Array ( [0] => {{Short description|Organic matter in soils resulting from decay of plant and animal materials}} [1] => {{About|the organic matter in soil|the food|Hummus|the band|Humus (band)}} [2] => {{Use dmy dates|date=April 2014}} [3] => [[File:Soil Horizons.svg|thumb|Humus has a characteristic black or dark brown color and is an accumulation of organic [[Soil carbon|carbon]]. Besides the three major soil horizons of (A) surface/topsoil, (B) subsoil, and (C) substratum, some soils have an organic horizon (O) on the very surface. Hard bedrock (R) is not in a strict sense soil. [4] => ]] [5] => In classical [6] => {{citation [7] => |title= A Soil-Science Revolution Upends Plans to Fight Climate Change [8] => |last=Popkin [9] => |first=Gabriel [10] => |date=27 July 2021 [11] => |url=https://www.quantamagazine.org/a-soil-science-revolution-upends-plans-to-fight-climate-change-20210727/ [12] => |publisher=Quanta Magazine [13] => |quote=“The latest edition of The Nature and Properties of Soils, published in 2016, cites Lehmann’s 2015 paper and acknowledges that “our understanding of the nature and genesis of soil humus has advanced greatly since the turn of the century, requiring that some long-accepted concepts be revised or abandoned.”}} [14] => [[soil science]], '''humus''' is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of [[soil organic matter]]. It is rich in nutrients and retains moisture in the soil. Humus is the Latin word for "earth" or "ground".{{cite web |title=Humus |url=http://dictionary.reference.com/browse/humus |access-date=23 September 2008 |via=Dictionary.com ''Random House Dictionary Unabridged''}} [15] => [16] => In [[agriculture]], "humus" sometimes also is used to describe mature or natural [[compost]] extracted from a woodland or other spontaneous source for use as a [[soil conditioner]].{{cite encyclopedia |title=Humus |encyclopedia=[[Encyclopaedia Britannica]] Online |date=2011 |access-date=24 November 2011 |url= https://www.britannica.com/EBchecked/topic/276408/humus}} It is also used to describe a [[topsoil]] [[Soil horizon|horizon]] that contains [[organic matter]] (''humus type'',{{cite journal |last1=Chertov |first1=O. G. |last2=Kornarov |first2=A. S. |last3=Crocker |first3=G. |last4=Grace |first4=P. |last5=Klir |first5=J. |last6=Körschens |first6=M. |last7=Poulton |first7=P. R. |last8=Richter |first8=D. |date=1997 |title=Simulating trends of soil organic carbon in seven long-term experiments using the SOMM model of the humus types |journal=Geoderma |volume=81 |issue=1–2 |pages=121–135 |doi=10.1016/S0016-7061(97)00085-2 |bibcode=1997Geode..81..121C}} ''humus form'',{{cite book |last=Baritz |first=R. |date=2003 |title=Humus Forms in Forests of the Northern German Lowlands |publisher=Schweizerbart |location=Stuttgart |url= http://www.schweizerbart.de/pubs/isbn/bgr/sonderheft-3510959086-desc.html}} or ''humus profile''{{cite journal |last1=Bunting |first1=B. T. |last2=Lundberg |first2=J. |date=1995 |title=The humus profile-concept, class and reality |journal=Geoderma |volume=40 |issue=1–2 |pages=17–36 |doi=10.1016/0016-7061(87)90011-5 |bibcode=1987Geode..40...17B}}). [17] => [18] => Humus has many nutrients that improve the health of soil, [[nitrogen]] being the most important. The ratio of [[carbon]] to nitrogen (C:N) of humus commonly ranges between 8:1 and 15:1 with the median being about 12:1.{{cite book | last1=Weil | first1=Ray R. | last2=Brady | first2=Nyle C. | title=The Nature and Properties of Soils | url=https://www.pearson.com/us/higher-education/program/Weil-Nature-and-Properties-of-Soils-The-15th-Edition/PGM219427.html| date=2017 | edition=15th | publication-date=April 2017 |publisher=Pearson Education | location=Columbus, Ohio | language=en | isbn=978-0-13-325448-8 |lccn=2016008568 |oclc=936004363 | page=536}} It also significantly affects the [[bulk density]] of soil. Humus is amorphous and lacks the cellular structure characteristic of plants, microorganisms or animals.