Magnesium is very essential for Photosynthesis and maintaining healthy, green plant growth.  A lack of magnesium causes a general loss of green colour between the veins of leaves and becomes more evident in older leaves.  Yellowing of plant tissue rapidly increases to a stage where premature defoliation and death can result. 

Manutec Magnesium Sulfate is completely soluble in water and quickly corrects the deficiency in soils and pots.