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. 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 John Stevens Henslow 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 that 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 Rothamsted (later an agricultural research station), naming the 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 Joseph Fisons. These operations were 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-phosph