Potassium (K) is an essential element required by plants; it comes after nitrogen and phosphorus. It is one of the primary elements needed for metabolism, physiological and life cycle of developments. Potassium availability to plants depends on its intensity in the soil solution, capacity of the available pools as well as the buffering capacity of the solid phase (Bilias and Barbayiannis, 2017).

The intensity refers to the potassium concentration in the soil solution, and the buffering capacity is a measure of the total amount of potassium in the solid phase of the soil which can be available in the soil solution while the replenishment rate in the soil represents the transfer rate of potassium from the solid phase of the soil to soil solution (Aminul et al., 2017). Potassium influences the population of microorganisms in the rhizosphere and plays key role in the nutrition and health of man and livestock. Potassium exists in four forms in the soil: the solution form, exchangeable form, non-exchangeable form or fixed form and mineral or structural form (Romheld and Neumann 2006).