Editing Ultisol

{{short description|Soil type}}
{{redirect|Red clay|other terms|Red clay (disambiguation)|and|Red dirt (disambiguation)}}
{{Infobox soil
|name=Ultisol
|alternative_name=Red Clay Soil
|image=Ultisol.jpg
|image_size=250px
|image_caption=A Ultisol profile
|classification_system=[[USDA soil taxonomy]]
|profile=
|parent_material=
|process=[[weathering]]
|climate=[[tropical climate|tropical]], [[humid subtropical climate|humid subtropical]], [[oceanic climate|oceanic]]
}}

'''Ultisol''', commonly known as '''red clay soil''', is one of twelve soil orders in the [[USDA soil taxonomy|United States Department of Agriculture soil taxonomy]]. The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate product of continuous [[weathering]] of minerals in a humid, temperate climate without new [[soil formation]] via [[glaciation]]. They are defined as mineral soils which contain no [[calcareous]] ([[Limestone|calcium carbonate]] containing) material anywhere within the soil, have less than 10% weatherable minerals in the extreme top layer of soil, and have less than 35% [[base (chemistry)|base]] saturation throughout the soil. Ultisols occur in humid temperate or tropical regions. While the term is usually applied to the red clay soils of the [[Southern United States]], Ultisols are also found in regions of Africa, Asia, Australia and South America.

In the [[World Reference Base for Soil Resources]] (WRB), most Ultisols are known as [[Acrisol]]s and [[Alisol]]s. Some belong to the [[Retisol]]s or to the [[Nitisol]]s. Aquults are typically [[Stagnosol]]s or [[Planosol]]s. Humults may be [[Umbrisol]]s.<ref>{{Cite web|url = http://www.fao.org/3/i3794en/I3794en.pdf|title = World Reference Base for Soil Resources 2014, Update 2015|author=IUSS Working Group WRB|year = 2015|publisher = World Soil Resources Reports 106, FAO, Rome}}</ref>

== Introduction ==

Ultisols vary in color from purplish-red, to a bright reddish-orange, to pale yellowish-orange and (in cooler areas such as [[Pennsylvania]]) even some subdued yellowish-brown or grayish-brown tones. They are typically quite [[acid]]ic, often having a [[Soil pH|pH]] of less than 5. The red and yellow colors result from the accumulation of [[iron oxide]] (rust), which is highly insoluble in water. Major [[nutrient]]s, such as [[calcium]] and [[potassium]], are typically deficient in Ultisols,<ref name="VitousekSanford1986">{{Cite journal |last1=Vitousek |first1=P. M. |last2=Sanford |first2=R. L. |date=1986 |title=Nutrient Cycling in Moist Tropical Forest |url=https://www.jstor.org/stable/2096992 |journal=Annual Review of Ecology and Systematics |volume=17 |issue=1 |pages=137–167 |doi=10.1146/annurev.es.17.110186.001033 |jstor=2096992 |bibcode=1986AnRES..17..137V |issn=0066-4162|url-access=subscription }}</ref> which means they generally cannot be used for sedentary agriculture without the aid of [[agricultural lime|lime]] and other [[fertilizer]]s, such as [[superphosphate]]. They can be easily exhausted, and require more careful management than [[Alfisols]] or [[Mollisols]]. However, they can be cultivated over a relatively wide range of moisture conditions. Where the organic matter content is high, as in Humults like the [[Olympic (soil)|Olympic series]], the soil is relatively fertile.

Ultisols can have a variety of clay minerals, but in many cases the dominant mineral is [[kaolinite]]. This clay has good [[bearing capacity]] and no [[shrink–swell capacity|shrink–swell property]]. Consequently, well-drained kaolinitic Ultisols such as the [[Cecil (soil)|Cecil series]] are suitable for urban development.

Ultisols are the dominant soils in the [[Southern United States]] (where the Cecil series is most famous), southeastern China, Southeast Asia, and some other subtropical and tropical areas. Their northern limit (except [[fossil]] soils) is very sharply defined in North America by the limits of maximum glaciation during the [[Pleistocene]], because Ultisols typically take hundreds of thousands of years to form—far longer than the length of an [[interglacial]] period today.

The oldest fossil Ultisols are known from the [[Carboniferous]] period when forests first developed. Though known from far north of their present range as recently as the [[Miocene]], Ultisols are surprisingly rare as fossils overall, since they would have been expected to be very common in the warm [[Mesozoic]] and [[Tertiary]] paleoclimates.

