Editing Soil (section)

==Degradation==
{{Main|Soil retrogression and degradation|Soil conservation}}
[[Land degradation]] is a human-induced or natural process which impairs the capacity of [[land (economics)|land]] to function.<ref>{{cite journal |last1=Johnson |first1=Dan L. |last2=Ambrose |first2=Stanley H. |last3=Bassett |first3=Thomas J. |last4=Bowen |first4=Merle L. |last5=Crummey |first5=Donald E. |last6=Isaacson |first6=John S. |last7=Johnson |first7=David N. |last8=Lamb |first8=Peter |last9=Saul |first9=Mahir |last10=Winter-Nelson |first10=Alex E. |year=1997 |title=Meanings of environmental terms |url=https://www.researchgate.net/publication/240784159 |journal=[[Journal of Environmental Quality]] |volume=26 |issue=3 |pages=581–589 |doi=10.2134/jeq1997.00472425002600030002x |bibcode=1997JEnvQ..26..581J |access-date=29 August 2021}}</ref> [[Soil degradation]] involves [[Soil acidification|acidification]], [[soil contamination|contamination]], [[desertification]], [[erosion]] or [[Soil salinity|salination]].<ref>{{cite book |last=Oldeman |first=L. Roel |year=1993 |chapter=Global extent of soil degradation |title=ISRIC Bi-Annual Report 1991–1992 |pages=19–36 |chapter-url=https://library.wur.nl/WebQuery/wurpubs/fulltext/299739 |publisher=[[International Soil Reference and Information Centre]](ISRIC) |location=Wageningen, The Netherlands |access-date=29 August 2021}}</ref>

=== Acidification ===
Soil acidification is beneficial in the case of [[alkaline soil]]s, but it degrades land when it lowers [[crop productivity]], soil biological activity and increases soil vulnerability to [[contamination]] and erosion. Soils are initially acid and remain such when their parent materials are low in basic [[cation]]s (calcium, magnesium, potassium and [[sodium]]). On parent materials richer in [[mineral weathering|weatherable minerals]] acidification occurs when basic cations are [[Leaching (pedology)|leached]] from the soil profile by rainfall or exported by the harvesting of forest or agricultural crops. Soil acidification is accelerated by the use of acid-forming [[nitrogenous fertilizer]]s and by the effects of [[acid precipitation]]. [[Deforestation]] is another cause of soil acidification, mediated by increased leaching of soil nutrients in the absence of [[tree canopies]].<ref>{{cite book |last1=Sumner |first1=Malcolm E. |last2=Noble |first2=Andrew D. |year=2003 |chapter=Soil acidification: the world story |title=Handbook of soil acidity |pages=1–28 |editor-last=Rengel |editor-first=Zdenko |chapter-url=https://pdf-drive.com/pdf/Zdenko20Rengel20-20Handbook20of20Soil20Acidity2028Books20in20Soils2C20Plants2C20and20the20Environment292028200329.pdf#page=16 |publisher=[[Marcel Dekker]] |location=New York, NY, USA |access-date=29 August 2021 |archive-date=14 August 2021 |archive-url=https://web.archive.org/web/20210814115102/https://pdf-drive.com/pdf/Zdenko20Rengel20-20Handbook20of20Soil20Acidity2028Books20in20Soils2C20Plants2C20and20the20Environment292028200329.pdf#page=16 |url-status=dead }}</ref>