{{cite journal |last1=Whitehead |first1=D. C. |last2=Tinsley |first2=J. |date=1963 |title=The biochemistry of humus formation |journal=Journal of the Science of Food and Agriculture |volume=14 |issue=12 |pages=849–857 |doi=10.1002/jsfa.2740141201|bibcode=1963JSFA...14..849W }} [19] => [20] => ==Description== [21] => [22] => The primary materials needed for the process of humification are plant materials. The composition of humus varies dependent on the composition of the primary materials and the secondary microbial and animal products. The decomposition rate of the different compounds will affect the composition of the humus.{{cite journal |last1=Kögel-Knabner |first1=Ingrid |last2=Zech |first2=Wolfgang |last3=Hatcher |first3=Patrick G. |date=1988 |title=Chemical composition of the organic matter in forest soils: The humus layer |language=de |journal=Zeitschrift für Pflanzenernährung und Bodenkunde |volume=151 |issue=5 |pages=331–340 |doi=10.1002/jpln.19881510512}} [23] => [24] => It is difficult to define humus precisely because it is a very complex substance which is not fully understood. Humus is different from decomposing [[soil organic matter]]. The latter looks rough and has visible remains of the original plant or animal matter. Fully humified humus, on the contrary, has a uniformly dark, spongy, and jelly-like appearance, and is amorphous; it may gradually decay over several years or persist for millennia.{{cite journal |last1=Di Giovanni |first1=C. |last2=Disnar |first2=J. R. |last3=Bichet |first3=V. |last4=Campy |first4=M. |date=1998 |title=Sur la présence de matières organiques mésocénozoïques dans des humus actuels (bassin de Chaillexon, Doubs, France) |language=fr |journal=Comptes Rendus de l'Académie des Sciences, Série IIA |volume=326 |issue=8 |pages=553–559 |doi=10.1016/S1251-8050(98)80206-1 |bibcode=1998CRASE.326..553D}} It has no determinate shape, structure, or quality. However, when examined under a microscope, humus may reveal tiny plant, animal, or microbial remains that have been mechanically, but not chemically, degraded.{{cite journal |author=Nicolas Bernier and Jean-François Ponge |date=1994 |title=Humus form dynamics during the sylvogenetic cycle in a mountain spruce forest |journal=Soil Biology and Biochemistry |volume=26 |issue=2 |pages=183–220 |doi=10.1016/0038-0717(94)90161-9 |url= https://www.researchgate.net/publication/46312511 |format=PDF |citeseerx=10.1.1.635.6402}} This suggests an ambiguous boundary between humus and soil organic matter. While distinct, humus is an integral part of soil organic matter.{{Cite web |url= http://www.humintech.com/001/articles/article_definition_of_soil_organic_matter.html |title=Humintech® {{!}} Definition of Soil Organic Matter & Humic Acids Based Products |access-date=5 April 2009 |archive-url= https://web.archive.org/web/20150921224035/http://www.humintech.com/001/articles/article_definition_of_soil_organic_matter.html |archive-date=21 September 2015 |url-status=dead |df=dmy-all}} [25] => [26] => [36] => [37] => There is little data available on the composition of forest humus because it is a complex mixture that is challenging for researchers to analyze. Researchers in the 1940s and 1960s tried using chemical separation to analyze plant and humic compounds in forest soil, but this proved impossible. Further research has been done in more recent years, though it remains an active field of study.