Organic fertilizer

Last updated
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. Manure 01.JPG
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 Spreading lime on a Devon field.jpg
Liming soil
Bone meal and meat meal can be added to soil to stimulate root growth and to release phosphorus. Bone meal and meat meal.jpg
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. [1] 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. [2] Inorganic "organic fertilizers" include minerals and ash. Organic 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.

Contents

Examples and sources

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

Minerals

Minerals can be mined from 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.

Animal sources

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, [9] and one hen has the potential to produce a cubic foot of manure every six months. [10] By adding manure to crops it adds nitrogen, potassium, phosphorus, sulfur, magnesium and calcium. [11] 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. [11]

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. [12] 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. [12]

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. [13] 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. [9]

A large commercial compost operation Krechty kompostarna.jpg
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 to synthetic fertilizers. [14] It contains similar minerals to other manures, while also having trace amounts of copper, zinc, magnesium, boron, and chloride. [13] 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. [13]

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. [15]

Bat guano has been used as a fertilizer for thousands of years, most prominently by the Incans, who valued bats and their guano so much, the penalty for killing a bat was death. Bat guano is high in elements such as carbon, nitrogen, sulfur, and phosphorus. Guano typically contains about 10% nitrogen, which helps plants keep a healthy and vibrant green color and promotes rapid growth. Guano compared to manufactured fertilizers is safe to use inside and outside of the house, large gardens or small plants, and does not leach from the soil but rather remains and continues to slowly feed the plants and enhance the soil. Guano is also rich in bio-remediation microbes which helps to clean unnatural toxins from the soil that can prevent plant growth and cause rapid decay. [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] The amount of potassium in urine is variable, and depends on the amount of potassium in the person's diet. [21] [23] While animal urine, as from cattle and pigs, is widely used on farmer's fields, human urine other than as part of sewage sludge is not currently allowed to be used in any[ clarification needed ] commercial agricultural operations. However, there are ongoing studies that have shown that aging urine in closed 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 HomeComposting Roubaix Fr59.JPG
Compost bin for small-scale production of organic fertilizer

Plant

Processed organic fertilizers include compost, liquid plant manures, 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. Compost does help microorganisms proliferate which in turn breaks down decaying plant material into substantial bio-available nutrients for plant to easily assimilate. [27] Compost does not need to be fully plant-based: it is often made with a mix of carbon-rich plant waste and nitrogen-rich animal waste including human excreta as a means to remove pathogens and odor from the latter. [28]

Grain meals can be made of corn gluten, alfalfa, cottonseed, or soybean.  Most supply nitrogen and potassium, but soybean meal provides nitrogen and phosphorus. [27]   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. [29]

Ash produced by plant combustion is also an important K fertilizer. [30]

Peat

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. [31] [11] It is sometimes credited as being the most widely use organic fertilizer and by volume is the top organic amendment.

Human waste

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 bio-solids 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. [32]

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.[ citation needed ]

Decomposing animal manure is an organic fertilizer source Hestemoj.jpg
Decomposing animal manure is an organic fertilizer source

Farming application

In non-organic farming, a compromise between the use of artificial and organic fertilizers is common[ citation needed ], often 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.

Cover crops are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere; [33] as well as phosphorus (through nutrient mobilization) [34] content of soils.

Fertilizer trees aid organic farming by bringing nutrients from the depths of the soil, and by assisting in the regulation of water usage. [35]

Leguminous cover crops or fertilizer trees are also grown to enrich soil as a green manure through nitrogen fixation from the atmosphere; [36] as well as phosphorus (through nutrient mobilization) [37] content of soils.

Comparison

Bulk density

In general, the nutrients in organic fertilizer for gardens are both more diluted and also much less readily available to plants. This may be however desired as a form of slow-release fertilizer containing insoluble nitrogen. By their nature, organic fertilizers increase physical and biological nutrient storage mechanisms in soils, mitigating risks of over-fertilization. Organic fertilizer nutrient content, solubility, and nutrient release rates are typically much lower than mineral (inorganic) fertilizers. [38] [39] A University of North Carolina study found that potential mineralizable nitrogen (PMN) in the soil was 182–285% higher in organic mulched systems than in the synthetics control. [40]

There do exist 'fast-release' organic fertilizers with a risk of fertilizer burn. These include uncomposted animal manures, fish emulsion, blood meal, and urine. Composting converts nitrogen in these sources into more stable forms (with some loss). [41]

Soil biology

Organic fertilizers have been known to improve biodiversity (soil life) and long-term productivity of soil, [42] [43] and may prove a large depository for excess carbon dioxide. [44] [45] [46]

Organic nutrients increase the abundance of soil organisms by providing organic matter and micronutrients for organismal relationships such as fungal mycorrhiza, [47] (which aid plants in absorbing nutrients), and can drastically reduce external inputs of pesticides, energy and fertilizer, at the cost of decreased yield. [48]

Consistency

Organic fertilizers from composts and other sources can be quite variable from one batch to the next. [49] Without batch testing, amounts of applied nutrient cannot be precisely known. Nevertheless, one or more studies have shown they are at least as effective as chemical fertilizers over longer periods of use. [50]

See also

See also

Related Research Articles

<span class="mw-page-title-main">Compost</span> Mixture used to improve soil fertility

Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.

