K-soil stock

The K-soil stock figure shows the amount of K in the exchangeable fractions.  The figures are based on the amount on the cation exchange capacity (CEC) which is considered “exchangeable”. Whilst not as readily available as the K-plant available, the exchangeable part (K-soil stock) would be available to supply the soil solution as it becomes depleted over time. Because of this, there is easily the potential for there to be a large disparity in the two figures given how little K can be present in an exchangeable format any given time compared to what has the potential to become available.