Editing Soil salinity (section)

==Salt tolerance of crops==
{{main|Salt tolerance of crops}}
{{see|Maas–Hoffman model|Van Genuchten–Gupta model}}
High levels of soil salinity can be tolerated if salt-tolerant plants are grown.  Sensitive crops lose their vigor already in slightly saline soils, most crops are negatively affected by (moderately) saline soils, and only salinity-resistant crops thrive in severely saline soils. The University of Wyoming<ref name="Alan">Alan D. Blaylock, 1994, ''Soil Salinity and Salt tolerance of Horticultural and Landscape Plants.'' [http://ces.uwyo.edu/pubs/Wy988.pdf University of Wyoming] {{webarchive|url=https://web.archive.org/web/20100508143456/http://ces.uwyo.edu/PUBS/Wy988.pdf |date=2010-05-08 }}</ref> and the Government of Alberta<ref name="Albert">Government of Alberta, [http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3303 ''Salt tolerance of Plants''] {{Webarchive|url=https://web.archive.org/web/20100221211018/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3303 |date=2010-02-21 }}</ref> report data on the salt tolerance of plants.

Field data in irrigated lands, under farmers' conditions, are scarce, especially in developing countries. However, some on-farm surveys have been made in Egypt,<ref>H.J. Nijland and S. El Guindy, ''Crop yields, watertable depth and soil salinity in the Nile Delta, Egypt''. In: Annual report 1983. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands.</ref> India,<ref>D. P. Sharma, K. N. Singh and K. V. G. K. Rao (1990), ''Crop Production and soil salinity: evaluation of field data from India''. Paper published in Proceedings of the Symposium on Land Drainage for Salinity Control in Arid and Semi-Arid Regions, February, 25th to March 2nd, 1990, Cairo, Egypt, Vol. 3, Session V, p. 373–383. On line: [https://www.waterlog.info/pdf/segmregr.pdf]</ref> and Pakistan.<ref>R.J. Oosterbaan, ''Crop yields, soil salinity and water table depth in Pakistan''. In: Annual Report 1981, pp. 50–54. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, reprinted in Indus 24 (1983) 2, pp. 29–33. On line [https://www.waterlog.info/pdf/pakistan.pdf]</ref> Some examples are shown in the following gallery, with crops arranged from sensitive to very tolerant.<ref>{{Cite web|title=Crop tolerance for soil salinity in farmers' fields|url=https://www.waterlog.info/croptol.htm|access-date=2023-02-08|website=www.waterlog.info}}</ref><ref>''Crop Tolerance to Soil Salinity, Statistical Analysis of Data Measured in Farm Lands''. In: International Journal of Agricultural Science, October 2018. On line: [https://www.iaras.org/iaras/filedownloads/ijas/2018/014-0008(2018).pdf]</ref>

<gallery caption="Graphs of crop yield and soil salinity in farmers' fields ordered by increasing salt tolerance." perrow="3" widths="250" heights="150">
File:berseem egypt.png|Fig. 1. Berseem (clover), cultivated in Egypt's Nile Delta, is a salt-sensitive crop and tolerates an ECe value up to 2.4 dS/m, whereafter yields start to decline.
File:wheat sampla.png|Fig. 2. Wheat grown in Sampla, Haryana, India, is slightly sensitive, tolerating an ECe value of 4.9 dS/m.
File: wheat gohana.png|Fig. 3. The field measurements in wheat fields in Gohana, Haryana, India, showed a higher tolerance level of ECe = 7.1 dS/m. <br/> (The Egyptian wheat, not shown here, exhibited a tolerance point of 7.8 dS/m).
File:cotton egypt.png|Fig. 4. The cotton grown in the Nile Delta can be called salt-tolerant, with a critical ECe value of 8.0 dS/m. However, due to scarcity of data beyond 8 dS/m, the maximum tolerance level cannot be precisely determined and may actually be higher than that.
File: sorghum pakistan.png| Fig. 5. Sorghum from Khairpur, Pakistan, is quite tolerant; it grows well up to ECe = 10.5 dS/m.
File: cotton pakistan.png| Fig. 6. Cotton from Khairpur, Pakistan, is very tolerant; it grows well up to ECe = 15.5 dS/m.
</gallery>

Calcium has been found to have a positive effect in combating salinity in soils. It has been shown to ameliorate the negative effects that salinity has such as reduced water usage of plants.<ref>{{Cite journal|last1=Kaya|first1=C|last2=Kirnak|first2=H|last3=Higgs|first3=D|last4=Saltali|first4=K|date=2002-02-28|title=Supplementary calcium enhances plant growth and fruit yield in strawberry cultivars grown at high (NaCl) salinity|journal=Scientia Horticulturae|volume=93|issue=1|pages=65–74|doi=10.1016/S0304-4238(01)00313-2}}</ref>

Soil salinity activates [[gene]]s associated with stress conditions for plants.<ref name="FH">{{cite journal |first1= Kamile |last1= Ulukapi | first2= Ayse Gul |last2= Nasircilar | title = The role of exogenous glutamine on germination, plant development and transcriptional expression of some stress-related genes in onion under salt stres | url = https://sciendo.com/article/10.2478/fhort-2024-0002 | journal = [[Folia Horticulturae]] | volume = 36 | issue = 1 | pages = 1–17 | date = February 2024 | pmid = | doi = 10.2478/fhort-2024-0002 | publisher = Polish Society of Horticultural Science | s2cid = 19887643 | doi-access = free }}</ref> These genes initiate the production of plant stress [[enzyme]]s such as [[superoxide dismutase]], [[L-ascorbate oxidase]],  and Delta 1 [[DNA polymerase]].  Limiting this process can be achieved by administering exogenous [[glutamine]] to plants. The decrease in the level of expression of genes responsible for the synthesis of superoxide dismutase increases with the increase in glutamine concentration.<ref name="FH"/>