What are organic fertilizers?

The term "organic" can mean several things, but in the case of fertilizers it refers to sources of plant nutrients that are naturally occurring such as:

• End products of plants and animals such as compost, manure, bone meal, and green manure crops. (These will be covered shortly.)

• Minerals like rock phosphate that are mined from the earth and used without undergoing any chemical treatment.

Unlike the organics, chemical fertilizers are derived from a chemical manufacturing or synthesizing process. Some examples are urea (made by combining carbon dioxide and ammonia), single superphosphate (made from rock phosphate and sulfuric acid). The distinction between chemical and organic fertilizers can be confusing, because the term "organic" technically refers to any compound containing carbon. Urea contains carbon, yet is considered a chemical fertilizer; likewise, rock phosphate has no carbon, yet is considered an organic fertilizer. That's because the moat popular meaning of "organic" is "naturally occuring".