<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">Outline of organic gardening and farming</span> Overview of and topical guide to organic gardening and farming

The following outline is provided as an overview of and topical guide to organic gardening and farming:

<span class="mw-page-title-main">Green manure</span> Organic material left on an agricultural field to be used as a mulch or soil amendment

In agriculture, a green manure is a crop specifically cultivated to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal is to add organic matter to the soil for its benefits. Green manuring is often used with legume crops to add nitrogen to the soil for following crops, especially in organic farming, but is also used in conventional farming.

<span class="mw-page-title-main">Biosolids</span> Decontaminated sewage sludge

Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use sewage sludge from local wastewater treatment plants. Scientific research over many years has confirmed that these biosolids contain similar nutrients to those in animal manures. Biosolids that are used as fertilizer in farming are usually treated to help to prevent disease-causing pathogens from spreading to the public. Some sewage sludge can not qualify as biosolids due to persistent, bioaccumulative and toxic chemicals, radionuclides, and heavy metals at levels sufficient to contaminate soil and water when applied to land.

<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:

A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility and sometimes its mechanics. In general usage, the term "soil conditioner" is often thought of as a subset of the category soil amendments, which more often is understood to include a wide range of fertilizers and non-organic materials. In the context of construction soil conditioning is also called soil stabilization.

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.

<span class="mw-page-title-main">Digestate</span> Material remaining after the anaerobic digestion of a biodegradable feedstock

Digestate is the material remaining after the anaerobic digestion of a biodegradable feedstock. Anaerobic digestion produces two main products: digestate and biogas. Digestate is produced both by acidogenesis and methanogenesis and each has different characteristics. These characteristics stem from the original feedstock source as well as the processes themselves.

<span class="mw-page-title-main">Organic coffee</span>

Organic coffee is coffee produced without the aid of artificial chemical substances, such as certain additives or some pesticides and herbicides.

<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.

Animal-free agriculture, also known as plant agriculture, plant-based agriculture, veganic agriculture, stockfree farming, plant farming or veganic farming, consists of farming methods that do not use animals or animal products.

<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">Biofertilizer</span> Substance with micro-organisms

A biofertilizer is a substance which contains living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers add nutrients through the natural processes of nitrogen fixation, solubilizing phosphorus, and stimulating plant growth through the synthesis of growth-promoting substances. The micro-organisms in biofertilizers restore the soil's natural nutrient cycle and build soil organic matter. Through the use of biofertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil. Biofertilizers can be expected to reduce the use of synthetic fertilizers and pesticides, but they are not yet able to replace their use. As of 2024, more than 340 biofertilizer products have been approved for commercial use in the US.

<span class="mw-page-title-main">Chicken manure</span> Feces of chickens used as an organic fertilizer, especially for soil low in nitrogen

Chicken manure is the feces of chickens used as an organic fertilizer, especially for soil low in nitrogen. Of all animal manures, it has the highest amount of nitrogen, phosphorus, and potassium. Chicken manure is sometimes pelletized for use as a fertilizer, and this product may have additional phosphorus, potassium or nitrogen added. Optimal storage conditions for chicken manure include keeping it in a covered area and retaining its liquid, because a significant amount of nitrogen exists in the urine.

Soil management is the application of operations, practices, and treatments to protect soil and enhance its performance. It includes soil conservation, soil amendment, and optimal soil health. In agriculture, some amount of soil management is needed both in nonorganic and organic types to prevent agricultural land from becoming poorly productive over decades. Organic farming in particular emphasizes optimal soil management, because it uses soil health as the exclusive or nearly exclusive source of its fertilization and pest control.

<span class="mw-page-title-main">Manure</span> Organic matter, mostly derived from animal feces, which can be used as fertilizer

Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nutrients, such as nitrogen, that are utilised by bacteria, fungi and other organisms in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.

Korean natural farming (KNF) is an organic agricultural method that takes advantage of indigenous microorganisms (IMO) to produce rich soil that yields high output without the use of herbicides or pesticides.

