Fertilizers are soil amendments A soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. The type of conditioner added depends on the current soil composition, climate, and the type of plant. Some soils lack nutrients necessary for proper plant growth and others hold too much or too little water. A conditioner or a applied to promote plant growth; the main nutrients Plant nutrition is the study of the chemical elements that are necessary for plant growth. A nutrient that is able to limit plant growth according to Liebig's law of the minimum, is considered an essential plant nutrient if the plant can not complete its full life cycle without it. There are 16 essential plant nutrients. Carbon and oxygen are present in fertilizer are nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere, phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms – white phosphorus and red phosphorus. Although the term "phosphorescence", meaning glow after, and potassium Potassium is the chemical element with the symbol K (Latin: kalium, from Arabic: القَلْيَه‎ al-qalyah "plant ashes" cf. Alkali from the same root, more commonly known in Modern Standard Arabic as بوتاسيوم ‹bwtasywm›), atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash. Elemental (the 'macronutrients') and other nutrients ('micronutrients') are added in smaller amounts. Fertilizers are usually directly applied to soil, and also sprayed on leaves ('foliar feeding A popular version of the feeding is to use sea-based nutrient mixes, especially algae, because they contain many of the fifty "trace nutrients"; the more "trace" is needed, the harder it is to balance the element within the soil. Trace elements are considered most fit for delivery by foliar feeding. Algae also contains some').

Fertilizers are roughly broken up between organic and inorganic fertilizer, with the main difference between the two being sourcing, and not necessarily differences in nutrient content.

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 The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, and transport had a profound effect on the socioeconomic and cultural conditions starting in the United Kingdom, then subsequently spreading throughout Europe, North America, and eventually the world. The onset of the. Increased understanding and use of fertilizers were important parts of the pre-industrial British Agricultural Revolution The British Agricultural Revolution describes a period of development in Britain between the 17th century and the end of the 19th century, which saw a massive increase in agricultural productivity and net output. This in turn supported unprecedented population growth, freeing up a significant percentage of the workforce, and thereby helped drive and the industrial green revolution Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between 1943 and the late 1970s, that increased industrialized agriculture production in many developing nations of the 20th century.

Fertilizers typically provide, in varying proportions In mathematics, two quantities are said to be proportional if they vary in such a way that one of the quantities is a constant multiple of the other, or equivalently if they have a constant ratio:

• the three primary macronutrients: nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere (N), phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms – white phosphorus and red phosphorus. Although the term "phosphorescence", meaning glow after (P), and potassium Potassium is the chemical element with the symbol K (Latin: kalium, from Arabic: القَلْيَه‎ al-qalyah "plant ashes" cf. Alkali from the same root, more commonly known in Modern Standard Arabic as بوتاسيوم ‹bwtasywm›), atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash. Elemental (K).
• the three secondary macronutrients: calcium Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, (Ca), sulfur Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a bright yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals. It is an essential element for life and is found in (S), magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole. This preponderance of magnesium is related to the fact that it is easily (Mg).
• and the micronutrients Micronutrients are nutrients needed throughout life in small quantities. They are dietary minerals needed by the human body in very small quantities as opposed to macrominerals which are required in larger quantities. The Microminerals or trace elements include at least iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc and or trace minerals: boron Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a trivalent metalloid element which occurs abundantly in the evaporite ores borax and ulexite (B), chlorine Chlorine (pronounced /ˈklɔəriːn/ KLOR-een, from the Greek word 'χλωρóς' , is the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and other compounds, it is abundant in nature and necessary to (Cl), manganese Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals. As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels (Mn), iron Iron is the most common element in the earth as a whole, and the fourth most common in the Earth's crust. It is produced as a result of stellar fusion in high-mass stars, and it is the heaviest stable element produced by stellar fusion because the fusion of iron is the last nuclear fusion reaction that is exothermic. Iron is the most widely used (Fe), zinc Zinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in the (Zn), copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a (Cu), molybdenum Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, (Mo) and selenium Selenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature (Se).

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.^[1]

Labeling of fertilizers

Macronutrient fertilizers

Macronutrient fertilizers are labeled with an NPK analysis and also "N-P-K-S" in Australia^[2].

