Superphosphate

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Superphosphate is a chemical fertiliser first synthesised in the 1840s by reacting bones with sulfuric acid. The process was subsequently improved by reacting phosphate coprolites with sulfuric acid. Subsequently other phosphate-rich deposits such as phosphorite were discovered and used. Soluble phosphate is an essential nutrient for all plants, and the availability of superphosphate revolutionised agricultural productivity.

Contents

History

The earliest phosphate-rich fertilisers were made from guano, animal manure or crushed bones. [1] So valuable were these resources during the Industrial Revolution that graveyards and catacombs across Europe were pillaged for human bones to satisfy demand. [1]

In 1842 the Reverend Hounslow found coprolites - fossilised dinosaur dung - in the cliffs of south Suffolk in England. He was aware of previous research in Dorset by William Buckland, which showed that coprolites were rich in phosphate which could be made available for plants by dissolution in sulfuric acid. John Bennet Lawes, who farmed in Hertfordshire, learnt of these discoveries and conducted his own research at his farm at Rothamstead (later an agricultural research station) and named his resultant product, "super phosphate of lime". [2] He patented the discovery and in 1842 started producing superphosphate from fossilised dinosaur dung on an industrial scale; this was the first chemical manure produced in the world. [1]

Edward Packard, recognising the significance of Lawes' work, converted a mill in Ipswich to produce this new fertiliser from coprolites excavated in the village of Kirton. He moved his operation in the 1850s to Bramford next to a similar new factory operated by Mt Fisons. These operations were subsequently destined to form part of the Fisons fertiliser company. The street where the original mill stood is still called Coprolite Street. [3]

Agricultural significance

All plants and animals need phosphorus compounds to carry out their normal metabolism even though in the case of plants it may constitute as little as 2% of their dry matter. [4] The phosphorus can be in the form of soluble inorganic phosphates or organic compounds containing phosphorus. In the living cell, energy is accumulated or expended using a complex range of biochemical processes which involve the transformation of adenosine triphosphate to adenosine diphosphate when energy is being expended and the reverse when energy is being accumulated as in photosynthesis. [5]

Superphosphate is relatively cheap [6] compared to other available sources of phosphate. The lower price contributes to its widespread adoption, particularly in developing regions where the costs of agricultural inputs are a significant consideration. [7]

The fate of phosphates in soil is complicated as they readily form complexes with other minerals such as clays, and aluminium and iron salts, [4] and may be generally unavailable to plants except by weathering and through the action of bacterial and the soil microbiome. [4] The advantage of superphosphate fertilisers is that a significant proportion of the phosphate content is soluble and is immediately available to plants. It thus provides a very quick boost to plant growth. However, the complex soil dynamics tend to immobilize phosphate in mineral complexes or organic ligands reducing the availability to plants. Phosphates are also lost to the soil and plant environment when crops are harvested or consumed by animals or otherwise lost to the local system. Phosphates tend to be tightly bound to fine sediments in the soil. [8] Leaching of sediments from soil can lead to elevated phosphate concentrations in the receiving watercourse. [9]

The addition of phosphorus as super-phosphate enables much greater crop yields. [4] Although there is some replenishment of soil phosphorus from mineral sources and release from soil complexes by physical and biological mechanisms, the rate of re-solubilisation is too low to support modern agricultural productivity. Organic phosphorus contained within plant or animal matter is much more readily re-solubilised as the material decomposes through microbial action. [4]

However, the key quality that made superphosphate so attractive—the solubility of the phosphate—also created an ongoing demand for the product as the soluble phosphorus salts and phosphate bound to fine sediments are eluted from fields into rivers and streams where they became lost to agriculture [10] but help to encourage unwelcome eutrophication. [5]

Manufacture

Superphosphates are manufactured in all the main industrial centres of the world, including Europe, China and the US. [11] In 2021 about 689,916 tonnes of superphosphate were produced with more than half from Poland and substantial amounts from Indonesia, Bangladesh, China and Japan. [12]

Formulations

All formulations of superphosphate contain a significant proportion of soluble and available phosphate ions which is the key quality that has made them essential for modern agriculture. [7]

Single superphosphate

Single superphosphate is produced using the traditional method of extraction of phosphate rock with sulfuric acid, an approximate 1:1 mixture of Ca(H2PO4)2 and CaSO4. [13]

Double superphosphate

The term, "double superphosphate", refers to a mixture of triple and single superphosphate, resulting from the extraction of phosphate rock with a mixture of phosphoric and sulfuric acids. [13]

Triple superphosphate

Triple superphosphate is a component of many proprietary fertilizers. It primarily consists of monocalcium phosphate, Ca(H2PO4)2. It is obtained by treating phosphate rock with phosphoric acid. Many proprietary fertilisers are derived from triple superphosphate, for example by blending with ammonium sulfate and potassium chloride. Typical fertiliser-grade triple superphosphate contains 45% P2O5eq, single superphosphate 20% P2O5eq. [13]

