Fertilizer - Wikipedia, The Free Encyclopedia

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Tennessee Valley Authority: "Results

of Fertilizer" demonstration 1942

A large, modern fertilizer spreader

A Lite-Trac Agri-Spread lime andfertilizer spreader at an agricultural

show

FertilizerFrom Wikipedia, the free encyclopedia

Fertilizer(orfertiliser) is any organic or inorganic material of natural or

synthetic origin (other than liming materials) that is added to a soil to

supply one or more plant nutrients essential to the growth of plants.[1]

Conservative estimates report 30 to 50% of crop yields are attributed to

natural or synthetic commercial fertilizer.[2]European fertilizer market is

expected to grow to 15.3 billion by 2018.[3]

Mined inorganic fertilizers have been used for many centuries, whereas

chemically synthesized inorganic fertilizers were only widely developed

during the industrial revolution. Increased understanding and use of

fertilizers were important parts of the pre-industrial British Agricultural

Revolution and the industrial Green Revolution of the 20th century.

Inorganic fertilizer use has also significantly supported global population

growth it has been estimated that almost half the people on the Earthare currently fed as a result of synthetic nitrogen fertilizer use.[4]

Mined inorganic fertilizers typically provide, in varying proportions:

six macronutrients: nitrogen (N), phosphorus (P), potassium (K),calcium (Ca), magnesium (Mg), and sulfur (S);

eight micronutrients: boron (B), chlorine (Cl), copper (Cu), iron(Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel

(Ni) (1987).

The macronutrients are consumed in larger quantities and are present in

plant tissue in quantities from 0.15% to 6.0% on a dry matter (0%

moisture) basis (DM). Micronutrients are consumed in smaller quantities

and are present in plant tissue on the order of parts per million (ppm),

ranging from 0.15 to 400 ppm DM, or less than 0.04% DM.[5][6]

Only three other macronutrients are required by all plants: carbon,

hydrogen, and oxygen. These nutrients are supplied by water (through

rainfall or irrigation) and carbon dioxide in the atmosphere.

Contents

1 Labeling of chemical fertilizer2 History

3 Forms4 Inorganic commercial fertilizer

4.1 Controlled-release types4.2 Application

4.3 Problems with inorganic fertilizer

izer - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/

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4.3.1 Water pollution

4.3.2 Contamination with impurities

4.3.3 Fertilizer dependency4.3.4 Soil acidification

4.3.5 Trace mineral depletion4.3.6 Overfertilization

4.3.7 High energy consumption

4.3.8 Contribution to climate change4.3.9 Impacts on mycorrhizas

4.3.10 Lack of long-term sustainability5 Organic fertilizer

5.1 Benefits of organic fertilizer5.2 Disadvantages of organic fertilizers

5.3 Comparison with inorganic fertilizer5.3.1 Examples of organic fertilizer

5.4 Organic fertilizer sources

5.4.1 Animal5.4.2 Plant

5.4.3 Mineral6 Negative environmental effects

6.1 Water quality6.1.1 Eutrophication

6.1.2 Blue baby syndrome

6.2 Soil6.2.1 Soil acidification

6.2.2 Persistent organic pollutants6.2.3 Heavy metal accumulation

6.2.4 Radioactive element accumulation6.3 Atmosphere

6.4 Other problems6.4.1 Increased pest fitness

7 See also

8 References9 External links

Labeling of chemical fertilizer

Main article: Labeling of fertilizer

In the US and Canada, the labeling scheme presents three numbers separated by dashes (e.g. 10-10-10 or

16-4-8).[7][8]

The first number represents the percentage of Nitrogen in the product; the second number,

Phosphorus; and the third, Potassium. The generalized form is N-P-K. A 50-pound bag of fertilizer labeled

16-4-8 contains 8 pounds of nitrogen (16% of the 50 pounds), 2 pounds of phosphorus (4% of 50 pounds), and 4

pounds of potassium (8% of 50 pounds). Australian convention adds a fourth number for Sulphur.[9]

History

Main article: History of fertilizer


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Founded in 1812, Mirat, producer ofmanures and fertilizers, is claimed to

be the oldest industrial business in

Salamanca (Spain).

