NPK compound fertilizer is a chemical fertilizer containing two or more nutrients. Through a specific granulation process, multiple nutrients are mixed or combined in a 15-15-15 or 18-18-18 ratio to provide plants with comprehensive and balanced nutrition. NPK compound fertilizer can simultaneously meet the needs of plants for multiple nutrients at different growth stages, helping to improve crop yield and quality, and enhance plant resistance to diseases and pests and environmental adaptability. Compared with single fertilizers, compound fertilizers have advantages such as high nutrient content, fewer by-products, and better physical properties. They are more convenient and efficient to use, reducing the frequency of fertilization and labor costs, and are widely used in agricultural production. Common compound fertilizers include nitrogen-phosphorus-potassium compound fertilizers, diammonium phosphate, and potassium nitrate.