[https://soilcarboncoalition.org/files/Waksman-Humus.pdf Waksman SA. (1936). Humus. Origin, Chemical Composition and Importance in Nature. New York, NY: Williams and Wilkins]Stevenson FJ. Humus Chemistry: Genesis, Composition, Reactions. (2nd). Wiley, 1994. {{isbn|978-0-471-59474-1}}Maier RM. [38] => Chapter 16 - Biogeochemical Cycling. Environmental Microbiology (3rd). Academic Press, 2015. pp 339-373. {{isbn|9780123946263}} {{doi|10.1016/B978-0-12-394626-3.00016-8}} [39] => [40] => ==Humification== [41] => [[Microorganism]]s decompose a large portion of the soil organic matter into inorganic minerals that the roots of plants can absorb as nutrients. This process is termed "[[mineralization (soil science)|mineralization]]". In this process, [[nitrogen]] ([[nitrogen cycle]]) and the other nutrients ([[nutrient cycle]]) in the decomposed organic matter are recycled. Depending on the conditions in which the decomposition occurs, a fraction of the organic matter does not mineralize and instead is transformed by a process called "humification". Prior to modern analytical methods, early evidence led scientists to believe that humification resulted in concatenations of organic [[polymer]] resistant to the action of microorganisms,{{cite book | last1=Weil | first1=Ray R. | last2=Brady | first2=Nyle C. | title=The Nature and Properties of Soils | url=https://www.pearson.com/us/higher-education/program/Weil-Nature-and-Properties-of-Soils-The-15th-Edition/PGM219427.html| date=2017 | edition=15th | publication-date=April 2017 |publisher=Pearson Education | location=Columbus, Ohio | language=en | isbn=978-0-13-325448-8 |lccn=2016008568 |oclc=936004363 | page=549|quote=It is now thought that humic substances in soil extracts do not represent the nature of most of the organic matter as it exists in soil. [42] => }} however recent research has demonstrated that microorganisms are capable of digesting humus.{{cite web|url=https://www.quantamagazine.org/a-soil-science-revolution-upends-plans-to-fight-climate-change-20210727/|title=A Soil-Science Revolution Upends Plans to Fight Climate Change|quote=Soil researchers have concluded that even the largest, most complex molecules can be quickly devoured by soil’s abundant and voracious microbes.|work=Quanta magazine|last=Popkin|first=G.|year=2021}} [43] => [44] => Humification can occur naturally in [[soil]] or artificially in the production of [[compost]]. Organic matter is humified by a combination of [[Saprotrophic nutrition|saprotrophic]] fungi, bacteria, microbes and animals such as earthworms, nematodes, protozoa, and arthropods.[[Soil biology]]{{Circular reference|date=February 2017}} Plant remains, including those that animals digested and excreted, contain organic compounds: sugars, starches, proteins, carbohydrates, lignins, waxes, resins, and organic acids. Decay in the soil begins with the decomposition of sugars and starches from carbohydrates, which decompose easily as [[detritivore]]s initially invade the dead plant organs, while the remaining [[cellulose]] and [[lignin]] decompose more slowly.{{cite book |last1=Berg |first1=B. |last2=McClaugherty |first2=C. |date=2007 |title=Plant Litter: Decomposition, Humus Formation, Carbon Sequestration |edition=2nd |publisher=Springer |isbn=978-3-540-74922-6}}{{page needed|date=July 2020}} Simple proteins, organic acids, starches, and sugars decompose rapidly, while crude proteins, fats, waxes, and resins remain relatively unchanged for longer periods of time. [45] => [46] => Lignin, which is quickly transformed by [[Wood-decay fungus#White rot|white-rot fungi]],{{cite journal |last1=Levin |first1=L. |last2=Forchiassin |first2=F. |last3=Ramos |first3=A. M. |date=2002 |title=Copper