Salinity

July 1997
AG-SO-03

SALINITY AND PLANT TOLERANCE
Jan Kotuby-Amacher, Director, Utah State University Analytical Labs
Rich Koenig, Extension Soils Specialist
Boyd Kitchen, Uintah County Extension Agent

Introduction

Soil salinity is a measure of the total amount of soluble salt in soil. As salinity levels increase, plants extract water less easily from soil, aggravating water stress conditions. High soil salinity can also cause nutrient imbalances, result in the accumulation of elements toxic to plants, and reduce water infiltration if the level of one salt element--sodium--is high. In many areas throughout Utah, soil salinity is the factor limiting plant growth.

Salt-affected plants are stunted with dark green leaves which, in some cases, are thicker and more succulent than normal. In woody species, high soil salinity may lead to leaf burn and defoliation. High salinity causes alfalfa yield to decrease while the leaf-to-stem ratio increases, influencing forage quality. Grasses also appear dark green and stunted with leaf burn symptoms.

Salinity tolerance is influenced by many plant, soil, and environmental factors and their interrelationships. Generally, fruits, vegetables, and ornamentals are more salt sensitive than forage or field crops. In addition, certain varieties, cultivars, or rootstalks may tolerate higher salt levels than others. Plants are more sensitive to high salinity during seedling stages, immediately after transplanting, and when subject to other (e.g., disease, insect, nutrient) stresses.

Climate and irrigation also influence salinity tolerance. As soil dries, salts become concentrated in the soil solution, increasing salt stress. Therefore, salt problems are more severe under hot, dry conditions than under cool, humid conditions. Increasing irrigation frequency and applying water in excess of plant demand may be required during hot, dry periods to minimize salinity stress.

Sources of Soil Salinity

Salts are a common and necessary component of soil, and many salts (e.g., nitrates and potassium) are essential plant nutrients. Salts originate from mineral weathering, inorganic fertilizers, soil amendments (e.g., gypsum, composts and manures), and irrigation waters. An additional, important source of salts in many landscape soils comes from ice melters used on roads and sidewalks. The addition of virtually any soluble material will increase soil salinity. It is only when salts are present in relatively high amounts that plant growth is adversely affected.

Salinity Measurement

Soil salinity is determined by measuring the electrical conductivity of solution extracted from a water-saturated soil paste. Salinity is abbreviated as EC_e (Electrical Conductivity of the extract) with units of decisiemens per meter (dS/m) or millimhos per centimeter (mmhos/cm). Both are equivalent units of measurement and give the same numerical value. The Utah State University Soil Testing Lab charges $5.00 per sample to test for soil salinity. This is a small investment relative to the cost of seed and vegetation planted in fields and landscapes.

Managing Soil Salinity

In principle, soil salinity is not difficult to manage. The first requisite for managing soil salinity is adequate drainage, either natural or man-made. Determine salinity level by collecting a representative soil sample to a 12 inch depth and having it analyzed by a lab. If the salinity level is too high for the desired vegetation (see attached tables), remove salts by leaching the soil with clean (low salt) water. Application of 6 inches of water will reduce salinity levels by approximately 50%, 12 inches of water will reduce salinity by approximately 80%, and 24 inches by approximately 90%. The manner in which water is applied is important. Water must drain through the soil rather than run off the surface. Internal drainage is imperative and may require deep tillage to break up any restrictive layer impeding water movement. Sprinkler irrigation systems generally allow better control of water application rates; however, flood irrigation can be used if sites are level and water application is controlled. Collect and test another soil sample after leaching the site to determine whether salinity level is now suitable for planting.

Plant Responses to Soil Salinity

Table 1 describes general plant responses to different soil salinity ranges. Due to economic and/or environmental limitations (e.g., inadequate drainage), it may not be possible to leach salt from soil. In these situations, select plants which are tolerant of the salinity level in soil. Tables 2 through 8 describe the salt tolerances of common agricultural, horticultural, and ornamental plants grown in Utah. Tolerance values should be used as a guide when selecting vegetation. Varietal differences and environmental conditions may make plants more or less salt tolerant than indicated in the tables.

