The Money Mineral.

Part 2: Making potassium work, not just applying it.

Picking up from where we left off, if Part 1 was about understanding potassium, this is about making it work.

Because most of the time, the issue is not a lack of potassium. It is a lack of access, and that comes down to how the soil, the roots, and the biology are functioning together.

The important thing to understand is that the system to supply potassium already exists. Plants are not passive. They actively try to access it. They’re not sat there waiting for a spreader to turn up. Roots release organic acids; microbes do the same; mycorrhizal fungi physically access potassium between clay layers; and bacteria release compounds that help mobilise it.

So there is already a system designed to supply potassium. The question is whether it is working well enough.

This is where biology comes in, and it does not need overcomplicating. There are known groups of microbes that help release potassium. Bacillus species produce organic acids and enzymes that free potassium from soil particles. Pseudomonas support nutrient cycling and root interaction, improving access. Other organisms contribute through acidification and general nutrient turnover.

If that system is supported, particularly with a carbon source to feed it, activity increases, and more potassium becomes available.

That is not a theory; that is how nutrient cycling works.

What that means in practice is that if you improve biological activity, you improve potassium availability. That leads to a more consistent nutrient supply, better nitrogen efficiency, improved stress tolerance, and more reliable crop performance.

You are not replacing fertiliser. You are making it work better.

There is still a place for applied potassium. Sulphate forms tend to be more compatible than chloride. Organic sources like manures, composts, and residues all play a role in the potassium cycle. And foliar potassium has a very clear place when demand peaks.

The key is not relying on one approach, but combining them.

Timing is where most of the value is gained. Potassium demand is not constant. It spikes at key points in the season, particularly during grain fill, fruit set, and bulking. That is when potassium is doing the heavy lifting.

This is why foliar potassium later in the season often gives a strong response. By that point, demand can outstrip what the soil can supply, especially if conditions are dry or root function is limited. If you wait until the deficiency shows, you are already behind. By that point, the crop has already made a few decisions without you.

In practice, I tend to look at it in three phases.

Early season is about getting the system working, not firefighting it later . That means supporting biology, improving root function, and starting to unlock soil reserves.

Mid-season is about balance. This is where potassium supports nitrogen, helping keep growth controlled and efficient.

Later in the season is about demand. This is where foliar potassium comes into play, supporting grain fill, fruit sizing, or bulking when the plant needs it most.

This is where I see the value in combining approaches.

Rather than just supplying potassium, the focus is on supporting availability as well. Using something like Bio-K early on to help unlock soil reserves and drive activity around the root fits into that first phase. (Think microbes doing the work for you, rather than waiting for you to do it for them)

Then, bringing in foliar options like Vitaplex Foli K + Mg when demand lifts supports the plant directly when it needs it most. (Plant-available potassium, backed up by biology that keeps it moving)

Later on: Complex Foli-N + K helps keep the crop balanced, improving nitrogen use rather than simply increasing growth. (Think nitrogen assisted by K and biology)

It is not about replacing everything else. It is about making the whole programme work better.

The takeaway from this is simple.

Potassium is not just about how much you apply. It is about how well the system supplies it.

And in many cases, improving that system is where the biggest gains come from.

When potassium works properly, nitrogen works better, crops handle stress more effectively, and yields become more consistent.

And that is usually what we are all trying to achieve. Or at least that’s the plan at the start of the season.

If you’re looking at potassium differently this season, it’s worth stepping back and asking not just what you’re applying, but how available it actually is.

If you want to talk through how that fits on your farm, or how to build it into what you’re already doing without overcomplicating things, get in touch.

Email: info@soilfertilityservices.co.uk

Steve Holloway

Technical Manager.