Use: What is Needed to Support Sustainability?

Abstract

Increased demands for agricultural output per unit of land area must be met in a way that encourages improved efficiency and better stewardship of natural resources, including phosphate rock. Modern crops remove between 5 and 35 kg P/ha, with P removal exceeding 45 kg P/ha for high-yielding maize. In situations such as Sub-Saharan Africa, where soil fertility is low and P removal exceeds average inputs of 2 kg P/ha/year, the resulting nutrient depletion severely restricts yields (e.g., maize yields < 1,000 kg/ha/year) and accelerates soil degradation. In other regions, excessive P inputs produce economic inefficiencies and increase the risk of P loss, with negative environmental consequences. During the year of application, plants recover 15–25 % of the added P, with the remaining fraction converting to less soluble forms or residual P which becomes plant available over time. Improving P efficiency requires a balance between the imperatives to produce more food while minimizing P losses. Utilizing transdisciplinary approaches, a number of social, economic, and environmental goals can be simultaneously achieved if progress is made toward short- and long-term food security and global P sustainability. This chapter provides an overview of efforts to improve P use efficiency in agriculture ranging from promising germplasm, improved crop, and soil management scenarios, additives in animal diets to reduce P inputs and surplus P in the manure, and opportunities for P recycling in food and household waste. Challenges and opportunities associated with each option are discussed and transdisciplinary case studies outlined.

Appendices

Health Dimensions of Phosphorus

• James J. Elser 

1. Arizona State University, Downtown Phoenix campus, 411 N. Central Avenue, Phoenix, AZ, 85004, USA

   James J. Elser

Phosphorus is an essential element for all living things, needed (in the form of phosphate, PO₄) in cells for construction and renewal of DNA & RNA, of phospholipids, and of energy transduction molecules such as ATP. In vertebrates, PO₄ (P_i, hereafter) is a main component of the mineral apatite (a form of calcium phosphate) in bones. Thus, human health depends on an adequate dietary supply of P every day (DACH 2008, Reference Values for Nutrient Intake): 700 mg for an adult, 500–1,250 mg for children and youth). The body tightly regulates P_i homeostasis, primarily by modulating P_i excretion in the kidney, closely in concert with calcium (Ca) due to their joint role in bone formation.

Deficiency

Deficiencies of P are well studied in association with Vitamin D metabolism, as Vitamin D regulates levels of Ca and P in the bloodstream and thus controls bone growth and remodeling (Perwad and Portale 2011). Vitamin D deficiency leads primarily to bone fragilization (“rickets”), a relatively rare condition in the modern world. Direct deficiency of P (“hypophosphatemia”) is also relatively rare for humans nowadays, as P_i is relatively abundant in many foods and easily assimilated in the gut. However, it can occur independent of Vitamin D deficiency in, for example, cases of general malnutrition, alcoholism, damage to the gastrointestinal tract, or tumors that produce the P_i-regulating hormone FGF23.

Excess

Elemental P: Nearly all P on Earth is in the oxidized form, as phosphate (PO₄). However, various industrial processes involve production and use of two molecular forms of elemental P: white phosphorus (P₄) and red phosphorus (a polymer based on the P₄ unit). These forms of P are used in production of matches, munitions, and illicitly methamphetamines. Elemental P is highly unstable and reactive, readily reacting with oxygen. Thus, exposure to elemental P is damaging to tissues, and use and exposure in industrial settings are usually subjected to close regulation.

Dietary PO ₄ and kidney dialysis: A significant challenge facing kidney disease patients is proper regulation of body PO ₄ because existing dialysis methods are relatively inefficient in removing PO ₄ (Kuhlmann 2007). Thus, patients with kidney disease often exhibit excess serum phosphate (“hyperphosphatemia”) that must be addressed using PO ₄ -binding medications and/or by reducing levels of dietary P intake. The latter can be challenging because foods with high P content are often the same as those with high protein content (thus patients can become protein deficient) and because many foods contain PO ₄ additives used as preservatives (e.g., deli meats, many processed foods) or flavorants (e.g., phosphoric acid in some soft drinks).

Dietary PO ₄ , cardiovascular disease, aging, and cancer: The health risks of P are well established for elemental forms and for patients with kidney disease. However, tentative epidemiological and animal data also suggest link between P_i intake (both high and low) and certain degenerative diseases and cancers. For example, P_i has been called the “new cholesterol” (Ellam and Chico 2012) due to evidence linking high P_i intake to cardiovascular disease via a mechanism in which P_i reacts with Ca in formation of mineral plaques that contribute to atherosclerosis (“hardening of the arteries”). The reader should bear in mind, however, that such epidemiological studies cannot conclusively establish such links and considerably more work is needed. Some data connecting elevated P_i intake to accelerated aging have recently appeared, in the form of studies of mice-bearing mutations in the gene Klotho (John et al. 2011), which acts with FGF23 to regulate kidney P_i transport. Mice lacking either FGF23 or Klotho show hyperphosphatemia and develop multiple aging-like symptoms. This work is in a preliminary stage and has not been extensively evaluated for its relevance to humans. Finally, it has recently been proposed that dietary P_i has a mechanistic link to tumor progression because of the high P demands needed to construct ribosomal RNA in rapidly growing tumor cells (Elser et al. 2003). Tentative support for this hypothesis has appeared from comparative study of human tumors (Elser et al. 2007) and experimental dietary P manipulations in mice (Wulaningsih et al. 2013). As with P_i’s possible association with aging, much further work remains to confirm or reject a putative connection to human cancer.

