manure, term used in the United States to refer to excreta of animals, with or without added bedding; also called barnyard manure. In other countries the term often refers to any material used to fertilize the soil. Properly managed, barnyard manure is a valuable fertilizer because of its nitrogen and phosphate content; its composition varies greatly depending upon the animals that produce it. Often it is reinforced with additions of superphosphate to make it a better balanced fertilizer and to reduce the loss of nitrogen as ammonia. Other organic manures are fish scrap, guano, seaweed, and compost. The claim by so-called organic farmers that crops fertilized by organic manures are more nutritious than those grown with artificial manures (i.e., chemical fertilizers) has not been substantiated. The term green manure is applied to crops grown for plowing under (see cover crop) and to manure that has not undergone decay.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.