15.15.15 COMPOSITE FERTILIZER – BASE FERTILIZER It is a compound fertilizer suitable for soils needing nitrogen, phosphorus and potassium. There are 15 kg nitrogen (N), 15 kg phosphorus (P2O5) and 15 kg potassium (K2O) in 100 kg of this fertilizer. After the soil analysis is done, it should be used in soils that need nitrogen, phosphorus and potassium.