Soil Salinity and Salt Tolerance
of Horticultural Landscape Plants

Soil Salinity

Plants absorb essential nutrients in the form of soluble salts. But accumulation of soluble salts can reduce plant growth and development. Soil salinity is common in arid and semi-arid regions. Salts can be released from weathered minerals in the soil. They can also be applied to the soil in irrigation water and fertilizers, or can migrate upward in the soil from shallow groundwater. When precipitation or irrigation is not enough to leach salts down through the soil profile, salts accumulate in the soil and salinity results.

The most common cause of soil salinity is poor soil drainage. Poor quality irrigation water can also cause salinity problems. Inadequate irrigation management can increase the risk of soil salinity developing. To prevent salt buildup, enough water must pass through the root zone to leach out salts. Keep in mind that some of these salts, such as nitrates, are also essential plant nutrients. Excess nitrates, for example, become water pollutants if leached into groundwater.

When soil salinity is high, plants use extra energy to get the water that would otherwise by used for growth, flowering, or fruiting. As salt concentrations increase in the soil, water becomes more difficult for plants to absorb. Plants can even die from water stress or drought in moist soil if the soil salt concentration is high enough.

Nutritional imbalances can also occur in saline soils. Some elements, such as sodium, chlorine, and boron, can be toxic to plants in and of themselves. High salt levels in the soil can

Snowberry (Symphoricarpos albus) is more tolerant of salt than other shrubs (Table 1).

B-988R

Revised June 2020

Karen Panter, Extension Horticulture Specialist,
Department of Plant Sciences, University of Wyoming

upset the nutrient balance in plants or interfere with nutrient uptake because many salts are also plant nutrients.

Soil testing labs estimate salt content by extracting solution from a soil sample and measuring the ability of that solution to conduct electricity. The more electricity is conducted through the solution, the higher the salt content is in the soil. The electrical conductivity of an extracted solution is referred to as EC. It is expressed in deciSiemens/meter (dS/m) or millimhos/centimeter (mmhos/cm). Both units are equivalent ways of reporting electrical conductivity: 1 dS/m = 1 mmho/cm.

Plant Responses

Symptoms of salt injury in plants mimic those of drought damage. Both conditions can result in wilting and reduced growth. Exposure to long stretches of high soil salinity causes stunted plants and tissue death. Growth is reduced more and more as salinity increases.

Some plants are salt tolerant and can adjust to the effect of high soil salinity better than salt sensitive plants. Salt tolerant plants are able to absorb more water from saline soils than sensitive plants. A listing of some examples of salt sensitive and tolerant plants is available in Table 1. Use the table as a guide for comparing tolerances among plants.

Other factors play roles in salt tolerance, including climate, soil conditions, cultural practices, and variety selection. During cool weather when water demands from plants are low, salt injury will be less than during hot, dry weather.

Also, salt tolerance of young plants during germination and emergence, is often less than mature plants. One example is beets. The seedlings are more sensitive to soil salinity than another common plant, corn. Reducing soil salinity at the time of seed sowing will help. Salinity can be reduced by leaching with excess water before sowing seeds and planting on the sides of sloping beds.

Table 2 lists salinity ranges expected to give a specific growth or yield for relative tolerances of plants. Use Table 2 along with the results of a soil testing lab EC report. Many laboratories in the western United States routinely perform soil salinity tests.

Soil salinity can be difficult to manage. Salts can be removed from the soil by leaching if drainage is not restricted. Watering plants more frequently can reduce salt injury. Using good management practices, including adequate fertilization, can reduce the effects of high salts in the soil. If you think soil salinity may be a problem, contact your local county University of Wyoming extension educator. Your extension professional can help you get more information on soil salinity, where to get your soil tested for EC, and ways to correct high EC levels.

References

Adapted from: Alan D. Blaylock. Soil salinity, salt tolerance, and growth potential of horticultural and landscape plants. University of Wyoming Cooperative Extension Service, Bulletin B-988, February 1994.

Beckerman, J. and B. Rosie Lerner. 2009. Salt damage in landscape plants. Purdue Extension, ID-412-W, Purdue University. https://www.extension.purdue.edu/extmedia/id/id-412-w.pdf

Pier, J. and D. Barlow, Eds. 2018. Western Fertilizer Handbook, Third Horticulture Edition. Waveland Press, Long Grove, IL.

