Definition

The K-soil stock figure represents the amount of potassium (K) present in the exchangeable fraction of the soil. This value is based on the soil’s cation exchange capacity (CEC), which indicates the portion of potassium considered “exchangeable.”

Why K-soil stock matters

Although exchangeable potassium is not as immediately available as plant-available potassium, it serves as a reserve. As the soil solution becomes depleted, this exchangeable potassium can gradually supply the plant.

However, the amount of potassium in an exchangeable form at any given time is relatively small compared to the potential total availability. This can lead to significant differences between the K-soil stock and K-plant available figures.

Key considerations

CEC-based measurement: Reflects the soil’s ability to hold and exchange potassium.

Reserve function: Exchangeable potassium replenishes the soil solution over time.

Disparity in values: Plant-available potassium may differ greatly from exchangeable potassium due to soil dynamics.

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