The present invention provides a new liquid fertilizer comprised of potassium sulfite and potassium bisulfite, with neutral to slightly alkaline pH, relatively lower salt index and potentially lower phytotoxicity damage compared to other sources of potassium and sulfur products applied in equal amounts as a starter fertilizer. More specifically, the present invention further relates to methods for fertilizing using a composition of potassium sulfite and potassium bisulfite, particularly as a starter fertilizer, in-furrow fertilizer, side dress fertilizer, and for foliar, broadcast, soil injection and fertigation applications. The fertilizer composition is comprised primarily of potassium sulfite and potassium bisulfite (with the fertilizer grade of 0-0-23-8S).