Fertilizer is any organic or inorganic material
of natural or synthetic origin that is added to soil to supply one or more plant nutrients
essential to the growth of plants. Conservative estimates report 30 to 50% of crop yields
are attributed to natural or synthetic commercial fertilizer. Global market value is likely
to rise to more than US$185 billion until 2019. The European fertilizer market will
grow to earn revenues of approx. €15.3 billion in 2018.
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 Earth are currently fed as a result
of synthetic nitrogen fertilizer use. Fertilizers typically provide, in varying
proportions: six macronutrients: nitrogen, phosphorus,
potassium, calcium, magnesium, and sulfur; eight micronutrients: boron, chlorine, copper,
iron, manganese, molybdenum, zinc and nickel. 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 basis. Micronutrients are consumed in smaller quantities and are present in plant
tissue on the order of parts per million, ranging from 0.15 to 400 ppm DM, or less than
0.04% DM. Only three other structural elements are required
by all plants: carbon, hydrogen, and oxygen. These nutrients are supplied by water and
carbon dioxide in the atmosphere. Labeling of chemical fertilizer In the US and Canada, the labeling scheme
presents three numbers separated by dashes. 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, 2 pounds of phosphorus, and 4 pounds of potassium. Australian convention
adds a fourth number for Sulphur. History 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 formed by 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. The Birkeland–Eyde 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.
This process was used to fix atmospheric nitrogen into nitric acid, one of several chemical
processes generally referred to as nitrogen fixation. The resultant nitric acid was then
used as a source of nitrate 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. 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 from methane gas and molecular nitrogen. The ammonia from the Haber process
is then converted into nitric acid in the Ostwald process.
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 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’ or ‘staged nutrient
release’ of fertilizer nutrients. More recently, organic fertilizer is on the
rise as people are resorting to environmental friendly 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 which build the soil’s structure
and moisture- and nutrient-retaining capabilities. Inorganic commercial fertilizer
Fertilizers are broadly divided into organic fertilizers, 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 organic matter decays—this 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 NH3 or NO3 compounds. The usable phosphorus compounds
are usually in the form of phosphoric acid and the potassium is typically in the form
of potassium chloride. 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 decay—they can be used almost immediately after water is applied. Inorganic
fertilizers are usually much more concentrated with up to 64% 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. Nitrogen fertilizers are often made using
the Haber-Bosch process which uses natural gas for the hydrogen and nitrogen gas from
the air at an elevated temperature and pressure in the presence of a catalyst to form ammonia
as the end product. This ammonia is used as a feedstock for other nitrogen fertilizers,
such as anhydrous ammonium nitrate and urea2). These concentrated products may be diluted
with water to form a concentrated liquid fertilizer. Deposits of sodium nitrate are also found
the Atacama desert in Chile and was one of the original nitrogen rich inorganic fertilizers
used. It is still mined for fertilizer. In the Nitrophosphate process or Odda Process,
phosphate rock with up to a 20% phosphorus content is dissolved with nitric acid to produce
a mixture of phosphoric acid and calcium nitrate2). This can be combined with a potassium fertilizer
to produce a compound fertilizer with the three macronutrients N, P and K in easily
dissolved form. Phosphate rock can also be processed into
water-soluble phosphate with the addition of sulfuric acid 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 fertilizers. All commercial potash deposits come originally
from marine deposits and are often buried deep in the earth. Potash ores are typically
rich in potassium chloride and sodium chloride 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 fertilizer—KCl
dissolves readily in water and is available quickly for plant nutrition.
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,
phosphate and potash 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. Without commercial fertilizers it is estimated
that about one-third of the food produced now could not be produced. 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 6–9 tonnes of grain per hectare requires 31–50 kg
of phosphate fertilizer to be applied, soybean requires 20–25 kg per hectare. Yara International
is the world’s largest producer of nitrogen based fertilizers.
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. The early
product had 60 percent of the total nitrogen cold-water-insoluble, and the unreacted 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. 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 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 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. 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, fix nitrogen 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 of these crops, while having a
beneficial effect on soil nitrogen levels for the main crop planted during the summer
season. 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 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 a distinctive 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 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. In Europe these problems are being addressed by the European Union’s
Nitrates Directive. Within Britain farmers are encouraged to manage their land more sustainably
in ‘catchment-sensitive farming’. 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. Contamination with impurities
Phosphate rocks all contain hazardous elements such as fluorine, heavy metals and radioactive
elements. Consequently, 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 fertilizer 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, both in the United States, have fertilizer registration programs
with on-line databases listing chemical analyses of fertilizers.
