A recent BaselineRx consultation uncovered something that shouldn’t have happened, at least according to traditional soil testing.

One area of a field tested at 206 ppm potassium. The hilltops on the same field tested between 124 -140 ppm. Most recommendations would treat those areas very differently.

But when we measured what was actually available to the crop, both areas came back with the exact same plant-available potassium level.

So what happened?

Grant breaks down the surprising role magnesium played, why ppm doesn’t tell the whole story, and how growers are using better soil data to make more profitable fertility decisions.

The Numbers Didn’t Add Up

One area of the farm tested at 206 ppm potassium. According to traditional recommendations, that field would be considered adequately supplied with potassium. Most agronomists would look at that number and move on. When we looked at the plant-available potassium through BaselineRx, the number came back at 68. (Our target is generally 70+.)

Then things got interesting.

On the hilltops, potassium levels ranged from 124 to 140 ppm. Conventional thinking would suggest those areas should be significantly more deficient at supplying K to the plants than the low ground. But when we measured plant-available potassium with BaselineRx, the hilltops also came back at 68.

Exactly the same.

How Is That Possible?

If one area has 206 ppm potassium and another has 124 ppm, how can both have the same amount of potassium available to the crop?

The answer is magnesium.

The hilltops were significantly lower in Mg, allowing K to release more freely from the soil. Meanwhile, the hill bottoms contained much higher Mg levels; even though there was more total potassium present, it was held more tightly and was less available to the plant.

In other words, the crop doesn’t care how much potassium is sitting in the soil bank. It cares how much it can actually access, and BaselineRx can actually measure that.

Why This Matters More Than Ever

Potash prices remain elevated. Phosphate is even higher. When nutrients cost hundreds of dollars per ton, making fertility decisions based solely on ppm levels can become an expensive mistake.

Input costs have changed. The value of precision has changed. The way we make fertility decisions should change too.

The Goal Isn’t More Fertilizer

The goal isn’t to sell more fertilizer. The goal is to understand what your soil is already capable of supplying.

When we know what nutrients are truly available, we can:

• Reduce unnecessary fertilizer applications
• Improve cash flow
• Increase nutrient efficiency
• Protect yield potential

Most importantly, we can make decisions based on what the crop can actually use, not just what a lab report says is sitting in the soil.

The Bottom Line

This grower’s field had areas testing 206 ppm potassium and areas testing 124 ppm potassium. Traditional soil tests suggested they were very different.

Plant-available nutrient testing through BaselineRx showed they were essentially the same.

That’s why we’re seeing more growers adopt BaselineRx and rethink how fertility decisions are made. We’re already scheduling acres for Fall 2026. If you’re tired of guessing and want to know what your soil can actually supply, let’s take a look.