For harvested crops, threshold values indicate soil salinity levels where plants begin to experience yield-reducing effects. Above the threshold, salinity levels associated with expected yield losses of 10%, 25% and 50% are indicated. Ornamental plants are grouped according to their relative salinity tolerance (low, medium or high) with EC_e ranges indicated for each category. With the exception of turf, relatively little research has been done on landscape and ornamental plant salinity tolerance. Most research conducted on ornamentals has addressed tolerance to salt spray deposited on foliage. A high tolerance to salt spray, however, may indicate a high tolerance to salinity in the root zone.

Table 1. General guidelines for plant response to soil salinity.
Salinity (EC_e, dS/m) Plant response

0 to 2
2 to 4
4 to 8
8 to 16
above 16 mostly negligible
growth of sensitive plants may be restricted
growth of many plants is restricted
only tolerant plants grow satisfactorily
only a few, very tolerant plants grow satisfactorily

**Table 1. General guidelines for plant response to soil salinity.**
Salinity (EC_e, dS/m)	Plant response
0 to 2 2 to 4 4 to 8 8 to 16 above 16	mostly negligible growth of sensitive plants may be restricted growth of many plants is restricted only tolerant plants grow satisfactorily only a few, very tolerant plants grow satisfactorily

Table 2. Salinity tolerance of common field crops grown in Utah.
Crop Threshold value 10%
yield loss 25%
yield loss 50%
yield loss

EC_e (dS/m) EC_e (dS/m) EC_e (dS/m) EC_e (dS/m)

Barley
Beans (field)
Canola
Corn (grain)
Oats (grain)
Rye (grain)
Safflower
Sorghum
Sugarbeets
Sunflower
Triticale (grain)
Wheat 8.0
1.0
2.5
2.7
5.2
5.9
5.3
4.0
6.7
2.3
6.1
4.7 9.6
1.5
3.9
3.7
6.7
7.7
8.0
5.1
8.7
3.2
8.1
7.0 13.0
2.3
6.0
6.0
9.0
12.1
11.0
7.1
11.0
4.7
12.0
9.5 17.0
3.6
9.5
7.0
12.8
16.5
14.0
10.0
15.0
6.3
14.2
13.0

Table 2. **Salinity tolerance of common field crops grown in Utah.**
Crop	Threshold value	10% yield loss	25% yield loss	50% yield loss
	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)
Barley Beans (field) Canola Corn (grain) Oats (grain) Rye (grain) Safflower Sorghum Sugarbeets Sunflower Triticale (grain) Wheat	8.0 1.0 2.5 2.7 5.2 5.9 5.3 4.0 6.7 2.3 6.1 4.7	9.6 1.5 3.9 3.7 6.7 7.7 8.0 5.1 8.7 3.2 8.1 7.0	13.0 2.3 6.0 6.0 9.0 12.1 11.0 7.1 11.0 4.7 12.0 9.5	17.0 3.6 9.5 7.0 12.8 16.5 14.0 10.0 15.0 6.3 14.2 13.0

Table 3. Salinity tolerance of common forages grown in Utah.
Crop Threshold
value 10%
yield loss 25%
yield loss 50%
yield loss

EC_e (dS/m) EC_e (dS/m) EC_e (dS/m) EC_e (dS/m)

Alfalfa
Barley (forage)
Beardless Wild Rye
Bermuda Grass
Birdsfoot Trefoil
Brome, Meadow
Brome, Smooth
Clovers (Berseem Strawberry)
Clovers (Alsike, Ladino, Red)
Corn (silage)
Field Peas
Harding Grass
Newhy/Hoffman
Lovegrass
Meadow Foxtail
Oats (forage)
Orchard Grass
Perennial Ryegrass
Rye (forage)
Sweet Clover
Sudangrass
Tall Fescue
Timothy
Triticale (forage)
Vetch (spring)
Crested Wheatgrass
Tall Wheatgrass 2.0
5.3
2.7
6.9
4.0
4.4
2.5
1.5
1.3
1.8
1.3
4.6
4.8
2.2
1.3
2.6
1.5
5.6
2.5
4.0
2.8
3.9
2.0
6.1
3.0
3.5
7.5
3.4
7.4
4.0
8.5
6.0
5.5
3.1
3.2
2.3
2.7
2.0
5.9
6.4
3.2
2.0
3.2
3.1
6.9
3.5
6.0
5.1
5.8
2.7
8.1
3.9
6.0
9.9
5.4
9.5
7.0
10.8
7.5
8.0
4.0
5.9
3.6
6.8
3.1
7.9
8.0
5.0
3.5
4.1
5.5
8.9
5.1
7.5
8.6
8.6
3.8
10.4
5.3
9.8
13.0
8.8
13.0
11.0
14.7
10.0
11.6
5.0
10.3
5.7
8.6
4.9
11.0
16.0
8.0
6.5
6.8
9.6
12.0
7.2
10.0
14.0
13.3
5.0
13.5
7.6
16.0
19.0

