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Nitrogen fertilizer is often synthesized using the Haber-Bosch process, which produces ammonia. This ammonia is applied directly to the soil or used to produce other compounds, notably ammonium nitrate and urea, both dry, concentrated products that may be used as fertilizer materials or mixed with water to form a concentrated liquid nitrogen fertilizer, UAN. Ammonia can also be used in the Odda Process in combination with rock phosphate and potassium fertilizer to produce compound fertilizers such as 10-10-10 or 15-15-15.

The production of ammonia currently consumes about 5 percent of global natural gas consumption, which is somewhat under 2 percent of world energy production.10 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.11 The price increases in natural gas in the past decade, among other factors such as increasing demand, have contributed to an increase in fertilizer price.

Nitrogen-based fertilizers are most commonly used to treat fields used for growing maize, followed by barley, sorghum, rapeseed, soyabean and sunflower.

Health and sustainability issues

Inorganic fertilizers sometimes do not replace trace mineral elements in the soil which become gradually depleted by crops grown there. This has been linked to studies which have shown a marked fall (up to 75 percent) in the quantities of such minerals present in fruit and vegetables.12 One exception to this is in Western Australia where deficiencies of zinc, copper, manganese, iron and molybdenum were identified as limiting the growth of crops and pastures in the 1940s and 1950s. Soils in Western Australia are very old, highly weathered and deficient in many of the major nutrients and trace elements. Since this time these trace elements are routinely added to inorganic fertilizers used in agriculture in this state.

In many countries there is the public perception that inorganic fertilizers "poison the soil" and result in "low quality" produce. However, there is very little (if any) scientific evidence to support these views. When used appropriately, inorganic fertilizers enhance plant growth, the accumulation of organic matter and the biological activity of the soil, while reducing the risk of water run-off, overgrazing and soil erosion. The nutritional value of plants for human and animal consumption is typically improved when inorganic fertilizers are used appropriately.

There are concerns though about arsenic, cadmium and uranium accumulating in fields treated with phosphate fertilizers. The phosphate minerals contain trace amounts of these elements and if no cleaning step is applied after mining the continuous use of phosphate fertilizers leads towards an accumulation of these elements in the soil. Eventually these can build up to unacceptable levels and get into the produce. (See cadmium poisoning.)

Another problem with inorganic fertilizers is that they are presently produced in ways which cannot be continued indefinitely. Potassium and phosphorus come from mines (or from saline lakes such as the Dead Sea in the case of potassium fertilizers) and resources are limited. Nitrogen is unlimited, but nitrogen fertilizers are presently made using fossil fuels such as natural gas. Theoretically fertilizers could be made from sea water or atmospheric nitrogen using renewable energy, but doing so would require huge investment and is not competitive with today's unsustainable methods. Innovative thermal depolymerization biofuel schemes are trialling the production of byproducts with 9 percent nitrogen fertilizer sourced from organic waste1314

Organic fertilizers

A compost bin.
  • Examples of naturally occurring organic fertilizers include manure, slurry, worm castings, peat, seaweed, sewage , and guano. Green manure crops including legumes like clovers and vetches are also grown to add nutrients to the soil. Summer plantings can be millet, forage sorghum, or buckwheat. 15. Naturally occurring minerals such as mine rock phosphate, sulfate of potash and limestone are also considered Organic Fertilizers.
  • Examples of manufactured organic fertilizers include compost, bloodmeal, bone meal and seaweed extracts. Other examples are natural enzyme digested proteins, fish meal, and feather meal.

The decomposing crop residue from prior years is another source of fertility. Though not strictly considered "fertilizer," the distinction seems more a matter of words than reality.

Some ambiguity in the usage of the term 'organic' exists because some of synthetic fertilizers, such as urea and urea formaldehyde, are fully organic in the sense of organic chemistry. In fact, it would be difficult to chemically distinguish between urea of biological origin and that produced synthetically. On the other hand, some fertilizer materials commonly approved for organic agriculture, such as powdered limestone, mined "rock phosphate" and Chilean saltpeter, are inorganic in the use of the term by chemistry.

Although the density of nutrients in organic material is comparatively modest, they have some advantages. For one thing organic growers typically produce some or all of their fertilizer on-site, thus lowering operating costs considerably. Then there is the matter of how effective they are at promoting plant growth, chemical soil test results aside. The answers are encouraging. Since the majority of nitrogen supplying organic fertilizers contain insoluble nitrogen and are slow release fertilizers their effectiveness can be greater than conventional nitrogen fertilizers.

