you want to learn more about your soil, follow the instructions to find out more data, such as the levels of nitrogen, phosphorus, and potassium.

What is Soil pH?

Soil pH Update

Soil pH is a way to measure the amount of acidity or alkalinity — in your lawn, garden soil, or anything else. It is measured in pH units on a scale from 0 to 14. Extreme acidity is at the low end of the scale, extreme alkalinity is at the top end. Lawn soil pH at the midpoint, number 7, is neutral soil, neither acidic nor alkaline.

The “p” in pH stands for “potential. The “H” is for hydrogen. While the science of pH gets complicated, everyone is familiar with things that are more or less acidic. Pure water is a neutral 7. 

Materials such as baking soda are alkaline. Alkalines have less hydrogen ion concentration than pure water, and much less than acidic items such as orange juice.

So pH can be defined as the level of hydrogen ion activity in a substance, including soil.

Your soil conditions may be naturally acidic or alkaline. There are many localized exceptions, but as a general rule, soils in the Eastern and Southern United States tend to be acidic.

The Midwest tends to be more neutral, while soils in the Southwest and West tend toward alkalinity.  The level of acidity originates from three main sources: rain, microbial activity, and nitrogen fertilizers.

  • Rain. Rain is intrinsically acidic, says Friedericks. It carries with it a certain amount of nitric, sulfuric, and carbonic acid absorbed from the atmosphere. Your location makes a difference as well. 

Rain is great for a rain garden, but rain downwind of a metropolitan area can create a soil pH as low as 4.2. That’s because there is more nitric and sulfuric acid in the atmosphere near a city.

In areas that receive more than 25 inches of rain annually, nutrients such as calcium, magnesium, and sodium are leached from the topsoil. That, too, creates acidic conditions. 

All of which translates to: If you live in a rainy area, your soil may tend to be acidic.

  • Microbial activity reduces soil pH levels. The decomposition of organic matter releases nutrients into the soil, producing soil acidity. 

As soil microbes decompose plants and other residues, carbon dioxide is produced and stored in the soil. This reacts with the soil moisture to form carbonic acid and results in increased acidity.

  • Fertilizer. Nitrogen fertilizers containing ammonium sulfate also lower the soil’s pH, says Friedericks. Ammonium sulfate creates acidity when it naturally converts to nitrate in the soil.

“An acid soil has a pH less than 7.0, and as the number decreases the acidity becomes more intense,” says Friedericks. 

“Soil with a pH of less than 5.0 is considered strongly acidic and is a challenging environment for most plants. As the soil pH increases above 7.0 it becomes more basic, or alkaline. A pH above 8.5 is unusual and also is challenging for plant growth.”

The pH That Turfgrasses Like

Most lawns and turf grasses thrive at a pH range of between 6.0 and 7.0. PH has an effect on plant growth, and important nutrients for plants tend to be available in soil when the pH is at those levels. 

Soil pH and plant nutrients
The chart shows how effectively plants take up key nutrients at various pH levels.

“With a very low pH there are risks of toxicity for aluminum and manganese as well as interactions between elements that reduce the availability as well,” says Friedericks. Highly acidic soil can also directly damage roots.

Soil Testing: Kit Versus Lab

A soil test kit will let you know if the soil has a low or high pH, or if it suffers from a nutritional deficiency.

Can you use a store-bought test kit to test your soil? Those kits can tell you the difference between a normal to adequate nutrient supply and a very deficient supply, Friedericks explains, but they are not precise enough to make a specific recommendation to fix the problems. 

“It’s best to use a soil testing laboratory that follows uniform methods that are directly related to university research and the recommendations that come from that research.”

A soil pH meter from a garden center or a pH test strip could also be misleading with its result. Numbers matter when it comes to the pH of your soil, and even a slight difference on the pH scale can mean a big change to your lawn’s acidity. 

The best thing to do is to send a sample for testing by a qualified laboratory, which will give you accurate readings of pH levels and nutrients.

Nearly all Cooperative Extension Service offices offer low-cost soil testing services. Check with your local Cooperative Extension Office for details on how to take a soil sample and where to send it for a pH test. They can help you find a testing service that is familiar with your particular locale or send it for testing through their office.

Make sure to use the same lab every time you test the soil for pH readings. Soil tests vary by locale. They may use different testing methods and test for different nutrients. Most laboratories will provide interpretive guides for their test results and recommendations. 

