27 Things You Must Know About The pH Level of Soil (And How To Test Your Soil)


scientist testing pH level of soil with strip

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If you’re reading this article, you’re probably here for one of two reasons – first, you’re just a generally curious person who wants to learn more about the pH levels of soil. The rest of you (and probably the majority) likely have one or more plants that are struggling, and you think the soil’s pH could be the culprit.

Soil pH can sometimes confuse even a seasoned gardener – but it doesn’t have to. With the information in this article, you’ll be on your way to mastering the alkaline and acidic needs of your plants and veggies.

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What Does Soil pH Mean?

The pH level is a measurement of its alkalinity or acidity. The pH of soil is measured on a scale of 1 to 14, with 7 being the neutral value. The ideal pH for most plants is between 6 and 7 (slightly acidic to neutral). The reason soil pH is important has to do with nutrient availability. Specific pH values make it easier or more difficult for plants to access essential nutrients.

Interested in testing your soil’s pH? Start with a simple pH test.

To put it simply, even if you fertilize your soil, your plants will struggle to access the nutrients unless the pH is correct. Further, different plants require different amounts of nutrients from the soil to thrive. Proper pH levels can help your lovely flowers, grass, plants, and veggies have access to what they need most.

A plant that requires more iron, for instance, would likely need to be in soil with greater acidity.

Here’s a handy chart from Cornell University that shows how pH affects your availability of essential plant nutrients.

pH vs Availability of Nutrients chart

Fun Fact

In most circles, pH refers to “potential hydrogen.” When doing a pH test, you’re determining how many hydrogen ions are present in the soil. A higher number indicates more alkaline soils. A lower number suggests a more acidic soil.

Microorganic Activity

Not only does this does pH affect the availability of nutrients, but it can also attract or deter microorganisms. A more neutral pH in the soil is a good home for our microscopic friends that decompose organic materials. The amount of organic matter can create chemical changes, making nitrogen, phosphorous, and sulfur more readily available. These are building blocks for good plant growth.

What Is The pH Level Of Soil?

The pH of most soils is between 3.5 and 10. The natural pH of soils in rainier locations typically ranges from 5 to 7 (more acidic), while in drier areas, the pH ranges from 6.5 to 9 (more alkaline). The pH of the soil is influenced by thousands of years of erosion of native rocks, different types of decomposing organic matter, climate, weather, terrain, and physical surroundings.

In the United States, the Pacific Northwest, Eastern, and Southeastern areas of the country generally have moderately acidic soils. Conversely, most western states with less rainfall typically have more alkaline soils. While we can’t say that certain areas will always be more or less acidic/alkaline, a naturally rainy area is a good cue that the soil is moderately more acidic than other areas.

The water in rainier areas leaches basic ions like calcium, magnesium, and potassium and replaces them with acidic ions like hydrogen and aluminum.

How To Test The pH Level In Soil

Before changing your pH levels, you should always start with a soil test to see your starting point. You can purchase a testing kit online to determine your soil’s pH level – or you can go to a local extension office and pay a fee to have it done for you.

If you’re growing plants hydroponically, we highly recommend a pH meter. You simply stick it in the water to measure the pH levels.

yellow and blue pH test meter

Interested in growing hydroponically? Start with our Gardyn review and iharvest review.

How To Test Soil pH?

When testing your soil’s ph level, there are typically some basic steps you’ll need to take.

Purchase a Soil Test Or Find A Testing Laboratory

This can either be with a testing kit that you purchase online or through testing services provided by your local extension office.

Locate Sample Site

Separate soil samples should be collected from different areas of your yard, landscape, or garden. You should take from other areas of the soil to get an accurate sampling for your test. You must collect samples from several regions of your land with unique characteristics.

Prepare Tools

A soil probe or auger are perfect tools for collecting your soil sample. As a general rule, you shouldn’t use a spade, as it makes you less likely to take an accurate sample. You’ll need to put the samples in a bucket to mix, and then in a clean plastic container, such as a plastic grocery bag or ziplock bag. Some of the online options have a test lab sample box included.