Acknowledgements

The author is grateful for the helpful comments of Haley C. Steven, Roland W. Scholz, Marc Vermeulen and two anonymous reviewers, whose input helped clarify important issues in the text.

References

• Camalier CE, Young MR, Bobe G, Perella CM, Colburn NH, Beck GR, Jr. (2010) Elevated Phosphate Activates N-ras and Promotes Cell Transformation and Skin Tumorigenesis. Cancer Prevention Research 3 (3):359-370. doi:10.1158/1940-6207.capr-09-0068

• DACH (2008) Referenzwerte für Nährstoffzufuhr, 3rd edn. http://www.sge-ssn.ch/de/ich-und-du/rund-um-lebensmittel/Referenzwerte-fuer-die-Naehrstoffzufuhr/

• Ellam TJ, Chico TJA (2012) Phosphate: the new cholesterol? The role of the phosphate axis in non-uremic vascular disease. Atherosclerosis 220(2):310–318. doi:10.1016/j.atherosclerosis.2011.09.002

• Elser JJ, Kuang Y, Nagy J (2003) Biological stoichiometry of tumor dynamics: an ecological perspective. BioScience 53:1112–1120

• Elser JJ, Kyle M, Smith M, Nagy J (2007) Biological stoichiometry in human cancer. PLoS ONE 10:e1028. doi:10.1371/journal.pone.0001028

• Jin H, Xu C-X, Lim H-T, Park S-J, Shin J-Y, Chung Y-S, Park S-C, Chang S-H, Youn H-J, Lee K-H, Lee Y-S, Ha Y-C, Chae C-H, Beck GR, Jr., Cho M-H (2009) High dietary inorganic phosphate increases lung zumorigenesis and alters Akt signaling. American Journal of Respiratory and Critical Care Medicine 179 (1):59-68. doi:10.1164/rccm.200802-306OC

• John GB, Cheng CY, Kuro-o M (2011) Role of Klotho in aging, phosphate metabolism, and CKD. Am J Kidney Dis 58(1):127–134. doi:10.1053/j.ajkd.2010.12.027

• Kuhlmann MK (2007) Practical approaches to management of hyperphosphatemia: can we improve the current situation? Blood Purif 25(1):120–124. doi:10.1159/000096410

• Perwad F, Portale AA (2011) Vitamin D metabolism in the kidney: regulation by phosphorus and fibroblast growth factor 23. Mol Cell Endocrinol 347(1–2):17–24. doi:10.1016/j.mce.2011.08.030

• Wulaningsih W, Michaelsson K, Garmo H, Hammar N, Jungner I, Walldius G, Holmberg L, Van Hemelrijck M (2013) Inorganic phosphate and the risk of cancer in the Swedish AMORIS study. Bmc Cancer Unsp 13:257. doi:10.1186/1471-2407-13-257

Phosphorus in the Diet and Human Health

• Rainer Schnee,
• Haley Curtis Stevens &
• Marc Vermeulen 

1. Chemische Fabrik Budenheim KG, Rheinstrasse 27, 55257, Budenheim, Germany

   Rainer Schnee

2. International Food Additives Council (IFAC), 1100 Johnson Ferry Road, Suite 300, Atlanta, GA, 30342, USA

   Haley Curtis Stevens

3. Phosphoric Acid & Phosphates (PAPA), European Chemical Industry Council, Avenue E. van Nieuwenhuyse 4 , 1160, Brussels, Belgium

   Rainer Schnee & Marc Vermeulen

A minimum of phosphorus in human diets is essential for health, because the body needs phosphorus (P) for bones, teeth, DNA, energy metabolism and many other functions. The recommended daily requirement for health (DV) for P is 1,000 mg/day (Council for Responsible Nutrition 2013, based on US Food and Drug Administration data). However, modern Western diets often have higher levels of P, because of improved diets, increased meat and dairy product intake (rich in P, calcium and other minerals) and food phosphates used to ensure safety (bacteria free preservation) or processing of many modern foods, such as cakes, soft cheese, cold meats, pre-prepared meals. Today in Europe, dietary P intake is around 1.3–2.7 g P/day (Flynn et al. 2009). The balance between P and dietary calcium is important.

The dietary contribution of food phosphate additives is around 0.15 g P/day, based on an estimate by the Phosphoric Acid and Phosphates Producers Association of 25,000 t P/year in food additives for EU25 in 2006. This is well below the MTDI (Maximum Tolerable Daily Intake) for food phosphates considered safe (JECFA 1982). The large majority of P in diets comes from natural sources, such as milk and dairy products, meat and many other foods.

For patients with kidney problems, it is generally recognized that P accumulation in the body can cause significant health damage. This is because P is normally balanced in the body by excretion of unneeded intake by the kidneys.

