I have vivid memories of chemistry class in high school, sitting in the lab with other students and trying to remember the pH of different substances. I always had trouble recalling the scale and which numbers represented whether something was basic or acidic.
Nowadays, I feel like even though I’m far from a scientist, I have a better grasp of pH simply due to my love of gardening. In fact, a few weeks ago, my husband, who is a teacher, was trying to come up with some lesson ideas surrounding the topic of pH. I suggested talking about soil pH and the needs of different plants.
The pH of the soil measures how acidic or basic (alkaline) it is. The scale goes from 0 to 14. Right in the middle, at a pH of 7, things are neutral. Higher than 7 and your substance is basic and on the lower end are items that are acidic. Plants typically enjoy a pH that’s more or less neutral, somewhere between 6.0 and 7.5.
So why does pH matter? Nailing the right pH is the difference between a thriving crop and a floundering one. Fortunately, it's not something that is too difficult to master. We'll show you how to test soil pH to completely transform your garden.
Why is Testing Soil pH Important?
Even though plants may be able to survive in a soil that falls outside of their ideal pH zone, nutrient absorption may be compromised, which can lead to all sorts of problems with your plants, like nutrient deficiencies.
It’s why learning how to test soil pH is so necessary. Even if you suspect a deficiency, simply adding a nutrient isn’t going to do much good if your soil’s pH is outside of an ideal range. You may be adding nutrients that cannot be absorbed by the plant.
pH that is too alkaline can actually encourage excess nutrient uptake, which on the other end of the spectrum, is also not good for your plants.
Don’t try to adjust your soil’s pH without testing your soil. You don't want to play a guessing game. Adjusting your soil’s pH or nutrient content without first getting access to data about your soil is a recipe for disaster.
What Can Impact Soil pH?
A few different things may affect the acidity of the soil. Here are some examples:
- Rain. Excess rainfall may actually increase the acidity of the earth. In areas where there is more rainfall, the soil may be naturally acidic.
- Certain plants. Planting crops such as beans affects not only the nitrogen content in the soil but also tends to create a more acidic environment.
- Fertilizing. Adding the wrong amount of fertilizer may also affect soil pH and render it overly acidic. Adding too much fertilizer that’s high in nitrogen can cause problems down the road.
- Improper crop rotation.
- Poor irrigation and flooding.
Can I Spot a pH Issue Without Testing My Soil?
Unfortunately, there’s no surefire way to detect a pH issue without testing your soil. If your soil is too acidic, you may notice that fertilizing your plants isn’t helping at all. Your plants may show signs of nutrient deficiency.
The problem is that there’s no way to find out why that deficiency is occurring without getting your soil tested. Just like you shouldn’t self-diagnose and head to WebMD without seeing a doctor, you shouldn’t assume you know what’s going on with your garden plants.
Yellowing of leaves and other signs of nutrient deficiencies may be the result of soil that’s too acidic, which would prevent your plants from gaining access to micro and macronutrients despite their presence in the soil.
Adding any fertilizer in this situation would simply contribute further to the problem. The short of it? Don’t assume you can diagnose the problem without getting a glimpse of your soil nutrient and pH profile.
How to Test Soil pH
You can test your soil yourself using an at-home kit or get the soil tested by a lab. The choice is yours.
The benefit of sending soil samples to a lab is that you’re guaranteed an accurate assessment and you’ll not only get info back on soil pH, but on your soil’s nutrient composition as well.
Most at-home pH testing kits include indicator strips, like you may have used back in chemistry class. They’re easy to use, and since most kits include multiple testing strips, it’s easy to keep an eye on your soil’s pH. They aren't quite as comprehensive, but they'll give you a good idea of what your soil needs.
There are also some no-cost, at-home testing methods that allow you to verify the pH of your soil. These no-frills experiments are great if you're in a pinch and need a quick answer, but cannot provide you with info about exact pH levels. Still being able to check for acidity or alkalinity is a useful trick to know.
This is a quick-and-dirty method that isn't particularly specific, but it's handy to have when you need a general idea about your soil's pH.
How to test soil pH
- Grab a soil sample of about 1 cup (you may want to test multiple samples from different areas).
- Wet the soil until it reaches a mud-like consistency.
- Add around a 1/2 cup of vinegar (regular white vinegar will do).
- If there's a reaction and you notice bubbling and/or fizzing the sample is basic (alkaline).
- To test for acidity, take your soil sample and add 1/2 cup of baking soda. If a reaction occurs, you have acidic soil on your hands.
