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Fertilizers are broadly divided into ''[[organic compound|organic]] fertilizers'' (composed of enriched organic matter—plant or animal), or ''[[inorganic compound|inorganic]] fertilizers'' (composed of [[Organic compound#Synthetic compounds|synthetic]] chemicals and/or minerals).
Fertilizers are broadly divided into ''[[organic compound|organic]] fertilizers'' (composed of enriched organic matter—plant or animal), or ''[[inorganic compound|inorganic]] fertilizers'' (composed of [[Organic compound#Synthetic compounds|synthetic]] chemicals and/or minerals).


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Inorganic fertilizer is often synthesized using the [[Haber process|Haber-Bosch process]], which produces [[ammonia]] as the end product. This ammonia is used as a [[feedstock]] for other nitrogen fertilizers, such as [[ammonium nitrate|anhydrous ammonium nitrate]] and [[urea]]. These concentrated products may be diluted with water to form a concentrated liquid fertilizer (e.g. [[UAN]]). Ammonia can be combined with [[rock phosphate]] and potassium fertilizer in the [[Odda Process]] to produce ''compound fertilizer''.


The use of synthetic nitrogen 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.<ref name="glass">{{cite journal|last=Glass|first=Anthony |date=September 2003|title=Nitrogen Use Efficiency of Crop Plants: Physiological Constraints upon Nitrogen Absorption |journal=Critical Reviews in Plant Sciences|volume=22|issue=5|url=http://www.ingentaconnect.com/content/tandf/bpts/2003/00000022/00000005/art00003|doi=10.1080/713989757|page=453}}</ref> 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&nbsp;kg of [[phosphate fertilizer]] to be applied, soybean requires 20–25&nbsp;kg per hectare.<ref>{{cite journal|last=Vance|coauthors=Uhde-Stone & Allan|year=2003|title=Phosphorus acquisition and use: critical adaptations by plants for securing a non renewable resource.|journal=New Phythologist|volume=157|pages=423–447|url=http://www.jstor.org/pss/1514050|author1=Vance, Carroll P|issue=3|publisher=Blackwell Publishing|doi=10.1046/j.1469-8137.2003.00695.x}}</ref> [[Yara International]] is the world's largest producer of nitrogen based fertilizers.<ref>{{cite news|url=http://www.economist.com/businessfinance/displaystory.cfm?story_id=15549105|title=Mergers in the fertiliser industry |date=18 February 2010|publisher=The Economist|accessdate=21 February 2010}}</ref>
The use of synthetic nitrogen 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.<ref name="glass">{{cite journal|last=Glass|first=Anthony |date=September 2003|title=Nitrogen Use Efficiency of Crop Plants: Physiological Constraints upon Nitrogen Absorption |journal=Critical Reviews in Plant Sciences|volume=22|issue=5|url=http://www.ingentaconnect.com/content/tandf/bpts/2003/00000022/00000005/art00003|doi=10.1080/713989757|page=453}}</ref> 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&nbsp;kg of [[phosphate fertilizer]] to be applied, soybean requires 20–25&nbsp;kg per hectare.<ref>{{cite journal|last=Vance|coauthors=Uhde-Stone & Allan|year=2003|title=Phosphorus acquisition and use: critical adaptations by plants for securing a non renewable resource.|journal=New Phythologist|volume=157|pages=423–447|url=http://www.jstor.org/pss/1514050|author1=Vance, Carroll P|issue=3|publisher=Blackwell Publishing|doi=10.1046/j.1469-8137.2003.00695.x}}</ref> [[Yara International]] is the world's largest producer of nitrogen based fertilizers.<ref>{{cite news|url=http://www.economist.com/businessfinance/displaystory.cfm?story_id=15549105|title=Mergers in the fertiliser industry |date=18 February 2010|publisher=The Economist|accessdate=21 February 2010}}</ref>

Revision as of 23:17, 17 February 2011

Tennessee Valley Authority: "Results of Fertilizer" demonstration 1942
A large, modern fertilizer spreader

Fertilizers (or fertilisers) are substances that supply plant nutrients or amend soil fertility. They are the most effective (30 -80 per cent increase in yields)[quantify] means of increasing crop production and of improving the quality of food and fodder. Fertilizers are used in order to supplement nutrient supply in the soil, especially to correct yield-limiting factors.

Fertilizers are applied to promote plant growth; the main nutrients present in fertilizer are nitrogen, phosphorus, and potassium (the 'macronutrients') and other nutrients ('micronutrients') are added in smaller amounts. Fertilizers are usually directly applied to soil, and can also be sprayed on leaves as a foliar feeding.