An example of labeling for the fertilizer potash Potash is the common name for potassium carbonate and various mined and manufactured salts that contain the element potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains is composed of 1:1 potassium to carbonate by volume, or 47:53 by weight (owing to differences in molecular weight between the potassium and carbonate). Traditional analysis of 100g of KCl would yield 60g of 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, not 0-0-52.

History

The modern understanding of plant nutrition dates to the 19th century and the work of Justus von Liebig Justus von Liebig was a German chemist who made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. As a professor, he devised the modern laboratory-oriented teaching method, and for such innovations, he is regarded as one of the greatest chemistry teachers of all time. He is known as, among others. Management of soil fertility Nitrogen is the element in the soil that is most often lacking. Phosphorus and potassium are also needed in substantial amounts. For this reason these three elements are always included in commercial fertilizers and the content of each of these items is included on the bags of fertilizer. For example a 10-10-15 fertilizer has 10 percent nitrogen, 1, however, has been the pre-occupation of farmers for thousands of years.

Type of Fertilizer

Fertilizers come in various shapes and forms. The most typical form is granular fertilizer (powder form), usually come in a bag / box. The next most common form is liquid fertilizer; some advantages of liquid lawn fertilizer are its immediate effect and wide coverage. Moreover, there is also a form of slow-release fertilizer which solves the problem of "burning" the plants due to excessive nutrients. This kind of fertilizer come in various form like fertilizer spikes, tabs, etc. Finally, organic fertilizer is on the rise as people are resorting to a green / environmental friendly products. Although organic fertilizer usually contain less nutrients, some people still prefer organic due to natural ingredients.

Inorganic fertilizer (synthetic fertilizer)

Fertilizers are broadly divided into organic An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The distinction between "organic" and " fertilizers (composed of enriched organic matter—plant or animal), or inorganic Traditionally, inorganic compounds are considered to be of a mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin. Over the past century, the precise classification of inorganic vs organic compounds has become less important to scientists, primarily because the majority of fertilizers (composed of synthetic Synthetic is usually used in the sense of synthesis, the combination of two or more parts, whether by design or by natural processes. Furthermore, it may imply being prepar chemicals and/or minerals).

Inorganic fertilizer is often synthesized using the Haber-Bosch process The Haber process, also called the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen gas and hydrogen gas, over an enriched iron catalyst, to produce ammonia. The Haber process is important because ammonia is difficult to produce on an industrial scale, and the fertilizer generated from the ammonia is responsible for sustaining, which produces ammonia Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of as the end product. This ammonia is used as a feedstock A raw material is something that is acted upon or used by or by human labor or industry, for use as a building material to create some product or structure.[citation needed] Often the term is used to denote material that came from nature and is in an unprocessed or minimally processed state. Iron ore, logs, and crude oil, would be examples. A non- for other nitrogen fertilizers, such as anhydrous ammonium nitrate The chemical compound ammonium nitrate, the nitrate of ammonia with the chemical formula N and urea Urea or carbamide is an organic compound with the chemical formula (N . These concentrated products may be diluted with water to form a concentrated liquid fertilizer (e.g. UAN). Ammonia can be combined with rock phosphate Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of phosphorite is at least 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%. The phosphate is present as fluorapatite typically in and potassium fertilizer in the Odda Process The nitrophosphate process was a method for the industrial production of nitrogen fertilizers invented by Erling Johnson in the city of Odda, Norway around 1927 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 1 billion tonnes of nitrogen per year.^[3] 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 30–50 kg of phosphate fertilizer to be applied, soybean requires 20–25 kg per hectare.^[4] Yara International Yara International ASA is a Norwegian-based company which is a world leading supplier of plant nutrients in the form of mineral fertilizers. The core business of Yara is production and marketing of nitrogen fertilizer such as urea and nitrates. Yara also produces and sells ammonia, the key raw material for all nitrogen fertilizers is the world's largest producer of nitrogen based fertilizers.^[5]

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.^[7]

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.^[8]

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

Over-fertilization of a vital nutrient can be as detrimental as underfertilization.^[9] "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.^[10]

High energy consumption

The production of synthetic ammonia currently consumes about 5% of global natural gas consumption, which is somewhat under 2% of world energy production.^[11]

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.^[12] 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^[13].