induction of lignin-modifying enzymes in the white-rot fungus ''Trametes trogii'' |url= http://www.mycologia.org/cgi/content/full/94/3/377 |journal=Mycologia |volume=94 |issue=3 |pages=377–383 |doi=10.2307/3761771 |jstor=3761771|pmid=21156508 }} is one of the primary precursors of humus,{{cite journal |last1=González-Pérez |first1=M. |last2=Vidal Torrado |first2=P. |last3=Colnago |first3=L. A. |last4=Martin-Neto |first4=L. |last5=Otero |first5=X. L. |last6=Milori |first6=D. M. B. P. |last7=Haenel Gomes |first7=F. |date=2008 |title=13C NMR and FTIR spectroscopy characterization of humic acids in spodosols under tropical rain forest in southeastern Brazil |journal=Geoderma |volume=146 |issue=3–4 |pages=425–433 |doi=10.1016/j.geoderma.2008.06.018 |bibcode=2008Geode.146..425G}} together with by-products of microbial{{cite journal |last1=Knicker |first1=H. |last2=Almendros |first2=G. |last3=González-Vila |first3=F. J. |last4=Lüdemann |first4=H. D. |last5=Martin |first5=F. |date=1995 |title=13C and 15N NMR analysis of some fungal melanins in comparison with soil organic matter |journal=Organic Geochemistry |volume=23 |issue=11–12 |pages=1023–1028 |doi=10.1016/0146-6380(95)00094-1|bibcode=1995OrGeo..23.1023K }} and animal{{cite journal |last1=Muscoloa |first1=A. |last2=Bovalob |first2=F. |last3=Gionfriddob |first3=F. |last4=Nardi |first4=S. |date=1999 |title=Earthworm humic matter produces auxin-like effects on Daucus carota cell growth and nitrate metabolism |journal=Soil Biology and Biochemistry |volume=31 |issue=9 |pages=1303–1311 |doi=10.1016/S0038-0717(99)00049-8}} activity. The humus produced by humification is thus a mixture of compounds and complex biological chemicals of plant, animal, or microbial origin that has many functions and benefits in soil. Some judge earthworm humus ([[vermicompost]]) to be the optimal organic [[manure]].{{Cite web |url= http://agri.and.nic.in/vermi_culture.htm |title=Vermiculture/Vermicompost |date=18 June 2011 |work=Agri.And.Nic.in |publisher=Department of Agriculture, Andaman & Nicobar Administration |location=[[Port Blair]] |access-date=17 April 2009 |archive-url= https://web.archive.org/web/20160117031922/http://agri.and.nic.in/vermi_culture.htm |archive-date=17 January 2016 |url-status=dead}} [47] => [48] => ==Stability== [49] => Much of the humus in most soils has persisted for more than 100 years, rather than having been decomposed into CO2, and can be regarded as stable; this organic matter has been protected from decomposition by microbial or enzyme action because it is hidden (occluded) inside small aggregates of soil particles, or tightly [[Sorption|sorbed]] or [[Complex (chemistry)|complexed]] to [[clay]]s.{{cite journal |last1=Dungait |first1=J. A. |last2=Hopkins |first2=D. W. |last3=Gregory |first3=A. S. |last4=Whitmore |first4=A. P. |title=Soil organic matter turnover is governed by accessibility not recalcitrance |journal=Global Change Biology |date=2012 |volume=18 |issue=6 |pages=1781–1796 |doi=10.1111/j.1365-2486.2012.02665.x |url= ftp://195.37.229.5/pub/outgoing/mbraak/Eurosoil/literature/RoundTable/Dungait%20et%20al.,%202012%20-%20Soil%20organic%20matter%20turnover%20is%20governed%20by%20accessibility%20not%20recalcitrance.pdf |access-date=30 August 2014 |bibcode=2012GCBio..18.1781D|s2cid=86741232 }}{{dead link|date=April 2017 |bot=InternetArchiveBot |fix-attempted=yes}} Most humus that is not protected in this way is decomposed within 10 years and can be regarded as less stable or more [[Lability#Soils|labile]]. [50] => [51] => Stable humus contributes few plant-available nutrients in soil, but it helps maintain its physical structure.