===Contamination===
Soil [[contamination]] at low levels is often within a soil's capacity to treat and assimilate [[waste]] material. [[Soil biota]] can treat waste by transforming it, mainly through microbial [[Enzyme|enzymatic]] activity.<ref>{{cite journal |last1=Karam |first1=Jean |last2=Nicell |first2=James A. |year=1997 |title=Potential applications of enzymes in waste treatment |url=https://www.researchgate.net/publication/30002097 |journal=[[Journal of Chemical Technology & Biotechnology]] |volume=69 |issue=2 |pages=141–153 |doi=10.1002/(SICI)1097-4660(199706)69:2<141::AID-JCTB694>3.0.CO;2-U |bibcode=1997JCTB...69..141K |access-date=5 September 2021}}</ref> Soil organic matter and soil minerals can adsorb the waste material and decrease its [[toxicity]],<ref>{{cite journal |last1=Sheng |first1=Guangyao |last2=Johnston |first2=Cliff T. |last3=Teppen |first3=Brian J. |last4=Boyd |first4=Stephen A. |year=2001 |title=Potential contributions of smectite clays and organic matter to pesticide retention in soils |url=https://www.academia.edu/4875079 |journal=[[Journal of Agricultural and Food Chemistry]] |volume=49 |issue=6 |pages=2899–2907 |doi=10.1021/jf001485d |pmid=11409985 |bibcode=2001JAFC...49.2899S |access-date=5 September 2021}}</ref> although when in colloidal form they may transport the adsorbed contaminants to subsurface environments.<ref>{{cite journal |last1=Sprague |first1=Lori A. |last2=Herman |first2=Janet S. |last3=Hornberger |first3=George M. |last4=Mills |first4=Aaron L. |year=2000 |title=Atrazine adsorption and colloid-facilitated transport through the unsaturated zone |url=https://lmecol.evsc.virginia.edu/pubs/73-Sprague_JEQ2000.pdf |journal=[[Journal of Environmental Quality]] |volume=29 |issue=5 |pages=1632–1641 |doi=10.2134/jeq2000.00472425002900050034x |bibcode=2000JEnvQ..29.1632S |access-date=5 September 2021 |archive-date=14 August 2021 |archive-url=https://web.archive.org/web/20210814121821/https://lmecol.evsc.virginia.edu/pubs/73-Sprague_JEQ2000.pdf |url-status=dead }}</ref> Many waste treatment processes rely on this natural [[bioremediation]] capacity. Exceeding treatment capacity can damage soil biota and limit soil function. Derelict soils occur where industrial contamination or other development activity damages the soil to such a degree that the land cannot be used safely or productively. [[Environmental remediation|Remediation]] of derelict soil uses principles of geology, physics, chemistry and biology to degrade, attenuate, isolate or remove soil contaminants to restore [[soil functions]] and values. Techniques include [[Leaching (chemistry)|leaching]], [[air sparging]], [[soil conditioner]]s, [[phytoremediation]], bioremediation and [[In situ bioremediation|Monitored Natural Attenuation]]. An example of diffuse pollution with contaminants is copper accumulation in [[vineyard]]s and [[orchard]]s to which fungicides are repeatedly applied, even in [[organic farming]].<ref>{{Cite journal |last1=Ballabio |first1=Cristiano |last2=Panagos |first2=Panos |last3=Lugato |first3=Emanuele |last4=Huang |first4=Jen-How |last5=Orgiazzi |first5=Alberto |last6=Jones |first6=Arwyn |last7=Fernández-Ugalde |first7=Oihane |last8=Borrelli |first8=Pasquale |last9=Montanarella |first9=Luca |date=15 September 2018 |title=Copper distribution in European topsoils: an assessment based on LUCAS soil survey |journal=[[Science of the Total Environment]] |volume=636 |pages=282–298 |doi=10.1016/j.scitotenv.2018.04.268 |pmid=29709848 |issn=0048-9697 |bibcode=2018ScTEn.636..282B |doi-access=free}}</ref>

[[Microfiber|Microfibres]] from synthetic textiles are another type of plastic soil contamination, 100% of agricultural soil samples from southwestern China contained plastic particles, 92% of which were microfibres. Sources of microfibres likely included string or twine, as well as irrigation water in which clothes had been washed.<ref name="auto">{{Cite web |last=Environment |first=U. N. |date=2021-10-21 |title=Drowning in Plastics – Marine Litter and Plastic Waste Vital Graphics |url=http://www.unep.org/resources/report/drowning-plastics-marine-litter-and-plastic-waste-vital-graphics |access-date=2022-03-23 |website=UNEP - UN Environment Programme |language=en}}</ref>

