To conserve our water resources, the State of California

encourages the use of recycled water in place of potable

water for applications such as landscape irrigation.

However, irrigators are concerned that salinity in

recycled water can affect the growth and health of plants.

This brochure shows that recycled water can be safely

used for landscape irrigation and that salinity can be

addressed through proper management strategies.

To conserve our water resources, the State of California

encourages the use of recycled water in place of potable

water for applications such as landscape irrigation.

However, irrigators are concerned that salinity in

recycled water can affect the growth and health of plants.

This brochure shows that recycled water can be safely

used for landscape irrigation and that salinity can be

addressed through proper management strategies.

The Link BetweenPlants, Soils, Salts,and Recycled Water

Why Recycle?Over the next 25 years, California will gain an additional 17 millionpeople, bringing the population to 52 million. To meet the waterdemands of this growing population, water agencies are taking proactivesteps in conserving and augmenting our limited water resources.

One solution is to recycle more water.

Recycled water is municipal wastewater that has been extensivelytreated and, in most cases, is safe to reuse for irrigation and otherpurposes.

Using recycled water has several benefits:

• Recycled water is abundant and reliable – which is especiallyimportant to many arid regions in California that have to importwater (often, at high costs).

• It provides protection against drought.

• It is cost-effective.

• It diversifies our sources of water supply and reduces the needto develop new water supplies that are costly and energydemanding.

• It conserves the potable supply.

• It contains nutrients that reduce the need for full applicationof fertilizers.

Uses of Recycled WaterFor over 100 years, California has been using recycled water in avariety of ways, such as for irrigating pastures and crops, flushingtoilets and urinals in office buildings, making artificial snow, andreplenishing aquifers.

Recycled water is also used for landscape irrigation. Golf courses areoften the main customers. Other uses include the irrigation ofschoolyards, parks, athletic fields, cemeteries, nurseries, roadsidevegetation, and some residential areas.

The California Department ofWater Resources estimates thatof the 525,000 acre-feet ofrecycled water used annually inthe state, approximately21 percent is used for land-scape irrigation.

What Is Salinity?Referred to as total dissolvedsolids (TDS), salinity is theconcentration of dissolvedmineral salts in water. Allnatural waters containdissolved salts (Table 1).

The salts enter into the water as a result of chemical weatheringand other natural processes, as well as from certain agricultural andindustrial purposes.

Salt Damage to PlantsThe salts associated with salinity can affect the growth and health ofplants in several ways.

One is referred to the “osmotic effect,” in which salts attract waterand compete with plants for it, meaning that as salinity rises, plantshave to expend more energy to take in water (energy that wouldotherwise be used for growing, flowering, or fruiting). The end resultis negative: stunted growth, wilting, and other damage.

Another major concern is that constituents making up salinity – forexample, sodium and chloride ions, as well asboron – can be toxic to sensitive plants,causing severe damage, such as leaf burn,leaf drop, and plant death.

Some plants are more suscep-tible to salt damage than others.For instance, among turf-grasses, Colonial bentgrass isextremely salt sensitive, whileBermudagrass and Seashorepaspalum are highly salt tolerant (Table 2).

Salinity in Recycled WatersRecycled water typically is of higher salinity than freshwater but usuallynot high enough, however, to make it unsuitable for irrigation.

Because residential and commercial uses add salts to wastewater,increases in salinity levels of local recycled waters vary from under400 to 900 ppm.

Sometimes, however, high levels of salinity originate with the sourcewater itself and not the recycling process. For example, much ofSouthern California receives imported Colorado River water fordrinking-water purposes. The Colorado River’s salinity level averages

about 750 ppm – high enoughthat, in some situations, it maybe detrimental to certain salt-sensitive plants.

Salinity levels in groundwater,another source of potable water,can also vary, ranging from 200ppm to as high as 10,000 ppm.

Thus, whether you use drinkingwater or recycled water forirrigation, you may end up withsalt damage (especially withfoliar wetting) to sensitiveplants, such as rose, gardenia,and ginkgo tree.

Table 1. Salinity Levels of Natural Source Waters in California

Natural Source WaterTotal Dissolved Solids

(parts per million)

Snowfall and Rainfall 5 to 15

Snowmelt and Rainfall Runoff in Watersheds 50 to 100

Sacramento River at the City of Sacramento 120

Groundwater Pumped from Granitic Alluvium 200 to 400

Groundwater Pumped from Sedimentary Alluvium 600 to 10,000

Colorado River at Imperial Dam 750

Ocean Water 35,000

Leaf Burn

Foliar damage

Reddish-TipNeedle Burn

Leaf Burn

Foliar Damage

Reddish-TipNeedle Burn

The Solution to SalinitySalinity can hinder the development of plant life and, if not properlymanaged, salts may accumulate in the soil.

A number of management strategies are available to solve salinityproblems in landscapes. For instance:

• Applying water in excess of the plant’s water needs to maintainsalt balance in the root zone.

• Maintaining adequate soil drainage.

• Avoiding the spray wetting of salt-sensitive plant foliage.

• Blending saline water with less-saline water.