The fluoride content of many widely used phosphate fertilizers has increased soil fluoride concentrations,
prompting considerable research into the possibility that soil productivity and food quality may
be compromised. It has been found that food contamination from fertilizer is of little
concern as plants accumulate little fluoride from the soil; of greater concern is the possibility
of fluoride toxicity to livestock that ingest contaminated soils. Also of possible concern
are the effects of fluoride on soil microorganisms. 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 Scientific investigations have indicated a
trend of decreasing concentrations of minerals in many foods over the last 50-60 years. Intensive
farming practices, including the use of inorganic fertilizers are frequently suggested as reasons
for these declines and organic farming is often suggested as a solution. Although improved
crop yields resulting from inorganic NPK fertilizers are known to dilute the concentrations of
other nutrients in plants, much of the measured decline can be attributed to the use of progressively
higher-yielding crop varieties which produce foods with lower mineral concentrations than
their less productive ancestors. It is, therefore, unlikely that organic farming or reduced use
of inorganic fertilizers will solve the problem; foods with high nutrient density are more
likely to be achieved using older, lower-yielding varieties or the development of new high-yield,
nutrient-dense varieties. Inorganic fertilizers are, in fact, more likely
to solve trace mineral deficiency problems than cause them: 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. Soils in Western Australia are
very old, highly weathered and deficient in many of the major nutrients and trace elements.
Since this time these trace elements are routinely added to inorganic fertilizers used in agriculture
in this state. Many other soils around the world are deficient in zinc, leading to deficiency
in both plants and humans, and inorganic zinc fertilizers are widely used to solve this
problem. Overfertilization Over-fertilization of a vital nutrient can
be as detrimental as underfertilization. “Fertilizer burn” can occur when too much fertilizer is
applied, resulting in drying out of the leaves and damage or even death of the plant.
Fertilizers vary in their tendency to burn roughly in accordance with their salt index.
High energy consumption In the USA in 2004, 317 billion cubic feet
of natural gas were consumed in the industrial production of ammonia, less than 1.5% of total
U.S. annual consumption of natural gas. 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. Ammonia is overwhelmingly produced from natural
gas, but other energy sources, together with a hydrogen source such as water, can be used
for the production of nitrogen compounds suitable for fertilizers. The cost of natural gas makes
up about 90% of the cost of producing ammonia. 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. Contribution to climate change
The greenhouse gases carbon dioxide, methane and nitrous oxide are produced during the
manufacture of nitrogen fertilizer. The effects can be combined into an equivalent amount
of carbon dioxide. The amount varies according to the efficiency of the process. The figure
for the United Kingdom is over 2 kilogrammes of carbon dioxide equivalent for each kilogramme
of ammonium nitrate. 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. 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 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
nitrogen is effectively unlimited, but this is not in a form useful to plants. To make
nitrogen accessible to plants requires nitrogen fixation.
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 to
supply the necessary energy for the process, though the amount of land and resources necessary
for such a project may be prohibitive. Organic fertilizer Organic fertilizers include naturally occurring
organic materials, or naturally occurring mineral deposits. 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. The extent of imbalance in the phosphate and
other mineral cycles is such that if all human, animal and plant wastes were recovered to
the extent practical and used for fertilizer, mineral fertilizers and synthetic nitrogen
would be needed to make up for losses impractical to recover through leaching, atmospheric dispersion
and runoff. Benefits of organic fertilizer
Organic fertilizers have been known to improve biodiversity and long-term productivity of
soil, and may prove a large depository for excess carbon dioxide.
Organic nutrients increase the abundance of soil organisms by providing organic matter
and micronutrients for organismal relationships such as fungal mycorrhiza,, and can drastically
reduce external inputs of pesticides, energy and fertilizer, at the cost of decreased yield.
Disadvantages of complex fertilizers Some composted biowastes used as organic fertilizers
may support the growth of pathogens and other disease causing organisms if not properly
composted. Nutrient contents are variable and their release
to available forms that the plant can use may not occur at the right plant growth stage.
Comparison with inorganic fertilizer Organic fertilizer nutrient content, solubility,
and nutrient release rates are typically all lower than inorganic fertilizers. One study
found that over a 140-day period, after 7 leachings:
Organic fertilizers had released between 25% and 60% of their nitrogen content
Controlled release fertilizers had a relatively constant rate of release
Soluble fertilizer released most of its nitrogen content at the first leaching
In general, the nutrients in organic fertilizer are both more diluted and also much less readily
available to plants. Although most organic fertilizers are ‘slow-release’ fertilizers
and cannot cause nitrogen burn or fertilizer burn, some can burn seedlings.
Organic fertilizers from composts and other sources can be quite variable from one batch
to the next. Without batch testing, amounts of applied nutrient cannot be precisely known.
