manure salts: see potassium chloride.

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.

Organic material that is used to fertilize land, usually consisting of the feces and urine of domestic livestock, with or without litter such as straw, hay, or bedding. Some countries also use human excrement (“night soil”). Though livestock manure is less rich in nitrogen, phosphorus, and potash than synthetic fertilizers and therefore must be applied in much greater quantities, it is rich in organic matter, or humus, and thus improves the capacity of the soil to absorb and store water, thereby preventing erosion. Because manure must be carefully stored and spread in order to derive the most benefit, some farmers decline to expend the necessary time and effort. Manufactured chemical fertilizers, though more concentrated and efficient, are also more costly and more likely to cause excess runoff and pollution. Seealso green manure.

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