Organic fertilizer
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224809960
2008-07-10T14:48:57Z
Inwind
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[[Image:Havekompostbunke.jpg|right|thumb|A compost bin]]
Naturally occurring '''[[organic matter|organic]] [[fertilizer]]s''' include [[manure]], [[slurry]], [[worm castings]], [[peat]], [[seaweed]], [[sewage]] , and [[guano]]. [[Green manure]] crops are also grown to add nutrients to the [[soil]]. Naturally occurring minerals such as mine rock phosphate, sulfate of potash and limestone are also considered Organic Fertilizers.
Manufactured organic fertilizers include [[compost]], [[bloodmeal]], [[bone meal]] and [[seaweed]] extracts. Other examples are natural enzyme digested proteins, [[fish meal]], and feather meal.
The decomposing [[crop residue]] from prior years is another source of fertility. Though not strictly considered "fertilizer", the distinction seems more a matter of words than reality.
Biomineral soil management, a total mineral and biological concept evolved by the South Australian Geomite company, utilizes the interaction of an 'insoluble' minerals base with specific micro-organisms to provide nutrition, structure and enhanced biology in soils. It proposes that plants feed by releasing root exudates of precise chemical composition to activate those soil fungi and bacteria which will solubilize elements required by the plant at that time. The exudate composition varies throughout the life of the plant, and any stresses imposed upon it result in further compensatory changes - in essence, the plant practises self medication. The term 'nature's smorgasbord' was coined to explain this process. It provides a possible explanation for the prevalence of pest and disease attack in crops fertilized by chemical means - applied soluble fertilizer masks the 'smorgasbord' process, eliminating correct nutrition.
Some ambiguity in the usage of the term 'organic' exists because some of synthetic fertilizers, such as [[urea]] and [[Urea-Formaldehyde|urea formaldehyde]], are fully organic in the sense of [[organic chemistry]]. In fact, it would be difficult to chemically distinguish between urea of biological origin and that produced synthetically. On the other hand, some fertilizer materials commonly approved for organic agriculture, such as powdered [[limestone]], mined [[rock phosphate]] and [[sodium nitrate|Chilean saltpeter]], are inorganic in the use of the term by chemistry.
Although the density of nutrients in organic material is comparatively modest, they have some advantages. Some or all organic fertilizer can be produced on-site, lowering transport costs. The majority of nitrogen supplying organic fertilizers contain insoluble nitrogen and act as a slow-release fertilizer.
Modern theories of organic agriculture admit the obvious success of [[Justus von Liebig|Leibig]]'s theory, but stress that there are serious limitations to the current methods of implementing it via chemical fertilization. They re-emphasize the role of humus and other organic components of soil, which are believed to play several important roles:
* Mobilizing existing soil nutrients, so that good growth is achieved with lower nutrient densities while wasting less
* Releasing nutrients at a slower, more consistent rate, helping to avoid a boom-and-bust pattern
* Helping to retain soil moisture, reducing the stress due to temporary moisture stress
* Improving the [[soil structure]]
Organics also have the advantage of avoiding certain problems associated with the regular heavy use of artificial fertilizers:
* the possibility of "burning" plants with the concentrated chemicals (i.e. an over supply of some nutrients)
* the progressive decrease of real or perceived "soil health", apparent in loss of structure, reduced ability to absorb precipitation, lightening of soil color, etc.
* the necessity of reapplying artificial fertilizers regularly (and perhaps in increasing quantities) to maintain fertility
* extensive runoff of soluble nitrogen and phosphorus, leading to eutrophication
* the cost (substantial and rising in recent years) and resulting lack of independence
Organic fertilizers can have disadvantages:
* As, typically, a dilute source of nutrients when compared to inorganic fertilizers, applying significant amounts of nutrients in a distant location from the source would incur increased costs for transportation
* The composition of organic fertilizers tends to be more complex and variable than a standardized inorganic product.
* Improperly-processed organic fertilizers may contain [[pathogen]]s from plant or animal matter that are harmful to humans or plants. However, proper [[composting]] should remove them.<ref name="ciwmb">[http://www.ciwmb.ca.gov/Publications/Organics/44200014.doc ciwmb.ca.gov - organics document]</ref>
In non-[[organic farming]] a compromise between the use of artificial and organic fertilizers is common, often using inorganic fertilizers supplemented with the application of organics that are readily available such as the return of crop residues or the application of manure.
[[Category:Organic fertilizers]]