NPK is the abbreviation of nitrogen (N), phosphorus (P), potassium (K), representing a compound fertilizer, also known as a ternary compound fertilizer. NPK compound fertilizer is a compound fertilizer made of nitrogen, phosphorus and potassium by chemical methods. It provides the three essential elements necessary for plant growth, namely nitrogen, phosphorus and potassium, which play a vital role in plant growth and development. On fertilizer bags, we usually see the NPK letters and corresponding numbers that indicate the percentage content of each element. For example, a “10-20-10″ NPK fertilizer means that the fertilizer contains 10% nitrogen, 20% phosphorus (measured in P2O5) and 10% potassium (measured in K2O). This labeling method helps farmers or gardeners choose the right fertilizer for their plants’ needs.