A number of studies suggest a statistical relationship between blood phosphorus concentrations (serum P) and indicators of cardiovascular disease (CVD) in the general population. Some recent studies (Westerberg et al. 2013; Itkonen et al. 2013), however, show no link after taking into account other factors. It is thus unclear whether P and/or other minerals (e.g., calcium) contribute to these risks, or whether both are consequences of other factors such as unhealthy diet, obesity, undeclared kidney insufficiency, or other body metabolism problems.

While it is recognized that deterioration of kidney function leads to increased blood P (serum P), there is no evidence that higher dietary P levels lead to increased serum P (except immediately after the P containing meal) in persons not suffering from kidney function deficiency. Indeed, correctly functioning kidneys normally maintain an optimal serum P level. Analysis of the numerous studies available comparing P intake to serum P show that many do not contain relevant data (diet not known, data only for very short term such as one dose of high dietary P), and that those containing useful data do not enable any conclusion because they reach conflicting conclusions.

Very few studies are available comparing dietary P levels directly with heart disease (as opposed to comparing P intake to serum P or serum P to heart disease), and the studies which do exist show contradictory results, some suggesting a correlation and others suggesting no correlation or an inverse correlation (dietary phosphorus inversely related to heart disease symptoms) (Alonso et al. 2010; Elliott et al. 2008; Joffres et al. 1987).

Thus scientific data does not at present indicate that the P content of Western diets increases heart disease risk. Further investigation is warranted to better understand the roles of diet and life style in the etiology of heart disease.

Although several publications suggest a possible link between dietary P and other health impacts these are based on metabolic hypotheses, with very little in vitro basis and virtually no experimental evidence. Because there are very few experimental data, it must be considered that these may be caused by artifacts. The experimental evidence regarding cancer concerns only genetically modified mice, artificially susceptible to cancer. It can be considered that these results cannot be reliably extrapolated to normal mice, or to humans (IFAC 2009). In the most cited case (Jin et al. 2009) a later similar experiment by the same authors with the same genetically modified mice produced the contrary result: a low phosphate diet increased lung cancer (Cheng-Xiong et al. 2010). We face the problem of extrapolation of experimental findings to human in vivo conditions also with a study suggesting that high dietary P in Drosphila flies reduced their lifespan (aging), which again cannot be reliably extrapolated to humans, has been completed by a further study suggesting that this is due to impairment of flies’ equivalent to kidneys (Bergwitz et al. 2013).

A few epidemiological or in vitro studies with humans suggest a statistical relationship between dietary P and cancer occurrence, but others show no relationship (Berndt et al. 2002; Chan et al. 1998; Giovannucci et al. 1998; Tavani et al. 2005), and others an inverse relationship (increased dietary P related to lower cancer incidence; Brinkman et al. 2010; Chan et al. 2000; Kesse et al. 2005; Spina et al. 2012; Takata et al. 2013; van Lee et al. 2011) or positive/negative relationships for different forms of cancer (Wulaningsih et al. 2013). Other recent publications suggest a possible link between low dietary P and obesity (Celik and Andiran 2011; Lindegarde and Trell 1977; Haglin et al. 2001; Lind et al. 1993; Obeid 2013) or between dietary P and reduced cholesterol (Kim et al. 2013; Ditscheid et al. 2005; Lippi et al. 2009; Trautvetter et al. 2012). There are many other studies which indicate that P intake is safe at current levels (see e.g., JECFA 1982; Weiner et al. 2001).

Based on the current scientific evidence, it can be concluded that normal Western levels of dietary P intake are safe: no studies have reported a clear link to human health risks. This is to conform to the conclusions of the European EFSA scientific panel (EFSA 2005).

Acknowledgements

Thanks to James J. Elser, Myra Weiner, Roland W. Scholz and two anonymous reviewer, whose input helped to improve the text.

References

• Alonso A, Nettleton JA, Ix JH, de Boer IH, Folsom AR, Bidulescu A, Kestenbaum BR, Chambless LE, Jacobs DR Jr (2010) Dietary phosphorus, blood pressure, and incidence of hypertension in the atherosclerosis risk in communities study and the multi-ethnic study of atherosclerosis. Hypertension 55 (3):776–U109. doi:10.1161/hypertensionaha.109.143461

• Bergwitz C, Wee MJ, Sinha S, Huang J, DeRobertis C, Mensah LB, Cohen J, Friedman A, Kulkarni M, Hu Y, Vinayagam A, Schnall-Levin M, Berger B, Perkins LA, Mohr SE, Perrimon N (2013) Genetic Determinants of Phosphate Response in Drosophila. Plos One 8(3): e56753. doi:10.1371/journal.pone.0056753

• Berndt SI, Carter HB, Landis PK, Tucker KL, Hsieh LJ, Metter EJ, Platz EA (2002) Calcium intake and prostate cancer risk in a long-term aging study: the Baltimore longitudinal study of aging. Urology 60(6):1118–1123. doi:10.1016/s0090-4295(02)01991-x