Be sure to compare the recommended fertilizer with your city regulations. Not all cities allow all fertilizers.

When Should You Test?

“It is a good idea to sample a lawn or turf area in the spring or early fall,” says Friedericks. “This will allow time to make the fertilizer and lime applications either in the spring as needed or to use the results from the fall sample to plan for the year ahead.”

  • Chill out. Follow the recommendations from the soil pH testing report, but be patient. It could take a year or more to see the results of a lime application, for instance.
  • Split the application. Spread the recommended application into two or three applications over a couple of months. Water the lime into the soil.
  • Season accordingly. Also, split nitrogen applications over the spring and summer to avoid leaching loss and to keep the grass healthy. 

Apply phosphorus in the spring to help establish a strong, well-rooted plant. “Applying some of the potassium in the fall can also help the grass create a good store of energy in the roots to improve overwintering.”

  • It’s a do-over. Keep on top of any problems after the initial test. Experts recommend that you take a soil sample and test soil pH every three to four years.
  • Don’t soak the samples. Dig your soil samples when it is neither too wet nor too dry, so you get a representative sample. Dry the soil completely before you place it in the soil sample bag or box.

Your Ultimate Goal: Healthy, Loamy Soil

It could take time and repeated soil amendments, but over time you will get the soil under your lawn where it needs to be. It will have a balance of air, organic material, minerals, and micronutrients that help the grass grow.

Give yourself, and the lawn, time. Plan to test the pH of soil for alkalinity or acidity, make amendments, and level and grade soil before seeding or sodding. ”The ideal soil is considered to be a loam, which is a mix of sand, silt, and clay,” according to the Northeast Beginning Farmers Project.

“Loams take advantage of the balance of water holding and nutrient availability between the three.”

FAQ About Testing Soil for pH

Do DIY Soil Test Kits Work?

DIY soil test kits work, but they’re not always accurate. According to the University of New Hampshire, the most accurate soil tests are from a lab. Here are a few reasons why:

•Home tests vary in accuracy.
•Although we homeowners try our best, we’re not trained scientists, and some inaccuracy can be due to human error.
•Unlike lab testing, home tests don’t typically come with “next step” recommendations for your lawn.

However, lab testing may not be an option for everyone. If that case, you can:

•Skip the test for now and use a previous year’s soil recommendation.
•If this is your first time testing soil, use a home kit, but do some research about soil in your area. If your results are wildly different, you may want to consider retesting or using a different soil test kit.
•If you’re using a home kit, you can use these fact sheets to help guide you: 

How to Choose the Right Lawn Fertilizer

How to Fertilize Your Lawn

Fertilizing Vegetable Gardens

Fertilizing Fruit Trees

Fertilizing Trees and Shrubs

How Much Does it Cost to Get Soil pH Tested?

According to the Natural Resources Conservation Service (part of the USDA), it typically costs about $7-$10 to send your soil sample into a lab. A home test kit price will vary, but they typically cost about $10-$60.

Does Soil pH Affect Flower Color?

No, flowers’ color is genetically programmed, so the soil pH won’t alter the color, except for hydrangeas. However, the pH of the soil will affect the health of the flower.

What Plants Grow Well in Acidic Soil?

According to horticulture educator Ron Wolford, there is a long list of acid-loving plants. Here are some acid-loving plants you may be familiar with:

•Blueberry
•Dogwood
•Holly
•Juniper
•Magnolia
•Rhododendron
•Spruce

What Plants Grow Well in Alkaline Soil?

The University of Florida released an article that discusses alkaline-loving plants. Here are a few that you may know:

•California poppy
•Zinnias
•Cosmos
•Firebush
•Pinks
•Flowering quince
•Burford holly

Phase in pH with a Professional

Whether you’re familiar with pH testing or you’re a newbie, the topic is so extensive that you’ll never learn it all. When you get those results, figuring out how to best fertilize your soil can make your head spin. However, if you want a green, healthy lawn, finding out your soil’s pH must be done. But you don’t have to do it alone.Time is a precious commodity, so don’t spend yours worrying about your lawn care. Local, experienced, highly rated professionals in your area can take the load off your shoulders without costing an arm and a leg. Call or click now for a free, no-obligation quote.

Main Image Credit: sherez / Adobe Stock

Rosie Wolf Williams

Rosie Wolf Williams

Rosie Wolf Williams has kept bees, grown vegetables and flowers for farmers markets, and never misses an opportunity to have a conversation with an interesting tree.