Understanding This One Number Can Change How You See Soil Health

We’ve all heard it. Soil health is everything. And we nod along because it sounds important.

But if we’re honest, most of us aren’t totally sure what it actually means. We know healthy soil grows better plants. We know it should be “rich” or “alive.” We know it’s the foundation of everything we grow. But what makes soil healthy?

And how do we know if we’re getting it right?

When I first started gardening, I didn’t even know you could test your soil. But once I started digging deeper (literally), I discovered there are three key things to look at when trying to understand your soil:

• Soil texture – What’s the makeup of your soil? (Clay, sand, silt?)
• Organic matter – How much life and decomposed plant material is in it?
• Soil pH – Is your soil acidic, alkaline, or somewhere in the middle?

In Gardenary Soil School, we go into all three in depth, but today, I want to talk about that last one: pH. Because this little number might seem technical, but it tells us a lot about how alive (and balanced) our soil actually is.

What Is Soil pH, Really?

Let’s break it down. pH stands for "potential of hydrogen," and it measures how acidic or alkaline something is. The scale runs from 0 to 14:

• 0-6.9 = acidic
• 7 = neutral
• 7.1-14 = alkaline

Soil pH influences which nutrients are available to your plants and how well your plants can absorb them. If the soil is too acidic (low soil pH), your plants might not be able to use the nitrogen, phosphorus, and potassium available in the soil. If your soil is too alkaline (high soil pH), then your plants won't have access to the iron, manganese, and phosphorus they need for healthy growth.

In other words: You could have rich soil filled with nutrients, but if the pH is off, your plants still might struggle.

Soil pH is not just about chemistry. It’s about balance—specifically, the balance of life underground. When your soil pH is within the ideal range, it usually means something deeper:

Microorganisms are active. Worms are at work. Organic matter is being broken down and nutrients are being shared.

That’s because pH is a reflection of how well decomposed material is mixing with the minerals (clay, sand, and silt) in your soil.

And that mixing? That movement? It’s caused by life—by organisms that are constantly eating, tunneling, and leaving behind castings that bring nutrients into the system.

What’s the Best pH for Vegetables?

Most plants thrive in a slightly acidic to neutral pH, since this is when most nutrients are readily available to them (and when more beneficial microorganisms are active). The ideal soil pH for your vegetable garden is between 6.2 and 6.8, though many vegetables will grow just fine between 6.0 and 7.5.

Here's a chart with different vegetables and their preferred pH range.

You can see that every veggie falls into this 6.0 to 7.5 range, except for potatoes, which like things a bit more on the acidic side. Let's look closer at some plants and their pH preferences.

Plants That Prefer Acidic Soil (pH 5.0 - 6.0)

• Blueberries
• Potatoes
• Strawberries

Plants That Prefer Alkaline Soil (pH 7.0 - 8.0)

• Lavender
• Asparagus
• Cabbage
• Kale
• Rosemary

Plants That Prefer Balanced or Slightly Acidic Soil (pH 6.0 - 7.0)

• Tomatoes
• Lettuce
• Peppers
• Carrots
• Beans
• Basil

How to Test Your Soil pH

Not sure what your soil pH is? You can use a simple soil test kit or, for a more comprehensive assessment, send a sample of your garden soil to a professional laboratory or nearby agricultural center. These analyses provide detailed information on not just your soil pH, but also nutrient levels (calcium, phosphorous, potassium, organic matter, etc.), organic matter content, and even potential contaminants. 

If you’re DIY’ing your soil tests, then grab a soil pH test kit or an inexpensive digital soil pH meter (which is often combined with a soil moisture meter). These products will reveal if your soil is too acidic or too alkaline. 

Here are the steps to use a soil pH test kit:

1. Collect a soil sample from your garden. Mix it with distilled water to create a slurry.
2. Insert the pH test probe or use the provided solution.
3. Compare the resulting color to the kit’s chart to determine your soil’s pH level.

Even without doing a soil pH test, just observing what grows (or struggles) in your garden can offer a few helpful clues. If you see a lot of yellowing leaves, stunted growth, or slow-growing plants, it's a good idea to check both your soil pH and nutrient levels.

I recommend testing your soil fertility and pH every 3 to 5 years, or after a disappointing season in the garden.

How to Fix Soil pH (Without Chemicals)

So what if your soil pH is off? There are various soil amendments you can add to your garden if your pH is outside the ideal range. Lime, for example, can be used to raise the pH, while sulfur and organic matter can lower it.

But don't just dump an entire bag of lime or sulfur into your garden and expect it to be a magic fix. You haven't solved the real problem, which is the lack of life in your soil.

The best way to balance soil pH is by feeding the life in the soil.

That means:

• Adding organic matter (like compost)
• Introducing earthworm castings (aka worm poop), which is full of beneficial microbes

Together, these two ingredients jumpstart microbial activity—and those microbes are what really balance your soil over time.

As worms move through your garden bed, digesting plant matter and leaving behind castings, they literally transform the chemistry and structure of your soil. They break down decayed matter, open up airways, and spread nutrients.

And in doing so, they bring your soil back into balance.

How to Maintain Soil pH

The best way to maintain your soil pH once you've built up your soil health is by skipping synthetic fertilizers like Miracle-Gro. Regular applications of these products lead to a buildup of salts and chemicals your plants can't use. Over time, this acidifies the soil. While this phenomenon occurs naturally due to factors like rainfall, ammonium-based nitrogen fertilizers accelerate it.

The consequences of soil acidification are significant for both plant health and soil fertility. As soil pH decreases, the availability of vital nutrients to plants diminishes, while the solubility of toxic elements such as aluminum increases. Elevated aluminum levels can inhibit root growth and function, leading to stunted plant development. Moreover, acidification adversely affects soil microbial activity, disrupting essential processes like nitrogen fixation and organic matter decomposition.

Stick to natural soil amendments like compost and worm castings.

Treat pH as a Symptom of Your Garden's Overall Health

If your soil pH is off, that's not a problem to be solved with a quick chemical fix. It’s a signal. It’s a reflection. It’s the soil saying, “I need more life down here.”

So the next time your pH is a little too low or too high, feed your soil. Add compost. Add worm castings. And let the living system underground restore the balance.

Want to learn how to test and build your soil the natural way?

You’ll find my recipe for the ideal soil blend in my book Kitchen Garden Revival, and you can go deeper inside my new course, Gardenary Soil School, where we cover soil texture, organic matter, and pH—step by step.

Because once you understand what’s happening beneath your feet, your garden will never be the same again.

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Sources

Penn State Extension

USDA Natural Resources Conservation Service