Management of soil fertility has been the pre-occupation of farmers for

thousands of years. The start of the modern science of plant nutrition

dates to the 19th century and the work of German chemist Justus von

Liebig, among others.

John Bennet Lawes, an English entrepreneur, began to experiment on the

effects of various manures on plants growing in pots in 1837, and a year

or two later the experiments were extended to crops in the field. One

immediate consequence was that in 1842 he patented a manure formedby treating phosphates with sulphuric acid, and thus was the first to

create the artificial manure industry. In the succeeding year he enlisted

the services of Joseph Henry Gilbert, with whom he carried on for more

than half a century on experiments in raising crops at the Rothamsted

Experimental Station.[10]

The BirkelandEyde process was one of the competing industrial processes in the beginning of nitrogen based

fertilizer production. It was developed by Norwegian industrialist and scientist Kristian Birkeland along with his

business partner Sam Eyde in 1903, based on a method used by Henry Cavendish in 1784.[11]

This process was

used to fix atmospheric nitrogen (N2) into nitric acid (HNO3), one of several chemical processes generallyreferred to as nitrogen fixation. The resultant nitric acid was then used as a source of nitrate (NO3

-) in the

reaction

HNO3 H++ NO3

-

which may take place in the presence of water or another proton acceptor. Nitrate is an ion which plants can

absorb.

A factory based on the process was built in Rjukan and Notodden in Norway, combined with the building of

large hydroelectric power facilities.[12]

The Birkeland-Eyde process is relatively inefficient in terms of energy consumption. Therefore, in the 1910s and

1920s, it was gradually replaced in Norway by a combination of the Haber process and the Ostwald process. The

Haber process produces ammonia (NH3) from methane (CH4) gas and molecular nitrogen (N2). The ammonia

from the Haber process is then converted into nitric acid (HNO3) in the Ostwald process.[13]

Forms

Fertilizers come in various forms. The most typical form is solid fertilizer in granulated or powdered forms. The

next most common form is liquid fertilizer; some advantages of liquid fertilizer are its immediate effect and wide

coverage.

There are also slow-release fertilizers (various forms including fertilizer spikes, tabs, etc.) which reduce the

problem of "burning" the plants due to excess nitrogen. Polymer coating of fertilizer ingredients gives tablets and

spikes a true time-release (http://www.agritab.com) or staged nutrient release (SNR) of fertilizer nutrients.

More recently, organic fertilizer is on the rise as people are resorting to environmental friendly (or green)

products. Although organic fertilizers usually contain a lower concentration of nutrients, this lower concentration

avoids complication of nitrogen burn harming the plants. In addition, organic fertilizers such as compost and

worm castings break down slowly into complex organic structures (humus) which build the soils structure and


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moisture- and nutrient-retaining capabilities.[citation needed]

Inorganic commercial fertilizer

Fertilizers are broadly divided into organic fertilizers(composed of organic plant or animal matter), or

inorganic or commercial fertilizers. Plants can only absorb their required nutrients if they are present in easily

dissolved chemical compounds. Both organic and inorganic fertilizers provide the same needed chemical

compounds. Organic fertilizers provided other macro and micro plant nutrients and are released as the organicmatter decaysthis may take months or years. Organic fertilizers nearly always have much lower concentrations

of plant nutrients and have the usual problems of economical collection, treatment, transportation and

distribution.

Inorganic fertilizers nearly always are readily dissolved and unless added have few other macro and micro plant

nutrients nor added any bulk to the soil. Nearly all nitrogen that plants use is in the form of NH3or NO3compounds. The usable phosphorus compounds are usually in the form of phosphoric acid (H3PO4) and the

potassium (K) is typically in the form of potassium chloride (KCl). In organic fertilizers nitrogen, phosphorus and

potassium compounds are released from the complex organic compounds as the animal or plant matter decays.