How can you tell if your soil's pH is neutral? Nothing will happen with either test.
You can purchase pH test kits online. Be sure to read reviews to determine if the kit is a good one, because the quality can vary. These aren't as accurate as lab tests, but they give you a good general idea.
Follow the directions included in the kit. Generally, this involves filling a vial with soil and water and adding a capsule or dipping a strip into the mix. The vial or strip will change colors, which you can compare to the kit's chart to determine your pH level.
You can also purchase a pocket meter that you stick in the ground to test soil pH.
If you elect to go the lab route, expect to spend around $20 and to wait a few weeks. Most labs will provide you with specific instructions, but generally, you will want to take a few soil samples and send them into the lab.
More specifically, you will want to take a few soil samples from a garden area, avoiding fences, areas where water pools or where livestock defecates. Take each sample at about 4-inches deep in the soil. Air dry them and place them in a clean container.
Be sure to label your container so you know where the soil came from, especially if you are sending in multiple samples. Send the samples straight away to ensure accuracy.
A Live Soil pH Monitor for Your Garden
The lazy gardener not interested in how to test soil pH the hard way or who’s interested in a potential science experiment should consider planting a hydrangea bush. The blooms will change color depending on the soil’s pH. It’s a neat plant to include in the garden if you have kids and want to teach them about the soil and pH levels. It’s also happens to be a lovely plant to have around. You’ll get blue flowers if the soil pH sits between 4.0 and 5.0. Blooms will be pink if the earth’s pH is between 6.0 and 7.0.
What Happens if My Soil is Too ACIDIC?
Now that you know how to test soil pH, you may be wondering what to do about it. Soil that’s too acidic may prevent water uptake and impede nutrient access. High acidity also affects the organisms living in the soil, some which may not be able to survive at all.
Adding lime can rectify the problem by raising pH. The texture of your soil dictates the amount of lime you’ll need to apply to adjust its pH. Thicker, clay-like soils typically require more lime to rectify a too-acidic pH.
Examples of lime-containing products:
- Limestone (this is the purest form of lime)
- Dolomitic lime
- Sugar beet lime
- Shell meal
- Wood ash
- Eggshells (ground up)
In general, you will need about 5 pounds of lime for 100 square feet of earth to raise pH 1 point.
How to Lower pH if Your Soil is Too BASIC
To lower the acidity of your soil, sulfur is the most commonly suggested amendment. Materials that may be used include:
- Spaghnum peat moss
- Pine needles
- Sulfur in granular form
- Aluminum sulfate
- Wood chips
- Coffee grounds
Lowering a soil’s natural pH can take a long time, so be prepared to commit to the effort. In general, you will want to add about 5.5 pounds of sulfur to 100 square feet of soil to lower pH by 2 points.
Once I’ve fixed the issue, is this problem over?
As noted above, soil pH can be affected without you even touching your garden. Things like rainfall can meddle with soil acidity so keeping the levels in check is an ongoing task. Get a soil test yearly to keep an eye on the health of your earth.
It’s also important to remember that it’s not easy to adjust soil pH. Even with the above-suggested amendments, altering the pH is difficult. You may have to alter your expectations and change what you plant.
If the earth around your property is not ideal for planting because the pH is too low or too high, consider building raised beds. You’ll have greater control over the soil’s composition and pH levels.
Plants with Unique pH Needs
While most plants thrive in what’s considered to be a fairly neutral pH zone (6.0 to 7.0), some plants do better in soil that’s either slightly alkaline or slightly acidic. Knowing this before planting is useful since you can select a separate spot to put these plants with different needs.
Plants that prefer slightly alkaline soil
- Canna Lilies
- Garlic (tolerates a wide pH range between 5.5 and 8.0)
Plants that prefer slightly acidic soil
- And a host of other berries
- Certain squashes
- Sweet potatoes
These are just a few examples. If you’re wondering about the pH requirements for a specific plant, check its seed packet or the label on the pot. Still can’t seem to find the information? Ask your local nursery worker or perform a quick Google search.
When Not to Worry
Now that you've mastered how to test soil pH, don't let it become an obsession. You really don't need to worry too much about a pH level that's just outside the range of optimal for your plants. If you're planting a vegetable garden, chances are you'll have varieties that prefer different ‘ideal' pH levels. Don't obsess over a pH level that's 0.5 away from the optimal range. If you're not seeing any issues in your garden, you're also probably safe. It's a good idea to monitor your soil health over time, but if you're not encountering problems don't rush to try to fix the problem without first diagnosing it.