**Table 3. Salinity tolerance of common forages grown in Utah.**
Crop	Threshold value	10% yield loss	25% yield loss	50% yield loss
	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)
Alfalfa Barley (forage) Beardless Wild Rye Bermuda Grass Birdsfoot Trefoil Brome, Meadow Brome, Smooth Clovers (Berseem Strawberry) Clovers (Alsike, Ladino, Red) Corn (silage) Field Peas Harding Grass Newhy/Hoffman Lovegrass Meadow Foxtail Oats (forage) Orchard Grass Perennial Ryegrass Rye (forage) Sweet Clover Sudangrass Tall Fescue Timothy Triticale (forage) Vetch (spring) Crested Wheatgrass Tall Wheatgrass	2.0 5.3 2.7 6.9 4.0 4.4 2.5 1.5 1.3 1.8 1.3 4.6 4.8 2.2 1.3 2.6 1.5 5.6 2.5 4.0 2.8 3.9 2.0 6.1 3.0 3.5 7.5	3.4 7.4 4.0 8.5 6.0 5.5 3.1 3.2 2.3 2.7 2.0 5.9 6.4 3.2 2.0 3.2 3.1 6.9 3.5 6.0 5.1 5.8 2.7 8.1 3.9 6.0 9.9	5.4 9.5 7.0 10.8 7.5 8.0 4.0 5.9 3.6 6.8 3.1 7.9 8.0 5.0 3.5 4.1 5.5 8.9 5.1 7.5 8.6 8.6 3.8 10.4 5.3 9.8 13.0	8.8 13.0 11.0 14.7 10.0 11.6 5.0 10.3 5.7 8.6 4.9 11.0 16.0 8.0 6.5 6.8 9.6 12.0 7.2 10.0 14.0 13.3 5.0 13.5 7.6 16.0 19.0

Table 4. Salinity tolerance of common vetetables grown in Utah.
Crop Threshold
value 10%
yield loss 25%
yield loss 50%
yield loss

EC_e (dS/m) EC_e (dS/m) EC _e (dS/m) EC_e (dS/m)

Asparagus
Beans
Beets
Broccoli
Cabbage
Cantaloupe
Carrot
Cauliflower
Celery
Corn, Sweet
Cucumber
Lettuce
Onion
Peas
Pepper, Bell
Potato
Radish
Spinach
Squash/pumpkins
Sweet Potato
Tomato
Turnips
Watermelon 5.0
1.0
5.3
2.7
1.8
2.2
1.0
2.7
1.8
1.7
2.5
1.3
1.2
0.9
1.3
1.7
1.2
3.7
3.9
1.5
2.5
0.9
2.0 8.0
1.5
8.0
3.5
2.8
3.6
1.7
3.5
3.5
2.5
3.3
2.1
1.8
2.0
2.2
2.5
2.0
5.5
4.9
2.4
3.5
1.9
2.5 11.0
2.3
10.0
5.5
4.4
5.7
2.8
4.7
5.8
4.0
4.4
3.2
2.8
3.7
3.3
3.8
3.0
7.0
5.9
3.8
5.0
3.1
3.5 13.0
3.6
12.0
8.2
7.0
9.1
4.6
5.9
10.1
6.0
6.3
5.2
4.3
6.5
5.1
5.9
8.0
8.0
7.9
6.0
7.6
4.9
4.5