In commercial fertilizers the same required compounds are available in easily dissolved compounds that require

no decaythey can be used almost immediately after water is applied. Inorganic fertilizers are usually muchmore concentrated with up to 64% (18-46-0) of their weight being a given plant nutrient, compared to organic

fertilizers that only provide 0.4% or less of their weight as a given plant nutrient.[14]

Nitrogen fertilizers are often made using the Haber-Bosch process (invented about 1915) which uses natural gas

(CH4+)for the hydrogen and nitrogen gas (N2) from the air at an elevated temperature and pressure in the

presence of a catalyst to form ammonia (NH3) as the end product. This ammonia is used as a feedstock for other

nitrogen fertilizers, such as anhydrous ammonium nitrate (NH4NO3) and urea (CO(NH2)2). These concentrated

products may be diluted with water to form a concentrated liquid fertilizer (e.g. UAN). Deposits of sodium

nitrate (NaNO3) (saltpeter) are also found the Atacama desert in Chile and was one of the original (1830)

nitrogen rich inorganic fertilizers used. It is still mined for fertilizer.[citation needed]

In the Nitrophosphate process or Odda Process (invented in 1927), phosphate rock with up to a 20% phosphorus

(P) content is dissolved with nitric acid (HNO3) to produce a mixture of phosphoric acid (H3PO4) and calcium

nitrate (Ca(NO3)2). This can be combined with a potassium fertilizer to produce a compound fertilizerwith all

three N:P:K: plant nutrients in easily dissolved form.

Phosphate rock can also be processed into water-soluble phosphate (P2O5) with the addition of sulfuric acid

(H2SO4) to make the phosphoric acid in phosphate fertilizers. Phosphate can also be reduced in an electric

furnace to make high purity phosphorus; however, this is more expensive than the acid process.

Potash can be used to make potassium (K) fertilizers. All commercial potash deposits come originally frommarine deposits and are often buried deep in the earth. Potash ores are typically rich in potassium chloride (KCl)

and sodium chloride (NaCl) and are obtained by conventional shaft mining with the extracted ore ground into a

powder. For deep potash deposits hot water is injected into the potash which is dissolved and then pumped to the

surface where it is concentrated by solar induced evaporation. Amine reagents are then added to either the

mined or evaporated solutions. The amine coats the KCl but not NaCl. Air bubbles cling to the amine + KCl and

float it to the surface while the NaCl and clay sink to the bottom. The surface is skimmed for the amine + KCl

which is then dried and packaged for use as a K rich fertilizerKCl dissolves readily in water and is available

quickly for plant nutrition.[15]


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Compound fertilizers often combine N, P and K fertilizers into easily dissolved pellets. The N:P:K ratios quoted

on fertilizers give the weight percent of the fertilizer in nitrogen (N), phosphate (P2O5) and potash (K2O

equivalent)

The use of commercial inorganic fertilizers has increased steadily in the last 50 years, rising almost 20-fold to the

current rate of 100 million tonnes of nitrogen per year.[16]Without commercial fertilizers it is estimated that

about one-third of the food produced now could not be produced.[17]The use of phosphate fertilizers has also

increased from 9 million tonnes per year in 1960 to 40 million tonnes per year in 2000. A maize crop yielding

69 tonnes of grain per hectare requires 3150 kg of phosphate fertilizer to be applied, soybean requires

2025 kg per hectare.[18] Yara International is the worlds largest producer of nitrogen based fertilizers.[19]

Controlled-release types

Urea and formaldehyde, reacted together to produce sparingly soluble polymers of various molecular weights, is

one of the oldest controlled-nitrogen-release technologies, having been first produced in 1936 and

commercialized in 1955.[20]

The early product had 60 percent of the total nitrogen cold-water-insoluble, and the

unreacted (quick release) less than 15%. Methylene ureas were commercialized in the 1960s and 1970s, having

25 and 60% of the nitrogen cold-water-insoluble, and unreacted urea nitrogen in the range of 15 to 30%.

Isobutylidene diurea, unlike the methylurea polymers, is a single crystalline solid of relatively uniform properties,with about 90% of the nitrogen water-insoluble.

In the 1960s, the National Fertilizer Development Center began developing Sulfur-coated urea; sulfur was used

as the principle coating material because of its low cost and its value as a secondary nutrient. [20]Usually there is

another wax or polymer which seals the sulfur; the slow release properties depend on the degradation of the

secondary sealant by soil microbes as well as mechanical imperfections (cracks, etc.) in the sulfur. They typically

provide 6 to 16 weeks of delayed release in turf applications. When a hard polymer is used as the secondary

coating, the properties are a cross between diffusion-controlled particles and traditional sulfur-coated.

