Organic fertilizer

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A cement reservoir containing cow manure mixed with water. This is common in rural Hainan Province, China. Note the bucket on a stick that the farmer uses to apply the mixture.
Liming soil
Bone meal and meat meal can be added to soil to stimulate root growth and to release phosphorus.

Organic fertilizers are fertilizers that are naturally produced and contain carbon (C).[1] Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include mineral sources, all animal waste including meat processing, manure, slurry, and guano, plant based fertilizers, such as compost, and biosolids.[2] There are also other abiotic non-chemical, fertilizer methods that meet the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture.

Examples and sources[edit]

The main organic fertilizers are, peat, animal wastes, plant wastes from agriculture, and treated sewage sludge.[3][4]


Minerals can be mined or fossil products of animal activity, such as greensand (anaerobic marine deposits), some limestones (fossil shell deposits),[5] and some rock phosphates (fossil guano).[6] Adding limestone or “liming” a soil is a way to raise pH.[7] By raising the pH of a soil, microbial growth can be stimulated, which in turn increases biological processes, enabling nutrients to flow more freely through the soil.[8] When nutrients flow freely they are more accessible to plants and therefore can increase plant health and mass. If the soil is already pH balanced, liming the soil, would be ineffective.


Peat, or turf, is plant material that is only partially decomposed. It is a source of organic matter.  Soil with higher levels of organic matter are less likely to compact, which improves the soil aeration and water drainage, as well as assists in supporting soil microbial health.[9][10] It is sometimes credited as being the most widely use organic fertilizer and by volume is the top organic amendment.

Animal Sources[edit]

Animal sourced materials include both animal manures and residues from the slaughter of animals.[2] Manures are derived from milk-producing dairy animals, egg-producing poultry, and animals raised for meat and hide production, or sport and recreation. Manure is an abundant resource with estimations for cattle manure in the US alone reaching two billion tons annually,[11] and one hen has the potential to produce a cubic foot of manure every six months.[12] By adding manure to crops it adds nitrogen, potassium, phosphorus, sulfur, magnesium and calcium.[10] While also increasing soil stability by increasing organic material, increasing water infiltration, it can add bacteria diversity and over time reduce the impacts of soil erosion.[10] However, there is organic manure and non-organic manure.  In order for manure to be considered organic it must come from organic livestock or certified organic growers.[13] If organic manure is not available, they are permitted to use non-organic manure as long as the animals have room to roam, are not kept in the dark, and growers abstain from using genetically modified feeds.[13] Fresh manure, right from the stall, can cause issues because it can be too high in ammonia, or contain bacteria from the animal’s gut.  This can have an adverse effect on plants as the ammonia can burn the roots and microbes from the animal’s gut can harm the microorganisms in the soil, killing them, or contaminate produce, such as E. coli and salmonella.[14] There is also a risk of introducing weeds, as seeds can pass through the gut of an animal relatively unharmed, or there can be seeds in the bedding of the livestock, which is often mixed in with the manure. Therefore, manure is required to be composted which will ideally kill any seeds or pathogens and reduce the ammonia content.[11]

A large commercial compost operation

Chicken litter, which consists of chicken manure and bedding, is an organic fertilizer that has been proposed to be superior for conditioning soil for harvest than synthetic fertilizers.[15] It contains similar minerals to other manures, while also having trace amounts of copper, zinc, magnesium, boron, and chloride.[14] Depending on the type of chicken litter obtained, it may contain bird remains. This type of chicken litter should not be spread on crops, and can pose a risk to grazing livestock due to botulism, a disease caused by bacteria within decaying birds.[14]

Horse manure contains the perfect balance of Carbon to Nitrogen for composting (30:1) and is a traditional garden soil amendment. However, careful organic sourcing is critical because feed (and bedding materials) from fields treated with the picolinic acid family of herbicides including aminopyralid, clopyralid, and picloram (marketed in the US as Milestone and Grazon-)can pass through a horse’s digestive tract, remaining unchanged in manure and compost piles for long periods. These chemicals commonly affect potatoes, tomatoes, and beans, causing deformed plants and poor or non-existent yields. Also, horse de-wormers like Ivermectin can be detected in manure at levels harmful to beneficial insects and organisms for up to 45 days. Tainted compost can not only kill plants and beneficial organisms, but can create liability issues for owners.[16]