Appleton, B., V. Greene, A. Smith, S. French, B. Kane, L. Fox, A. Downing, and T. Gilland. 2015. Trees and shrubs that tolerate saline soils and salt spray drift. Virginia Cooperative Extension publication 430-031. https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/430/430-031/430-031_pdf.pdf

Badurek, T. 2014. Salt tolerant vegetable gardening. University of Florida Extension blog. http://blogs.ifas.ufl.edu/pinellasco/2014/03/28/salt-tolerant-vegetable-gardening/

Table 1. Salt sensitivity

Salt sensitive	Moderately sensitive	Moderately tolerant	Tolerant
Trees and shrubs
Alnus - alder	Abies - fir	Euonymus - euonymus	Caragana – peashrub
Amelanchier – serviceberry	Acer – maple	Juniperus - juniper	Gleditsia – honeylocust
Celtis – hackberry	Cotoneaster – cotoneaster	Potentilla - cinquefoil	Juniperus – juniper
Cornus - dogwood	Crataegus – hawthorn	Rhus – sumac	Lonicera - honeysuckle
Mahonia - mahonia	Forsythia - forsythia	Shepherdia – buffaloberry	Robinia – black locust
Rosa - rose	Fraxinus – ash	Syringa - lilac	Quercus – bur oak
Spiraea - spirea	Gymnocladus – Kentucky coffee tree	Ulmus - elm	Symphoricarpos - snowberry
Symphoricarpos - snowberry	Lonicera – honeysuckle
Tilia - linden	Philadelphus – mock orange
	Picea - spruce
	Pinus - pine
	Populus – cottonwood, poplar, aspen
	Quercus – oak
	Sorbus – mountain ash
Annual and perennial flowering plants
Saintpaulia – African violet	Aster – aster	Chrysanthemum - chrysanthemum
Salvia – mealy cup sage	Catharanthus - periwinkle	Dianthus – Sweet William
Verbena - verbena	Clematis – clematis
	Gladiolus – gladiola
	Hemerocallis – daylily
	Iris - iris
	Portulaca – moss rose
	Viburnum - viburnum

 

Salt sensitive	Moderately sensitive	Moderately tolerant	Tolerant
Vegetables
Allium – onion	Capsicum - pepper	Brassica – cauliflower	Asparagus officinalis – asparagus
Apium graveolens – celery	Citrullus lanatus - watermelon	Cucurbita – squash	Beta vulgaris – beet
Cucumis sativus - cucumber	Cucumis – muskmelon, cantaloupe	Daucus – carrot	Brassica – broccoli, cabbage, cauliflower, kale, turnip
Daucus - carrot	Cucurbita – pumpkin, squash	Lactuca – lettuce	Capsicum – bell pepper
Pastinaca – parsnip	Lactuca sativa - lettuce	Pisum – peas	Spinacea – spinach
Phaseolus – bean	Pisum sativum - pea	Solanum tuberosum – potatoes	Solanum lycopersicum - tomato
Raphanus sativus - radish	Raphanus sativus - radish
	Solanum lycopersicum - tomato
	Solanum tuberosum - potato
	Spinacea oleracea - spinach
	Zea mays - corn
Fruits
Malus – apple, crabapple	Ribes - currant
Prunus – apricot, cherry, plum	Vitis – grape
Rubus – raspberry
Grasses
	Poa pratensis – Kentucky bluegrass	Agrostis – creeping bentgrass	Puccinellia - alkali grass
	Festuca – fine fescue, tall fescue	Bouteloua gracilis – blue grama
		Buchloe dactyloides - buffalo grass
		Agropyron cristatum - crested wheatgrass
		Lolium perenne - perennial ryegrass

 

 

Issued in furtherance of extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kelly Crane, director, University of Wyoming Extension, University of Wyoming, Laramie, Wyoming 82071. • The University’s policy has been, and will continue to be, one of nondiscrimination, offering equal opportunity to all employees and applicants for employment on the basis of their demonstrated ability and competence without regard to such matters as race, sex, gender, color, religion, national origin, disability, age, veteran status, sexual orientation, genetic information, political belief, or other status protected by state and federal statutes or University Regulations.

B-988R

Revised June 2020

Karen Panter, Extension Horticulture Specialist, Department of Plant Sciences, University of Wyoming

Editor: Katie Shockley, University of Wyoming Extension

Design: Tanya Engel, University of Wyoming Extension

February 1994. Alan D. Blaylock, Department of Plant, Soil, and Insect Sciences, University of Wyoming

Table 2. Soil salinity levels and potential yield losses of salt tolerance categories of horticultural plants.

Relative salt tolerance	Expected loss of yield or growth (%)
	0%	25%	50%	100%
	Soil salinity (dS/m, mmho/cm)
Sensitive	<1.3	1.4-2.7	2.6-4.2	>8.0
Moderately sensitive	<3.0	2.7-6.3	4.2-9.5	>16.0
Moderately tolerant	<6.0	6.3-10.5	9.5-15.0	>24.0
Tolerant	<10.0	10.5-15.5	15.0-21.0	>32.0