Other coated products use thermoplastics (and sometimes ethylene-vinyl acetate and surfactants, etc.) to

produce diffusion-controlled release of urea or soluble inorganic fertilizers. "Reactive Layer Coating" can

produce thinner, hence cheaper, membrane coatings by applying reactive monomers simultaneously to the

soluble particles. "Multicote" is a process applying layers of low-cost fatty acid salts with a paraffin topcoat.

Besides being more efficient in the utilization of the applied nutrients, slow-release technologies also reduce the

impact on the environment and the contamination of the subsurface water.[20]

Application

Synthetic fertilizers are commonly used for growing all crops, with application rates depending on the soil

fertility, usually as measured by a soil test and according to the particular crop. Legumes, for example, fixnitrogen from the atmosphere and generally do not require nitrogen fertilizer.

Studies have shown that application of nitrogen fertilizer on off-season cover crops can increase the biomass

(and subsequent green manure value) of these crops, while having a beneficial effect on soil nitrogen levels for

the main crop planted during the summer season.[22]

Nutrients in soil can be thrown out of balance with high concentrations of fertilizers. The interconnectedness and

complexity of this soil food web means any appraisal of soil function must necessarily take into account

interactions with the living communities that exist within the soil. Stability of the system is reduced by the use of


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Country

Total N use

(Mt pa)

Amt. used for feed/pasture

(Mt pa)

China 18.7 3.0

U.S. 9.1 4.7

France 2.5 1.3

Germany 2.0 1.2

Brazil 1.7 0.7

Canada 1.6 0.9

Turkey 1.5 0.3

UK 1.3 0.9

Mexico 1.3 0.3

Spain 1.2 0.5Argentina 0.4 0.1

Top users of nitrogen-based fertilizer[21]nitrogen-containing fertilizers, which cause soil

acidification.

Applying excessive amounts of fertilizer has negative

environmental effects, and wastes the growers time and

money. To avoid over-application, the nutrient status of

crops should be assessed. Nutrient deficiency can be

detected by visually assessing the physical symptoms of

the crop. Nitrogen deficiency, for example has adistinctive presentation in some species. However,

quantitative tests are more reliable for detecting nutrient

deficiency before it has significantly affected the crop.

Both soil tests and Plant Tissue Tests are used in

agriculture to fine-tune nutrient management to the

crops needs.

Problems with inorganic fertilizer

See also Negative environmental effects

Water pollution

The nutrients, especially nitrates, in fertilizers can cause problems for natural habitats and for human health if

they are washed off soil into watercourses or leached through soil into groundwater.[23]In Europe these

problems are being addressed by the European Unions Nitrates Directive.[24]Within Britain farmers are

encouraged to manage their land more sustainably in catchment-sensitive farming.[25]

In the US, excess

fertilizer runoff is classified as non-point source pollutants due to the inability to quantify the amount entering

bodies of water and shallow aquifers.[26]

Contamination with impurities

Common agricultural grade phosphate fertilizers usually contain impurities such as fluorides, cadmium and

uranium, although concentrations of the latter two heavy metals are dependent on the source of the phosphate

and the production process. These potentially harmful impurities can be removed; however, this significantly

increases cost. Highly pure fertilizers are widely available and perhaps best known as the highly water soluble

fertilizers containing blue dyes used around households. These highly water soluble fertilizers are used in the

plant nursery business and are available in larger packages at significantly less cost than retail quantities. There

are also some inexpensive retail granular garden fertilizers made with high purity ingredients.

Oregon and Washington in U. S. have fertilizer registration programs with on-line databases listing chemicalanalyses of fertilizers.[27][28]

The most widely used inorganic fertilizer is super-phosphate and its double and triple strengthed derivatives

double super and triple super. Super phosphate was first developed by Lawes at the Rothamstead Agricultural

Research Institute in England in the early 19th Century.[29]

Lawes added sulfuric acid to conventional rock

phosphate containing the mineral apatite, a calcium fluoro-phosphate. The resulting water soluble phosphorus

was able to significantly improve yields on a variety of crops at the Rothamstead Centre and the Superphosphate

industry was born. Unfortunately over decades of subsequent usage - it became clear that the solubilisation of

fluorine also occurred in the process and this had the same effect as the other halogen sterilants(chlorine,