Organic fertilizers and some 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 artificial nitrogen fertilizer use.[1]

Fertilizers typically provide, in varying proportions:

The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0% (on a dry matter weight basis). Micronutrients are consumed in smaller quantities and are present in plant tissue in quantities measured in parts per million (ppm), ranging from 5 to 200 ppm, or less than 0.02% dry weight.[2]

The nitrogen-rich fertilizer ammonium nitrate is also used as an oxidizing agent in improvised explosive devices, sometimes called fertilizer bombs, leading to sale regulations[citation needed].

Labeling

Main article: labeling of fertilizers

Labeling of fertilizers take place in some appointed factories. There are some appointed officers who keep a record of the various fertilizers with their advantages as well as disadvantages.

Macronutrient fertilizers

Macronutrient fertilizers are labeled with an NPK analysis (also "N-P-K-S" in Australia).[3]

Fertilizer is described by a three number designator; for example, 20-20-10. These numbers are percentages of three elements: nitrogen, phosphorus, and potassium, respectively. Therefore, 20-20-10 fertilizer contains 20% nitrogen, 20% phosphorus, and 10% potassium by weight.

Example of labeling

The fertilizer potash (potassium carbonate) is composed of 1:1 potassium to carbonate by volume (47:53 by wt., owing to differences in molecular weight between potassium and carbonate)[citation needed].

Traditional analysis of 100g of potassium chloride (KCl) would yield 60g of potassium oxide ([[K2O]]). The percentage yield of K2O from the original 100g of fertilizer is the number shown on the label. A potash fertilizer would thus be labeled 0-0-60, and not 0-0-52.

History

Main articles: History of organic farming and History of fertilizer

The modern understanding of plant nutrition dates to the 19th century and the work of Justus von Liebig, among others. Management of soil fertility, however, has been the pre-occupation of farmers for thousands of years. as my fat ass

Forms

Fertilizers come in various forms. The most typical[citation needed] form is granular fertilizer (powder form). The next most common form is liquid fertilizer[citation needed]; 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.

Finally, organic fertilizer is on the rise[citation needed] as people are resorting to environmental friendly (or 'green') products. Although organic fertilizer usually contain less nutrients[citation needed], some people[which?] still prefer organic due to natural ingredients.

Inorganic fertilizer (synthetic fertilizer)

Fertilizers are broadly divided into organic fertilizers (composed of enriched organic matter—plant or animal), or inorganic fertilizers (composed of synthetic chemicals and/or minerals).

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The use of synthetic nitrogen 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.[4] 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.[5] Yara International is the world's largest producer of nitrogen based fertilizers.[6]

Top users of nitrogen-based fertilizer[7]
Country Total N use

(Mt pa)

Amt. used

(feed/pasture)

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
U.K. 1.3 0.9
Mexico 1.3 0.3
Spain 1.2 0.5
Argentina 0.4 0.1

Application

Synthetic fertilizers are commonly used to treat fields used for growing maize, followed by barley, sorghum, rapeseed, soy and sunflower[citation needed]. One study has 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.[8]

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[citation needed].

Applying excessive amounts of fertilizer has environmental impacts, and wastes the growers time and money. To avoid over application, the nutrient status of crops can 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 and Plant Tissue Tests are used in agriculture to fine-tune nutrient management to the crops needs.

Problems with inorganic fertilizer

Trace mineral depletion

Many inorganic fertilizers may not replace trace mineral elements in 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.[9]

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[citation needed]. Soils in Western Australia are very old, highly weathered and deficient in many of the major nutrients and trace elements[citation needed]. Since this time these trace elements are routinely added to inorganic fertilizers used in agriculture in this state[citation needed].

Overfertilization

See also: Fertilizer burn
Fertilizer burn

Over-fertilization of a vital nutrient can be as detrimental as underfertilization.[10] "Fertilizer burn" can occur when too much fertilizer is applied, resulting in a drying out of the roots and damage or even death of the plant.[11]

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. [12] 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.[13]

Natural gas is overwhelmingly used for the production of ammonia, but other energy sources, together with a hydrogen source, 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.[14] 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.[15]

Long-Term Sustainability

Inorganic fertilizers are now produced in ways which theoretically cannot be continued indefinitely[citation needed]. Potassium and phosphorus come from mines (or saline lakes such as the Dead Sea) and such resources are limited. More effective fertilizer utilization practices may, however, 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 (see Energy conservation in the United States).

Organic fertilizer

Main article: Organic fertilizer
Compost bin for small-scale production of organic fertilizer
A large commercial compost operation

Organic fertilizers include naturally occurring organic materials, (e.g. manure, worm castings, compost, seaweed, guano), or naturally occurring mineral deposits (e.g. saltpeter).

