Non-essential element in plant is

Magnesium, potassium, and calcium are essential mineral elements. Magnesium is an essential constituent of chlorophyll. Potassium is important in the movement of guard cells and activity of enzymes. Calcium is required for the formation of the cell wall in plants. All three of these are essential macronutrients. Whereas barium does not play an important role and thus is the non-essential element in plants.