Potassium deficiency is most commonly associated with sandy soils. The optimal level will vary with crop, yield, and soil type. It is an immobile nutrient like phosphorus and levels change slowly. Calcium deficiency is rare in most calcareous soil where soil pH is adequate. The need for calcium as a nutrient is directly related with soil pH. The level in the soil can exceed 4,000 ppm without evidence of excess in the plant.
Magnesium deficiencies are more common than calcium.
Some of the total soil magnesium is found in non-exchangeable form. Thus, the exchangeable magnesium level changes slowly with time because of equilibrium with minerals. Where elevated levels are found, soil amendments such as gypsum or elemental sulfur are applied. Sodium is not considered and essential plant nutrient and consequently a VL and L value or range is desired. Soil amendments such as gypsum and elemental sulfur can be used to reduce the amount of exchangeable sodium.