Cattle urine patches

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Urine patches in cattle pastures generate large concentrations of the greenhouse gas nitrous oxide through nitrification and denitrification processes in urine-contaminated soils. [1] [2] Over the past few decades, the cattle population has increased more rapidly than the human population. [3] Between the years 2000 and 2050, the cattle population is expected to increase from 1.5 billion to 2.6 billion. [4] When large populations of cattle are packed into pastures, excessive amounts of urine soak into soils. This increases the rate at which nitrification and denitrification occur and produce nitrous oxide. Currently, nitrous oxide is one of the single most important ozone-depleting emissions and is expected to remain the largest throughout the 21st century. [5]

Contents

Pasture cows take a break from the hot Louisiana sun to relax in the shade. Pasture cows in shade.jpg
Pasture cows take a break from the hot Louisiana sun to relax in the shade.

Nitrous oxide environmental impacts

Nitrous oxide is a greenhouse gas with a global warming potential 298 times that of carbon dioxide. [6] Global warming potential is a way to compare global warming impacts of different gases relative to carbon dioxide emissions. Since nitrous oxide has such a high global warming potential, it is able to warm the earth more effectively compared to other greenhouse gases. [7] Although generally unreactive in the troposphere, nitrous oxide is destroyed during photolysis or reactions with excited oxygen atoms and catalyzes the destruction of ozone in the stratosphere. [8] The net loss of ozone molecules occurs in a series of photochemical reactions represented below: [9]

Destruction of stratospheric ozone leaves the biosphere vulnerable to penetrating rays of ultraviolet radiation. [9] Exposure to high amounts of ultraviolet radiation can affect the environment by affecting productivity of crops the human population depends on for food. [10]

Cattle urine composition

Nitrogen concentration of cattle urine varies between approximately 3.0 and 10.5 g/L. Although many nitrogenous constituents are involved in the chemical make-up of cattle urine, urea is dominant. Urea concentration represents 52.0% to 93.5% of total urinary nitrogen and is dependent upon the amount of dietary protein consumed by cattle. [6] Through a process known as ureolysis, the enzyme urease completely hydrolyzes urea to ammonia within one to two days of being excreted and soaked into soils. [6] [11] This reaction is outlined below: [11]

Ammonia is the key product of this reaction that goes on to fuel nitrification. [6]

The role of the nitrogen cycle in urine-contaminated soils

Nitrification and denitrification are two microbial processes that are part of the nitrogen cycle. While denitrification contributes to the bulk production of nitrous oxide, small amounts are also produced during nitrification. [9] When specific environmental factors are met, both processes will occur more quickly and produce higher emissions of nitrous oxide. For example, soils with relatively high temperatures and water-filled pore spaces ranging from 60 to 80% are required for peak performances of both processes. [6]

Nitrification

Nitrification will occur once ammonia becomes readily available in urine-contaminated soils. Ammonia is oxidized into nitrite and nitrate via nitrifying bacteria. [12] Nitrification is chemically-expressed in two distinct steps as shown below:

Step 1

Step 1 details the oxidation of ammonia into nitrite via ammonia-oxidizing bacteria. The most frequent genus of bacteria identified as being the facilitator of this step is Nitrosomonas . [12] These bacteria will produce small quantities of nitrous oxide from produced nitrite in a side reaction. [13] Nitrous oxide emissions increase as soil pH concentration increases or becomes more basic. [1] [12]

Step 2

Step 2 details the oxidation of nitrite to nitrate via nitrite-oxidizing bacteria. The most frequent genus of bacteria identified as being the facilitator of this step is Nitrobacter . While no quantities of nitrous oxide are produced in this step, the resulting nitrate is used to fuel denitrification. [12]

Denitrification

Denitrification is the process that produces the most nitrous oxide. [14] [15] Denitrification involves the reduction of nitrites and nitrates produced during nitrification into nitrous oxide by denitrifying bacteria. Nitrous oxide is subsequently reduced to dinitrogen, the key product of the nitrogen cycle. Nitrous oxide is merely a free obligatory intermediate and is not a major product. [13] Different strains of denitrifying bacteria utilize unique pathways in order to perform denitrification. While these pathways differ from each other, the substrates and products of this process remain the same. Below are two proposed schemes carried out by common denitrifying bacteria:

