Provided is an iron-ion supply material capable of efficiently supplying iron ions to a plant. An iron-ion supply material serving as an iron-ion supply source for supplying iron ions which contribute to the growth of a plant, the iron-ion supply material being characterized by comprising an iron powder having an iron content of 80 mass% or higher, and in that the particle diameter of at least 50 mass% of the iron powder overall is 100µm to 10mm, inclusive.
