pH isn’t the problem; it’s the signal

Soil pH gets talked about a lot, but most of the time it’s treated as the problem, not what it actually is.

When a test comes back at pH 5.7, the instinct is simple: it’s too acidic, we need lime.

That only makes sense if you believe pH is the issue.

Spoiler: It isn’t.

pH is just a reading. A snapshot of what’s going on at that moment. It’s telling you something, not causing it. If you treat the number without understanding what’s driving it, you’ll spend money fixing something that just drifts straight back again.

It’s also worth keeping in mind that not all pH numbers are equal. Different labs use slightly different methods, so you can see variation between results. This makes direct comparisons difficult, especially if you’re switching labs or looking back at older data. The trend is usually more useful than the exact number.

Once you step back from the number itself, the next question becomes more useful: What is pH actually measuring?

It isn’t nutrients. It’s hydrogen.

More specifically, how much hydrogen is sitting in the soil and on the exchange sites. When hydrogen builds, pH drops. When hydrogen is reduced or pushed off, pH rises.

So instead of asking what’s my pH, it makes more sense to ask why is hydrogen building up in the first place.

That’s where things start to join up.

Hydrogen builds gradually through normal farming. Rainfall is a big part of it. As water moves through the soil, it carries nutrients like calcium, magnesium, potassium and sodium down the profile. As those leave, hydrogen takes their place.

At the same time, the water itself plays a part. H²O moving through the soil is constantly being split through biological and chemical activity. The oxygen is used or moves on, and the hydrogen is left behind. It’s not dramatic in one go, but over time it contributes to the overall shift.

Layer onto that nitrogen use, where ammonium turning into nitrate releases hydrogen, and crop removal steadily exporting cations, and you start to see the direction of travel. If the system isn’t holding or cycling nutrients well, hydrogen quietly fills the gaps.

So a pH of 5.7 isn’t really about acidity in isolation, it’s the end result of a system that’s losing more than it’s holding. The pH is just reporting that position.

This is where CEC starts to matter, because it defines how that system behaves.

A soil with a CEC of 9 is a small tank. It doesn’t hold much, and what it does hold moves quickly.

So when you see a soil base saturation of 60 percent calcium, it’s easy to assume there’s plenty there. In reality, it just means 60 percent of a small capacity is calcium. The total amount can still be relatively low.

More importantly, in a low CEC soil, that calcium is mobile. It can leach out and be replaced by hydrogen quite easily, so the balance is always shifting rather than sitting still.

This is also where it’s worth bringing in the Albrecht approach, because it often gets quoted in these conversations.

William Albrecht talked about aiming for around 60–65 percent calcium base saturation, and in the right context, that makes sense. On a heavier soil with a decent CEC, where the system has some stability, those ratios can help create a balanced structure and support good function.

But that only works if the soil can hold that balance.

On a low CEC soil, like a CEC 9, the system is moving all the time. The tank is small, and what’s in it doesn’t stay put. So hitting 60 percent calcium on a test doesn’t mean you’ve achieved balance; it just means that on that day, calcium was sitting at that level.

That’s the difference. Albrecht’s thinking assumes stability. In lighter soils, you’re dealing with movement. That’s where proper interpretation matters.

So it’s not that the target is wrong, it’s that it isn’t universal.

Once you look at it that way, lime starts to make more sense.

Lime doesn’t fix pH; it supplies calcium. That calcium competes with hydrogen for space on the exchange sites and pushes it off. The hydrogen then moves into solution and is leached away, and as that happens, the pH rises.

So rather than correcting acidity, you’re just shifting the balance between calcium and hydrogen.

That’s useful, but it also explains why it doesn’t always last.

If the underlying drivers are still there, rainfall, leaching, nitrogen use, weak cycling, then the system will simply move back again. Calcium leaves, hydrogen replaces it, and the pH drops back.

That’s the loop many end up in.

It also shows where over-liming can create problems. If you keep pushing calcium higher, you don’t just move pH; you start to affect how other nutrients behave.

Phosphate is the one that shows up most clearly. As calcium dominates, phosphate can become tied up in forms the plant struggles to access. On paper, it looks fine, in the field the crop says otherwise.

On lighter soils, you can also tighten things chemically quite quickly, simply because everything is more mobile and the balance shifts faster.

So when you see a soil already sitting around 60 percent calcium, the question isn’t simply, do we add more or not. It’s whether the system is capable of holding that level, or whether it’s just passing through.

At the other end of the scale, high pH soils bring a different version of the same problem.

Here, hydrogen is low, and the system is often dominated by calcium, sometimes with free lime or carbonates buffering it. That keeps pH high, but it doesn’t mean nutrients are more available.

In fact, it’s usually the opposite. As pH rises, elements like phosphate, manganese, zinc, iron and boron become less available. They’re still there, but the plant struggles to access them.

That’s why high pH soils can look well supplied on paper and still underperform in the field.

Trying to drag pH down across the whole field is difficult and rarely lasts, because the soil resists that change.

So again, it comes back to where you work.

The plant doesn’t operate across the whole field; it operates in a very small zone around the root. That’s where chemistry, biology and the plant itself all interact.

Roots release exudates, microbes respond, and together they can change the conditions in that immediate area. That can mean releasing nutrients locally, even when the wider soil is tying them up.

That’s where biology starts to give you another lever.

Certain microbes actively influence pH in that rhizosphere zone, not across the field, but exactly where the plant needs it. They produce compounds that help free up nutrients like phosphate and keep them moving.

Bacillus species are a good example of that. They sit within our Megabacter consortium and run through a number of products, including BetterGrass Liquid Xtra and Vitaplex V8. Their role isn’t to change field pH; it’s to influence that root zone, helping to mobilise nutrients and support more consistent uptake.

So you can have a field sitting at 5.7, or pushing into the high 7s, and still have a very different situation right at the root if, the system is working.

That’s why chasing a field pH number on its own doesn’t always translate into performance. You’re managing an average, while the plant is working in a micro environment.

So should you lime?

Sometimes yes, if you need a short-term correction to support the crop.

But if it’s the only tool being used, it tends to lead back to the same place.

The better question is what’s driving the system in that direction, what’s pushing hydrogen in or locking nutrients up, and how do you build something that holds and cycles rather than leaks or locks.

Once you start looking at it that way, pH stops being something to fix and becomes something you read as part of the wider picture.

That’s usually when things start to make more sense in the field.

Steve Holloway

Technical Manager.

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