Sul-Cal-Mag Did you know Sulfur, Calcium, and Magnesium are also Macronutrients? Sulfur is a structural component of amino acids and vitamins, and is essential in the manufacturing of chloroplasts. Calcium regulates transport of other nutrients and is particularly important in root development, with roles in cell division, cell elongation, and the detoxification of hydrogen ions. The outstanding role of magnesium in plant nutrition is as a constituent of the chlorophyll molecule. As a carrier, it is also involved in numerous enzyme reactions. Application: Mix 1/2 - 1 tsp per gallon of water. Apply every 1-2 weeks, depending on feeding schedule and plant cycle. See Meigs feeding schedule.