The word manure means some types of organic matter used as fertilizer for land. The word is also sometime used as a polite word for an animal's faeces.
There are these classes of manures in soil management: green manures and animal manures. Compost is in a different category, as it has been described as a "bizarre artifical soil ecosystem".
Animal manure is often the droppings, dung, feces (faeces) or 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 faeces and urine.
Green manures are plants grown for the express purpose of plowing them under. Such plants, like clover, may also "fix" nitrogen in specialized nodes in the root structure, further contributing to the fertility of the soil by feeding the fungi in the soil.
Other types of plant matter used as manure or fertiliser include: the contents of the rumens of slaughtered ruminants; spent hops left over from making beer.
Manures contribute to the fertility of the soil by adding nitrogen that is trapped by bacteria which is part of the soil composition. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.
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 cattle is spread on fields using a spreader. Due to the lack of proteins in grasses, which herbivores eat, it has a much milder smell than that of carnivores - for example, elephant dung is practically odorless. Poultry droppings are harmful to plants when fresh but after a period of composting are valuable fertilizer.
The dried manure of animals has also been used as fuel throughout history. For example, dried manure of camels and other animals (usually known as dung) was an important fuel source in deserts where wood was scarce. It was used for many purposes, in cooking fires and to combat the cold desert nights.
Another use of manure is to make paper, this has been done with dung from elephants where it is a small industry in Africa and Asia, and also horses, llamas, and kangaroos. These animals are not ruminants and thus tend to pass plant fibres undigested in their dung.
Manure generates heat as it decomposes, and it is not unheard of for manure to spontaneously ignite should it be stored in a massive pile. Once such a large pile of manure is burning, it will foul the air over a very large area and require considerable effort to extinguish. Large feedlots must therefore take care to ensure that piles of fresh manure do not get excessively large. There is no serious risk of spontaneous combustion in smaller operations.
There is also the risk of flies landing on exposed faeces and then flying away and landing on food; and also of flies breeding in manure.
The word manure came from French "main-oeuvre" = "hand work" and originally meant the work involved in manuring land.