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bromine, iodine) over time - soil sterilization.[30]

Fertilizer dependency

Effectively farmers unknowingly became 100% dependent on bought in water soluble, inorganic fertilizers since

the sterilization of soil microflora including its mycorrhiza, reduced the availability of other natural and trace

minerals within the soil. This to some extent explains the resurgence of interest in organic and particularly

biodynamic farming systems since these systems replace the essential soil organisms so essential to convertingsoil minerals into plant available (but rarely water soluble) nutrients.[31]They do this by a variety of processes

including chelation whereby essential minerals become plant available - as measured by weak citric acid

extraction techniques. Hence the citric acid solubility of phosphate rocks has emerged as a measure of plant

availability and enabled so-called reactive phosphate rocks to be used as fertilizer minerals. These should not be

confused with high fluorine apatite rocks in which the fluoride content performs a similar function to its role in

hardening teeth enamel, i.e. immobilizing phosphorus. This explains the oceanic origins of many of these high

fluorine rocks (Christmas Island, Ocean Island) since the fluorine absorbed from the sea has prevented what

were originally massive deposits of bird guano - from being leached from the coral based limestone rocks on

which they were originally deposited.

Soil acidification

Also regular use of acidulated fertilizers generally contribute to the accumulation of soil acidity in soils which

progressively increases aluminium availability and hence toxicity. The use of such acidulated fertilizers in the

tropical and semi-tropical regions of Indonesia and Malaysia has contributed to soil degradation on a large scale

from aluminium toxicity, which can only be countered by applications of limestone or preferably magnesian

dolomite, which neutralises acid soil pH and also provides essential magnesium.

Trace mineral depletion

Many inorganic fertilizers, particularly those based on superphosphate, may not replace trace mineral elementsin the soil which become gradually depleted by crops. This depletion has been linked to studies which have

shown a marked fall (up to 75%) in the quantities of such minerals present in fruit and vegetables.[32]

Explanations for this include the early encouragement of so-called "luxury consumption" of trace elements as a

result of their acidulation and subsequent dissolution in soil water, by free sulphuric acid sourced from

superphosphate. This mechanism has also been identified as a possible causal agent for take-up of the heavy

metal cadmium from superphosphate based fertilizers. In Western Australia deficiencies of zinc, copper,

manganese, iron and molybdenum were identified as limiting the growth of broad-acre crops and pastures in the

1940s and 1950s.[33]Such nutrients are described as rate limiting nutrients. Soils in Western Australia are very

old, highly weathered and deficient in many of the major nutrients and trace elements. [33]Since this time these

trace elements are routinely added to inorganic fertilizers used in agriculture in this state.[33]

Many soils around the world are deficient in zinc, leading to deficiency in plants and humans.[34]

Overfertilization

See also: Fertilizer burn

Over-fertilization of a vital nutrient can be as detrimental as underfertilization.[35]

"Fertilizer burn" can occur

when too much fertilizer is applied, resulting in drying out of the leaves and damage or even death of the


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Fertilizer burn

plant.[36]

Fertilizers vary in their tendency to burn roughly in accordance with their salt

index.[37]

High energy consumption

In the USA in 2004, 317 billion cubic feet of natural gas was consumed in theindustrial production of ammonia, less than 1.5% of total U.S. annual

consumption of natural gas.[38]A 2002 report suggested that the production of

ammonia consumes about 5% of global natural gas consumption, which is

somewhat under 2% of world energy production.[39]

Ammonia is overwhelmingly produced from natural gas, but other energy

sources, together with a hydrogen source such as water (via water splitting or

electrolysis),[40]can be used for the production of nitrogen compounds suitable

for fertilizers.[41]The cost of natural gas makes up about 90% of the cost of producing ammonia.[42]The

increase in price of natural gases over the past decade, along with other factors such as increasing demand, have

contributed to an increase in fertilizer price.[43]

Contribution to climate change

Nitrogen fertilizer can be converted by soil bacteria to nitrous oxide, a greenhouse gas.

