Fertilizer
Fertilizer Fertilizer, natural or synthetic chemical substance or mixture used to enrich soil so as to promote plant growth. Plants do not require complex chemical compounds analogous to the vitamins and amino acids required for human nutrition, because plants are able to synthesize whatever compounds they need. They do require more than a dozen different chemical elements and these elements must be present in such forms as to allow an adequate availability for plant use. Within this restriction, nitrogen, for example, can be supplied with equal effectiveness in the form of urea, nitrates, ammonium compounds, or pure ammonia. The term complete fertilizer often refers to any mixture containing all three important elements; such fertilizers are described by a set of three numbers. For example, 5-8-7 designates a fertilizer (usually in powder or granular form) containing 5 percent nitrogen, 8 percent phosphorus (calculated as phosphorus pentoxide), and 7 percent potassium (calculated as