The application of biosolids from sewage sludge and compost can introduce [[microplastics]] to soils. This adds to the burden of microplastics from other sources (e.g. the atmosphere). Approximately half the sewage sludge in Europe and North America is applied to agricultural land. In Europe it has been estimated that for every million inhabitants 113 to 770 tonnes of microplastics are added to agricultural soils each year.<ref name="auto"/>

===Desertification===
[[File:Soil erosion, Southfield - geograph.org.uk - 367917.jpg|thumb|Desertification]]

[[Desertification]], an environmental process of ecosystem degradation in arid and semi-arid regions, is often caused by badly adapted human activities such as [[overgrazing]] or excess harvesting of [[firewood]]. It is a common misconception that [[drought]] causes desertification.<ref>{{Cite journal |last=Le Houérou |first=Henry N. |year=1996 |title=Climate change, drought and desertification |journal=[[Journal of Arid Environments]] |volume=34 |issue=2 |pages=133–185 |doi=10.1006/jare.1996.0099 |bibcode=1996JArEn..34..133L |url=http://www7.nau.edu/mpcer/direnet/publications/publications_l/files/LeHouerou_1996.pdf |access-date=5 September 2021}}</ref> Droughts are common in arid and semiarid lands. Well-managed lands can recover from drought when the rains return. [[Soil management]] tools include maintaining soil nutrient and organic matter levels, reduced tillage and increased cover.<ref>{{Cite journal |last1=Lyu |first1=Yanli |last2=Shi |first2=Peijun |last3=Han |first3=Guoyi |last4=Liu |first4=Lianyou |last5=Guo |first5=Lanlan |last6=Hu |first6=Xia |last7=Zhang |first7=Guoming |year=2020 |title=Desertification control practices in China |journal=[[Sustainability (journal)|Sustainability]] |volume=12 |issue=8 |pages=3258 |doi=10.3390/su12083258 |issn=2071-1050 |doi-access=free|bibcode=2020Sust...12.3258L }}</ref> These practices help to control erosion and maintain productivity during periods when moisture is available. Continued land abuse during droughts, however, increases [[land degradation]]. Increased population and livestock pressure on marginal lands accelerates desertification.<ref>{{Cite journal |last1=Kéfi |first1=Sonia |last2=Rietkerk |first2=Max |last3=Alados |first3=Concepción L. |last4=Pueyo |first4=Yolanda |last5=Papanastasis |first5=Vasilios P. |last6=El Aich |first6=Ahmed |last7=de Ruiter |first7=Peter C. |year=2007 |title=Spatial vegetation patterns and imminent desertification in Mediterranean arid ecosystems |journal=[[Nature (journal)|Nature]] |volume=449 |issue=7159 |pages=213–217 |doi=10.1038/nature06111 |pmid=17851524 |bibcode=2007Natur.449..213K |hdl=1874/25682 |s2cid=4411922 |url=https://www.researchgate.net/publication/232801317 |access-date=5 September 2021}}</ref> It is now questioned whether present-day climate warming will favour or disfavour desertification, with contradictory reports about predicted rainfall trends associated with increased temperature, and strong discrepancies among regions, even in the same country.<ref>{{Cite journal |last1=Wang |first1=Xunming |last2=Yang |first2=Yi |last3=Dong |first3=Zhibao |last4=Zhang |first4=Caixia |year=2009 |title=Responses of dune activity and desertification in China to global warming in the twenty-first century |journal=[[Global and Planetary Change]] |volume=67 |issue=3–4 |pages=167–185 |doi=10.1016/j.gloplacha.2009.02.004 |bibcode=2009GPC....67..167W |url=https://www.researchgate.net/publication/229103975 |access-date=5 September 2021}}</ref>

===Erosion===
[[File:Riparian buffer on Bear Creek in Story County, Iowa.JPG|thumb|upright|Erosion control]]

