Manure
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Animal manure is often a mixture of animal's feces and bedding straw, as in this example from a stable. |
Manure is
organic matter used as
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 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.
There are two 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 (variously called "droppings" or "dung" etc) 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.
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 fertiliser include: the contents of the
rumens of slaughtered
ruminants; spent
hops left over from making
beer.
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Dung cakes being prepared for fuel on the Ile de Brehat, Brittany, c. 1900 |
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.
The dried manure of animals has been used as
fuel throughout history. Dried manure of camels and other animals (usually known as dung) was, and in some places still is, an important fuel source in treeless regions such as deserts. On the Oregon Trail, pioneering families collected large quantities of "buffalo chips" in lieu of scarce firewood. It has been 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
ignite spontaneously 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 (feces) 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 feces and then flying away and landing on food and also of flies breeding in manure.
The
McGillicuddy Serious Party of
New Zealand campaigned on a policy of free dung.
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