Urine, from humans as well as animals, is a fertilizer: urea in urine is a nitrogen compound, and urine also contains phosphorus and potassium.[17][18][19][20] Human urine typically has about 3 times as much nitrogen as potassium, and more than 20 times as much nitrogen as phosphorus.[21][22][23] The amount of potassium in urine is variable, and depends on the amount of potassium in the person's diet.[22][24] Urine is not currently allowed to be used in any commercial agricultural operations. However, there are ongoing studies that have shown that aging urine in concealed containers for 12–16 months eliminates 99% of harmful bacteria, due to increasing urea content and therefore pH.[17]

Animal by-products. When any animal is butchered, only about 40% to 60% of the live animal is converted to market product, with the remaining 40% to 60% classed as by-products. These by-products of animal slaughter, mostly inedible—blood, bone, feathers, hides, hoofs, horns, -- can be refined into agricultural fertilizers including blood meal, bone meal[3] fish meal, and feather meal.

Compost bin for small-scale production of organic fertilizer


Processed organic fertilizers include compost, humic acid, grain meal, amino acids, and seaweed extracts. Other examples are natural enzyme-digested proteins. Decomposing crop residue (green manure) from prior years is another source of fertility.

Compost provides little in the means of nutrients to plants, but it does provide soil stability through increasing organic matter.[25]

Grain meals can be made of corn gluten, alfalfa, cottonseed, or soybean.  Most supply nitrogen and potassium, but soybean meal provides nitrogen and phosphorus.[25]  When initially spread they can cause an increase in ammonia within the soil and burn seeds, it is recommended to use these after plants have developed, to ensure crop success.

Other ARS studies have found that algae used to capture nitrogen and phosphorus runoff from agricultural fields can not only prevent water contamination of these nutrients, but also can be used as an organic fertilizer. ARS scientists originally developed the "algal turf scrubber" to reduce nutrient runoff and increase quality of water flowing into streams, rivers, and lakes. They found that this nutrient-rich algae, once dried, can be applied to cucumber and corn seedlings and result in growth comparable to that seen using synthetic fertilizers.[26]

Treated Sewage Sludge[edit]

Sewage sludge, also known as biosolids, is effluent that has been treated, blended, composted, and sometimes dried until deemed biologically safe. As a fertilizer it is most commonly used on non-agricultural crops such as in silviculture or in soil remediation. Use of biosolids in agricultural production is less common, and the National Organic Program of the USDA (NOP) has ruled that biosolids are not permitted in organic food production in the U.S.; while biologic in origin (vs mineral), sludge is unacceptable due to toxic metal accumulation, pharmaceuticals, hormones, and other factors.[27]

With concerns about human borne pathogens coupled with a growing preference for flush toilets and centralized sewage treatment, biosolids have been replacing night soil (from human excreta), a traditional organic fertilizer that is minimally processed.

Decomposing animal manure is an organic fertilizer source


See also[edit]