Scheme 1

Scheme 1 details the denitrification process by Paracoccus denitrificans and Pseudomonas aeruginosa denitrifying bacteria. [13]

Scheme 2

Scheme 2 represents the denitrification process by Pseudomonas stutzeri . In the above formula, (X) represents a common mononitrogen intermediate such as nitrogen monoxide. [13]

Efforts to lessen environmental impacts

Research suggests lessening the concentrations of nitrous oxide entering the stratosphere will serve to enhance recovery of the damaged stratospheric ozone layer. [5]

Louisiana local observes cow pasture. Louisiana local observes cow pasture.jpg
Louisiana local observes cow pasture.

Biochar

The incorporation of biochar into soil has been investigated to reduce nitrous oxide emissions from ruminant urine patches. Biochar is a carbon-rich compound manufactured from the thermal decomposition of organic matter in oxygen-deprived conditions at relatively low temperatures. Biochar serves to reduce nitrous oxide emissions by altering nitrogen transformation rates in urine-contaminated soils. Detailed field data such as seasonal effects and repeated soil exposure are still lacking and research on this subject is ongoing. [16] However, nitrous oxide emissions have been demonstrated as being reduced by 50 and 80% following the incorporation of biochar into affected soils. [17]

Organic agriculture

Organic agriculture has shown decreased nitrous oxide emissions through limiting the number of cattle present per hectare of pasture. A decreased number of cattle in one hectare leads to less nitrogenous constituents deposited into the soil at one time and strains the occurrence of nitrification and denitrification. [18] This in turn limits the total amount of nitrous oxide that can be produced.

Related Research Articles

<span class="mw-page-title-main">Nitrous oxide</span> Colourless non-flammable greenhouse gas

Nitrous oxide, commonly known as laughing gas, nitrous, factitious air, among others, is a chemical compound, an oxide of nitrogen with the formula N
2O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

<span class="mw-page-title-main">Nitrogen cycle</span> Biogeochemical cycle by which nitrogen is converted into various chemical forms

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.

<span class="mw-page-title-main">Nitrification</span> Biological oxidation of ammonia/ammonium to nitrate

Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite. Nitrification is an important step in the nitrogen cycle in soil. The process of complete nitrification may occur through separate organisms or entirely within one organism, as in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.

<span class="mw-page-title-main">Denitrification</span> Microbially facilitated process

Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO3−, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak N2O, which is an ozone-depleting substance and a greenhouse gas that can have a considerable influence on global warming.

<i>Nitrosomonas</i> Genus of bacteria

Nitrosomonas is a genus of Gram-negative bacteria, belonging to the Betaproteobacteria. It is one of the five genera of ammonia-oxidizing bacteria and, as an obligate chemolithoautotroph, uses ammonia as an energy source and carbon dioxide as a carbon source in presence of oxygen. Nitrosomonas are important in the global biogeochemical nitrogen cycle, since they increase the bioavailability of nitrogen to plants and in the denitrification, which is important for the release of nitrous oxide, a powerful greenhouse gas. This microbe is photophobic, and usually generate a biofilm matrix, or form clumps with other microbes, to avoid light. Nitrosomonas can be divided into six lineages: the first one includes the species Nitrosomonas europea, Nitrosomonas eutropha, Nitrosomonas halophila, and Nitrosomonas mobilis. The second lineage presents the species Nitrosomonas communis, N. sp. I and N. sp. II, meanwhile the third lineage includes only Nitrosomonas nitrosa. The fourth lineage includes the species Nitrosomonas ureae and Nitrosomonas oligotropha and the fifth and sixth lineages include the species Nitrosomonas marina, N. sp. III, Nitrosomonas estuarii and Nitrosomonas cryotolerans.