{{cite journal |last1=Oades |first1=J. M. |title=Soil organic matter and structural stability: Mechanisms and implications for management |journal=Plant and Soil |date=1984 |volume=76 |issue=1–3 |pages=319–337 |doi=10.1007/BF02205590|s2cid=7195036 }} A very stable form of humus is formed from the slow oxidation ([[redox]]) of [[soil carbon]] after the incorporation of finely powdered [[Biochar|charcoal]] into the [[topsoil]]. This process is speculated to have been important in the formation of the unusually fertile Amazonian {{lang|es|[[Terra preta|terra preta do Indio]]}}.{{cite book |last1=Lehmann |first1=J. |last2=Kern |first2=D. C. |last3=Glaser |first3=B. |last4=Woods |first4=W. I. |date=2004 |title=Amazonian Dark Earths: Origin, Properties, Management |publisher=Springer |isbn=978-1-4020-1839-8}}{{page needed|date=July 2020}} However, recent work{{cite journal |last1=Lehmann |first1=Johannes |title=The contentious nature of soil organic matter |journal=Nature |date=2015-12-01 |volume=528 |issue=7580 |pages=60–68 |doi=10.1038/nature16069 |pmid=26595271 |bibcode=2015Natur.528...60L |s2cid=205246638 |ref=Lehmann2015|doi-access=free }} suggests that complex soil organic molecules may be much less stable than previously thought: “the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds.″ [52] => [53] => ==Horizons== [54] => Humus has a characteristic black or dark brown color and is organic due to an accumulation of organic carbon. Soil scientists use the capital letters O, A, B, C, and E to identify the master horizons, and lowercase letters for distinctions of these horizons. Most soils have three major horizons: the surface horizon (A), the subsoil (B), and the substratum (C). Some soils have an organic horizon (O) on the surface, but this horizon can also be buried. The master horizon (E) is used for subsurface horizons that have significantly lost minerals ([[eluviation]]). Bedrock, which is not soil, uses the letter R. [55] => [56] => ==Benefits of soil organic matter and humus== [57] => [58] => The importance of chemically stable humus is thought by some to be the [[Soil fertility|fertility]] it provides to soils in both a physical and chemical sense,{{cite journal |last1=Hargitai |first1=L. |date=1993 |title=The soil of organic matter content and humus quality in the maintenance of soil fertility and in environmental protection |journal=Landscape and Urban Planning |volume=27 |issue=2–4 |pages=161–167 |doi=10.1016/0169-2046(93)90044-E}} though some agricultural experts put a greater focus on other features of it, such as its ability to suppress disease.{{cite journal |last1=Hoitink |first1=H. A. |last2=Fahy |first2=P. C. |date=1986 |title=Basic for the control of soilborne plant pathogens with composts |journal=Annual Review of Phytopathology |volume=24 |pages=93–114 |doi=10.1146/annurev.py.24.090186.000521}} It helps the soil retain moistureC.Michael Hogan. 2010. [http://www.eoearth.org/article/Abiotic_factor?topic=49461 ''Abiotic factor''. Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the Environment] {{webarchive |url= https://web.archive.org/web/20130608071757/http://www.eoearth.org/article/Abiotic_factor?topic=49461 |date=8 June 2013}}. Washington DC by increasing [[Porosity|microporosity]]{{cite journal |last1=De Macedo |first1=J. R. |last2=Do Amaral |first2=Meneguelli |last3=Ottoni |first3=T. B. |last4=Araujo |first4=Jorge Araújo |last5=de Sousa Lima |first5=J. |date=2002 |title=Estimation of field capacity and moisture retention based on regression analysis involving chemical and physical properties in Alfisols and Ultisols of the state of Rio de Janeiro |journal=Communications in Soil Science and Plant Analysis |volume=33 |issue=13–14 |pages=2037–2055 |doi=10.1081/CSS-120005747|s2cid=98466747 }} and encourages the formation of good [[soil structure]].