• Brinkman MT, Karagas MR, Zens MS, Schned A, Reulen RC, Zeegers MP (2010) Minerals and vitamins and the risk of bladder cancer: results from the New Hampshire study. Cancer Causes Control 21(4):609–619. doi:10.1007/s10552-009-9490-0

• Celik N, Andiran N (2011) The relationship between serum phosphate levels with childhood obesity and insulin resistance. J Pediatr Endocrinol Metab 24(1–2):81–83. doi:10.1515/jpem.2011.116

• Chan JM, Giovannucci E, Andersson SO, Yuen J, Adami HO, Wolk A (1998) Dairy products, calcium, phosphorous, vitamin D, and risk of prostate cancer (Sweden). Cancer Causes Control 9(6):559–566. doi:10.1023/a:1008823601897

• Chan JM, Pietinen P, Virtanen M, Malila N, Tangrea J, Albanes D, Virtamo J (2000) Diet and prostate cancer risk in a cohort of smokers, with a specific focus on calcium and phosphorus (Finland). Cancer Causes Control 11(9):859–867. doi:10.1023/a:1008947201132

• Cheng-Xiong X, Hua J, Hwang-Tae L, Yoon-Cheol H, Chan-Hee C, Gil-Hwan A, Kee-Ho L, Myung-Haing C (2010) Low dietary inorganic phosphate stimulates lung tumorigenesis through altering protein translation and cell cycle in K- rasLA1 mice. Nutr Cancer 62(4):525–532

• Council for Responsible Nutrition (CRN) (2013) Vitamin and mineral recommendations. http://www.crnusa.org/about_recs.html

• Ditscheid B, Keller S, Jahreis G (2005) Cholesterol metabolism is affected by calcium phosphate supplementation in humans. J Nutr 135(7):1678–1682

• EFSA (2005) Opinion of the scientific panel on dietetic products, nutrition and allergies on a request from the commission related to the tolerable upper intake level of phosphorus. EFSA J 233:1–19 (http://www.efsa.europa.eu/de/efsajournal/doc/233.pdf)

• Elliott P, Kesteloot H, Appel LJ, Dyer AR, Ueshima H, Chan Q, Brown IJ, Zhao L, Stamler J, Grp ICR (2008) Dietary phosphorus and blood pressure—international study of Macro- and Micro-nutrients and blood pressure. Hypertension 51(3):669–675. doi:10.1161/hypertensionaha.107.103747

• Flynn A, Hirvonen T, Mensink GBM, Ocke MC, Serra-Majem L, Stos K, Szponar L, Tetens I, Turrini A, Fletcher R, Wildemann T (2009) Intake of selected nutrients from foods, from fortification and from supplements in various European countries. Food Nutr Res 53:20–20. doi:10.3402/fnr.v53i0.2038

• Giovannucci E, Rimm EB, Wolk A, Ascherio A, Stampfer MJ, Colditz GA, Willett WC (1998) Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res 58(3):442–447

• Haglin L, Lindblad A, Bygren LO (2001) Hypophosphataemia in the metabolic syndrome. Gender differences in body weight and blood glucose. Eur J Clin Nutr 55(6):493–498. doi:10.1038/sj.ejcn.1601209

• IFAC (2009) Statement of the international food additives council and the European chemical industry council. www.cefic.org/Documents/Other/Backgrounder_of_et_al_1-21-09.doc

• Itkonen ST, Karp HJ, Kemi VE, Kokkonen EM, Saarnio EM, Pekkinen MH, Karkkainen MUM, Laitinen EKA, Turanlahti MI, Lamberg-Allardt CJE (2013) Associations among total and food additive phosphorus intake and carotid intima-media thickness—a cross-sectional study in a middle-aged population in Southern Finland. Nutrition J 12:94. doi:10.1186/1475-2891-12-94

• JECFA (World Health Organisation Joint Expert Committee on Food Additives) (1982) International programme on chemical safety, WHO food additives series 17. http://www.inchem.org/documents/jecfa/jecmono/v17je22.htm

• Jin H, Xu C-X, Lim H-T, Park S-J, Shin J-Y, Chung Y-S, Park S-C, Chang S-H, Youn H-J, Lee K-H, Lee Y-S, Ha Y-C, Chae C-H, Beck GR Jr, Cho M-H (2009) High dietary inorganic phosphate increases lung zumorigenesis and alters Akt signaling. Am J Respir Crit Care Med 179(1):59–68. doi:10.1164/rccm.200802-306OC

• Joffres MR, Reed DM, Yano K (1987) Relationship of magnesium intake and other dietary factors to blood-pressure—the Honolulu heart-study. Am J Clin Nutr 45(2):469–475

• Kesse E, Boutron-Ruault MC, Norat T, Riboli E, Clavel-Chapelon F, Grp EN (2005) Dietary calcium, phosphorus, vitamin D, dairy products and the risk of colorectal adenoma and cancer among French women of the E3N-EPIC prospective study. Int J Cancer 117(1):137–144. doi:10.1002/ijc.21148

• Kim WS, Lee D-H, Youn H-J (2013) Calcium-phosphorus product concentration is a risk factor of coronary artery disease in metabolic syndrome. Atherosclerosis 229(1):253–257. doi:10.1016/j.atherosclerosis.2013.04.028

