Keyterra Magnesium sulfate is a water soluble fertilizer containing 16% MgO. White crystalline appearance. Magnesium, another mineral that a healthy plant needs, is the building block of chlorophyll molecules in the leaves. Anion-cation balance and pH values of the leaves of a plant which can get enough magnesium from the soil are realized at the desired level. The plant is capable of healthier photosynthesis and provides maximum benefit from sunlight and develops accordingly.