  1. ^ Christians, Nick E.; Patton, Aaron J.; Law, Quincy D. (2016-11-21). Fundamentals of Turfgrass Management, Fifth Edition. Hoboken, NJ, USA: John Wiley & Sons, Inc. doi:10.1002/9781119308867. ISBN 978-1-119-30886-7.
  2. ^ a b Guertal, E. A.; Green, B. D. (2012). "Evaluation of organic fertilizer sources for south-eastern (USA) turfgrass maintenance". Acta Agriculturae Scandinavica, Section B. 62 (sup1): 130–138. doi:10.1080/09064710.2012.683201. ISSN 0906-4710.
  3. ^ a b Heinrich Dittmar, Manfred Drach, Ralf Vosskamp, Martin E. Trenkel, Reinhold Gutser, Günter Steffens "Fertilizers, 2. Types" in Ullmann's Encyclopedia of Industrial Chemistry, 2009, Wiley-VCH, Weinheim. doi:10.1002/14356007.n10_n01
  4. ^ "Nitrogen-Phosphorus-Potassium Values of Organic Fertilizers". Retrieved 2021-05-16.
  5. ^ Barker, Allen V. (2012). "Plant Growth in Response to Phosphorus Fertilizers in Acidic Soil Amended with Limestone or Organic Matter". Communications in Soil Science and Plant Analysis. 43 (13): 1800–1810. doi:10.1080/00103624.2012.684829. ISSN 0010-3624.
  6. ^ Hillel, Daniel (2008), "SOIL FERTILITY AND PLANT NUTRITION", Soil in the Environment, Elsevier, pp. 151–162, doi:10.1016/b978-0-12-348536-6.50016-2, ISBN 978-0-12-348536-6, retrieved 2021-04-08
  7. ^ Barker, Allen V. (2012). "Plant Growth in Response to Phosphorus Fertilizers in Acidic Soil Amended with Limestone or Organic Matter". Communications in Soil Science and Plant Analysis. 43 (13): 1800–1810. doi:10.1080/00103624.2012.684829. ISSN 0010-3624.
  8. ^ Ahmad, Waqar; Singh, Balwant; Dijkstra, Feike A.; Dalal, R.C. (2013). "Inorganic and organic carbon dynamics in a limed acid soil are mediated by plants". Soil Biology and Biochemistry. 57: 549–555. doi:10.1016/j.soilbio.2012.10.013.
  9. ^ Saito, B.; Seckler, M. M. (2014). "Alkaline extraction of humic substances from peat applied to organic-mineral fertilizer production". Brazilian Journal of Chemical Engineering. 31 (3): 675–682. doi:10.1590/0104-6632.20140313s00002512. ISSN 0104-6632.
  10. ^ a b c "Manure and Nutrient Management - Beef Cattle Research Council". Manure and Nutrient Management - Beef Cattle Research Council. Retrieved 2021-04-09.
  11. ^ a b "The Poop on Manure". West Coast Seeds. Retrieved 2021-04-09.
  12. ^ "Using Chicken Manure Safely in Home Gardens and Landscapes". Extension | University of Nevada, Reno. Retrieved 2021-04-09.
  13. ^ a b "How do the Regenerative Organic Standards compare to the Canadian Organic Standards?". The Canadian Organic Grower. Retrieved 2021-04-09.
  14. ^ a b c "Best practice guidelines for using poultry litter on pastures". Retrieved 2021-04-09.
  15. ^ "Researchers Study Value of Chicken Litter in Cotton Production". 23 July 2010.
  16. ^ "The Worm Farmer's Handbook: Mid- to Large-Scale Vermicomposting for Farms, Businesses, Municipalities, Schools, and Institutions". Retrieved 2021-07-25.
  17. ^ a b "Urine fertilizer: 'Aging' effectively protects against transfer of antibiotic resistance". ScienceDaily. Retrieved 2021-04-09.
  18. ^ "Yes wee can: study gives green light to use urine as crop fertiliser". the Guardian. 2020-01-22. Retrieved 2021-01-01.
  19. ^ "Can Human Urine Replace Chemical Fertilizers?". Modern Farmer. 2014-01-13. Retrieved 2021-05-16.
  20. ^ Brown, Sally; scientist, ContributorSoil; chef; swimmer (2017-01-16). "Pee for Plants". HuffPost. Retrieved 2021-05-16.
  21. ^ "Urine Urea Nitrogen Test: Purpose, Procedure, and Results". Healthline. 2018-02-27. Retrieved 2021-05-16.
  22. ^ a b "Potassium - Urine". Retrieved 2021-05-16.
  23. ^ "Phosphate in Urine". Retrieved 2021-05-16.
  24. ^ Mente, Andrew; Irvine, E. Jan; Honey, R. John D'A; Logan, Alexander G. (April 2009). "Urinary potassium is a clinically useful test to detect a poor quality diet". The Journal of Nutrition. 139 (4): 743–749. doi:10.3945/jn.108.098319. ISSN 1541-6100. PMID 19211830.
  25. ^ a b "Plant-Based Fertilizers for Organic Gardens". dummies. Retrieved 2021-04-10.
  26. ^ "Algae: A Mean, Green Cleaning Machine". USDA Agricultural Research Service. 7 May 2010.
  27. ^ "Organic Farming | Agriculture | US EPA". Retrieved 2012-01-09.
  28. ^ "Managing Potassium for Organic Crop Production" (PDF). CO State Extension.
  29. ^ "Phosphorus Fertilizers for Organic Farming Systems". CO State Extension.
  30. ^ "Maintaining Soil Fertility in an Organic Fruit and Vegetable Crops System". University of MN Extension.
  31. ^ "Organic Materials as *Nitrogen Fertilizers". CO State Extension.