Kieserite is a naturally occurring mineral that is chemically known as magnesium sulphate monohydrate. It is mined from ancient marine deposits and used in the agricultural industry as a fertiliser source for magnesium and sulphur. Kieserite is slowly water soluble and suitable for soil application to a wide range of horticultural and broad acre crops. Kieserite is not suitable for fertigation or foliar application.