**Table 4. Salinity tolerance of common vetetables grown in Utah.**
Crop	Threshold value	10% yield loss	25% yield loss	50% yield loss
	EC_e (dS/m)	EC_e (dS/m)	EC _e (dS/m)	EC_e (dS/m)
Asparagus Beans Beets Broccoli Cabbage Cantaloupe Carrot Cauliflower Celery Corn, Sweet Cucumber Lettuce Onion Peas Pepper, Bell Potato Radish Spinach Squash/pumpkins Sweet Potato Tomato Turnips Watermelon	5.0 1.0 5.3 2.7 1.8 2.2 1.0 2.7 1.8 1.7 2.5 1.3 1.2 0.9 1.3 1.7 1.2 3.7 3.9 1.5 2.5 0.9 2.0	8.0 1.5 8.0 3.5 2.8 3.6 1.7 3.5 3.5 2.5 3.3 2.1 1.8 2.0 2.2 2.5 2.0 5.5 4.9 2.4 3.5 1.9 2.5	11.0 2.3 10.0 5.5 4.4 5.7 2.8 4.7 5.8 4.0 4.4 3.2 2.8 3.7 3.3 3.8 3.0 7.0 5.9 3.8 5.0 3.1 3.5	13.0 3.6 12.0 8.2 7.0 9.1 4.6 5.9 10.1 6.0 6.3 5.2 4.3 6.5 5.1 5.9 8.0 8.0 7.9 6.0 7.6 4.9 4.5

Table 5. Salinity tolerance of common fruit and nut crops grown in Utah.
Crop Threshold
value 10%
yield loss 25%
yield loss 50%
yield loss

EC_e (dS/m) EC_e (dS/m) EC_e (dS/m) EC_e (dS/m)

Apple
Almond
Apricot
Blackberry
Boysenberry
Cherries, Sweet and Tart
Grape
Nectarines
Peach
Pear
Pecan
Plum
Raspberry
Strawberry
Walnut 1.7
1.5
1.5
1.0
1.3
0.9
1.5
1.6
1.7
1.7
1.9
1.5
1.0
1.0
1.7 2.3
2.0
2.0
2.0
2.0
1.9
2.5
2.0
2.2
2.3
2.5
2.1
1.4
1.3
2.3 3.3
2.8
2.6
2.6
3.0
2.2
4.1
2.6
2.9
3.3
3.5
2.9
2.1
1.8
3.3 4.8
4.1
3.7
3.8
4.0
3.1
6.7
3.7
4.1
4.8
4.9
4.3
3.2
2.5
4.8

**Table 5. Salinity tolerance of common fruit and nut crops grown in Utah.**
Crop	Threshold value	10% yield loss	25% yield loss	50% yield loss
	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)	EC_e (dS/m)
Apple Almond Apricot Blackberry Boysenberry Cherries, Sweet and Tart Grape Nectarines Peach Pear Pecan Plum Raspberry Strawberry Walnut	1.7 1.5 1.5 1.0 1.3 0.9 1.5 1.6 1.7 1.7 1.9 1.5 1.0 1.0 1.7	2.3 2.0 2.0 2.0 2.0 1.9 2.5 2.0 2.2 2.3 2.5 2.1 1.4 1.3 2.3	3.3 2.8 2.6 2.6 3.0 2.2 4.1 2.6 2.9 3.3 3.5 2.9 2.1 1.8 3.3	4.8 4.1 3.7 3.8 4.0 3.1 6.7 3.7 4.1 4.8 4.9 4.3 3.2 2.5 4.8

Table 6. Salinity tolerance of selected flowers grown in Utah.
Low tolerance Moderate tolerance High tolerance

EC_e less than 2.0 dS/m* EC_e = 2.0 to 3.0 dS/m* EC_e = 3.0 to 4.0 dS/m*

China Aster
Geranium
Lily
Gladiolus
Gardenia
Azalea Carnation
Poinsettia
Chrysanthemum Rose

*Approximate tolerance ranges. Very little research has been done on the salinity tolerance of flowers.