Remove Debris

Before taking your sample, you want to remove any organic material on top of the soil, such as grass, mulch, leaves, or twigs, from the sample location.

Depth Of Sampling

Some sources say that you only need to go down 4 inches deep for a pH test, but most suggest you get a sampling of at least 6 inches for a garden.

Number Of Samples

For best results, you want several samples for each area. A garden would be a specific area, as would a yard or the bushes used for landscaping around your house. You only need 4-6 garden soil samples from different parts of the space for a basic outdoor garden.

Combining Samples

Once you have your samples for an area, combine them in a bucket, remove any rocks or other debris and let the soil dry. Then take one pint of soil and put it in your plastic bag or container.

Submit Your Samples

Whether through an at-home test or a local laboratory, take your soil samples for testing.

pH Strip Testing

If testing with a pH strip, take 4 oz of your sample and put them in a clean plastic cup (a 10 oz cup works well). Add 4 oz of distilled water to the cup, mix the sample thoroughly with a spoon, and let it sit for 30 minutes.

From here, dip your pH strip into the soil solution. The strip will change colors, indicating how acidic or alkaline your soil is.

When Should You Test Your Soil’s pH?

You typically want to take a pH reading every 2-3 years to keep track of any pH change. That said, you may test it more regularly if you have concerns about your soil conditions or pH. You should take your samples between late fall and early spring, and make sure you take your samples at the same time of the year.

This might sound like a lot, but soil testing is a necessary part of plant health. Knowing the pH of your soil can improve yields and the overall wellness of your garden or yard.

What Is The Best pH Level For Soil?

Most plants want a soil pH between 6.0 and 7.0. This is usually considered the optimum pH range for the best crop yields. A soil pH below 5.6 is considered too low for most crops, excluding a few acid-loving plants.

Plants That Prefer More Acidic Soil

Several plants prefer a low pH, which is defined as a pH below 7. Most prefer to be in the slightly acidic range, typically above 6 and under 7. Except for a few plants, like blueberries, huckleberries, and cranberries, most plants prefer soil with a pH above 5. Healthy acid soils are excellent for most vegetables in the garden.

list of acidic plants chart

Plants That Prefer More Neutral or Alkaline Soil

While there are certainly fewer plants that prefer a strictly alkaline pH, a wide variety can tolerate either a slightly acidic or slightly alkaline pH. Of the few that pretty strictly prefer neutral or alkaline soil, here are some fan favorites:

list of alkaline and neutral plants chart

How To Lower pH In Soil

If your soil has an alkaline level too high for your plants, there are a few options for making it more acidic. The most common way to acidify high pH soils is to add elemental sulfur or ammonium sulfate. That said, both iron sulfate and aluminum sulfate have been shown to lower your pH as well.

If you’re adding sulfur, the amount needed depends on the type of soil. You’ll typically need to add 18 to 23 pounds per 1,000 square feet for clay soils. Sandy soils require far less, between 9 and 14 pounds per 1,000 square feet.

Here’s an excellent and straightforward video on lowering pH for blueberry plants:

While not as common as sulfur, certain types of peat moss can also be used to acidify the soil. For example, peat moss made from hynum moss or reed-sedge peat typically has an acidic to slightly acidic pH.

Sphagnum peat moss is likely your best bet, though, with a pH between 3 and 4.5.

Gardening Myth: Pine Needles

A common myth is that pine trees and pine needles can make your soil more acidic. While pines do grow in areas with acidic soil, their presence doesn’t lower the pH of the ground.

See the full article about this myth from the University of New Hampshire Cooperative Extension team.

How To Raise pH In Soil

To make the soil in your garden or yard less acidic, you need to get calcium into the ground. The most common way of doing that is by adding a liming material from ground limestone rock (calcium carbonate). The finer the agricultural limestone particles, the faster it starts to work. 

With calcium carbonate, you typically have two choices for your soil amendment:

If your soil is high in magnesium already, consider using calcitic lime. Similarly, if your soil is low in magnesium, a dolomitic lime will introduce more magnesium, as well as raise the pH.