{{cite journal |last1=Hempfling |first1=R. |last2=Schulten |first2=H. R. |last3=Horn |first3=R. |date=1990 |title=Relevance of humus composition to the physical/mechanical stability of agricultural soils: a study by direct pyrolysis-mass spectrometry |journal=Journal of Analytical and Applied Pyrolysis |volume=17 |issue=3 |pages=275–281 |doi=10.1016/0165-2370(90)85016-G}}[http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/soil_systems/soil_development_soil_properties.html Soil Development: Soil Properties] {{webarchive |url= https://web.archive.org/web/20121128125005/http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/soil_systems/soil_development_soil_properties.html |date=28 November 2012}} The incorporation of [[oxygen]] into large organic molecular assemblages generates many active, negatively charged sites that bind to positively charged [[ion]]s (cations) of [[Plant nutrition|plant nutrients]], making them more available to the plant by way of [[ion exchange]].{{cite journal |last1=Szalay |first1=A. |date=1964 |title=Cation exchange properties of humic acids and their importance in the geochemical enrichment of UO2++ and other cations |journal=Geochimica et Cosmochimica Acta |volume=28 |issue=10 |pages=1605–1614 |doi=10.1016/0016-7037(64)90009-2 |bibcode=1964GeCoA..28.1605S}} Humus allows soil organisms to feed and reproduce and is often described as the "life-force" of the soil.{{cite journal |last1=Elo |first1=S. |last2=Maunuksela |first2=L. |last3=Salkinoja-Salonen |first3=M. |last4=Smolander |first4=A. |last5=Haahtela |first5=K. |date=2006 |title=Humus bacteria of Norway spruce stands: plant growth promoting properties and birch, red fescue and alder colonizing capacity |journal=FEMS Microbiology Ecology |volume=31 |issue=2 |pages=143–152 |doi=10.1111/j.1574-6941.2000.tb00679.x |pmid=10640667 |doi-access=free}}{{cite journal |last1=Vreeken-Buijs |first1=M. J. |last2=Hassink |first2=J. |last3=Brussaard |first3=L. |date=1998 |title=Relationships of soil microarthropod biomass with organic matter and pore size distribution in soils under different land use |journal=Soil Biology and Biochemistry |volume=30 |pages=97–106 |doi=10.1016/S0038-0717(97)00064-3}} [59] => [60] => * The process that converts soil organic matter into humus feeds the population of microorganisms and other creatures in the soil, and thus maintains high and healthy levels of soil life. [61] => * The rate at which soil organic matter is converted into humus promotes (when fast) or limits (when slow) the coexistence of plants, animals, and microorganisms in the soil. [62] => * Effective humus and stable humus are additional sources of nutrients for microbes: the former provides a readily available supply, and the latter acts as a long term storage reservoir. [63] => * Decomposition of dead plant material causes complex organic compounds to be slowly oxidized (lignin-like humus) or to decompose into simpler forms (sugars and [[amino sugar]]s, and [[Aliphatic compound|aliphatic]] and [[Naturally occurring phenols|phenolic]] [[organic acid]]s), which are further transformed into microbial biomass (microbial humus) or reorganized and further oxidized into humic assemblages ([[fulvic acid]]s and [[humic acid]]s), which bind to [[clay minerals]] and metal hydroxides. The ability of plants to absorb humic substances with their roots and [[Metabolism|metabolize]] them has been long debated. There is now a consensus that humus functions [[Plant hormone|hormonally]] rather than simply [[Plant nutrition|nutritionally]] in [[plant physiology]].