**Table 6. Salinity tolerance of selected flowers grown in Utah.**
Low tolerance	Moderate tolerance	High tolerance
EC_e less than 2.0 dS/m*	EC_e = 2.0 to 3.0 dS/m*	EC_e = 3.0 to 4.0 dS/m*
China Aster Geranium Lily Gladiolus Gardenia Azalea	Carnation Poinsettia Chrysanthemum	Rose

Table 7. Salinity tolerance of common turfgrasses grown in Utah.
Low tolerance Moderate tolerance High tolerance

EC_e less than 3.0 dS/m* EC_e = 3.0 to 6.0 dS/m* EC_e = 6.0 to 9.0 dS/m*

Kentucky Bluegrass
Annual Bluegrass Tall Fescue
Creeping Red Fescue
Chewings Fescue
Hard Fescue
Perennial Ryegrass
Creeping Bentgrass
Blue Grama
Buffalograss
Zoysiagrass Bermudagrass
Alkaligrass
Fairway Crested Wheatgrass

**Table 7. Salinity tolerance of common turfgrasses grown in Utah.**
Low tolerance	Moderate tolerance	High tolerance
EC_e less than 3.0 dS/m*	EC_e = 3.0 to 6.0 dS/m*	EC_e = 6.0 to 9.0 dS/m*
Kentucky Bluegrass Annual Bluegrass	Tall Fescue Creeping Red Fescue Chewings Fescue Hard Fescue Perennial Ryegrass Creeping Bentgrass Blue Grama Buffalograss Zoysiagrass	Bermudagrass Alkaligrass Fairway Crested Wheatgrass

Table 8. Salinity tolerance of ornamental and shade trees grown in Utah.
Low tolerance Moderate tolerance High tolerance

EC_e less than 2 dS/m* EC_e = 2 to 3 dS/m* EC_e = 3 to 4 dS/m*

Alders
Beech
Norway Spruce
Giant Sequoia
Dawn Redwood
Scots/Scotch pine
Japanese Arborvitae
Maples (Sugar, Red)
Filbert/Hazel
Littleleaf Linden
American Linden
Eastern Redbud
European Hornbeam
Yellow-Poplar Boxelder
Ohio Buckeye
Catalpas
Birchs (River, White)
Kentucky Coffeetree
Ginkgo
London Planetree
Hackberry
Hawthorn
American Holly
Silver Linden
Magnolia
Firs
Mountainash
Oaks (Bur, Gambel, Shingle)
American Sycamore
Walnut (Black, English)
Blue Spruce
Pines (Bristlecone, Limber,
Lodgepole, S.W. White,
Ponderosa, Pinyon)
Spruce (Englemann, White) Maples (Norway, Hedge)
Honeylocust
Cottonwoods
Ash (European, Green, White)
Flowering Crabapple
Poplars
Goldenraintree
Horsechestnut
Joshua Tree
Tamarack
Paper Birch
Willows
Junipers/ E. Redcedar
European Larch
Locust (Black, Idaho, NewMexico)
Austrian Pine
Chinese Date
Baldcypress
Oaks (English, Northern Red, White)

*approximate tolerance ranges.
For a more complete listing of ornamental tree tolerances to salinity and other conditions, see the Utah State University Extension Bulletin #HG460, Selecting and Planting Landscape Trees.

References
Agricultural Salinity Assessment and Management. 1990 K.K. Tanji, Editor, American Society of Civil Engineers, New York, N.Y.
The Western Fertilizer Handbook, 8th Edition, 1995. Interstate Publishers, Danville, Ill.
Diagnosis and improvement of saline and alkali soils. 1954. USDA (Handbook 60).
Acknowledgments
"Salinity and Plant Tolerance" is a revision of the earlier publication titled "Salinity and Crop Tolerance" authored by J. Kotuby-Amacher, J. Jurinak, V. P. Rasmussen, D. W. James, and R. W. Whitesides
Utah State University Extension is an affirmative action/equal employment opportunity employer and educational organization. We offer our programs to persons regardless of race, color, national origin, sex, religion, age or disability. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Robert L. Gilliland, Vice-President and Director, Cooperative Extension Service, Utah State University, Logan, Utah. (EP/DF/04-98)