The present invention provides process for production of potassium ammonium sulfate compound fertilizer through the reaction of Epsom salt, obtained in course of chilling of concentrated sea bittern (32-33° Be), with potassium bitartrate, precipitated from such bittern, and ammonium hydroxide. While process integration was achieved through utilisation of Epsom salt; partial desulphatation of bittern, through crystallization of Epsom salt, resulted in about 17% improvement in K+ precipitation efficiency.