• van Lee L, Heyworth J, McNaughton S, Iacopetta B, Clayforth C, Fritschi L (2011) Selected dietary micronutrients and the risk of right- and left-sided colorectal cancers: a case-control study in Western Australia. Ann Epidemiol 21(3):170–177. doi:10.1016/j.annepidem.2010.10.005

• Lind L, Lithell H, Hvarfner A, Pollare T, Ljunghall S (1993) On the relationships between mineral metabolism, obesity and fat distribution. Eur J Clin Invest 23(5):307–310. doi:10.1111/j.1365-2362.1993.tb00779.x

• Lindegarde F, Trell E (1977) Serum inorganic phosphate in middle-aged men I. Inverse relation to body weight. Acta Medica Scandinavica 202:307–311

• Lippi G, Miôntagna M, Salvagno GL, Targher G, Guidi GC (2009) Relationship between serum phosphate and cardiovascular risk factors in a large cohort of adult outpatients. Diab Res Clin Pract 84:e3–e5

• Obeid OA (2013) Low phosphorus status might contribute to the onset of obesity. Obes Rev 14(8):659–664

• Spina A, Sapio L, Esposito A, Di Maiolo F, Sorvillo L, Naviglio S (2012) Inorganic phosphate as a novel signaling molecule with antiproliferative action in MDA-MB-231. BioRes doi:10.1089/biores.2012.0266

• Takata Y, Shu X-O, Yang G, Li H, Dai Q, Gao J, Cai Q, Gao Y-T, Zheng W (2013) Calcium intake and lung cancer risk among female nonsmokers: a report from the Shanghai women’s health study. Cancer Epidemiol Biomark Prev 22(1):50–57. doi:10.1158/1055-9965.epi-12-0915-t

• Tavani A, Bertuccio P, Bosetti C, Talamini R, Negri E, Franceschi S, Montella M, La Vecchia C (2005) Dietary intake of calcium, vitamin D, phosphorus and the risk of prostate cancer. Eur Urol 48(1):27–33. doi:10.1016/j.eururo.2005.03.023

• Trautvetter U, Ditscheid B, Kiehntopf M, Jahreis G (2012) A combination of calcium phosphate and probiotics beneficially influences intestinal lactobacilli and cholesterol metabolism in humans. Clin Nutr 31(2):230–237. doi:10.1016/j.clnu.2011.09.013

• Weiner ML, Salminen WF, Larson PR, Barter RA, Kranetz JL, Simon GS (2001) Toxicological review of inorganic phosphates. Food Chem Toxicol 39:759–786

• Westerberg P-A, Tivesten A, Karlsson MK, Mellstrom D, Orwoll E, Ohlsson C, Larsson TE, Linde T, Ljunggren O (2013) Fibroblast growth factor 23, mineral metabolism and mortality among elderly men (Swedish MrOs). Bmc Nephrol 14:85. doi:10.1186/1471-2369-14-85

• Wulaningsih W, Michaelsson K, Garmo H, Hammar N, Jungner I, Walldius G, Holmberg L, Van Hemelrijck M (2013) Inorganic phosphate and the risk of cancer in the Swedish AMORIS study. Bmc Cancer 13:257. doi:10.1186/1471-2407-13-257

Technological Use of Phosphorus: The Non-fertilizer, Non-feed and Non-detergent Domain

• Oliver Gantner,
• Willem Schipper &
• Jan J. Weigand 

1. Resource Strategy, University of Augsburg, Universitätsstr. 1a, 86159, Augsburg, Germany

   Oliver Gantner

2. Willem Schipper Consulting, Middleburg, The Netherlands

   Willem Schipper

3. Department of Chemistry and Food Chemistry, TU Dresden, Mommsenstr, 4, 01062, Dresden, Germany

   Jan J. Weigand

Out of a total of 191 million tons phosphate rock mined yearly (2011 figure; Jasinski 2012), a large part is used to make fertilizers, via merchant grade phosphoric acid (MGA), and only a small part, typically 10–15 %, is used for non-fertilizer applications (IFA 2011).

Accurate figures for non-fertilizer uses are not available. IFA (2008) estimates about 7 % is used to make detergents, 10 % to make feed supplements for livestock, and 3 % is used in other applications. Recent estimates (CRU 2013) put feed usage at 5 %, detergents at 2 % and all other uses at 3 % combined. Most of these other applications, as well as a fair part of the detergent phosphate production, involve the manufacturing of elemental, white phosphorus P₄ (“thermal route”) which constitutes the only other relevant processing route for rock besides MGA/fertilizer (“wet acid route”).

The authors estimate a very approximate breakdown for world use of phosphorus (P) as follows:

• 85–90 % fertilizer

• ±5 % animal feeds

• 1 % food

• 2 % detergents

• 1 % glyphosate

• 1 % other P₄ derivatives

• 1 % other technical phosphates

These numbers are estimates reflecting the uncertainties and differences between published data and are given to the best of knowledge of the authors for the years 2010–2012. They serve above all to demonstrate the relative importance of each use segment. This spotlight focuses on the non-fertilizer uses of P, which include both MGA derived and P₄- derived products, hereafter referred to as the “technological use of P.” These include ortho- and polyphosphates, from either MGA (usually) or P₄, as well as a large catchall category of organophosphorus compounds and inorganic phosphorus derivatives that can only be manufactured from the element, P₄.

