In general when the fertigation is shifting from soil media to soilless  media which is almost  an inert one,(actually as hydroponics) the media has an almost zero nutrients retention capacity, a lack of  buffer capacity, the requirements for both water and nutrients are more intensive, therefore the nutrient solution has to supply all plant nutrients accurately based on the required amount per each physiological stage of the plant, and  unlike soil media any mistake might be resulted in crop damage.