In atmospheric chemistry, NOx is shorthand for nitric oxide and nitrogen dioxide, the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone.

Denitrifying bacteria are a diverse group of bacteria that encompass many different phyla. This group of bacteria, together with denitrifying fungi and archaea, is capable of performing denitrification as part of the nitrogen cycle. Denitrification is performed by a variety of denitrifying bacteria that are widely distributed in soils and sediments and that use oxidized nitrogen compounds such as nitrate and nitrite in the absence of oxygen as a terminal electron acceptor. They metabolize nitrogenous compounds using various enzymes, including nitrate reductase (NAR), nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (NOS), turning nitrogen oxides back to nitrogen gas or nitrous oxide.

<i>Nitrobacter</i> Genus of bacteria

Nitrobacter is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name Nitrobacter derives from the Latin neuter gender noun nitrum, nitri, alkalis; the Ancient Greek noun βακτηρία, βακτηρίᾱς, rod. They are non-motile and reproduce via budding or binary fission. Nitrobacter cells are obligate aerobes and have a doubling time of about 13 hours.

Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase, hydroxylamine oxidoreductase, and nitrite oxidoreductase.

Paracoccus denitrificans, is a coccoid bacterium known for its nitrate reducing properties, its ability to replicate under conditions of hypergravity and for being a relative of the eukaryotic mitochondrion.

Nitrospira translate into “a nitrate spiral” is a genus of bacteria within the monophyletic clade of the Nitrospirota phylum. The first member of this genus was described 1986 by Watson et al., isolated from the Gulf of Maine. The bacterium was named Nitrospira marina. Populations were initially thought to be limited to marine ecosystems, but it was later discovered to be well-suited for numerous habitats, including activated sludge of wastewater treatment systems, natural biological marine settings, water circulation biofilters in aquarium tanks, terrestrial systems, fresh and salt water ecosystems, agricultural lands and hot springs. Nitrospira is a ubiquitous bacterium that plays a role in the nitrogen cycle by performing nitrite oxidation in the second step of nitrification. Nitrospira live in a wide array of environments including but not limited to, drinking water systems, waste treatment plants, rice paddies, forest soils, geothermal springs, and sponge tissue. Despite being abundant in many natural and engineered ecosystems Nitrospira are difficult to culture, so most knowledge of them is from molecular and genomic data. However, due to their difficulty to be cultivated in laboratory settings, the entire genome was only sequenced in one species, Nitrospira defluvii. In addition, Nitrospira bacteria's 16S rRNA sequences are too dissimilar to use for PCR primers, thus some members go unnoticed. In addition, members of Nitrospira with the capabilities to perform complete nitrification has also been discovered and cultivated.

<span class="mw-page-title-main">Human impact on the nitrogen cycle</span>

Human impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen (N) inputs to the environment currently exceed inputs from natural N fixation. As a consequence of anthropogenic inputs, the global nitrogen cycle (Fig. 1) has been significantly altered over the past century. Global atmospheric nitrous oxide (N2O) mole fractions have increased from a pre-industrial value of ~270 nmol/mol to ~319 nmol/mol in 2005. Human activities account for over one-third of N2O emissions, most of which are due to the agricultural sector. This article is intended to give a brief review of the history of anthropogenic N inputs, and reported impacts of nitrogen inputs on selected terrestrial and aquatic ecosystems.

Nitric oxide reductase, an enzyme, catalyzes the reduction of nitric oxide (NO) to nitrous oxide (N2O). The enzyme participates in nitrogen metabolism and in the microbial defense against nitric oxide toxicity. The catalyzed reaction may be dependent on different participating small molecules: Cytochrome c (EC: 1.7.2.5, Nitric oxide reductase (cytochrome c)), NADPH (EC:1.7.1.14), or Menaquinone (EC:1.7.5.2).

<span class="mw-page-title-main">Nitrous-oxide reductase</span> Class of enzymes

In enzymology, a nitrous oxide reductase also known as nitrogen:acceptor oxidoreductase (N2O-forming) is an enzyme that catalyzes the final step in bacterial denitrification, the reduction of nitrous oxide to dinitrogen.