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

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 improve the biodiversity (soil life) and long-term productivity of soil^[14][15], and may prove a large depository for excess carbon dioxide^[16][17][18].

Organic nutrients increase the abundance of soil organisms by providing organic matter and micronutrients for organisms such as fungal mycorrhiza^[19], (which aid plants in absorbing nutrients), and can drastically reduce external inputs of pesticides, energy and fertilizer, at the cost of decreased yield^[20].

Comparison with inorganic fertilizer

Organic fertilizer nutrient content, solubility, and nutrient release rates are typically all lower than inorganic fertilizers^[21][22]. 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^[23].

Organic fertilizers from composts and other sources can be quite variable from one batch to the next{http://www.msuorganicfarm.com/Compost.pdf}, 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{http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=0002290EN&q=http%3A%2F%2Fwww.csa.com%2Fpartners%2Fviewrecord.php%3Frequester%3Dgs%26collection%3DTRD%26recid%3D0002290EN&uid=789131166&setcookie=yes}.

Organic fertilizer sources

Animal

Animal-sourced urea , are suitable for application organic agriculture, while pure synthetic forms of urea are not^[24][25]. 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]}

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)^[26][27][28]. The USDA now requires 3rd-party certification of high-nitrogen liquid organic fertilizers sold in the U.S.^[29]

Plant

Cover crops are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere^[30]; as well as phosphorus (through nutrient mobilization)^[31] content of soils.

Mineral

Naturally mined powdered limestone^[32], mined rock phosphate and sodium nitrate, are inorganic (in a chemical sense), are energetically intensive to harvest, yet are approved for usage in organic agriculture in minimal amounts^[32][33][34].

Environmental effects of fertilizer use

Water

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.^[35] 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.^[36] 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.

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.^[37][38][39] 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.^[40]

Blue Baby Syndrome

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)^[41].

Soil

Soil acidification

Nitrogen-containing inorganic and organic fertilizers can cause soil acidification when added ^[42]. [4]. This may lead to decreases in nutrient availability which may be offset by liming.

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^[43]

Heavy metal accumulation

The concentration of up to 100 mg/kg of cadmium in phosphate minerals (for example, minerals from Nauru^[44] and the Christmas islands^[45]) increases the contamination of soil with cadmium, for example in New Zealand.^[46]

Uranium is another example of a contaminant often found in phosphate fertilizers (at levels from 7 to 100 pCi/g)^[47]. Eventually these heavy metals can build up to unacceptable levels and build up in vegetable produce.^[46] (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^[48].

Steel industry wastes, recycled into fertilizers for their high levels of zinc (essential to plant growth), wastes can include the following toxic metals: lead^[49]arsenic, cadmium^[49], chromium, and nickel. The most common toxic elements in this type of fertilizer are mercury, lead, and arsenic.^[50][51] Concerns have been raised concerning fish meal mercury content by at least one source in Spain^[52]

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.^{[53][54] [55][56][57][58]}

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.

Other problems

Atmospheric effects

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.^[59]

Through the increasing use of nitrogen fertilizer, which is added at a rate of 1 billion tons per year presently^[60] 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.^[61]

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:^[62]

• animal manures and urea, which release methane, nitrous oxide, ammonia, and carbon dioxide in varying quantities depending on their 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]}

Increased pest health

Excessive nitrogen fertilizer applications can also lead to pest problems by increasing the birth rate, longevity and overall fitness of certain^[which?] agricultural pests.^{[63][64][65][66][67][68]}

See also

• Soil fertility
• Manure
• Organic fertilizer
• Fertigation
• NPK rating
• Fertilizer labeling
• Agriculture and the environment
• Phosphogypsum

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External links

• Nitrogen for Feeding Our Food, Its Earthly Origin, Haber Process
• The Texas Vegetable Growers' Handbook, Chapter 3 Soils and fertilizers in agriculture.
• The Fertilizer Institute (TFI) US Fertilizer Industry Association
• International Fertilizer Industry Association (IFA)
• European Fertiliser Manufacturers Association
• How to read fertilizer tags article

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