As MGA contains up to 5 % of sulfate and metallic impurities originating from the rock and manufacturing conditions, phosphates derived from MGA usually need some form of purification of the acid, by extraction, precipitation or crystallization, thus essentially forming a product that competes with high-purity acid and its derived phosphates as obtained through oxidation of P₄ and subsequent hydrolysis (“thermal acid”). Applications include technical fields (detergent, firefighting, flame retardants, water treatment, and many others), feed and food uses, and these determine the amount of purification needed.

Feed phosphates are added to livestock feed, typically as mono-, dicalcium, and several sodium phosphates. As purity requirements are not as strict as for human consumption, these are routinely made from partially purified MGA. This also includes a number of phosphates used in the pet food industry (pyro/polyphosphates).

Food phosphates and food grade phosphoric acid perform a host of functions, such as moisture retention, sequestering, and acidulation. These are made either from highly purified MGA or from thermal acid, with soda ash or caustic soda in most cases. Ammonium, calcium, magnesium, aluminum, and potassium salts are also commercially relevant.

Technical phosphates such as detergent sodium tripolyphosphate (STPP) or phosphates for water treatment, firefighting compositions, and ceramics can be made either from MGA (usual) or via the thermal route. The choice between the two routes is above all cost driven, as a higher quality requires more rigorous purification and hence additional cost (Table 1).

Table 1 Overview of phosphate containing applications (non-exhaustive) References Budenheim (2013), Emsley (2000), Phosphate Facts (2013), Prayon; Villalba et al. (2008)

The remaining P compounds all necessarily need to be made through the most reactive allotrope of the element, i.e., white phosphorus (P₄). This is obtained through electrothermal reduction of phosphate rock (apatite) in an electric arc furnace at 1,600 °C with coke (reducing agent) and gravel (slag former). White phosphorus as such has limited applications in military incendiaries, but otherwise serves as the father compound to a large palette of (organo) phosphorus compounds (OPCs) through its first derivatives: P chlorides (PCl₃, POCl₃, and PCl₅), sulfides (P₂S₅ and P₄S₃) and oxides (P₂O₅ and polyphosphoric acid; see Fig. 2). These consist of mono-, di- and triesters of phosphoric and phosphonic acid (phosphates and phosphonates).

Fig. 2

Technical use of P

Applications include crop protection agents, flame retardants, lubricant additives, extracting agents (e.g., uranyl salts for the fuel production for nuclear power plants), pharmaceuticals, biocides, battery electrolytes and many more. Glyphosate, an organic P compound, the largest volume agrochemical worldwide is a derivative of PCl₃. For 2017 this application will use 250,000 t of P which is 1 % of total P usage (PRWeb 2011).

Apart from these derivatives involving oxygen, chlorine and sulfur, sodium hypophosphite and red phosphorus play a role in respectively nickel electroplating and flame retardant compositions.

Phosphine (PH₃ derived) chemistry is very minor volume-wise but has a huge field of application in such diverse fields as extraction agents, catalyst ligands, fumigation and fine chemistry.

The rationale to choose the energy intensive “thermal” route through P₄ is that it gives access to compounds that could otherwise not be produced. Reasons to make P₄ and its derivatives include:

• creating water soluble molecules that perform a function such as chelating, surface treatment or antiscale action, often as a variation on structurally related carboxylic acids (such as phosphonates and acid organophosphates),

• introducing P into a plastic or other flammable material to obtain flame retardancy, with functional groups around the P atom to create compatibility with the material to be flameproofed, or particles made compatible with the matrix material, (e.g., phosphate esters, DOPO, phosphinates),

• mimicking a molecule from nature to obtain a pesticide/herbicide (such as glyphosate),

• providing functionality to obtain a catalytic action, usually together with a transition metal ion, usually by providing a lone pair, i.e. acting as a Lewis base, such as in hydrocarbonylation (i.e., polymerization and modification of petrochemical building blocks),

• chemical reduction (such as sodium hypophosphite which is difficult to replace in electroless nickel plating),

• certain P compounds provide specific functions, including chlorination (P chlorides) or a strong dehydrative power in reactions (phosphorus pentoxide, polyphosphoric acid) which are difficult to replace with other reagents.

Academic research continues to develop our understanding on different branches of P chemistry, as shown in the recently updated 1,500 page handbook on Phosphorus (Corbridge 2012). This includes superconductivity, interesting thermo-chemistry, and magnetic behavior (Pöttgen et al. 2005). Some compounds are also important in homogeneous and heterogeneous catalysis (Peruzzini and Gonsalvi 2011). With respect to P₄ routes, given the drawbacks of chlorine-based and heavy salt-waste syntheses, stringent, environmental, and transportation regulations increasingly demand not only new ways of P₄ functionalization to useful molecules, but also new economic and ecological ways to meet current challenges also in the non-fertilizer P use. The need to bypass P chlorides, e.g., to obtain OPCs straight from P₄ is a continuing research topic (Caporali et al. 2010). Recycling phosphine oxides as a by-product of the Wittig synthesis, which are currently treated as waste in most cases, is a typical example of smart re-use of P compounds in a small, dedicated loop (Feldmann et al. 2011).

