Manure is organic matter that comes from farmyard animal waste as well as from crop cover. Manure from cows, pigs, horses, chickens, rabbits, etc. is broken down into organic matter and used as organic fertilizer. “Green” manure is derived from planting a cover crop, such as clover, to be plowed directly back into the soil. Bacteria traps nitrogen and other nutrients in the soil which is released by adding the manure, which also aids in the fertility of the soil.
There are three types of manures used in the management of soil.
Manure coming from farmyard animals contains plant material, such as hay or straw. The use of the manure will differ depending on the animal it comes from as they each have their own qualities. For instance, sheep manure is high in nitrogen and potash while chicken manure is very high in nitrogen and protein.
Containment of the manure depends on the scope of the farming. A few head of cattle, a few chickens or rabbits will lend the farmer to use manure pits, or piles that allow the manure to break down before using. Farming on a larger scale will lend itself to creating farm slurry — liquid manure made in cement pits, without bedding material, but with water and then spread topically onto soil.
As manure breaks down it generates heat making it possible to ignite; therefore, manure piles should not be too large. Burning manure is hard to extinguish and will fill the air with acrid smoke. Manure piles should also be kept a distance from water and food supply as there is a risk of attracting insects that will carry feces making the food and water unsuitable for human consumption.
Crop cover such as clover, wheat, rye, or legumes is used to replenish the soil with nutrients between cash crop plantings. Cover crops also provide erosion protection from wind and rain. The type of cover crop used depends on the type of crop that will follow. For instance, legumes provide free nitrogen but will not combat weeds. (See cover crops for more info.)
Compost is generally the decomposition of plant material but often times includes animal dung along with bedding.
Uses of manure
Manures with strong odors, usually unpleasant, is tilled back into the soil in order to reduce the odor, especially manures derived from human sewage or pig slurry. Poultry manure should be used only after it has sat for a period of time (allowing for composting) as it can be harmful to plants when fresh.
Manure can be bought commercially, by the bag, making soil amendment on a small scale doable.
Organic vs. non-organic manure
Foods such as corn, lettuce, and potatoes accumulate antibiotics from soils that have been spread with animal manure that contains these drugs, according to a study conducted by the University of Minnesota in 2007.
Organic foods may be much more or much less likely to contain antibiotics, depending on their sources and treatment of manure.
According to the Soil Association Standard 4.7.38, as cited by Wikipedia, “most organic arable farmers either have their own supply of manure (which would, therefore, not normally contain drug residues) or else rely on green manure crops for the extra fertility (if any nonorganic manure is used by organic farmers, then it usually has to be rotted or composted to degrade any residues of drugs and eliminate any pathogenic bacteria).”
Having their own supply of manure will ensure that there are no drug residues being placed in the soil. Properly decomposed or rotted manure will reduce the presence of drug residue along with any pathogenic bacteria.