Ferrous sulfate is an important source of divalent iron used across agriculture, animal nutrition, water treatment and various industrial processes. Commercial and naturally occurring ferrous sulfate exists in several hydration states. Among them, ferrous sulfate heptahydrate (FeSO₄·7H₂O) and ferrous sulfate monohydrate (FeSO₄·H₂O) are the most commercially relevant, while ferrous sulfate tetrahydrate (FeSO₄·4H₂O) is mainly encountered as an intermediate hydration phase. Alth

Iron (Fe) is an essential micronutrient for plant growth and plays a critical role in chlorophyll formation, respiratory metabolism, electron transport, and various oxidation-reduction enzyme systems. It is indispensable for maintaining normal crop growth and development. Although iron is abundant in the Earth’s crust, the proportion of plant-available iron in agricultural soils is extremely low, often accounting for less than 10% of total soil iron.