Adverse impacts of superphosphate

Continuous use of superphosphate can lead to soil acidification, particularly on poorly buffered soils, altering pH levels and potentially limiting nutrient availability. [14] This necessitates careful monitoring and management of soil pH to prevent long-term soil degradation. [15]

Production and transport produce significant quantities of CO2 amounting in some estimates to 1.2kg/kg for the manufacture of superphosphate and 238 g/kg for transport. [16] Other sources note that assuming all the sulfur for the sulfuric acid is recovered from oil and gas sweetening, [17] and the reaction to produce superphosphate is exothermic: provided that the heat generated is fully re-used, the whole cycle may have a negative carbon footprint as low as -518 g/kg for production alone. [16]

While superphosphate enriches soil with phosphorus, excessive or imbalanced application can disrupt nutrient ratios, leading to deficiencies or toxicities in plants. Evidence is emerging that elevated levels may be associated with deadly infections by Phytophthora cinnamomi . [18] Sustainable fertilization practices, including soil testing and targeted applications, are essential to mitigate this risk. [19]

The availability of suitable phosphate-rich rocks is limited and estimates of "peak phosphorus" vary between 30 years from 2022, [20] or somewhere between 2051 and 2092. [21] As the human population increases and the demand for food increases the availability of superphosphate fertilisers in the future may be less secure, suggesting that alternative sources of phosphate may need to be developed. [10]

A significant number of plants, especially those that evolved in Gondwanaland, have a sensitivity to excess phosphorus, [18] getting all that they need from associations with Arbuscular mycorrhiza. Examples of plants that are intolerant of the application of superphosphate include Hakea prostrata and Grevillea crithmifolia . Many terrestrial orchids which rely on mycorrhizal associations may have similar sensitivities to elevated phosphate levels [22] and populations may be suppressed by applications of superphosphate containing fertiliser. [23]

Eutrophication of rivers, lakes and the sea has a very well-documented link to increasing phosphate concentrations. However, teasing out the contribution made to this problem by the use of superphosphate is difficult because of the wide range of other sources of phosphorus compounds in both human and animal waste streams. Recent issues on the River Wye have been traced back to intensive poultry rearing with the excess phosphate coming from poorly-managed chicken manure. [24] [25]

Related Research Articles

<span class="mw-page-title-main">Phosphorus</span> Chemical element, symbol P and atomic number 15

Phosphorus is a chemical element; it has symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. In minerals, phosphorus generally occurs as phosphate.

<span class="mw-page-title-main">Phosphate</span> Chemical compound

In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, a.k.a. phosphoric acid H3PO4.

<span class="mw-page-title-main">Fertilizer</span> Substance added to soils to supply plant nutrients for a better growth

A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Many sources of fertilizer exist, both natural and industrially produced. For most modern agricultural practices, fertilization focuses on three main macro nutrients: nitrogen (N), phosphorus (P), and potassium (K) with occasional addition of supplements like rock flour for micronutrients. Farmers apply these fertilizers in a variety of ways: through dry or pelletized or liquid application processes, using large agricultural equipment or hand-tool methods.

<span class="mw-page-title-main">Plant nutrition</span> Study of the chemical elements and compounds necessary for normal plant life

Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig's law of the minimum. The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil.

Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water. The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca5(OH)(PO4)3. Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination.

<span class="mw-page-title-main">Soil fertility</span> The ability of a soil to sustain agricultural plant growth

Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality. It also refers to the soil's ability to supply plant/crop nutrients in the right quantities and qualities over a sustained period of time. A fertile soil has the following properties:

<span class="mw-page-title-main">Diammonium phosphate</span> Chemical compound

Diammonium phosphate (DAP; IUPAC name diammonium hydrogen phosphate; chemical formula (NH4)2(HPO4) is one of a series of water-soluble ammonium phosphate salts that can be produced when ammonia reacts with phosphoric acid.

<span class="mw-page-title-main">Organic fertilizer</span> Fertilizer developed from natural processes

Organic fertilizers are fertilizers that are naturally produced. Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include all animal waste including meat processing waste, manure, slurry, and guano; plus plant based fertilizers such as compost; and biosolids. Inorganic "organic fertilizers" include minerals and ash. The organic-mess refers to the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture, not whether the fertilizer consists of organic compounds.

<span class="mw-page-title-main">Monocalcium phosphate</span> Chemical compound

Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H2PO4)2·H2O. Both salts are colourless solids. They are used mainly as superphosphate fertilizers and are also popular leavening agents.