References

• Budenheim (2013) Solutions for a better life. Accessed from https://www.budenheim.com/en/

• Caporali M, Gonsalvi L, Rossin A, Peruzzini M (2010) P4 activation by late transition metal complexes. Chem Rev 110:4178–4235

• Corbridge DEC (2012) Phosphorus: chemistry, biochemistry and technology, 6th edn. CRC Press/Taylor & Francis Group, Boca Raton

• CRU (2013) Ashok Shinh (presentation), Phosphates 2013 conference, Monte Carlo

• Emsley J (2000) The 13th element: the sordid tale of murder, fire, and phosphorus. Wiley, New York

• Feldmann K-O, Schulz S, Klotter F, Weigand JJ (2011) A Versatile protocol for the quantitative and smooth conversion of phosphane oxides into synthetically useful pyrazolylphosphonium salts. ChemSusChem 4(12):1805–1812

• IFA (2008) Accessed from http://www.fertilizer.org/

• IFA (2011) Global phosphate rock production trends from 1961 to 2010—reasons for the temporary set-back in 1988–1994. Feeding the Earth Series, Oct 2011. http://www.fertilizer.org/ifa/HomePage/LIBRARY/Publication-database.html/Global-Phosphate-Rock-Production-Trends-from-1961-to-2010.-Reasons-for-the-Temporary-Set-Back-in-1988-1994.html

• Jasinski SM (2012) Phosphate rock. In: Salazar K, McNutt MK (eds) Mineral commodity summaries 2012. USGS, Reston, p 118

• Peruzzini M, Gonsalvi L (2011) Phosphorus compounds: advanced tools in catalysis and material science in catalysis by metal complexes. Springer, Heidelberg

• Phosphate Facts (2013) Uses and applications. http://www.phosphatesfacts.org/uses_apps.asp

• Pöttgen R, Hönle W, von Schnering HG (2005) Phosphides: solid state chemistry

• Prayon (n.d.) Phosphates and phosphoric acid in everyday life. Accessed from http://www.prayon.com/media/pdf/publications/brochure-tech-en.pdf

• PRweb (2011) Global glyphosate market to reach 1.35 million metric tons by 2017. http://www.prweb.com/releases/glyphosate_agrochemical/technical_glyphosate/prweb8857231.htm

• Villalba G, Liu Y, Schroder H, Ayres RU (2008) Global phosphorus flows in the industrial economy from a production perspective. J Ind Ecol 12(4):557–569. doi:10.1111/j.1530-9290.2008.00050.x

Phosphorus in Organic Agriculture

• Bernhard Freyer 

1. University of Natural Resources and Life Sciences BOKU Vienna, Gregor Mendel Strasse 33, 1180, Wien, Vienna, Austria

   Bernhard Freyer

Today, worldwide more than 1.8 million farmers have a total 37.2 million ha of agricultural land that would meet the criteria for organic crop production (FAO 2009; Willer and Kilcher 2011). Organic Agriculture is defined by internationally accepted guidelines, standards, and certification systems (IFOAM-EU 2012). The organic system is built upon vision and understanding of the farm as an organism. With such an understanding, organic farmers seek to close their farm nutrient cycles, to reduce resource input from off farm sources and to increase the efficiency of resources used. These goals lead organic farmers (as well as other farmers) to consider nutrient balances as a management and decision making tool that leads to increased nutrient availability in soils, the efficiency of nutrient uptake in plants. In addition, organic farmers use mixed cropping systems along with the application of organic manures to promote microbial diversity that strengthens the antiphyto-pathogenic potential of the soil. Similarly, some fodder legumes (e.g., alfalfa, clover) improve overall soil fertility by biological fixing nitrogen (some of which is available to the subsequent crop), provide residues to maintain or improve soil physical and biological properties and promote nutrient re-cycling and access to water through deep rooting. The combination of rich root systems, residue production and humus production by legumes, and cropping systems with green manure mixtures, contributes to a permanent soil cover, minimizing soil erosion and thereby the loss of phosphorus (P) and other nutrients. Compost from plant residues and stable manure from livestock permits an efficient internally closed nutrient cycle on the farm.

Types of Farm External P-Sources

According to the organic guidelines, the readily available mineral fertilizers (e.g., triple superphosphate, DAP, etc.) are excluded, while the application of low soluble phosphate rock (hypherphos) is accepted. The use of Thomas-phosphate is restricted in almost all countries because of Cadmium content. Low energy input for the provision of mineral P-fertilizer is one reason for the use of P-mineral fertilizers with low solubility. A second reason is that the main strategy for ensuring proper plant nutrition in organic farming is to improve the conditions for nutrient mobilization from slightly soluble sources by plant–soil-microorganism interactions instead of directly fertilizing plants with readily available mineral fertilizers. Specifically, in acid soils, liming improves the availability of many nutrients including P. Accepted farm external organic P-sources are: communal biowaste composts (sewage sludge is excluded because of the risk of contamination with heavy metals and organic compounds); mineral fodder including P; diverse organic industrial P-fertilizers (e.g., slaughterhouse waste); fodder and organic manure from organic farms or conventional low input farms, with production intensity limited to the site-specific production potential.

