Fertilizing sago palms involves providing essential nutrients through balanced fertilizers. Organic, inorganic, and controlled-release fertilizers can be used, with application methods varying based on factors like palm growth stage and nutrient demands. Key nutrients include nitrogen, phosphorus, potassium, and magnesium, and their deficiency can impact growth and health. Maintaining soil fertility by monitoring nutrient levels and implementing soil preparation practices like tillage, drainage, and pH adjustment ensures adequate nutrient availability for optimal palm growth and yield.