Implicit in modern theories of organic agriculture is the idea that the pendulum has swung the other way to some extent in thinking about plant nutrition. While admitting the obvious success of Leibig's theory, they stress that there are serious limitations to the current methods of implementing it via chemical fertilization. They re-emphasize the role of humus and other organic components of soil, which are believed to play several important roles:

  • Mobilizing existing soil nutrients, so that good growth is achieved with lower nutrient densities while wasting less
  • Releasing nutrients at a slower, more consistent rate, helping to avoid a boom-and-bust pattern
  • Helping to retain soil moisture, reducing the stress due to temporary moisture stress
  • Improving the soil structure

Organics also have the advantage of avoiding certain long-term problems associated with the regular heavy use of artificial fertilizers:

  • the possibility of "burning" plants with the concentrated chemicals (i.e., an over supply of some nutrients)
  • the progressive decrease of real or perceived "soil health," apparent in loss of structure, reduced ability to absorb precipitation, lightening of soil color, etc.
  • the necessity of reapplying artificial fertilizers regularly (and perhaps in increasing quantities) to maintain fertility
  • the cost (substantial and rising in recent years) and resulting lack of independence

Organic fertilizers also have their disadvantages:

  • As acknowledged above, they are typically a dilute source of nutrients compared to inorganic fertilizers, and where significant amounts of nutrients are required for profitable yields, very large amounts of organic fertilizers must be applied. This results in prohibitive transportation and application costs, especially where the agriculture is practiced a long distance from the source of the organic fertilizer.
  • The composition of organic fertilizers tends to be highly variable, so that accurate application of nutrients to match plant production is difficult. Hence, large-scale agriculture tends to rely on inorganic fertilizers while organic fertilizers are cost-effective on small-scale horticultural or domestic gardens.
  • Improperly-processed organic fertilizers may contain pathogens harmful to humans or plants. Organic fertilizers are derived from natural sources, which may include animal feces or plant/animal matter contaminated with pathogens. However, proper composting of raw materials used in organic fertilizers will kill pathogens.16

In practice a compromise between the use of artificial and organic fertilizers is common, typically by using inorganic fertilizers supplemented with the application of organics that are readily available such as the return of crop residues or the application of manure.

It is important to differentiate between what we mean by organic fertilizers and fertilizers approved for use in organic farming and organic gardening by organizations and authorities who provide organic certification services. Some approved fertilizers may be inorganic, naturally occurring chemical compounds, e.g., minerals.

Risks of fertilizer use

The problem of over-fertilization is primarily associated with the use of artificial fertilizers, because of the massive quantities applied and the destructive nature of chemical fertilizers on soil nutrient holding structures. The high solubilities of chemical fertilizers also exacerbate their tendency to degrade ecosystems.

Storage and application of some nitrogen fertilizers in some weather or soil conditions can cause emissions of the greenhouse gas nitrous oxide (N2O). Ammonia gas (NH3) may be emitted following application of inorganic fertilizers, or manure or slurry. Besides supplying nitrogen, ammonia can also increase soil acidity (lower pH, or "souring"). Excessive nitrogen fertilizer applications can also lead to pest problems by increasing the birth rate, longevity and overall fitness of certain pests.171819202122

The concentration of up to 100 mg/kg of Cadmium in phosphate minerals (for example, minerals from Nauru23 and the Christmas islands24) increases the contamination of soil with Cadmium, for example in New Zealand.25 Uranium is another example of a contaminant often found in phosphate fertilizers.262728

For these reasons, it is recommended that knowledge of the nutrient content of the soil and nutrient requirements of the crop are carefully balanced with application of nutrients in inorganic fertilizer especially. This process is called nutrient budgeting. By careful monitoring of soil conditions, farmers can avoid wasting expensive fertilizers, and also avoid the potential costs of cleaning up any pollution created as a byproduct of their farming.

It is also possible to over-apply organic fertilizers; however, their nutrient content, their solubility, and their release rates are typically much lower than chemical fertilizers. By their nature, most organic fertilizers also provide increased physical and biological storage mechanisms to soils, which tend to mitigate their risks.

Global issues

The growth of the world's population to its current figure has only been possible through intensification of agriculture associated with the use of fertilizers2930. There is an impact on the sustainable consumption of other global resources as a consequence.

The use of fertilizers on a global scale emits significant quantities of greenhouse gas into the atmosphere. Emissions come about through the use of31:

  • 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 known as global warming.