Benefits of organic fertilizer

Organic fertilizers have been known to improve the biodiversity (soil life) and long-term productivity of soil,[16][17] and may prove a large depository for excess carbon dioxide.[18][19][20]

Organic nutrients increase the abundance of soil organisms by providing organic matter and micronutrients for organisms such as fungal mycorrhiza,[21] (which aid plants in absorbing nutrients), and can drastically reduce external inputs of pesticides, energy and fertilizer, at the cost of decreased yield.[22]

Disadvantages of organic fertilizers

  • Organic fertilizers may contain pathogens and other disease causing organisms if not properly composted
  • Nutrient contents are very variable and their release to available forms that the plant can use may not occur at the right plant growth stage
  • Organic fertilizers are comparatively voluminous and can be too bulky to deploy the right amount of nutrients that will be beneficial to plants

Comparison with inorganic fertilizer

Organic fertilizer nutrient content, solubility, and nutrient release rates are typically all lower than inorganic fertilizers.[23][24] One study[which?] 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 (CRFs) 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 dilute and also much less readily available to plants. According to UC IPM, all organic fertilizers are classified as 'slow-release' fertilizers, and therefore cannot cause nitrogen burn.[25]

Organic fertilizers from composts and other sources can be quite variable from one batch to the next.[26] Without batch testing, amounts of applied nutrient cannot be precisely known. Nevertheless they are at least as effective as chemical fertilizers over longer periods of use.[27]

Example 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[citation needed]. 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 with synthetic 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.[28]

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.[29]

Organic fertilizer sources

Animal

Decomposing animal manure, an organic fertilizer source

Animal-sourced and human urea, are suitable for application organic agriculture, while pure synthetic forms of urea are not.[30][31] The common thread that can be seen through these examples is that organic agriculture 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.[32] 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, a mineral whose production is rapidly decreasing (peak phosphorus) as the mines are running dry.

Sewage sludge use in organic agricultural operations in the U.S. has been extremely limited and rare due to USDA prohibition of the practice (due to toxic metal accumulation, among other factors).[33][34][35] The USDA now requires 3rd-party certification of high-nitrogen liquid organic fertilizers sold in the U.S.[36]

Plant

Leguminous cover crops are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere;[37] as well as phosphorus (through nutrient mobilization)[38] content of soils.

Mineral

Mined powdered limestone,[39] 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 in minimal amounts.[39][40][41]

Negative environmental effects

Runoff of soil and fertilizer during a rain storm
An algal bloom causing eutrophication
See also: Environmental effects of agriculture and Human impacts on the nitrogen cycle

On water quality

Eutrophication

The nitrogen-rich compounds found in fertilizer run-off is the primary cause of a serious depletion of oxygen 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.[42] 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.[43] As of 2006, the application of nitrogen fertilizer is being increasingly controlled in Britain and the United States[citation needed]. If eutrophication can be reversed, it may take decades[citation needed] 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.[44][45][46] 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 (by rain or irrigation) into runoff or groundwater.[47]

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).[48]

On soil

Soil acidification

See also: Soil pH

Nitrogen-containing inorganic and organic fertilizers can cause soil acidification when added.[49] [4]. This may lead to decreases in nutrient availability which may be offset by liming.

Persistent organic pollutants

Main article: Persistent organic pollutants

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[50]

Heavy metal accumulation

The concentration of up to 100 mg/kg of cadmium in phosphate minerals (for example, minerals from Nauru[51] and the Christmas islands[52]) increases the contamination of soil with cadmium, for example in New Zealand.[53]

Steel industry wastes, recycled into fertilizers for their high levels of zinc (essential to plant growth), wastes can include the following toxic metals: lead[54] arsenic, cadmium,[54] chromium, and nickel. The most common toxic elements in this type of fertilizer are mercury, lead, and arsenic.[55][56] Concerns have been raised concerning fish meal mercury content by at least one source in Spain[57]

Radioactive element accumulation

Uranium is another example of a contaminant often found in phosphate fertilizers (at levels from 7 to 100 pCi/g).[58] Eventually these heavy metals can build up to unacceptable levels and build up in vegetable produce.[53] (See cadmium poisoning) Average annual intake of uranium by adults is estimated to be about 0.5 mg (500 μg) from ingestion of food and water and 0.6 μg from breathing air.[59]

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.[60][61] [62][63][64][65]

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.

On atmosphere

Global methane concentrations (surface and atmospheric) for 2005; note distinct plumes

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.[66]

Through the increasing use of nitrogen fertilizer, which is added at a rate of 1 billion tons per year presently[67] 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.[68]

Storage and application of some nitrogen fertilizers in some[which?] weather or soil conditions can cause emissions of the potent greenhouse gas—nitrous oxide. Ammonia gas (NH3) may be emitted following application of 'inorganic' fertilizers and/or manures and slurries.[citation needed]

The use of fertilizers on a global scale emits significant quantities of greenhouse gas into the atmosphere. Emissions come about through the use of:[69]

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[which?] agricultural pests.[70][71][72][73][74][75]

See also

References

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