Aerobic denitrification, or co-respiration, the simultaneous use of both oxygen (O2) and nitrate (NO−3) as oxidizing agents, performed by various genera of microorganisms. This process differs from anaerobic denitrification not only in its insensitivity to the presence of oxygen, but also in its higher potential to form nitrous oxide (N2O) as a byproduct.

<span class="mw-page-title-main">Greenhouse gas emissions from wetlands</span> Source of gas emissions

Greenhouse gas emissions from wetlands of concern consist primarily of methane and nitrous oxide emissions. Wetlands are the largest natural source of atmospheric methane in the world, and are therefore a major area of concern with respect to climate change. Wetlands account for approximately 20–30% of atmospheric methane through emissions from soils and plants, and contribute an approximate average of 161 Tg of methane to the atmosphere per year.

Nitrososphaera is a mesophilic genus of ammonia-oxidizing Crenarchaeota. The first Nitrososphaera organism was discovered in garden soils at the University of Vienna leading to the categorization of a new genus, family, order and class of Archaea. This genus is contains three distinct species: N. viennensis, Ca. N. gargensis, and Ca N. evergladensis. Nitrososphaera are chemolithoautotrophs and have important biogeochemical roles as nitrifying organisms.

<span class="mw-page-title-main">Nitrapyrin</span> Chemical compound

Nitrapyrin is an organic compound with the formula ClC5H3NCCl3, and is described as a white crystalline solid with a sweet odor. It is used as a nitrification inhibitor and bactericide, which is applied to soils for the growing of agricultural crops since 1974. Nitrapyrin was put up for review by the EPA and deemed safe for use in 2005. Nitrapyrin is an effective nitrification inhibitor to the bacteria Nitrosomonas and has been shown to drastically the reduce the amount of N2O emissions from the soil.

Nitrogen-15 (15N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15N. Despite the different weights, 15N is involved in the same chemical reactions as the more abundant 14N and is therefore used to trace and quantify conversions of one nitrogen compound to another. 15N tracing is applied in biogeochemistry, soil science, environmental science, environmental microbiology and small molecule activation research.

Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, and then to ammonium (NO3− → NO2− → NH4+).

