Editing Soil pH (section)

==Plant pH preferences==
In general terms, different plant species are adapted to soils of different pH ranges. For many species, the suitable soil pH range is fairly well known.<ref>{{Cite web |title=Optimal Soil pH Levels for Vegetable Farming |url=https://www.agriculturelandusa.com/2024/10/optimal-soil-ph-levels-for-vegetable-farming.html |access-date=2024-10-21 |website=Agriculture land usa |language=en-US}}</ref> Online databases of plant characteristics, such as ''USDA PLANTS''<ref name="USDA2017">{{cite web |last1=USDA NRCS |title=Plants Database Characteristics Search |url=https://plants.usda.gov/home/characteristicsSearchResults?resultId=6e52d145-7c59-4537-b815-dfd960df195c |website=plants.usda.gov |publisher=[[Natural Resources Conservation Service|USDA NRCS]] |access-date=16 April 2023 |date=2023}}</ref> and ''Plants for a Future''<ref name="PFAF2017">{{cite web |last1=Plants for a future |title=Plant Database Search Page |url=https://pfaf.org/USER/plantsearch.aspx |website=www.pfaf.org |access-date=16 April 2023}}</ref> can be used to look up the suitable soil pH range of a wide range of plants. Documents like ''Ellenberg's indicator values for British plants''<ref name="Hill1999">{{cite book |last1=Hill |first1=Mark Oliver |last2=Mountford |first2=J. Owen |last3=Roy |first3=David B. |last4=Bunce |first4=Robert G.H. |title=Ellenberg's indicator values for British plants. ECOFACT Volume 2. Technical Annex |date=1999 |publisher=[[UK Centre for Ecology & Hydrology|Institute of Terrestrial Ecology]] |location=Huntingdon, United Kingdom |isbn=978-1870393485 |url=https://nora.nerc.ac.uk/id/eprint/6411/ |access-date=16 April 2023}}</ref> can also be consulted.

However, a plant may be intolerant of a particular pH in some soils as a result of a particular mechanism, and that mechanism may not apply in other soils. For example, a soil low in [[molybdenum]] may not be suitable for [[soybean]] plants at pH 5.5, but soils with sufficient molybdenum allow optimal growth at that pH.<ref name="Sumner2002"/> Similarly, some calcifuges (plants intolerant of high-pH soils) can tolerate calcareous soils if sufficient phosphorus is supplied.<ref name="Lee1998">{{cite journal |last1=Lee |first1=John A. |title=The calcicole-calcifuge problem revisited |journal=Advances in Botanical Research |date=1998 |volume=29 |page=13 |url=https://books.google.com/books?id=1YigNjS78xsC&pg=PA13 |access-date=23 April 2023 |isbn=9780080561837}}</ref> Another confounding factor is that different varieties of the same species often have different suitable soil pH ranges. Plant breeders can use this to breed varieties that can tolerate conditions that are otherwise considered unsuitable for that species – examples are projects to breed aluminium-tolerant and manganese-tolerant varieties of cereal crops for food production in strongly acidic soils.<ref name="Scott1989">{{cite book |last1=Scott |first1=Brendan J. |last2=Fisher |first2=J.A. |editor1-last=Robson |editor1-first=Alan D.|title=Soil acidity and plant growth |date=1989 |publisher=[[Academic Press]] |location=Sydney, Australia |isbn=978-0125906555 |pages=167–203 |url=https://lib-nhwjx7zkiyjoeipfyn7m37ed.late.re/book/2218580/813186 |access-date=23 April 2023 |chapter=Selection of genotypes tolerant of aluminium and manganese |doi=10.1016/B978-0-12-590655-5.50010-4}}</ref>

The table below gives suitable soil pH ranges for some widely cultivated plants as found in the ''USDA PLANTS Database''.<ref name="USDA2017"/> Some species (like ''[[Pinus radiata]]'' and ''[[Opuntia ficus-indica]]'') tolerate only a narrow range in soil pH, whereas others (such as ''[[Vetiveria zizanioides]]'') tolerate a very wide pH range.