<span class="mw-page-title-main">Reuse of human excreta</span> Safe, beneficial use of human excreta mainly in agriculture (after treatment)

Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may focus on using the plant-available nutrients that are contained in the treated excreta. They may also make use of the organic matter and energy contained in the excreta. To a lesser extent, reuse of the excreta's water content might also take place, although this is better known as water reclamation from municipal wastewater. The intended reuse applications for the nutrient content may include: soil conditioner or fertilizer in agriculture or horticultural activities. Other reuse applications, which focus more on the organic matter content of the excreta, include use as a fuel source or as an energy source in the form of biogas.

<span class="mw-page-title-main">Soil regeneration</span> Creation of new soil and rejuvenation of soil health

Soil regeneration, as a particular form of ecological regeneration within the field of restoration ecology, is creating new soil and rejuvenating soil health by: minimizing the loss of topsoil, retaining more carbon than is depleted, boosting biodiversity, and maintaining proper water and nutrient cycling. This has many benefits, such as: soil sequestration of carbon in response to a growing threat of climate change, a reduced risk of soil erosion, and increased overall soil resilience.

References

  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. 1 2 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. S2CID   83155937.
  3. 1 2 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". extension.oregonstate.edu. Archived from the original on 2021-01-02. 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. S2CID   98196453.
  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. S2CID   98196453.
  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. 1 2 "The Poop on Manure". West Coast Seeds. 24 January 2021. Retrieved 2021-04-09.
  10. ↑ "Using Chicken Manure Safely in Home Gardens and Landscapes". Extension | University of Nevada, Reno. Retrieved 2021-04-09.
  11. 1 2 3 "Manure and Nutrient Management - Beef Cattle Research Council". Manure and Nutrient Management - Beef Cattle Research Council. Archived from the original on 2020-05-23. Retrieved 2021-04-09.
  12. 1 2 "How do the Regenerative Organic Standards compare to the Canadian Organic Standards?". The Canadian Organic Grower. Retrieved 2021-04-09.
  13. 1 2 3 "Best practice guidelines for using poultry litter on pastures". www.thepoultrysite.com. Retrieved 2021-04-09.
  14. ↑ "Researchers Study Value of Chicken Litter in Cotton Production". 23 July 2010.
  15. ↑ "The Worm Farmer's Handbook: Mid- to Large-Scale Vermicomposting for Farms, Businesses, Municipalities, Schools, and Institutions" . Retrieved 2021-07-25.
  16. ↑ "GUANO: BATS' GIFT to GARDENERS". Bat Conservation International. Archived from the original on 2021-11-20. Retrieved 2021-12-02.
  17. 1 2 "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.{{cite web}}: |first2= has generic name (help)
  21. 1 2 "Potassium - Urine". ucsfhealth.org. Retrieved 2021-05-16.
  22. ↑ "Phosphate in Urine". myhealth.alberta.ca. Retrieved 2021-05-16.
  23. ↑ 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.
  24. ↑ "Phosphorus Fertilizers for Organic Farming Systems". CO State Extension.
  25. ↑ "Maintaining Soil Fertility in an Organic Fruit and Vegetable Crops System". University of MN Extension. Archived from the original on 2013-11-10. Retrieved 2014-07-26.
  26. ↑ "Organic Materials as *Nitrogen Fertilizers". CO State Extension. Archived from the original on 2013-11-10. Retrieved 2014-07-26.
  27. 1 2 "Plant-Based Fertilizers for Organic Gardens". dummies. Retrieved 2021-04-10.
  28. ↑ Robert, Graves (February 2000). "Composting" (PDF). Environmental Engineering National Engineering Handbook. pp. 2–22. Archived (PDF) from the original on 15 January 2021. Retrieved 19 October 2020.
  29. ↑ "Algae: A Mean, Green Cleaning Machine". USDA Agricultural Research Service. 7 May 2010.
  30. ↑ "Managing Potassium for Organic Crop Production" (PDF). CO State Extension.
  31. ↑ 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.
  32. ↑ "Organic Farming | Agriculture | US EPA". Epa.gov. Retrieved 2012-01-09.
  33. ↑ Gaw, HZ (2011-10-03). "Isolation and Study of Cultures of Chinese Vetch Nodule Bacteria". J Bacteriol. 48 (4): 483–9. doi:10.1128/JB.48.4.483-489.1944. PMC   373994 . PMID   16560855 . Retrieved 2012-01-09.
