The chemical elements primarily found in fertilizers are nitrogen, phosphorus and potassium. The composition of a fertilizer is typically expressed in a 15:30:15 ratio, with 15 parts nitrogen, 30 parts phosphorus and 15 parts potassium, often displayed as an "N-P-K" label on most commercial bags of fertilizer.
Fertilizers are compounds that supplement plants with some of the essential nutrients required for proper growth and improved crop yield. These compounds need to be mixed in water before their mineral constituents can be utilized by plants. Fertilizers are classified into two major categories: organic fertilizers and processed fertilizers. Organic fertilizers consist of natural materials containing a lower concentration of nutrients compared to processed products. Another advantage of manufactured fertilizers is the quick release of nutrients for plant consumption.
Some examples of organic fertilizers include wood ash, grass clippings, manure and blood meal. Wood ash and grass clippings are rich in potassium content, while manure and blood meal contain varying levels of nitrogen. Based on the N-P-K label, some commonly processed fertilizers include urea (46-0-0), ammonium nitrate (33-0-0), ammonium sulfate (21-0-0), calcium nitrate (15-0-0), triple superphosphate (0-46-0), monoammonium sulfate (11-52-0), potassium chloride (0-0-60) and potassium magnesium sulfate (0-0-22). Other elements present in fertilizers include oxygen, sulfur, magnesium, chlorine, calcium and carbon.