Different soils will require varying amounts of lime to modify the pH of the soil. When adjusting the pH value, consider the texture of the soil, the amount of organic matter in the soil, and the plants that will be grown. To achieve the same pH change, soils with low clay content require less lime than soils with high clay content. Soil type should always be considered when adjusting pH.

Because the limestone is not highly water-soluble, it is easy to work with. As lime or calcium carbonate dissolves in the soil, calcium (Ca) moves to the surface of soil particles, replacing the acidity. The carbonate (CO3) combines with the acidity to produce carbon dioxide (CO2) and water (H2O). As a result, the soil becomes less acidic (has a higher pH).

Here’s a great video on adding lime. It’s intended for large-scale farmers instead of gardeners or lawn enthusiasts, but the information is relevant to all situations:

Wood Ashes Option

Wood ashes are another option for raising the pH of soil. They’re high in potassium and calcium, with small phosphate levels, boron, and other elements.

Wood ashes aren’t as effective as limestone, but they can raise a soil’s pH value over time, especially if it is sandy.

Wood Ashes Option

Wood ashes are another option for raising the pH of soil. They’re high in potassium and calcium, with small phosphate levels, boron, and other elements.

Wood ashes aren’t as effective as limestone, but they can raise a soil’s pH value over time, especially if it is sandy.

During the winter, spread a thin coating and assimilate it into the soil in the spring. Check the pH of your soil every year, especially if you utilize wood ashes. Avoid using huge volumes of wood ashes since they might generate overly high pH levels and nutrient deficits. Coal ashes have little lime value and, depending on the source, may even be acidic.

Baking Soda Option

Baking soda may be the way to go if you’re looking for an organic solution to raise soil pH. Baking soda is mild on the soil and plants in the growing stage. It also provides several advantages, including the ability to keep your soil and plants healthy by avoiding fungus growth. In addition, it can prevent pests like bugs out of your garden in some situations.

Here’s an infographic from Bumper Crop Times about the way to use baking soda to raise pH:

infographics on how to raise ph in soil with baking soda

What Happens When The pH Level Is Too High?

If your soil pH is too high for your plants, it can cause them to have dangerous quantities of certain nutrients and not enough of others. For example, in large doses, molybdenum, which is generally a plant nutrient, turns harmful to plants. In a high pH environment, molybdenum levels in the soil rise. Similarly, a high pH will make it more difficult for your plants to access other nutrients, such as iron.

Why Does The pH In Soil Change?

It would be great if you could perfect your soil’s pH a single time and be done with it. But, unfortunately, it doesn’t always work that way. The pH of the soil can alter for a variety of reasons. One of the main ways is through calcium leaching during heavy rainfall.

Calcium naturally leaches away as heavy rainwater travels through the soil. As a result, soil pH drops as calcium is lost, and soils become acidic over time.

Calcium does not leach out as much in locations with little rainfall, and lawns can become overly alkaline.

On top of rainfall, regular lawn care can decrease your soil’s pH over time. Even adding fertilizers high in nitrogen, watering your plants/grass, or increasing the organic material in your yard can slowly cause drops in your pH.

How Do You Balance pH In Soil?

Aluminum sulfate and sulfur are two popular soil amendments used to lower pH in the soil. Liming material made from ground limestone rock can increase your pH. These are available at local garden centers or online. 

Conclusion

When trying to diagnose your garden or lawn problems, a soil test kit is always a great start. Not only will it tell you if the necessary nutrients are present, but it will also tell you if your pH is giving your plants access to those nutrients. Knowing your pH – and adjusting it as needed – is an essential element of a healthy garden. It’s one of the best ways – if not the best way – to understand your plants and give them what they need.

Start with a pH test every couple of years to measure your soil’s acidity and alkalinity. From there, you can add either sulfur or lime to adjust your soil as needed.

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Patrick Chism

Patrick likes to pretend that urban gardening is just a hobby, but he’s actually prepping for the apocalypse. He’s a practical grower, specializing in hydroponics systems and grow lights. His dream is to one day feed his family with just the food he grows in his Chicago-based condo.

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