Impacts on mycorrhizas

High levels of fertilizer may cause the breakdown of the symbiotic relationships between plant roots and

mycorrhizal fungi.[44]

Lack of long-term sustainability

Inorganic fertilizers are now produced in ways which theoretically cannot be continued indefinitely by definition

as the resources used in their production are non-renewable. Potassium and phosphorus come from mines (or

saline lakes such as the Dead Sea) and such resources are limited. However, more effective fertilizer utilization

practices may decrease present usage from mines. Improved knowledge of crop production practices can

potentially decrease fertilizer usage of P and K without reducing the critical need to improve and increase crop

yields. Atmospheric (unfixed) nitrogen is effectively unlimited (forming over 70% of the atmospheric gases), but

this is not in a form useful to plants. To make nitrogen accessible to plants requires nitrogen fixation (conversion

of atmospheric nitrogen to a plant-accessible form).

Artificial nitrogen fertilizers are typically synthesized using fossil fuels such as natural gas and coal, which are

limited resources. In lieu of converting natural gas to syngas for use in the Haber process, it is also possible to

convert renewable biomass to syngas (or wood gas) to supply the necessary energy for the process, though the

amount of land and resources (ironically often including fertilizer) necessary for such a project may be

prohibitive.

Organic fertilizer


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Compost bin for small-scale

production of organic fertilizer

A large commercial compost operation

Main article: Organic fertilizer

Organic fertilizers include naturally occurring organic materials, (e.g.

chicken litter, manure, worm castings, compost, seaweed, guano, bone

meal) or naturally occurring mineral deposits (e.g. saltpeter). Poultry

litter and cattle manure often create environmental and disposal

problems, making their use as fertilizer beneficial. Bones can be

processed into phosphate-rich bone meal; however, most are simply

buried in landfills.

Even if all bones, human, animal and plant wastes were recovered to the

extent practical and used for fertilizer, mineral fertilizers and synthetic

nitrogen would still be required to make for losses to leaching, to the

atmosphere, runoff and the losses impractical to recover.[citation needed]

Benefits of organic fertilizer

Organic fertilizers have been known to improve biodiversity (soil life)

and long-term productivity of soil,[45][46]

and may prove a largedepository for excess carbon dioxide.

[47][48][49]

Organic nutrients increase the abundance of soil organisms by providing

organic matter and micronutrients for organisms such as fungal

mycorrhiza,[50](which aid plants in absorbing nutrients), and can

drastically reduce external inputs of pesticides, energy and fertilizer, at

the cost of decreased yield.[51]

Disadvantages of organic fertilizers

Organic fertilizers may contain pathogens and other disease causing organisms if not properly

composted.[52]

Nutrient contents are variable and their release to available forms that the plant can use may not occur at

the right plant growth stage.[53]

Comparison with inorganic fertilizer

Organic fertilizer nutrient content, solubility, and nutrient release rates are typically all lower than inorganic

fertilizers.[54][55]One study found that over a 140-day period, after 7 leachings:

Organic fertilizers had released between 25% and 60% of their nitrogen contentControlled release fertilizers (CRFs) had a relatively constant rate of releaseSoluble fertilizer released most of its nitrogen content at the first leaching

In general, the nutrients in organic fertilizer are both more dilute and also much less readily available to plants.

According to the University of Californias integrated pest management program, all organic fertilizersare

classified as slow-release fertilizers, and therefore cannot cause nitrogen burn.[56]

Organic fertilizers from composts and other sources can be quite variable from one batch to the next. [57]

Without batch testing, amounts of applied nutrient cannot be precisely known. Nevertheless, one or more studies


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have shown they are at least as effective as chemical fertilizers over longer periods of use. [58]

Examples of organic fertilizer

Chicken litter, which consists of chicken manure mixed with sawdust, is an organic fertilizer that has been shown

to better condition soil for harvest than synthesized fertilizer. Researchers at the Agricultural Research Service

(ARS) studied the effects of using chicken litter, an organic fertilizer, versus synthetic fertilizers on cotton fields,

and found that fields fertilized with chicken litter had a 12% increase in cotton yields over fields fertilized withsynthetic fertilizer. In addition to higher yields, researchers valued commercially sold chicken litter at a $17/ton

premium (to a total valuation of $78/ton) over the traditional valuations of $61/ton due to value added as a soil

conditioner.[59]

