Get The Magnesium Boost Your Plants Need! This agricultural-grade magnesium sulfate heptahydrate is an exceptionally soluble and bioavailable source of magnesium and sulfur, promoting the health of both animals and plants. Magriculture contains essential plant nutrients like magnesium and sulfur, providing optimal solubility for creating clear solutions. It is compatible with most other soluble nutrients, except for concentrated calcium and phosphorus solutions.