{{cite journal |last1=Eyheraguibel |first1=B. |last2=Silvestrea |first2=J. Morard |date=2008 |title=Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize |url= https://hal.archives-ouvertes.fr/hal-00940093/file/Eyheraguibel_10804.pdf |journal=Bioresource Technology |volume=99 |issue=10 |pages=4206–4212 |doi=10.1016/j.biortech.2007.08.082 |pmid=17962015}}{{cite journal |last1=Zandonadi |first1=D. B. |last2=Santos |first2=M. P. |last3=Busato |first3=J. G. |last4=Peres |first4=L. E. P. |last5=Façanha |first5=A. R. |title=Plant physiology as affected by humified organic matter |journal=Theoretical and Experimental Plant Physiology |date=2013 |volume=25 |pages=13–25 |doi=10.1590/S2197-00252013000100003 |doi-access=free}} [64] => * Humus is a [[colloid]]al substance and increases the [[cation-exchange capacity]] of soil, hence its ability to store nutrients by [[chelation]]. While these nutrient cations are available to plants, they are held in the soil and prevented from being leached by rain or irrigation. [65] => * Humus can hold the equivalent of 80–90% of its weight in moisture and therefore increases the soil's capacity to withstand drought.{{cite journal |last1=Olness |first1=A. |last2=Archer |first2=D. |date=2005 |title=Effect of organic carbon on available water in soil |journal=Soil Science |volume=170 |issue=2 |pages=90–101 |doi=10.1097/00010694-200502000-00002|bibcode=2005SoilS.170...90O |s2cid=95336837 }}[http://journals.lww.com/soilsci/Abstract/2005/02000/Effect_of_Organic_Carbon_on_Available_Water_in.2.aspx Effect of Organic Carbon on Available Water in Soil : Soil Science] [66] => * The biochemical structure of humus enables it to moderate, i.e. buffer, excessive [[Soil pH|acidic]] or [[Alkali soil|alkaline]] soil conditions.{{cite journal |last1=Kikuchi |first1=R. |date=2004 |title=Deacidification effect of the litter layer on forest soil during snowmelt runoff: laboratory experiment and its basic formularization for simulation modeling |journal=Chemosphere |volume=54 |issue=8 |pages=1163–1169 |doi=10.1016/j.chemosphere.2003.10.025 |pmid=14664845 |bibcode=2004Chmsp..54.1163K}} [67] => * During humification, microbes secrete sticky, gum-like [[mucilage]]s; these contribute to the crumby structure (tilth) of the soil by adhering particles together and allowing greater [[Aeration#Aeration of soil|aeration]] of the soil.{{cite journal |last1=Caesar-Tonthat |first1=T. C. |date=2002 |title=Soil binding properties of mucilage produced by a basidiomycete fungus in a model system |url= https://zenodo.org/record/1235817 |journal=Mycological Research |volume=106 |issue=8 |pages=930–937 |doi=10.1017/S0953756202006330 |type=Submitted manuscript}} Toxic substances such as [[Heavy metal (chemistry)|heavy metals]] and excess nutrients can be chelated, i.e., bound to the organic molecules of humus, and so prevented from leaching away.{{cite journal |last1=Huang |first1=D. L. |last2=Zeng |first2=G. M. |last3=Feng |first3=C. L. |last4=Hu |first4=S. |last5=Jiang |first5=X. Y. |last6=Tang |first6=L. |last7=Su |first7=F. F. |last8=Zhang |first8=Y. |last9=Zeng |first9=W. |last10=Liu |first10=H. L. |date=2008 |title=Degradation of lead-contaminated lignocellulosic waste by Phanerochaete chrysosporium and the reduction of lead toxicity |journal=Environmental Science and Technology |volume=42 |issue=13 |pages=4946–4951 |doi=10.1021/es800072c |pmid=18678031 |bibcode=2008EnST...42.4946H}} [68] => * The dark, usually brown or black, color of humus helps to warm cold soils in spring. [69] => *Humus can contribute to [[climate change mitigation]] through its [[carbon sequestration]] potential.{{Cite journal|last1=Amelung|first1=W.|last2=Bossio|first2=D.|last3=de Vries|first3=W.|last4=Kögel-Knabner|first4=I.|last5=Lehmann|first5=J.