Other ARS studies have found that algae used to capture nitrogen and phosphorus runoff from agricultural fields

can not only prevent water contamination of these nutrients, but also can be used as an organic fertilizer. ARS

scientists originally developed the "algal turf scrubber" to reduce nutrient runoff and increase quality of water

flowing into streams, rivers, and lakes. They found that this nutrient-rich algae, once dried, can be applied to

cucumber and corn seedlings and result in growth comparable to that seen using synthetic fertilizers.[60]

Examples

Compost

Rock phosphate

Bone meal[61]

Manure

Alfalfa

Wood chips/sawdust[62]

Raw Langbeinite

Cover crops

Unprocessed natural potassium sulfate

Rock powder

Ash[63]

Blood meal

Fish meal

Fish emulsion[64]

Organic fertilizer sources

Animal

See also: Night soil

Animal-sourced and human urea are suitable for application organic agriculture, while pure synthetic forms of

urea are not.[65]The common thread that can be seen through these examples is that organicagriculture

attempts to define itself through minimal processing (in contrast to the man-made Haber process), as well as

being naturally occurring or via natural biological processes such as composting.[citation needed]

Besides immediate application of urea to the soil, urine can also be improved by converting it to struvite already

done with human urine by a Dutch firm.[66]The conversion is performed by adding magnesium to the urine. An

added economical advantage of using urine as fertilizer is that it contains a large amount of phosphorus.


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Decomposing animal manure, an

organic fertilizer source

Runoff of soil and fertilizer during a

rain storm

An algal bloom caused by

eutrophication

Recycled sewage sludge (aka biosolids) as soil amendment is only

available to less than 1% of US agricultural land. Industrial pollutants in

sewage sludge prevents recycling it as fertilizer. The USDA prohibits use

of sewage sludge in organic agricultural operations in the U.S. due to

industrial pollution, pharmaceuticals, hormones, heavy metals, and other

factors.[67][68][69]The USDA now requires 3rd-party certification of

high-nitrogen liquid organic fertilizers sold in the U.S.[70]

Plant

Leguminous cover crops are also grown to enrich soil as a green manure

through nitrogen fixation from the atmosphere;[71]as well as phosphorus

(through nutrient mobilization)[72]content of soils.

Mineral

Mined powdered limestone,[73]

rock phosphate and sodium nitrate, are inorganic (not of biologic origins)

compounds which are energetically intensive to harvest and are approved for usage in organic agriculture inminimalamounts.

[73][74][75]

Negative environmental effects

See also: Environmental impact of agriculture, Human impact on the nitrogen cycle, and Nitrogen

fertilizer#Problems with inorganic fertilizer

Water quality

Eutrophication

Main article: Eutrophication

The nitrogen-rich compounds found in fertilizer runoff are the primary

cause of serious oxygen depletion in many parts of the ocean, especially

in coastal zones. The resulting lack of dissolved oxygen is greatly

reducing the ability of these areas to sustain oceanic fauna.[76]Visually,

water may become cloudy and discolored (green, yellow, brown, or red).

About half of all the lakes in the United States are now eutrophic, while

the number of oceanic dead zones near inhabited coastlines are

increasing.[77]

As of 2006, the application of nitrogen fertilizer is being

increasingly controlled in Britain and the United States[citation needed]

. If

eutrophication canbe reversed, it may take decades[citation needed]

before

the accumulated nitrates in groundwater can be broken down by natural

processes.

Blue baby syndrome


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High application rates of inorganic nitrogen fertilizers in order to maximize crop yields, combined with the high

solubilities of these fertilizers leads to increased runoff into surface water as well as leaching into groundwater.[78][79][80]The use of ammonium nitrate in inorganicfertilizers is particularly damaging, as plants absorb

ammonium ions preferentially over nitrate ions, while excess nitrate ions which are not absorbed dissolve (by

rain or irrigation) into runoff or groundwater.[81]

Nitrate levels above 10 mg/L (10 ppm) in groundwater can cause blue baby syndrome (acquired

methemoglobinemia), leading to hypoxia (which can lead to coma and death if not treated).

[82]

Soil

Soil acidification

See also: Soil pH

Nitrogen-containing inorganic and organic fertilizers can cause soil acidification when added.[83][84]This may

lead to decreases in nutrient availability which may be offset by liming.

