Editing Soil (section)

== Formation ==
{{main|Soil formation}}
{{Further|Soil mechanics#Genesis}}
Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, [[humus]], [[iron oxide]], [[carbonate]], and [[gypsum]], producing a distinct layer called the B horizon. This is a somewhat arbitrary definition as mixtures of sand, silt, clay and humus will support biological and agricultural activity before that time.<ref>{{cite journal |last1=Sengupta |first1=Aditi |last2=Kushwaha |first2=Priyanka |last3=Jim |first3=Antonia |last4=Troch |first4=Peter A. |last5=Maier |first5=Raina |date=2020 |title=New soil, old plants, and ubiquitous microbes: evaluating the potential of incipient basaltic soil to support native plant growth and influence belowground soil microbial community composition |journal=[[Sustainability (journal)|Sustainability]] |volume=12 |issue=10 |pages=4209 |doi=10.3390/su12104209 |doi-access=free |bibcode=2020Sust...12.4209S }}</ref> These constituents are moved from one level to another by water and animal activity. As a result, layers (horizons) form in the soil profile. The alteration and movement of materials within a soil causes the formation of distinctive [[soil horizons]]. However, more recent definitions of soil embrace soils without any organic matter, such as those [[regolith]]s that formed on Mars<ref>{{cite journal |last1=Bishop |first1=Janice L. |last2=Murchie |first2=Scott L. |last3=Pieters |first3=Carlé L. |last4=Zent |first4=Aaron P. |date=2002 |title=A model for formation of dust, soil, and rock coatings on Mars: physical and chemical processes on the Martian surface |journal=[[Journal of Geophysical Research]] |volume=107 |issue=E11 |pages=7-1–7-17 |doi=10.1029/2001JE001581 |bibcode=2002JGRE..107.5097B |doi-access=free }}</ref> and analogous conditions in planet [[Earth]] deserts.<ref>{{cite journal |last1=Navarro-González |first1=Rafael |last2=Rainey |first2=Fred A. |last3=Molina |first3=Paola |last4=Bagaley |first4=Danielle R. |last5=Hollen |first5=Becky J. |last6=de la Rosa |first6=José |last7=Small |first7=Alanna M. |last8=Quinn |first8=Richard C. |last9=Grunthaner |first9=Frank J. |last10=Cáceres |first10=Luis |last11=Gomez-Silva |first11=Benito |last12=McKay |first12=Christopher P. |date=2003 |title=Mars-like soils in the Atacama desert, Chile, and the dry limit of microbial life |journal=[[Science (journal)|Science]] |volume=302 |issue=5647 |pages=1018–1021 |doi=10.1126/science.1089143 |pmid=14605363 |url=https://www.researchgate.net/publication/9020258 |access-date=19 January 2025 |bibcode=2003Sci...302.1018N |s2cid=18220447 }}</ref>