P-Cycles

The amount of external P-sources is strictly regulated through guidelines and control systems. Farmers are required to provide calculations on nutrient balances as a precondition for getting permission to apply farm external P-fertilizers. Negative balances could allow P use from mineral fertilizers limited to approximately 5–15 kg P ha⁻¹ y⁻¹. The input of P through industrial organic P fertilizers or from other sources is limited due to the site-specific yield potential. P import through mineral fodder is accepted up to approximately 4 kg P LU⁻¹ ha⁻¹ y⁻¹ (LU = Livestock Unit). P export with respect to farm types increases as follows: grassland farms with cattle < mixed arable farms with livestock < stockless cereal producing farms < stockless root crops producing farms < vegetable farms. Without P imports, P-balances decline by approximately 1 to 5 kg P ha⁻¹ y⁻¹ in the first farm type to 10–15 kg P ha⁻¹ y⁻¹ in the last farm type (Berner et al. 1999; Martin et al. 2007). Even under limited P-input conditions, P content in organic products is equal to those in conventional farms (Dangour et al. 2009). In smallholder farms under subtropical conditions, the P balances in low input/organic farms range from highly positive to negative demonstrating a lack of access to P inputs, and possibly awareness of P needs and farm management practices in general (Onwonga and Freyer 2006).

P-Dynamics

Sources of plant-available phosphate (PO₄ ³⁻) in many soils are the reserves of labile organic and inorganic soil pools, which have been built up over time through the use of mineral P fertilizers, rock phosphate, or other “organic” amendments including green manure residues, and livestock manure. Species-specific root exudates, microorganisms, and fungal enzymes induce the mineralization processes of phytates (storage of P in organic matter), thereby increasing the phosphate levels in the soils (Hinsinger et al. 2011). The extension of the root surface is highly relevant for plant P uptake. Optimal soil structure and organic manure will increase root growth and mycorrhiza colonization (Muthukumar and Udaiyan 2000) and with that the volume of the soil where P is accessible for uptake by roots. Finally, solubility of phosphate rock is supported by specific legume root exudates (Vanlauwe et al. 2000). To summarize, technologies including—lime for pH-regulation, farmyard manure, compost, phosphate rock and diversified legume based crop rotations are key for sustainable use of phosphorous (Onwonga et al. 2008).

References

• Berner A, Heller S, Mäder P (1999) Nährstoffbilanzen im biologischen Landbau. 5. Wissenschaftstagung zum Ökologischen Landbau. Berlin. Retrieved June 10 http://orgprints.org/00002908

• Dangour AD, Dodhia SK, Hayter A, Allen E, Lock K, Uauy R (2009) Nutritional quality of organic foods: a systematic review. Am J Clin Nutr 90(3):680–685

• FAO (2009) High level expert forum. FAO. Accessed 15 Aug 2013

• Hinsinger P, Betencourt E, Bernard L, Brauman A, Plassard C, Shen J, Zhang F (2011) P for two, sharing a scare resources: soil phosphorus acquisition in the rhizosphere of intercropped species. Plant Physiol 156(3):1078–1086

• IFOAM (2012) European organic guidelines. Retrieved 16 June 2012. http://www.ifoam-eu.org/positions/publications/regulation/

• Martin R, Lynch D, Frick B, van Straaten P (2007) Phosphorus status on Canadian organic farms. J Sci Food Agric 87:2737–2740

• Muthukumar T, Udaiyan K (2000) Influence of organic manures on arbuscular mycorrhizal fungi associated with Vigna unguiculata (L.) Walp. in relation to tissue nutrients and soluble carbohydrate in roots under field conditions. Biol Fertil Soils 31:114–120

• Onwonga R, Freyer B (2006) Impact of traditional farming practices on nutrient balances in smallholder farming systems of Nakuru district, Kenya. In: Asch F, Becker M (eds) Conference on international agricultural research for development, Tropentag, pp 158–161

• Onwonga RN, Lelei JJ, Freyer B, Friedel JK, Mwonga SM, Wandhawa P (2008) Low cost technologies for enhancing N and P availability and maize (Zea mays L.) performance on acid soils. World J Agric Sci 4(2):862–873

• Vanlauwe B, Diels J, Sanginga N, Carsky RJ, Deckers J, Merckx R (2000) Utilization of rock phosphate by crops on non-acidic soils on a toposequence in the Northern Guinea savanna zone of Nigeria, response by maize to previous herbaceous legume cropping and rock response by maize to previous herbaceous legume cropping and rock phosphate treatments. Soil Biol Biochem 32:2079–2090

• Willer H, Kilcher L (2011) The world of organic agriculture. Statistics and Emerging Trends 2011, IFOAM, Bonn and FiBL, Frick