• Adding water and soil amendments to correct sodium andalkalinity problems.

• Replacing salt-damaged plants with plants of higher salttolerance.

Sample Management StrategiesStanding Water and Chlorosis (Yellowing) on Turfgrass – At oneparticular playground, the soil was accumulating sodium ions, whichaffected the ability of turfgrass to take in water and caused standingwater. Subsequently, chlorosis resulted from the lack of soil aerationdue to water logging.

The solution was toapply gypsum as asoil amendment,which suppliedsoluble calcium ionsto replace excesssodium in the soiland resulted in in-creased water intakerates and improvedsoil aeration.

Burning on Foliage of a Conifer Tree – The patternof damage on the needles of a conifer tree indicatedthat water sprayed onto the plant was too saline.

Two solutions were offered: 1) avoid wetting theconifer with sprinkler irrigation by installing bubbleemitters for irrigation; or 2) replace the conifer witha more salt-tolerant species.

Defoliation and Dying Back of Leaves on Gum Tree –The typical symptoms of salt stress – leaf death anddefoliation – were caused by high levels of salinity ata depth of 4 feet in the soil (and not at soil surface).

Because this was a soil salinity problem and not a water salinityproblem, the solution was to heavily water the Sugar gum tree todisplace salts below the root zone and minimize salt damages.

Not All Problems Are Water-RelatedIt is important to note that sometimes the plant damage is not relatedto water, recycled or otherwise.

Water quality is notalways the issue.For instance, at golfcourses, turfgrassdamage may becaused by golferstwisting and turningwhile practicingtheir swings. Inother cases, the soilmay already becontaminated withnatural salinity. Or perhaps the topsoil is shallow, but a plant needsto develop a deep root system, so it cannot grow well.

These few examples underscore that care must be exercised whenassessing any landscape horticulture problem.

Plant Group Very Salt Sensitive Moderately Salt Sensitive Moderately Salt Tolerant Very Salt Tolerant

Turfgrasses Colonial bentgrass Creeping bentgrass Perennial ryegrass Bermudagrass

Annual bluegrass Red fescue Tall fescue • Kikuyugrass Seashore paspalum

Kentucky bluegrass Annual ryegrass Zoysia grass St. Augustinegrass

Landscape Trees Bluegum Coast redwood Aleppo pine Norfolk Island pine

Red maple Sweetgum (Liquidamber) Redgum (E. camaldulensis) Mexican stone pine

Lemon Chinese hackberry Italian Cypress Casuarina

Landscape Shrubs Abelia Crape myrtle Japanese boxwood Mock orange

Camellia Oregon grape Pittosporum Oleander

Cornelian cherry Croton Escallonia Century plant

Table 2. Salt Tolerance of Select Species of Landscape Plants

Abelia

Crape Myrtile

Escallonia

Mock Orange

Japanese Boxwood

Abelia

Crape Myrtile

Escallonia

Mock Orange

Japanese Boxwood

Water-Logged PlaygroundWater-Logged Playground

Golfer-Damaged TurfgrassGolfer-Damaged Turfgrass

Anew tool is available to help landscape professionals

accurately diagnose and manage salt-related problems.

The Salinity Management Guide is an interactive, user-

friendly CD that provides information varying from the

basics of salinity to the design or redesign of landscape

systems based on water needs, soil conditions, and the

salt-tolerance of plants.

Using data and images from the Guide, landscapers will be

able to compare their plants to photos of plants suffering

from salt damage. With a click of the mouse, they can

explore options such as selecting a

more salt-tolerant plant for the

landscape, checking water

application rates to determine if adequate water

has been used to meet the plant’s needs, or

changing the water application method from

one type of sprinkler to another to avoid salt

damage to foliage.

It is the only CD database of its kind that provides

information on the effects of water quality on plants,

soils, and water application systems.

CaliforniaDepartment of Water Resources

Sacramento, Californiawww.water.ca.gov

Central BasinMunicipal Water District

Carson, Californiawww.centralbasin.org

City ofCerritos

Cerritos, Californiawww.ci.cerritos.ca.us

Los AngelesDepartment of Water and Power

Los Angeles, Californiawww.ladwp.com

NationalWater Research InstituteFountain Valley, California

www.NWRI-USA.org

Southern CaliforniaSalinity Coalition

Fountain Valley, Californiawww.socalsalinity.org

Water Replenishment DistrictCerritos, California

www.wrd.org

WateReuse FoundationAlexandria, Virginia

www.watereuse.org/Foundation

West Basin Municipal Water DistrictCarson, California

www.westbasin.com

The Salinity Management Guide CD was funded from the following sources:

The Salinity Management Guide

Recycled water irrigation at golf courses isincreasingly common. At Torrey Pines in La Jolla,California, there is a wide variety of plantmaterials: fairway, rough, green, bedding plants,trees, and pond.

The Link Between Plants, Soils, Salts,and Recycled Water

Photo credits:UC ANR Media Library,

San Diego County,D. Shaw and J. Skorulski

To access the Salinity Management Guide online, please visit:www.salinitymanagement.org