{| class="wikitable sortable"
! rowspan=2|Scientific name !!  rowspan=2|Common name !! colspan=2|pH range
|-
!  Minimum !! Maximum
|-
| ''[[Chrysopogon zizanioides]]'' || vetiver grass || 3.0 || 8.0
|-
|''[[Pinus rigida]]''|| pitch pine || 3.5 || 5.1
|-
|''[[Rubus chamaemorus]]''|| cloudberry || 4.0 || 5.2
|-
|''[[Ananas comosus]]''|| pineapple|| 4.0|| 6.0
|-
|''[[Coffea arabica]]''|| Arabian coffee || 4.0|| 7.5
|-
|''[[Rhododendron arborescens]]''|| smooth azalea|| 4.2 || 5.7
|-
| ''[[Pinus radiata]]''|| Monterey pine|| 4.5|| 5.2
|-
| ''[[Carya illinoinensis]]''|| pecan|| 4.5|| 7.5
|-
| ''[[Tamarindus indica]]''|| tamarind|| 4.5|| 8.0
|-
| ''[[Vaccinium corymbosum]]''|| highbush blueberry|| 4.7|| 7.5
|-
| ''[[Manihot esculenta]]''|| cassava|| 5.0|| 5.5
|-
| ''[[Morus alba]]''||white mulberry||5.0||7.0
|-
| ''[[Malus]]''||apple||5.0||7.5
|-
| ''[[Pinus sylvestris]]''||Scots pine||5.0||7.5
|-
| ''[[Carica papaya]]''||papaya||5.0||8.0
|-
| ''[[Cajanus cajan]]''||pigeonpea||5.0||8.3
|-
| ''[[Pyrus communis]]''||common pear||5.2||6.7
|-
| ''[[Solanum lycopersicum]]''||garden tomato||5.5||7.0
|-
| ''[[Psidium guajava]]''||guava||5.5||7.0
|-
| ''[[Nerium oleander]]''||oleander||5.5||7.8
|-
| ''[[Punica granatum]]''||pomegranate||6.0||6.9
|-
| ''[[Viola sororia]]''||common blue violet||6.0||7.8
|-
| ''[[Caragana arborescens]]''||Siberian peashrub||6.0||9.0
|-
| ''[[Cotoneaster integerrimus]]''||cotoneaster||6.8||8.7
|-
| ''[[Opuntia ficus-indica]]''||Barbary fig (pricklypear)||7.0||8.5
|}

In natural or near-natural [[Plant community|plant communities]], the various pH preferences of plant species (or [[Ecotype|ecotypes]]) at least partly determine the composition and [[biodiversity]] of vegetation. While both very low and very high pH values are detrimental to plant growth, there is an increasing trend of plant biodiversity along the range from extremely acidic (pH 3.5) to strongly alkaline (pH 9) soils, i.e. there are more [[calcicole]] than [[calcifuge]] species, at least in terrestrial environments.<ref>{{cite journal |last1=Chytrý |first1=Milan |last2=Tichý |first2=Lubomír |last3=Rolček |first3=Jan |title=Local and regional patterns of species richness in Central European vegetation types along the pH/calcium gradient |journal=Folia Geobotanica |date=December 2003 |volume=38 |issue=4 |pages=429–42 |doi=10.1007/BF02803250 |bibcode=2003FolGe..38..429C |s2cid=13016841 |url=https://www.researchgate.net/publication/225452386 |access-date=7 May 2023}}</ref><ref>{{cite journal |last1=Pärtel |first1=Meelis |last2=Helm |first2=Aveliina |last3=Ingerpuu |first3=Nele |last4=Reier |first4=Ülle |last5=Tuvi |first5=Eva-Liis |title=Conservation of Northern European plant diversity: the correspondence with soil pH |journal=[[Biological Conservation (journal)|Biological Conservation]] |date=December 2004 |volume=120 |issue=4 |pages=525–31 |doi=10.1016/j.biocon.2004.03.025 |bibcode=2004BCons.120..525P |url=https://www.academia.edu/3276150 |access-date=7 May 2023}}</ref> Although widely reported and supported by experimental results,<ref>{{cite journal |last1=Crawley |first1=Michael J. |last2=Johnston |first2=A. Edward |last3=Silvertown |first3=Jonathan |last4=Dodd |first4=Mike |last5=de Mazancourt |first5=Claire |last6=Heard |first6=Matthew S. |last7=Henman |first7=D. F. |last8=Edwards |first8=Grant R. |title=Determinants of species richness in the Park Grass Experiment |journal=[[The American Naturalist|American Naturalist]] |date=February 2005 |volume=165 |issue=2 |pages=179–92 |doi=10.1086/427270 |pmid=15729649 |s2cid=7389457 |url=https://www.researchgate.net/publication/8003273 |access-date=14 May 2023}}</ref><ref>{{cite journal |last1=Poozesh |first1=Vahid |last2=Castillon |first2=Pierre |last3=Cruz |first3=Pablo |last4=Bertoni |first4=Georges |title=Re-evaluation of the liming-fertilization interaction in grasslands on poor and acid soils |journal=Grass and Forage Science |date=June 2010 |volume=65 |issue=2 |pages=260–72 |doi=10.1111/j.1365-2494.2010.00744.x |url=https://www.academia.edu/62428696 |access-date=14 May 2023}}</ref> the observed increase of plant species richness with pH is still in need of a clearcut explanation. [[Competitive exclusion principle|Competitive exclusion]] between plant species with overlapping pH ranges most probably contributes to the observed shifts of vegetation composition along pH gradients.<ref>{{cite journal |last1=Prince |first1=Candice M. |last2=MacDonald |first2=Gregory E. |last3=Ferrell |first3=Jason A. |last4=Sellers |first4=Brent A. |last5=Wang |first5=Jingjing |title=Impact of soil pH on cogongrass (Imperata cylindrica) and bahiagrass (Paspalum notatum) competition |journal=[[Weed Technology]] |date=2018 |volume=32 |issue=3 |pages=336–41 |doi=10.1017/wet.2018.3 |s2cid=91112353 |url=https://bioone.org/journals/weed-technology/volume-32/issue-3/wet.2018.3/Impact-of-Soil-pH-on-Cogongrass-Imperata-cylindrica-and-Bahiagrass/10.1017/wet.2018.3.short}}</ref>