<gallery widths="200px" heights="200px">
File:Nc-red-clay-soil-2.jpg|Red clay soil is common throughout the Southern United States, especially around the [[Piedmont (United States)|Piedmont]]. This photo was taken in North Carolina.
File:Ultisol-map-1.jpg|Map showing distribution and types of Ultisols throughout the United States; there is no Ultisol on the Ohio River flood plains, as the river has historically deposited other soil types there during its regular natural flooding.
File:Ultisol-map-2.gif|Map of the United States showing what percentage of the soil in a given area is classified as an Ultisol-type soil. The great majority of the land area classified in the highest category (75%-or-greater Ultisol) lies in the South and overlays with the [[Piedmont (United States)|Piedmont Plateau]], which runs as a diagonal line through the South from southeast (in Alabama) to northwest (up into parts of Maryland).
UltisolWorld.jpg|Utlisols of the world
</gallery>

== Gardening in Ultisol ==
The lack of organic matter in Ultisol makes it difficult for plants to grow without proper care and considerations. Soil amendments are generally required each year in order to sustain flourishing plant life in regions with primarily Ultisol soil.<ref>{{Cite news|url=http://www.caes.uga.edu/newswire/story.html?storyid=3722&story=Georgia-gardening-101|title=Tips on gardening for Georgia newcomers|access-date=2018-04-10|language=en}}</ref> The use of soil tests, coupled with the corresponding provisions, can alleviate issues of nutrition and irrigation that can result from non porous Ultisol.<ref>{{Cite news|url=http://www.caes.uga.edu/newswire/story.html?storyid=3722&story=Georgia-gardening-101|title=Tips on gardening for Georgia newcomers|access-date=2018-04-10|language=en}}</ref> Soil tests help indicate the [[pH]], and red clay soil typically has a low pH.<ref>{{Cite web|url=http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|title=Dealing With Red Clay|website=www4.ncsu.edu|access-date=2018-04-14|archive-date=2018-04-06|archive-url=https://web.archive.org/web/20180406184233/http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|url-status=dead}}</ref> The addition of [[Calcium oxide|lime]] is used to help to increase the pH in soil and can help increase the pH in Ultisol as well.<ref>{{Cite web|url=http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|title=Dealing With Red Clay|website=www4.ncsu.edu|access-date=2018-04-14|archive-date=2018-04-06|archive-url=https://web.archive.org/web/20180406184233/http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|url-status=dead}}</ref>

[[File:Mulch J1.jpg|thumb|[[Mulch]] can be used to help improve Ultisol]]

=== Possible solutions ===
Generally, gardeners aim to have 45% mineral, 5% organic matter and 50% pore space in their soil.<ref>{{Cite web|url=http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|title=Dealing With Red Clay|website=www4.ncsu.edu|access-date=2018-04-14|archive-date=2018-04-06|archive-url=https://web.archive.org/web/20180406184233/http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|url-status=dead}}</ref> The composition of Ultisol in North Carolina, for reference, is approximately 16% pore space, 2% organic matter and 82% mineral.<ref>{{Cite web|url=http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|title=Dealing With Red Clay|website=www4.ncsu.edu|access-date=2018-04-14|archive-date=2018-04-06|archive-url=https://web.archive.org/web/20180406184233/http://www4.ncsu.edu/~djgofort/Miscellaneous15.htm|url-status=dead}}</ref> The use of mulch is widespread in the [[Piedmont (United States)|Piedmont]] region of the United States as a solution to the high temperatures and saturation of the soil.<ref>{{Cite news|url=http://www.caes.uga.edu/newswire/story.html?storyid=3722&story=Georgia-gardening-101|title=Tips on gardening for Georgia newcomers|access-date=2018-04-10|language=en}}</ref> The addition of mulch helps to make the soil more porous.<ref>{{Cite web|url=https://garden.org/learn/articles/view/1310/|title=Improving Clay Soil – Garden.org|website=garden.org|language=en|access-date=2018-04-14}}</ref>