An example of the development of a soil would begin with the [[weathering]] of lava flow [[bedrock]], which would produce the purely mineral-based parent material from which the [[soil texture]] forms. Soil development would proceed most rapidly from bare rock of recent flows in a warm climate, under heavy and frequent rainfall. Under such conditions, plants (in a first stage [[nitrogen-fixing]] [[lichen]]s and [[cyanobacteria]] then [[epilithic]] [[higher plants]]) become established very quickly on [[basalt]]ic lava, even though there is very little organic material.<ref>{{cite journal |last1=Guo |first1=Yong |last2=Fujimura |first2=Reiko |last3=Sato |first3=Yoshinori |last4=Suda |first4=Wataru |last5=Kim |first5=Seok-won |last6=Oshima |first6=Kenshiro |last7=Hattori |first7=Masahira |last8=Kamijo |first8=Takashi |last9=Narisawa |first9=Kazuhiko |last10=Ohta |first10=Hiroyuki |date=2014 |title=Characterization of early microbial communities on volcanic deposits along a vegetation gradient on the island of Miyake, Japan |journal=Microbes and Environments |volume=29 |issue=1 |pages=38–49 |doi=10.1264/jsme2.ME13142 |pmid=24463576 |pmc=4041228 |doi-access=free }}</ref> Basaltic minerals commonly weather relatively quickly, according to the [[Goldich dissolution series]].<ref>{{cite journal |last=Goldich |first=Samuel S. |date=1938 |title=A study in rock-weathering |url=https://fr.1lib.sk/book/91942187/414bb2 |journal=[[The Journal of Geology]] |volume=46 |issue=1 |pages=17–58 |bibcode=1938JG.....46...17G |doi=10.1086/624619 |issn=0022-1376 |access-date=19 January 2025 |s2cid=128498195 |archive-date=27 March 2022 |archive-url=https://web.archive.org/web/20220327065200/https://fr.art1lib.org/book/60175497/a54b2b |url-status=live }}</ref> The plants are supported by the porous rock as it is filled with nutrient-bearing water that carries minerals dissolved from the rocks. Crevasses and pockets, local topography of the rocks, would hold fine materials and harbour plant roots. The developing plant roots are associated with mineral-weathering [[Mycorrhiza|mycorrhizal fungi]]<ref name="Van Schöll2006">{{cite journal |last1=Van Schöll |first1=Laura |last2=Smits |first2=Mark M. |last3=Hoffland |first3=Ellis |date=2006 |title=Ectomycorrhizal weathering of the soil minerals muscovite and hornblende |journal=[[New Phytologist]] |volume=171 |issue=4 |pages=805–814 |doi=10.1111/j.1469-8137.2006.01790.x |pmid=16918551 |doi-access=free |bibcode=2006NewPh.171..805V }}</ref> that assist in breaking up the porous lava, and by these means organic matter and a finer mineral soil accumulate with time. Such initial stages of soil development have been described on volcanoes,<ref>{{cite journal |last1=Stretch |first1=Rachelle C. |last2=Viles |first2=Heather A. |year=2002 |title=The nature and rate of weathering by lichens on lava flows on Lanzarote |journal=[[Geomorphology (journal)|Geomorphology]] |volume=47 |issue=1 |pages=87–94 |doi=10.1016/S0169-555X(02)00143-5 |bibcode=2002Geomo..47...87S |url=https://fr.1lib.sk/book/50018654/f73474 |access-date=19 January 2025 |archive-date=22 April 2023 |archive-url=https://web.archive.org/web/20230422182644/https://fr.art1lib.org/book/17831662/8253cd |url-status=live }}</ref> inselbergs,<ref>{{cite journal |last1=Dojani |first1=Stephanie |last2=Lakatos |first2=Michael |last3=Rascher |first3=Uwe |last4=Waneck |first4=Wolfgang |last5=Luettge |first5=Ulrich |last6=Büdel |first6=Burkhard |year=2007 |title=Nitrogen input by cyanobacterial biofilms of an inselberg into a tropical rainforest in French Guiana |journal=Flora |volume=202 |issue=7 |pages=521–529 |doi=10.1016/j.flora.2006.12.001 |bibcode=2007FMDFE.202..521D |url=https://www.researchgate.net/publication/224026482 |access-date=19 January 2025 }}</ref> and glacial moraines.<ref>{{cite journal |last1=Kabala |first1=Cesary |last2=Kubicz |first2=Justyna |year=2012 |title=Initial soil development and carbon accumulation on moraines of the rapidly retreating Werenskiold Glacier, SW Spitsbergen, Svalbard archipelago |journal=Geoderma |volume=175–176 |pages=9–20 |url=https://www.academia.edu/31221217 |doi=10.1016/j.geoderma.2012.01.025 |access-date=19 January 2025 |bibcode=2012Geode.175....9K }}</ref>

How soil formation proceeds is influenced by at least five classic factors that are intertwined in the evolution of a soil: parent material, climate, topography (relief), organisms, and time.<ref name="Jenny1941">{{cite book |last=Jenny |first=Hans |title=Factors of soil formation: a system of qunatitative pedology |year=1941 |publisher=[[McGraw-Hill]] |location=New York |url=https://netedu.xauat.edu.cn/sykc/hjx/content/ckzl/6/2.pdf |access-date=19 January 2025 |archive-url=https://web.archive.org/web/20170808104008/http://netedu.xauat.edu.cn/sykc/hjx/content/ckzl/6/2.pdf |archive-date=8 August 2017 |url-status=live }}</ref> When reordered to climate, relief, organisms, parent material, and time, they form the acronym CROPT.<ref>{{cite web |url=https://geo.libretexts.org/Bookshelves/Geography_(Physical)/The_Physical_Environment_(Ritter) |title=The physical environment: an introduction to physical geography |first=Michael E. |last=Ritter |date=4 July 2021 |access-date=19 January 2025 }}</ref>