ABSTRACT Oil palm (Elaeis guineensis Jacq.) is a plantation crop that is a leading commodity in Indonesia, especially in Riau Province. Riau Province has sandy soils (Dystrudepts) that are often used for oil palm plantations. This soil has a very fast percolation and high leaching risk, so it requires the selection of slow-release fertilizers namely Polyhalite and combined with KCl. The purpos…