RHP certified substrates provide an optimal start of the culture. With the RHP quality mark you increase the securtiy that the substrate meets the right quality requirements for water and air content, pH and for example EC. It also offers more security that the substrate is pure and clean and that it can be used without risks for the culture. The RHP quality mark monitors the quality of growing media in the chain, from raw materials production until processing and delivery at the company of the user. Since 1963 RHP has been the European knowledge centre for growing media.