  34. ↑ Uphoff, Norman; Ball, Andrew S.; Fernandes, Erick; Herren, Hans; Husson, Olivier; Laing, Mark; Palm, Cheryl; Pretty, Jules; Sanchez, Pedro; Sanginga, Nteranya; Thies, Janice (3 March 2006). Biological approaches to sustainable soil systems. CRC Press. ISBN   9781420017113 . Retrieved 2012-01-09.
  35. ↑ Langford, Kate (August 31, 2011). "Surviving drought through agroforestry". World Agroforestry Centre. Archived from the original on October 16, 2012. Retrieved August 29, 2012.
  36. ↑ "Isolation and Study of Cultures of Chinese Vetch Nodule Bacteria". Pubmedcentral.nih.gov. 6 July 2010. Retrieved 25 August 2010.
  37. ↑ Uphoff, Norman Thomas (2006). Biological approaches to sustainable ... CRC Press. ISBN   978-1-57444-583-1 . Retrieved 25 August 2010.
  38. ↑ "Acta Horticulturae". Actahort.org. Retrieved 2012-01-09.
  39. ↑ "AZ Master Gardener Manual: Organic Fetilizers". Ag.arizona.edu. Retrieved 2012-01-09.
  40. ↑ Tu, Cong; Ristaino, Jean B.; Hu, Shuijin (2006). "Soil microbial biomass and activity in organic tomato farming systems: Effects of organic inputs and straw mulching". Soil Biology and Biochemistry. 38 (2): 247–255. doi:10.1016/j.soilbio.2005.05.002. Archived from the original on 2009-01-29. Retrieved 2012-01-09.
  41. ↑ Fitzgerald, T. (2009). "Organic fertilizers" (PDF). spokane-county.wsu.edu. Washington State University. Archived from the original (PDF) on 16 September 2011. Retrieved 16 July 2014.
  42. ↑ Enwall, Karin; Laurent Philippot,2 and Sara Hallin1 (December 2005). "Activity and Composition of the Denitrifying Bacterial Community Respond Differently to Long-Term Fertilization". Applied and Environmental Microbiology. 71 (2). American Society for Microbiology: 8335–8343. Bibcode:2005ApEnM..71.8335E. doi:10.1128/AEM.71.12.8335-8343.2005. PMC   1317341 . PMID   16332820. Archived from the original on 2 October 2011. Retrieved 1 February 2010.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  43. ↑ Birkhofera, Klaus; T. Martijn Bezemerb, c, d, Jaap Bloeme, Michael Bonkowskia, Søren Christensenf, David Duboisg, Fleming Ekelundf, Andreas Fließbachh, Lucie Gunstg, Katarina Hedlundi, Paul Mäderh, Juha Mikolaj, Christophe Robink, Heikki Setäläj, Fabienne Tatin-Frouxk, Wim H. Van der Puttenb, c and Stefan Scheua (September 2008). "Long-term organic farming fosters below and aboveground biota: Implications for soil quality, biological control and productivity". Soil Biology and Biochemistry. 40 (9): 2297–2308. doi:10.1016/j.soilbio.2008.05.007. S2CID   53612353. Archived from the original on 2013-02-03. Retrieved 1 February 2010.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  44. ↑ Lal, R. (2004). "Soil Carbon Sequestration Impacts on Global Climate Change and Food Security". Science . 304 (5677): 1623–7. Bibcode:2004Sci...304.1623L. doi:10.1126/science.1097396. PMID   15192216. S2CID   8574723.
  45. ↑ Rees, Eifion (3 July 2009). "Change farming to cut CO2 emissions by 25 per cent". The Ecologist. Retrieved 2 February 2010.
  46. ↑ Fliessbach, A.; P Maeder(2), A Diop(3), LWM Luttikholt(1), N Scialabba(4), U Niggli(2), Paul Hepperly(3), T LaSalle(3) (2009). "ClimateChange: GlobalRisks,ChallengesandDecisions" (PDF). P24.17 Mitigation and adaptation strategies – organic agriculture. IOPConf. Series: EarthandEnvironmentalScience6(2009)242025: IOP Publishing. Retrieved 2 February 2010.{{cite web}}: CS1 maint: location (link) CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)[ permanent dead link ]
  47. ↑ PIMENTEL, David; PAUL HEPPERLY, JAMES HANSON, DAVID DOUDS, and RITA SEIDEL (July 2005). "Environmental, Energetic, and Economic Comparisons of Organic and Conventional Farming Systems". BioScience. 55 (7): 573. doi: 10.1641/0006-3568(2005)055[0573:EEAECO]2.0.CO;2 . ISSN   0006-3568. S2CID   53967547.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  48. ↑ Mäder, Paul; Andreas Fliebach,,1 David Dubois,2 Lucie Gunst,2 Padruot Fried,2 Urs Niggli1 (31 May 2002). "Soil Fertility and Biodiversity in Organic Farming". Science. 296 (5573): 1694–1697. Bibcode:2002Sci...296.1694M. doi:10.1126/science.1071148. PMID   12040197. S2CID   7635563 . Retrieved 1 February 2010.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  49. ↑ "Crazy about Compost" (PDF). Retrieved 25 August 2010.
  50. ↑ "CSA". Md1.csa.com. Retrieved 25 August 2010.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.