See also

Notes

  1. ↑ Haber & Bosch Most influential persons of the 20th century. Retrieved September 6, 2007.
  2. ↑ History of Fisons at Yara.com. Retrieved September 6, 2007.
  3. ↑ Competition Commission report. Retrieved September 6, 2007.
  4. ↑ History of Yara at Yara.com. Retrieved September 6, 2007.
  5. ↑ Crop Fertilization Improves Soil Quality. IPNI. Retrieved September 6, 2007.
  6. ↑ Harris, Glen and Shelby Baker Nitrogen Fertilization. Retrieved September 6, 2007.
  7. ↑ R.C. Harris, 2005. Avoiding Fertilizer Burn. Retrieved September 6, 2007.
  8. ↑ UK Fertilisers Regulations 1990, Schedule 2 Part 1, Para. 7. Retrieved September 6, 2007.
  9. ↑ Food and Agricultural Organization of the U.N. Table 3.3. Retrieved September 6, 2007.
  10. ↑ IFA - Statistics - Fertilizer Indicators - Details - Raw material reserves. Retrieved September 6, 2007.
  11. ↑ Sawyer J.E. 2001. Natural gas prices affect nitrogen fertilizer costs. IC-486. 1:8. Retrieved September 6, 2007.
  12. ↑ Felicity Lawrence. 2004. Not on the Label. (New York, NY: Penguin. ISBN 0141015667).
  13. ↑ Brad Lemley, 2006. Anything Into Oil. Discover Magazine. Retrieved September 6, 2007.
  14. ↑ Lemley, 2003. Anything Into Oil. Discover Magazine. Retrieved September 6, 2007.
  15. ↑ Preston Sullivan. Overview of Cover Crops and Green Manures: Fundamentals of Sustainable Agriculture 1. National Sustainable Agriculture Information Service. Retrieved May 18, 2008.
  16. ↑ ciwmb.ca.gov - organics document. Retrieved September 6, 2007.
  17. ↑ G.C. Jahn, 2004. Effect of soil nutrients on the growth, survival and fecundity of insect pests of rice: an overview and a theory of pest outbreaks with consideration of research approaches. Multitrophic interactions in Soil and Integrated Control. International Organization for Biological Control (IOBC) wprs Bulletin 27(1): 115-122.
  18. ↑ G.C. Jahn, E.R. Sanchez, P.G. Cox. 2001. The quest for connections: developing a research agenda for integrated pest and nutrient management. International Rice Research Institute - Discussion Paper 42: 18. Retrieved September 6, 2007.
  19. ↑ G.C. Jahn, P.G. Cox, E. Rubia-Sanchez, M. Cohen. 2001. The quest for connections: developing a research agenda for integrated pest and nutrient management. S. Peng and B. Hardy eds. "Rice Research for Food Security and Poverty Alleviation." Proceeding the International Rice Research Conference, 31 March - 3 April 2000, Los Baños, Philippines. Los Baños (Philippines): International Rice Research Institute.
  20. ↑ Jahn G.C., L.P. Almazan, J. Pacia. 2005. Effect of nitrogen fertilizer on the intrinsic rate of increase of the rusty plum aphid, Hysteroneura setariae (Thomas) (Homoptera: Aphididae) on rice (Oryza sativa L.). Environmental Entomology. 34:4:938-943. Retrieved September 6, 2007.
  21. ↑ Preap V., M.P. Zalucki, H.J. Nesbitt, G.C. Jahn. 2001. Effect of fertilizer, pesticide treatment, and plant variety on realized fecundity and survival rates of Nilaparvata lugens (Stål); Generating Outbreaks in Cambodia. Journal of Asia Pacific Entomology. 4:1:75-84.
  22. ↑ Preap V., M.P. Zalucki, G.C. Jahn. 2002. Effect of nitrogen fertilizer and host plant variety on fecundity and early instar survival of Nilaparvata lugens (Stål): immediate response. Proceedings of the 4th International Workshop on Inter-Country Forecasting System and Management for Planthopper in East Asia. 13-15 November 2002. Guilin China. Published by Rural Development Administration (RDA) and the Food and Agriculture Organization (FAO).
  23. ↑ J.K. Syers, A.D. Mackay, M.W. Brown, C.D. Currie. 1986. Chemical and physical characteristics of phosphate rock materials of varying reactivity. J Sci Food Agric 37: 1057-1064.
  24. ↑ N.A. Trueman. 1965. The phosphate, volcanic and carbonate rocks of Christmas Island (Indian Ocean). J Geol Soc Aust 12: 261-286.
  25. ↑ M.D. Taylor. 1997. Accumulation of Cadmium derived from fertilisers in New Zealand soils. Science of Total Environment 208: 123-126.
  26. ↑ E.M. Hussein. 1994. Radioactivity of phosphate ore, superphosphate, and phosphogypsum in Abu-zaabal phosphate. Health Physics 67: 280-282.
  27. ↑ D. Barisic, S. Lulic, P. Miletic. 1992. Radium and uranium in phosphate fertilizers and their impact on the radioactivity of waters. Water Research 26: 607-611.
  28. ↑ L.C. Scholten, C.W.M. Timmermans. 1992. Natural radioactivity in phosphate fertilizers. Nutrient cycling in agroecosystems 43: 103-107.
  29. ↑ Vaclav Smil. 1999. Detonator of the population explosion. Nature 400 (July 1999) available online 2.Retrieved May 18, 2008.
  30. ↑ Haber & Bosch: Most influential persons of the 20th century. Retrieved September 6, 2007.
  31. ↑ Food and Agricultural Organization of the U.N. Retrieved September 6, 2007.

References

  • California Plant Health Association. 2002. Western Fertilizer Handbook. Danville, IL: Interstate Publishers. ISBN 0813432103.
  • The Fertilizer Institute. 2007. About Fertilizer. The Fertilizer Institute. Retrieved September 1, 2007.
  • Havlin, John L., Samuel L. Tisdale, James D. Beaton, and Werner L. Nelson. 2004. Soil Fertility and Fertilizers: An Introduction to Nutrient Management, 7th ed. Upper Saddle River, NJ: Pearson Prentice Hall. ISBN 0130278246.
  • Walters, Charles. 2003. Eco-farm: An Acres U.S.A. Primer. Austin, TX: Acres U.S.A. ISBN 0911311742.

External links

All links retrieved April 6, 2017.

  • The International Fertilizer Industry Association.

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