|last6=Amundson|first6=R.|last7=Bol|first7=R.|last8=Collins|first8=C.|last9=Lal|first9=R.|last10=Leifeld|first10=J.|last11=Minasny|first11=B.|date=2020-10-27|title=Towards a global-scale soil climate mitigation strategy|journal=Nature Communications|language=en|volume=11|issue=1|pages=5427|doi=10.1038/s41467-020-18887-7|pmid=33110065|pmc=7591914|bibcode=2020NatCo..11.5427A|issn=2041-1723|doi-access=free}} Artificial humic acid and artificial fulvic acid synthesized from agricultural litter can increase the content of dissolved organic matter and total organic carbon in soil.{{Cite journal|last1=Tang|first1=Chunyu|last2=Li|first2=Yuelei|last3=Song|first3=Jingpeng|last4=Antonietti|first4=Markus|last5=Yang|first5=Fan|date=2021-06-25|title=Artificial humic substances improve microbial activity for binding CO2|journal=iScience|language=en|volume=24|issue=6|pages=102647|doi=10.1016/j.isci.2021.102647|pmid=34466779|pmc=8387571|bibcode=2021iSci...24j2647T|issn=2589-0042}} [70] => [71] => ==See also== [72] => {{div col|colwidth=30em}} [73] => *[[Biochar]] [74] => *[[Biomass]] [75] => *[[Biotic material]] [76] => *[[Detritus]] [77] => *[[Glomalin]] [78] => *[[Humic acid]] [79] => *[[Immobilization (soil science)]] [80] => *[[Mineralization (soil science)]] [81] => *[[Mycorrhizal fungi and soil carbon storage]] [82] => *[[Organic matter]] [83] => *[[Plant litter]] [84] => *[[Soil horizon]] [85] => *[[Soil science]] [86] => *[[Terra preta]] [87] => {{div col end}} [88] => [89] => ==References== [90] => {{Reflist}} [91] => [92] => ==External links== [93] => {{sisterlinks|wikt=humus|b=no|q=humus|s=no|commons=no|n=no|v=no|species=no}} [94] => *{{cite web |url= http://karnet.up.wroc.pl/~weber/typy2.htm |first=Jerzy |last=Weber |title=Types of humus in soils |publisher=Agricultural University of Wroclaw, Poland |access-date=12 December 2013}} [95] => *{{cite web |last1=Wershaw |first1=R. L. |title=Evaluation of conceptual models of natural organic matter (humus) from a consideration of the chemical and biochemical processes of humification |url= http://pubs.usgs.gov/sir/2004/5121/pdf/sir2004-5121.pdf |work=Pubs.USGU.gov |publisher=[[United States Geological Survey]] |access-date=14 March 2016}} [96] => *{{cite web |url= http://humic-substances.org/ |title=What are Humic Substances? |publisher=International Humic Substances Society |access-date=19 February 2018}} [97] => [98] => {{Authority control}} [99] => [100] => [[Category:Composting]] [101] => [[Category:Soil improvers]] [102] => [[Category:Soil science]] [103] => [[Category:Organic farming]] [] => )
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Humus

Humus refers to the organic component of soil, formed from the decomposition of plant and animal matter. It is dark brown or black in color and rich in nutrients, making it an essential part of soil fertility.

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It is dark brown or black in color and rich in nutrients, making it an essential part of soil fertility. Humus improves soil structure, retains water, and provides a habitat for microorganisms that aid in nutrient cycling and plant growth. It also helps in preventing erosion and increasing soil resilience against drought and other environmental stresses. Humus is created through a process called humification, where organic matter is broken down by microbes and converted into a stable, carbon-rich substance. This Wikipedia page provides a comprehensive overview of humus, including its composition, formation, and role in soil health. It also discusses various methods to enhance humus content in soil and the importance of sustainable soil management practices.

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