Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen that is trapped by bacteria in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.

The term "manure" was used for inorganic fertilizers in the past, but this usage is now very rare.

Etymology

The word manure came from Middle English "manuren" meaning "to cultivate land," and initially from French "main-oeuvre" = "hand work" alluding to the work which involved manuring land.

Types

There are two main classes of manures in soil management: green manures and animal manures. Compost is distinguished from manure in that it is the decomposed remnants of organic materials (which may, nevertheless, include manure).

Most animal manure is feces — excrement of plant-eating mammals (herbivores) and poultry — or plant material (often straw) which has been used as bedding for animals and thus is heavily contaminated with their feces and urine. Manure from different animals may have different qualities and require different dosage, common forms of animal manure includes horse manure, cow manure, pig manure, sheep manure, chicken and turkey manures, rabbit manure, seabird and bat Guano.

Green manures are crops grown for the express purpose of plowing them under. In so doing, fertility is increased through the nutrients and organic matter that are returned to the soil. Leguminous crops, such as clover, also "fix" nitrogen through rhizobia bacteria in specialized nodes in the root structure.

Other types of plant matter used as manure or fertilizer include: the contents of the rumens of slaughtered ruminants; spent hops left over from making beer.

Uses of manure

Manure has been used for centuries as a fertilizer for farming, as it is rich in nitrogen and other nutrients which facilitate the growth of plants. Liquid manure from pig/hog operations is usually knifed (injected) directly into the soil to reduce the unpleasant odors. Manure from hogs and cattle is spread on fields using a Manure spreader. Due to the relatively lower level of proteins in grasses, which herbivores eat, cattle manure has a milder smell than the dung of carnivores — for example, elephant dung is practically odorless. However, due to the quantity of manure applied to fields, odor can be a problem in some agricultural regions. Poultry droppings are harmful to plants when fresh but after a period of composting are valuable fertilizers.