Agrogeology is the study of the origins of minerals known as agrominerals and their applications. These minerals are of importance to farming and horticulture, especially with regard to soil fertility and fertilizer components. These minerals are usually essential plant nutrients. Agrogeology can also be defined as the application of geology to problems in agriculture, particularly in reference to soil productivity and health. This field is a combination of a few different fields, including geology, soil science, agronomy, and chemistry. The overall objective is to advance agricultural production by using geological resources to improve chemical and physical aspects of soil.

Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Chemically, this happens when a proton donor gets added to the soil. The donor can be an acid, such as nitric acid, sulfuric acid, or carbonic acid. It can also be a compound such as aluminium sulfate, which reacts in the soil to release protons. Acidification also occurs when base cations such as calcium, magnesium, potassium and sodium are leached from the soil.

<span class="mw-page-title-main">Phosphorus cycle</span> Biogeochemical movement

The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily. The production of phosphine gas occurs in isolated and specific conditions. Therefore, the phosphorus cycle is primarily viewed through terrestrial and aquatic ecosystems.

<span class="mw-page-title-main">Leaching (agriculture)</span> Loss of water-soluble plant nutrients from soil due to rain and irrigation

In agriculture, leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss. Leaching may also refer to the practice of applying a small amount of excess irrigation where the water has a high salt content to avoid salts from building up in the soil. Where this is practiced, drainage must also usually be employed, to carry away the excess water.

<span class="mw-page-title-main">Ammonium dihydrogen phosphate</span> Chemical compound

Ammonium dihydrogen phosphate (ADP), also known as monoammonium phosphate (MAP) is a chemical compound with the chemical formula (NH4)(H2PO4). ADP is a major ingredient of agricultural fertilizers and dry chemical fire extinguishers. It also has significant uses in optics and electronics.

<span class="mw-page-title-main">Agricultural pollution</span> Type of pollution caused by agriculture

Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pollution may come from a variety of sources, ranging from point source water pollution to more diffuse, landscape-level causes, also known as non-point source pollution and air pollution. Once in the environment these pollutants can have both direct effects in surrounding ecosystems, i.e. killing local wildlife or contaminating drinking water, and downstream effects such as dead zones caused by agricultural runoff is concentrated in large water bodies.

<span class="mw-page-title-main">Phosphorus deficiency</span> Plant disorder

Phosphorus deficiency is a plant disorder associated with insufficient supply of phosphorus. Phosphorus refers here to salts of phosphates (PO43−), monohydrogen phosphate (HPO42−), and dihydrogen phosphate (H2PO4−). These anions readily interconvert, and the predominant species is determined by the pH of the solution or soil. Phosphates are required for the biosynthesis of genetic material as well as ATP, essential for life. Phosphorus deficiency can be controlled by applying sources of phosphorus such as bone meal, rock phosphate, manure, and phosphate-fertilizers.

Phosphate rich organic manure is a type of fertilizer used as an alternative to diammonium phosphate and single super phosphate.

<span class="mw-page-title-main">History of fertilizer</span>

The history of fertilizer has largely shaped political, economic, and social circumstances in their traditional uses. Subsequently, there has been a radical reshaping of environmental conditions following the development of chemically synthesized fertilizers.

Many countries have standardized the labeling of fertilizers to indicate their contents of major nutrients. The most common labeling convention, the NPK or N-P-K label, shows the amounts of the chemical elements nitrogen, phosphorus, and potassium.

Seventeen elements or nutrients are essential for plant growth and reproduction. They are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), nickel (Ni) and chlorine (Cl). Nutrients required for plants to complete their life cycle are considered essential nutrients. Nutrients that enhance the growth of plants but are not necessary to complete the plant's life cycle are considered non-essential, although some of them, such as silicon (Si), have been shown to improve nutrent availability, hence the use of stinging nettle and horsetail macerations in Biodynamic agriculture. With the exception of carbon, hydrogen and oxygen, which are supplied by carbon dioxide and water, and nitrogen, provided through nitrogen fixation, the nutrients derive originally from the mineral component of the soil. The Law of the Minimum expresses that when the available form of a nutrient is not in enough proportion in the soil solution, then other nutrients cannot be taken up at an optimum rate by a plant. A particular nutrient ratio of the soil solution is thus mandatory for optimizing plant growth, a value which might differ from nutrient ratios calculated from plant composition.