Persistent organic pollutants

Main article: Persistent organic pollutant

Toxic persistent organic pollutants ("POPs"), such as Dioxins, polychlorinated dibenzo-p-dioxins (PCDDs), and

polychlorinated dibenzofurans (PCDFs) have been detected in agricultural fertilizers and soil amendments[85]

Heavy metal accumulation

The concentration of up to 100 mg/kg of cadmium in phosphate minerals (for example, minerals from Nauru[86]

and the Christmas islands[87]) increases the contamination of soil with cadmium, for example in New

Zealand.[88]

Steel industry wastes, recycled into fertilizers for their high levels of zinc (essential to plant growth), wastes can

include the following toxic metals: lead[89] arsenic, cadmium,[89]chromium, and nickel. The most common toxic

elements in this type of fertilizer are mercury, lead, and arsenic.[90][91]Concerns have been raised concerning

fish meal mercury content by at least one source in Spain[92]

Radioactive element accumulation

Uranium is another example of a contaminant often found in phosphate fertilizers (at levels from 7 to 100

pCi/g).[93]

Eventually these heavy metals can build up to unacceptable levels and build up in vegetable

produce.[88]Average annual intake of uranium by adults is estimated to be about 0.5 mg (500 g) from ingestion

of food and water and 0.6 g from breathing air.[94]

Also, highly radioactive Polonium-210 contained in phosphate fertilizers is absorbed by the roots of plants and

stored in its tissues; tobacco derived from plants fertilized by rock phosphates contains Polonium-210 which

emits alpha radiation estimated to cause about 11,700 lung cancer deaths each year worldwide.[95][96][97][98]

[99][100]


19 4/30/2013


13/19

Global methane concentrations

(surface and atmospheric) for 2005;

note distinct plumes

For these reasons, it is recommended that nutrient budgeting, through careful observation and monitoring of

crops, take place to mitigate the effects of excess fertilizer application.

Atmosphere

Methane emissions from crop fields (notably rice paddy fields) are

increased by the application of ammonium-based fertilizers; these

emissions contribute greatly to global climate change as methane is a

potent greenhouse gas.[101]

Through the increasing use of nitrogen fertilizer, which is added at a rate

of 1 billion tons per year presently[102]

to the already existing amount of

reactive nitrogen, nitrous oxide (N2O) has become the third most

important greenhouse gas after carbon dioxide and methane. It has a

global warming potential 296 times larger than an equal mass of carbon

dioxide and it also contributes to stratospheric ozone depletion.[103]

The use of fertilizers on a global scale emits significant quantities of

greenhouse gas into the atmosphere (citation needed). Emissions comeabout through the use of:

animal manures and urea, which release methane, nitrous oxide,

ammonia, and carbon dioxide in varying quantities depending ontheir form (solid or liquid) and management (collection, storage,

spreading)fertilizers that use nitric acid or ammonium bicarbonate, the production and application of which results in

emissions of nitrogen oxides, nitrous oxide, ammonia and carbon dioxide into the atmosphere.

By changing processes and procedures, it is possible to mitigate some, but not all, of these effects on

anthropogenic climate change.[citation needed]

Other problems

Increased pest fitness

Excessive nitrogen fertilizer applications can also lead to pest problems by increasing the birth rate, longevity

and overall fitness of certain agricultural pests, such as aphids (plant lice).[104][105][106][107][108][109]

See also

Fertigation

History of organic farmingPhosphogypsum

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External links

Nitrogen for Feeding Our Food, Its Earthly Origin, Haber Process (http://shakahara.com/nitrogen.shtml)

The Fertilizer Institute (TFI) (http://www.tfi.org/factsandstats/fertilizer.cfm) US Fertilizer Industry

Association

International Fertilizer Industry Association (IFA) (http://www.fertilizer.org)European Fertiliser Manufacturers Association (http://cms.efma.org/)How to read fertilizer tags article (http://www.agriculturesolutions.com/index.php?option=com_content&

Itemid=111&id=87&lang=en&task=view)Agriculture Guide, Complete Guide to Fertilizers and Fertilization (http://www.agricultureguide.org

/a-complete-guide-to-fertilization-and-choosing-best-fertilizers/)

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