Adding [[manure]] and [[compost]] can help boost the amount of organic material present in the soil, which in turn helps add essential [[Plant nutrition|nutrients]]. Specifically, adding a 2- to 3-inch layer of compost and manure should be mixed into the soil to match a shovel's depth.<ref>{{Cite web|url=https://garden.org/learn/articles/view/1310/|title=Improving Clay Soil – Garden.org|website=garden.org|language=en|access-date=2018-04-14}}</ref>  The addition of organic material also helps to improve the drainage, while decreasing the overall weight of the soil.<ref>{{Cite web|url=https://garden.org/learn/articles/view/1310/|title=Improving Clay Soil – Garden.org|website=garden.org|language=en|access-date=2018-04-14}}</ref>
[[File:Raised bed (30827889786).jpg|thumb|A garden planted in a raised bed]]
However, microorganisms in the soil consume the same nutrients that plants use to grow so certain nutrients will remain unavailable to plants until the microorganisms completely break down the organic material and release nutrients.<ref>{{Cite web|url=http://extension.oregonstate.edu/gardening/how-improve-clay-soil|title=How to improve clay soil {{!}} Oregon State University Extension Service {{!}} Gardening|website=extension.oregonstate.edu|date=28 February 2003 |language=en|access-date=2018-04-14}}</ref> Living organisms within the soil use, and subsequently convert, organic material into usable [[humus]].<ref>{{Cite web|url=http://extension.oregonstate.edu/gardening/how-improve-clay-soil|title=How to improve clay soil {{!}} Oregon State University Extension Service {{!}} Gardening|website=extension.oregonstate.edu|date=28 February 2003 |language=en|access-date=2018-04-14}}</ref> To avoid the delay presented by this process, adding manure in the fall is advisable.<ref>{{Cite web|url=http://extension.oregonstate.edu/gardening/how-improve-clay-soil|title=How to improve clay soil {{!}} Oregon State University Extension Service {{!}} Gardening|website=extension.oregonstate.edu|date=28 February 2003 |language=en|access-date=2018-04-14}}</ref> 

Some gardeners who live in areas with large amounts of red clay soil use [[Raised-bed gardening|raised beds]] or [[Hügelkultur]] to avoid having to amend the soil.<ref>{{Cite web|url=http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Factsheets/Clay%20Soils%20-%20Annuals5.pdf|title=Best Plants for Problem Clay Soils: Annuals, Bulbs, Needled Evergreens, Ornamental Grasses|last=Kemper|first=William|publisher=Missouri Botanical Gardens}}</ref> By using raised beds, gardeners avoid having to deal with Ultisols altogether.

=== Planting in Ultisol ===
Plants found native to regions with high amounts of Ultisol can thrive. Generally, these species adapt to poorly drained, damp soils.<ref>{{Cite web|url=http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Factsheets/Clay%20Soils%20-%20Annuals5.pdf|title=Best Plants for Problem Clay Soils: Annuals, Bulbs, Needled Evergreens, Ornamental Grasses|last=Kemper|first=William}}</ref> The [[Missouri Botanical Garden]] recommends [[Coreopsis|tickweed]], [[Impatiens capensis|spotted jewelweed]], [[Salvia farinacea|mealycup sage]], ''[[Camassia]]'', [[Ipheion uniflorum|spring starflower]], [[Matteuccia|ostrich fern]], [[Bouteloua curtipendula|sideoats grama]], ''[[Bouteloua curtipendula]]'', and [[Sporobolus heterolepis|prairie dropseed]].<ref>{{Cite web|url=http://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/Factsheets/Clay%20Soils%20-%20Annuals5.pdf|title=Best Plants for Problem Clay Soils: Annuals, Bulbs, Needled Evergreens, Ornamental Grasses|last=Kemper|first=William}}</ref>

==Suborders==
* '''Aquults''': Ultisols with a water table at or near the surface for much of the year
* '''Humults''': well-drained Ultisols that have high organic matter content
* '''Udults''': Ultisols of humid climates
* '''Ustults''': Ultisols of semiarid and subhumid climates
* '''Xerults''': temperate Ultisols with arid summers and moist winters

==See also==
* [[Pedogenesis]]
* [[Pedology (soil study)]]
* [[Soil classification]]
*[[Red soil|Red Soil]]

==References==
{{Reflist}}
* {{cite web |url=http://soils.usda.gov/technical/classification/orders/ultisols.html|title=Ultisols|publisher=United States Department of Agriculture|access-date=2008-01-04}}
* {{cite web|url=http://grunwald.ifas.ufl.edu/Nat_resources/soil_orders/ultisols.htm |title=Ultisols |publisher=University of Florida |access-date=2006-05-14 |date=April 2007 |url-status=dead |archive-url=https://web.archive.org/web/20040921024001/http://grunwald.ifas.ufl.edu/Nat_resources/soil_orders/ultisols.htm |archive-date=September 21, 2004 }}
* {{cite web | url =http://soils.ag.uidaho.edu/soilorders/ultisols.htm | title =Ultisols| publisher =University of Idaho
| access-date =2006-05-14}}

{{Soil type}}
{{Authority control}}

[[Category:Pedology]]
[[Category:Types of soil]]