[[Erosion]] of soil is caused by [[Water erosion#Rainfall|water]], [[Water erosion#Wind erosion|wind]], [[Water erosion#Glaciers|ice]], and [[Water erosion#Mass movement|movement in response to gravity]]. More than one kind of erosion can occur simultaneously. Erosion is distinguished from [[weathering]], since erosion also transports eroded soil away from its place of origin (soil in transit may be described as [[sediment]]). Erosion is an intrinsic natural process, but in many places it is greatly increased by human activity, especially unsuitable land use practices.<ref>{{Cite journal |last1=Yang |first1=Dawen |last2=Kanae |first2=Shinjiro |last3=Oki |first3=Taikan |last4=Koike |first4=Toshio |last5=Musiake |first5=Katumi |year=2003 |title=Global potential soil erosion with reference to land use and climate changes |journal=Hydrological Processes |volume=17 |issue=14 |pages=2913–28 |doi=10.1002/hyp.1441 |bibcode=2003HyPr...17.2913Y |s2cid=129355387 |url=https://www.oieau.org/eaudoc/system/files/documents/38/191115/191115_doc.pdf |access-date=5 September 2021 |archive-date=18 August 2021 |archive-url=https://web.archive.org/web/20210818043117/https://www.oieau.org/eaudoc/system/files/documents/38/191115/191115_doc.pdf |url-status=dead }}</ref> These include [[agriculture|agricultural]] activities which leave the soil bare during times of heavy rain or strong winds, [[overgrazing]], [[deforestation]], and improper [[construction]] activity. Improved management can limit erosion. [[Soil conservation#Erosion prevention|Soil conservation techniques]] which are employed include changes of land use (such as replacing erosion-prone [[crop]]s with [[grass]] or other soil-binding plants), changes to the timing or type of agricultural operations, [[Terrace (agriculture)|terrace]] building, use of erosion-suppressing cover materials (including [[Cover crop#Water management|cover crops]] and other plants), limiting disturbance during construction, and avoiding construction during erosion-prone periods and in erosion-prone places such as steep slopes.<ref>{{Cite journal |last1=Sheng |first1=Jian-an |last2=Liao |first2=An-zhong |year=1997 |title=Erosion control in South China |journal=Catena |issn=0341-8162 |volume=29 |issue=2 |pages=211–221 |doi=10.1016/S0341-8162(96)00057-4 |bibcode=1997Caten..29..211S |url=https://coek.info/pdf-erosion-control-in-south-china-.html |access-date=5 September 2021}}</ref> Historically, one of the best examples of large-scale soil erosion due to unsuitable land-use practices is wind erosion (the so-called [[Dust Bowl|dust bowl]]) which ruined American and Canadian prairies during the 1930s, when immigrant farmers, encouraged by the federal government of both countries, settled and converted the original [[shortgrass prairie]] to [[agricultural crops]] and [[cattle ranching]].

A serious and long-running water erosion problem occurs in [[China]], on the middle reaches of the [[Yellow River]] and the upper reaches of the [[Yangtze River]]. From the Yellow River, over 1.6&nbsp;billion tons of sediment flow each year into the ocean. The sediment originates primarily from water erosion (gully erosion) in the [[Loess Plateau]] region of northwest China.<ref>{{Cite journal |last1=Ran |first1=Lishan |last2=Lu |first2=Xi Xi |last3=Xin |first3=Zhongbao |year=2014 |title=Erosion-induced massive organic carbon burial and carbon emission in the Yellow River basin, China |journal=[[Biogeosciences]] |volume=11 |issue=4 |pages=945–959 |doi=10.5194/bg-11-945-2014 |bibcode=2014BGeo...11..945R |url=https://bg.copernicus.org/articles/11/945/2014/bg-11-945-2014.pdf |access-date=5 September 2021 |hdl=10722/228184 |hdl-access=free |doi-access=free }}</ref>