Nevertheless, one or more studies have shown they are at least as effective as chemical
fertilizers over longer periods of use. 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 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 with
synthetic fertilizer. In addition to higher yields, researchers valued commercially sold
chicken litter at a $17/ton premium over the traditional valuations of $61/ton due to value
added as a soil conditioner. 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. Examples
Compost Rock phosphate
Bone meal Manure
Alfalfa Wood chips/sawdust
Raw Langbeinite Cover crops
Unprocessed natural potassium sulfate Rock powder
Ash Blood meal
Fish meal Fish emulsion
Organic fertilizer sources Animal Animal-sourced and human urea are suitable
for application organic agriculture, while pure synthetic forms of urea are not. The
common thread that can be seen through these examples is that organic agriculture attempts
to define itself through minimal processing, as well as being naturally occurring or via
natural biological processes such as composting. 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. 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.
Recycled sewage sludge 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. The USDA
now requires 3rd-party certification of high-nitrogen liquid organic fertilizers sold in the U.S.
Plant Leguminous cover crops or fertilizer trees
are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere;
as well as phosphorus content of soils. Mineral
Mined powdered limestone, rock phosphate and sodium nitrate, are inorganic compounds which
are energetically intensive to harvest and are approved for usage in organic agriculture
in minimal amounts. Environmental effects 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. Visually, water may become cloudy and discolored.
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. As of 2006, the application
of nitrogen fertilizer is being increasingly controlled in northwestern Europe and the
United States. If eutrophication can be reversed, it may take decades before the accumulated
nitrates in groundwater can be broken down by natural processes.
Blue baby syndrome 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.
The use of ammonium nitrate in inorganic fertilizers is particularly damaging, as plants absorb
ammonium ions preferentially over nitrate ions, while excess nitrate ions which are
not absorbed dissolve into runoff or groundwater. Nitrate levels above 10 mg/L in groundwater
can cause ‘blue baby syndrome’, leading to hypoxia.
Soil acidification Nitrogen-containing inorganic and organic
fertilizers can cause soil acidification when added. This may lead to decreases in nutrient
availability which may be offset by liming. Persistent organic pollutants Toxic persistent organic pollutants, such
as Dioxins, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans have been
detected in agricultural fertilizers and soil amendments
Heavy metal accumulation The concentration of cadmium in phosphorus-containing
fertilizers varies considerably; for example, mono-ammonium phosphate fertilizer may have
a cadmium content of as low as 0.14 mg/kg or as high as 50.9 mg/kg. This is because
the phosphate rock used in their manufacture can contain as much as 188 mg/kg cadmium.
Continuous use of high-cadmium fertilizer can contaminate soil and plants. A proposal
to limit the cadmium content of phosphate fertilizers is being considered by the European
Commission. Steel industry wastes, recycled into fertilizers
for their high levels of zinc, wastes can include the following toxic metals: lead arsenic,
cadmium, chromium, and nickel. The most common toxic elements in this type of fertilizer
are mercury, lead, and arsenic. Radioactive element accumulation
Phosphate rocks and fertilizers derived from them contain radioactive elements of the uranium-238
series and thorium-232 series. Concentrations of these radionuclides in the fertilizers
vary considerably, and depend both on their concentrations in the parent phosphate rock,
and on the fertilizer production process. Uranium-238 concentrations range can range
from 7 to 100 pCi/g in phosphate rock and from 1 to 67 pCi/g in phosphate fertilizers.
Where high annual rates of phosphorus fertilizer are used, this can result in uranium-238 concentrations
in soils and drainange waters that are several times greater than are normally present. However,
the impact of these increases on the risk to human health from radinuclide contamination
of foods is very small. 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.
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 are increased
by the application of ammonium-based fertilizers; these emissions contribute greatly to global
climate change as methane is a potent greenhouse gas.
Through the increasing use of nitrogen fertilizer, which is was used at a rate of about 110 million
tons per year in 2012 to the already existing amount of reactive nitrogen, nitrous oxide
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. The use of fertilizers on a global scale emits
significant quantities of greenhouse gas into the atmosphere. Emissions come about through
the use of: animal manures and urea, which release methane,
nitrous oxide, ammonia, and carbon dioxide in varying quantities depending on their form
and management 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. 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. See also
Fertigation History of organic farming
Milorganite Phosphogypsum
Soil defertilisation History of fertilizer
References External links
Nitrogen for Feeding Our Food, Its Earthly Origin, Haber Process
The Fertilizer Institute US Fertilizer Industry Association
International Fertilizer Industry Association European Fertiliser Manufacturers Association
How to read fertilizer tags article Agriculture Guide, Complete Guide to Fertilizers
and Fertilization 4R’s Nutrient Stewardship program from The
Fertilizer Institute