References

  1. 1 2 3 O'Connor, Bernard (2005). "The Origins and Developments of the British Coprolite industry" (PDF). Mining History: The Bulletin of the Peak District Historical Society. 14 (5). Archived from the original (PDF) on 2017-02-02. Retrieved 27 March 2024.
  2. ↑ Ivell, David M. (2012). "Phosphate Fertilizer Production – From the 1830's to 2011 and Beyond". Procedia Engineering. 46: 166–171. doi: 10.1016/j.proeng.2012.09.461 . Retrieved 28 March 2024.
  3. ↑ "The Story of Corpolite Street". Ipswich Maritime Trust. 26 October 2019. Retrieved 28 March 2024.
  4. 1 2 3 4 5 "Phosphorus Basics: Understanding Phosphorus Forms and Their Cycling in the Soil". Alabama A&M and Auburn Universities. 19 April 2019. Retrieved 28 March 2024.
  5. 1 2 "Why phosphorus is important". New South Wales Department of Primary Industries. Retrieved 28 March 2024.
  6. ↑ "Story: Superphosphate". Encyclopaedia of New Zealand - Teara. 24 November 2008. Retrieved 8 April 2024.
  7. 1 2 "Phosphorus: a finite resource essential for life, critical for agriculture and food security". CSIRO _ Australia's Science Agency. 26 June 2019. Retrieved 28 March 2024.
  8. ↑ "Phosphorus". University of Hawaii at Manoa. Retrieved 8 April 2024.
  9. ↑ "Phosphorus leaching from soils". Altera Scientific Contributions -Wageningen University. 26 May 2015. Retrieved 8 April 2024.
  10. 1 2 "Phosphorus: Essential to Life—Are We Running Out?". Columbia Climate School. 1 April 2013. Retrieved 8 April 2024.
  11. ↑ "Normal superphosphates" (PDF). EPA. Retrieved 28 March 2024.
  12. ↑ "Superphosphate above 35% - production". Knoema. Retrieved 28 March 2024.
  13. 1 2 3 Kongshaug, Gunnar; Brentnall, Bernard A.; Chaney, Keith; Gregersen, Jan-Helge; Stokka, Per; Persson, Bjørn; Kolmeijer, Nick W.; Conradsen, Arne; Legard (2014). "Phosphate Fertilizers". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. pp. 1–49. doi:10.1002/14356007.a19_421.pub2. ISBN   978-3527306732.
  14. ↑ Horsnell, LJ (1985). "The growth of improved pastures on acid soils. 1. The effect of superphosphate and lime on soil pH and on the establishment and growth of phalaris and lucerne". Australian Journal of Experimental Agriculture. 25. CSIRO: 149. doi:10.1071/ea9850149 . Retrieved 28 March 2024.
  15. ↑ von Tucher, S.; Hörndl, D.; Schmidhalter, U. (24 November 2017). "Interaction of soil pH and phosphorus efficacy: Long-term effects of P fertilizer and lime applications on wheat, barley, and sugar beet". Ambio. 47 (Suppl 1): 41–49. doi:10.1007/s13280-017-0970-2. PMC   5722739 . PMID   29178058.
  16. 1 2 "Table 7: Greenhouse Gas Emission Factors for Phosphate Fertilisers" (PDF). Stanford University. June 2004. Retrieved 28 March 2024.
  17. ↑ "Mineral Resource of the Month - Sulfur". The American Geological Institute. July 2023. Retrieved 29 March 2024.
  18. 1 2 "Super-sensitive plants" (PDF). University of Western Australia. April 2024. Retrieved 28 March 2024.
  19. ↑ "Preventing Phytophthora Infestations in Restoration Nurseries". Oregon State University. January 2022. Retrieved 8 April 2024.
  20. ↑ "Approaching peak phosphorus". Nature Plants. 8. 15 September 2022. Retrieved 28 March 2024.
  21. ↑ Risks and Opportunities in the Global Phosphate Rock Market (PDF). The Hague Centre for Strategic Studies. ISBN   978-94-91040-69-6 . Retrieved 29 March 2024.
  22. ↑ Davis, B.; Lim, W. H.; Lambers, H.; Dixon, K. W.; Read, D. J. (12 May 2022). "Inorganic phosphorus nutrition in green-leaved terrestrial orchid seedlings". Annals of Botany. 129 (6): 669–678. doi:10.1093/aob/mcac030. PMC   9113155 . PMID   35247265.
  23. ↑ Nouri, E.; Surve, R.; Bapaume, L.; Stumpe, M.; Chen, M.; Zhang, Y.; Ruyter-Spira, C.; Bouwmeester, H.; Glauser, G.; Bruisson, S.; Reinhardt, D. (28 June 2021). "Phosphate Suppression of Arbuscular Mycorrhizal Symbiosis Involves Gibberellic Acid Signaling". Plant and Cell Physiology. 62 (6). National Library of Medicine: 959–970. doi:10.1093/pcp/pcab063. PMC   8504448 . PMID   34037236.
  24. ↑ "Analysis: A watershed moment for phosphates and the river Wye". MA Agriculture. 20 February 2023. Retrieved 29 March 2024.
  25. ↑ "River Wye: Pollution not caused by farming, says NFU". BBC News. 14 August 2023. Retrieved 29 March 2024.
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