References

  1. 1 2 van Groenigen, Jan; Velthof, Gerard; van der Bolt, Frank; Vos, An; Kuikman, Peter (2005). "Seasonal variation in N2O emissions from urine patches: effects of urine concentration, soil compaction and dung". Plant and Soil. 273 (1–2): 15–27. doi:10.1007/s11104-004-6261-2. S2CID   26826336.
  2. ↑ Vitousek, Peter; Aber, John; Howarth, Robert; Likens, Gene; Matson, Pamela; Schindler, David; Schlesinger, Wiliiam; Tilman, David (1997). "Human Alteration of the Global Nitrogen Cycle: Source and Consequences". Ecological Applications. 7 (3). Ecological Society of America: 739–40. doi:10.2307/2269431. JSTOR   2269431. S2CID   14832613.
  3. ↑ Oenema, Oene; Wrage, Nicole; Velthof, Gerard L.; van Groenigen, Jan Willem; Dolfing, Jan; Kuikman, Peter J. (2005). "Trends in global nitrous oxide emissions from animal production systems". Nutrient Cycling in Agroecosystems. 72 (1). Springer: 51–65. Bibcode:2005NCyAg..72...51O. doi:10.1007/s10705-004-7354-2. S2CID   207146740.
  4. ↑ Thornton, Philip K. (2010). "Livestock production: recent trends, future prospects". Philosophical Transactions of the Royal Society B. 365 (1554): 2853–2867. doi:10.1098/rstb.2010.0134. PMC   2935116 . PMID   20713389.
  5. 1 2 Ravishankara, A.R.; Daniel, John; Portmann, Robert (2009). "Nitrous Oxide (N2O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century". Science. 326 (5949). American Association for the Advancement of Science: 123–5. Bibcode:2009Sci...326..123R. doi: 10.1126/science.1176985 . ISSN   0036-8075. PMID   19713491. S2CID   2100618.
  6. 1 2 3 4 5 Dijkstra, J.; Oenema, O.; van Groenigen, J. W.; Spek, J. W.; van Vuuren, A. M.; Bannink, A. (2013). "Diet effects on urine composition of cattle and N2O emissions". Animal. 7. The Animal Consortium: 292–302. doi: 10.1017/S1751731113000578 . PMID   23739471.
  7. ↑ "Understanding Global Warming Potentials". EPA.gov. EPA. 12 January 2016. Retrieved November 15, 2016.
  8. ↑ Crutzen, P. J.; Ehhalt, D. H. (1977). "Effects of nitrogen fertilizers and combustion on the stratospheric ozone layer". Ambio. 6: 112–117.
  9. 1 2 3 Sahrawat, K.; Keeney, D. (1986). "Nitrous Oxide Emission from Soils" (PDF). Soil Restoration. Advances in Soil Science. Vol. 4. Springer-Verlag New York Inc. pp. 103–148. doi:10.1007/978-1-4613-8612-4_2. ISBN   978-1-4612-7684-5.
  10. ↑ Allen, Jeannie (September 6, 2001). "Ultraviolet Radiation: How it Affects Life on Earth". NASA. Retrieved November 14, 2016.
  11. 1 2 Udert, Kai M.; Larsen, Tove A.; Biebow, Martin; Gujer, Willi (2003). "Urea Hydrolysis and Precipitation Dynamics in a Urine-Collecting System". Water Research. 37 (11): 2571–2582. Bibcode:2003WatRe..37.2571U. doi:10.1016/s0043-1354(03)00065-4. PMID   12753834.
  12. 1 2 3 4 "Nitrification". AWWA with assistance from Economic and Engineering Services, Inc. 2002. Retrieved October 11, 2016.{{cite web}}: CS1 maint: others (link)
  13. 1 2 3 4 Roger; Knowles (1982). "Denitrification". Microbiological Reviews. 46 (1): 43–70. doi:10.1128/MR.46.1.43-70.1982. PMC   373209 . PMID   7045624.
  14. ↑ Monaghan, R. M.; Barraclough, D. (1993). "Nitrous oxide and dinitrogen emissions from urine-affected soil under controlled conditions". Plant and Soil. 151 (1): 127–138. Bibcode:1993PlSoi.151..127M. doi:10.1007/bf00010793. S2CID   34596444.
  15. ↑ Williams, P. H.; Jarvis, S. C.; Dixon, E. (1998). "Emission of nitric oxide and nitrous oxide from soil under field and laboratory conditions". Soil Biology & Biochemistry. 30 (14): 1885–1893. Bibcode:1998SBiBi..30.1885W. doi:10.1016/s0038-0717(98)00052-2.
  16. ↑ Taghizadeh-Toosi, Arezoo; Clough, Tim J.; Condron, Leo M.; Sherlock, Robert R.; Anderson, Craig R.; Craigie, Robin A. (2011). "Biochar Incorporation into Pasture Soil Suppresses in situ Nitrous Oxide Emissions from Ruminant Urine Patches". Journal of Environmental Quality. 40 (2). American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America: 468–476. Bibcode:2011JEnvQ..40..468T. doi: 10.2134/jeq2010.0419 . PMID   21520754.
  17. ↑ Rondon, M.; Ramirez, J.A.; Lehmann, J. (March 2005). "Charcoal additions reduce net emissions of greenhouse gases to the atmosphere". In Proc. of the 3rd Symp. On Greenhouse Gases and Carbon Sequestration, Baltimore, MD. Manhattan, KS: Soil Carbon Center: 21–24.
  18. ↑ Niggli, U.; Fließbach, A.; Hepperly, P.; Scialabba, N. (2009). "Low Greenhouse Gas Agriculture: Mitigation and Adaptation Potential of Sustainable Farming Systems". FAO: 1–16.{{cite journal}}: Cite journal requires |journal= (help)
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