Soil piping is a particular form of soil erosion that occurs below the soil surface.<ref>{{Cite journal |last1=Verachtert |first1=Els |last2=Van den Eeckhaut |first2=Miet |last3=Poesen |first3=Jean |last4=Deckers |first4=Jozef |year=2010 |title=Factors controlling the spatial distribution of soil piping erosion on loess-derived soils: a case study from central Belgium |journal=[[Geomorphology (journal)|Geomorphology]] |volume=118 |issue=3 |pages=339–348 |doi=10.1016/j.geomorph.2010.02.001 |bibcode=2010Geomo.118..339V |url=https://lirias.kuleuven.be/retrieve/109942 |access-date=5 September 2021}}</ref> It causes [[levee]] and dam failure, as well as [[Sinkhole|sink hole]] formation. Turbulent flow removes soil starting at the mouth of the [[Seep (hydrology)|seep]] flow and the [[subsoil]] erosion advances up-gradient.<ref>{{Cite journal |last=Jones |first=Anthony |title=Soil piping and stream channel initiation |journal=[[Water Resources Research]] |volume=7 |issue=3 |pages=602–610 |year=1976 |doi=10.1029/WR007i003p00602 |bibcode=1971WRR.....7..602J |url=https://booksc.eu/book/20668631/3ac27a |access-date=5 September 2021 |archive-date=5 September 2021 |archive-url=https://web.archive.org/web/20210905084319/https://booksc.eu/book/20668631/3ac27a |url-status=dead }}</ref> The term [[sand boil]] is used to describe the appearance of the discharging end of an active soil pipe.<ref>{{cite web|last=Dooley |first=Alan |title=Sandboils 101: Corps has experience dealing with common flood danger |website=Engineer Update |publisher=[[United States Army Corps of Engineers|US Army Corps of Engineers]] |date=June 2006 |url=http://www.hq.usace.army.mil/cepa/pubs/jun06/story8.htm |archive-url=https://web.archive.org/web/20080418185527/http://www.hq.usace.army.mil/cepa/pubs/jun06/story8.htm |archive-date=18 April 2008 |url-status=dead}}</ref>

===Salination===
[[Soil salination]] is the accumulation of free [[salt]]s to such an extent that it leads to degradation of the agricultural value of soils and vegetation. Consequences include [[corrosion]] damage, reduced plant growth, erosion due to loss of plant cover and soil structure, and [[water quality]] problems due to [[sedimentation]]. Salination occurs due to a combination of natural and human-caused processes. Arid conditions favour salt accumulation. This is especially apparent when soil parent material is saline. [[Surface irrigation|Irrigation]] of arid lands is especially problematic.<ref>{{cite web |last=Oosterbaan |first=Roland J. |title=Effectiveness and social/environmental impacts of irrigation projects: a critical review |series=Annual Reports of the International Institute for Land Reclamation and Improvement (ILRI) |year=1988 |pages=18–34 |location=Wageningen, The Netherlands |url=http://www.waterlog.info/pdf/irreff.pdf |url-status=live |archive-url=https://web.archive.org/web/20090219070320/http://waterlog.info/pdf/irreff.pdf |archive-date=19 February 2009 |df=dmy-all |access-date=5 September 2021}}</ref> All irrigation water has some level of salinity. Irrigation, especially when it involves leakage from canals and overirrigation in the field, often raises the underlying [[water table]]. Rapid salination occurs when the land surface is within the [[capillary fringe]] of saline groundwater. [[Soil salinity control]] involves [[watertable control]] and [[leaching model|flushing]] with higher levels of applied water in combination with [[tile drainage]] or another form of [[Drainage system (agriculture)|subsurface drainage]].<ref>{{Cite book |title=Drainage manual: a guide to integrating plant, soil, and water relationships for drainage of irrigated lands |year=1993 |publisher=[[United States Department of the Interior]], [[United States Bureau of Reclamation|Bureau of Reclamation]] |location=Washington, D.C. |url=https://www.usbr.gov/tsc/techreferences/mands/mands-pdfs/DrainMan.pdf |isbn=978-0-16-061623-5 |access-date=5 September 2021}}</ref><ref name="Waterlog">{{cite web |last=Oosterbaan |first=Roland J. |url=http://www.waterlog.info |title=Waterlogging, soil salinity, field irrigation, plant growth, subsurface drainage, groundwater modelling, surface runoff, land reclamation, and other crop production and water management aspects |access-date=5 September 2021 |url-status=live |archive-url=https://web.archive.org/web/20100816225219/http://www.waterlog.info/ |archive-date=16 August 2010}}</ref>