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Group Title: Circular Florida Cooperative Extension Service
Title: Management of saline irrigation water in the nursery
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Title: Management of saline irrigation water in the nursery
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 12 p. : ; 23 cm.
Language: English
Creator: Knox, Gary W
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1986?
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Subject: Saline irrigation   ( lcsh )
Plants -- Effect of salts on   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
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Bibliography: Bibliography: p. 12.
Statement of Responsibility: Gary W. Knox.
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Commercial


Management of
Water in tl


Irrigation


Gary W.


Florida Cooperative Extension Service / Ir
University of Florida /


and Agricultural Sciences
^ ")t .-^










Management of Saline Irrigation
Water in the Nursery

Gary W. Knox*



Introduction
A salinity problem with irrigation water can be serious but not
necessarily disastrous. Moderately saline irrigation water can be used to
successfully grow ornamentals if proper irrigation management is com-
bined with appropriate plant, growing medium, and fertilizer selection.
Improper management of saline irrigation water can result in high con-
centrations of soluble salts in the growing medium. Before discussing
approaches to this problem, some of the basics of soluble salts and water
uptake by plants should be reviewed.


Water and Nutrient Absorption
Plants absorb water and nutrients primarily through root hairs, minute
appendages of root cells that are in close contact with soil particles and
with the thin film of moisture around each soil particle. This film of water
contains dissolved nutrients and other compounds, collectively called
"soluble salts" or "salts." Water is attracted to and held by soil particles
and by the salts which are dissolved in the water. The attraction of water to
dissolved salts is called "osmosis," and causes water to move from areas
of low salt concentration to areas of high concentration.
Root hairs selectively absorb those compounds which plants require
for growth. Water absorption by roots occurs actively as a result of
nutrient uptake and passively as a result of water demand by shoots. The
osmotic effect of the salts accumulated in roots causes water to move from
the soil solution (area of low salt concentration) into roots (area of higher
salt concentration) and then throughout the plant.
High concentrations of soluble salts in the soil create problems for
plants for the following reasons: 1) salts in the soil solution become so
concentrated that the plant cannot "compete" with these salts to attract
water into the roots; 2) roots may be damaged if the osmotic effect of the
soil solution is great enough to draw water out of the roots; 3) a compound
may be so abundant that the roots absorb too much of that particular salt,
which then accumulates to toxic levels in the plant; and 4) if sodium is pre-

* Extension Water Management Specialist, Agricultural Research and
Education Center Monticello, Fla., IFAS, University of Florida,
Gainesville, 32611.









sent in high concentrations, it will displace other important nutrients
(such as calcium and magnesium), causing them to be leached out more
rapidly and thereby inducing nutrient deficiencies in the plant.

Toxicities

Problems associated with saline water sometimes result from toxic
effects of chloride or, occasionally, sodium. Chloride or sodium toxicities
may develop gradually over a long period of exposure. With some
species, sprinkler irrigation may induce toxicity problems because of
foliar absorption of chloride or sodium.
Chloride toxicity symptoms include leaf burn starting at the tip of older
leaves and progressing back along the edges with increasing severity.
Sodium toxicity is characterized by burning on the outer edges of older
leaves which progresses inward between the veins as severity increases.
Many ornamentals exhibit leaf bum when chloride or sodium levels
exceed 0.5 percent of the leaf dry weight. Periodic leaf analysis can detect
chloride or sodium accumulation.


Sodium Hazard of Saline Irrigation Water
Use of saline irrigation water may also result in nutritional or soil
permeability problems induced by sodium. An excess of sodium in the
medium will dislodge nutrients such as calcium and magnesium from the
medium and thereby induce deficiencies of these nutrients. In field soils,
excess sodium can result in reduced permeability of the soil to water. The
U.S. Salinity Laboratory (1954) has developed a formula called the Sodium
Absorption Ratio (SAR) to determine the potential hazard due to sodium:

SAR = Na -+,(Ca + Mg) + 2

where Na, Ca, and Mg are expressed in milliequivalents per liter (meq/1).
Sodium, calcium, and magnesium values that are expressed in parts per
million (ppm) or milligrams per liter (mg/1) can be converted to meq/1 by
the following formula:

meq/1 = mg/l (or ppm)
meq/1 =
eq. wt.

where "eq. wt." is the equivalent weight of the element. Equivalent
weights of sodium, calcium, and magnesium are 23, 20, and 12, respec-
tively.
Irrigation water with an SAR value less than 3 is ideal for nursery use,
while water with SAR values between 3 and 9 are acceptable for use in










nurseries (Farnham et al., 1985). Use of water with an SAR value greater
than 9 can lead to severe nutritional problems and, in field soils, degrada-
tion of soil structure and reduced water permeability. Problems with
permeability do not usually occur with highly organic container media
until SAR values exceed 35 (Farnham et al., 1985); at these values, most
plants would not survive anyway.


Sources of Soluble Salts
High soluble salts result when insufficient leaching allows accumula-
tion of salts in the medium. The salts may be naturally present in medium
components, or may be introduced by fertilizers or by irrigation water
that contains salt. Salts include fertilizer components and decay products
of organic matter as well as compounds derived from breakdown of the
potting medium. Wellwater may contain high concentrations of dissolved
calcium, magnesium, carbonates, and bicarbonates. With saline or
brackish water, the salts involved are sodium and chloride.


Measuring Soluble Salts
A part of every nursery's program should be regular monitoring of solu-
ble salts and pH, in addition to having thorough water, container media,
and leaf analysis tests run by a professional testing lab. During the growing
season, irrigation water and container media should be tested for soluble
salts at least monthly, and twice each week if fertilizer is injected through
the irrigation system. A solubridge or conductivity meter may be used to
measure soluble salts. These instruments operate on the principle that
water with salts dissolved in it will conduct electricity, whereas pure
water is a poor conductor of electricity. The electrical conductivity of a
solution is proportional to the concentration of dissolved salts. A
solubridge or conductivity meter is a wise investment for any nursery.
To measure soluble salts with one of these instruments, cores of con-
tainer medium should be collected from 8 to 10 containers and then
blended together. The saturated paste method is the preferred technique
for measuring soluble salts. This method involves saturating a small
volume of medium (about a half pint) with distilled water. Water is added
to the medium slowly while stirring until the medium surface is shiny but
no water moves across the surface when it is tilted. The sample should sit
for at least two hours to allow the salts to equilibrate. The soil solution is
extracted from the sample by vacuum-filtering the saturated medium.
The extract is poured into a suitable container, and the electrode is
immersed in it. The meter is read in deciSiemens/m, millimhos/cm, or
micromhos/cm, depending on the instrument and its scale. Soluble salts










Table 1. Interpretation of soluble salts levels forpotting media
as determined by saturated paste extractprocedures."

Soluble Salts Electrical Conductivity
Levels (dS/m or mmhos/cm)

Low <0.78
Acceptable 0.78-1.56
Optimum 1.56-2.34
High 2.34-3.91
Very High >3.91

a Adapted from Rhue et al. 1980.

in irrigation water are determined by directly immersing the electrode in a
water sample. Safe levels of soluble salts are given in Table 1 for media and
in Table 2 for irrigation water. (For a more detailed discussion of soluble
salts measurement, see University of Florida Extension Circular 556,
"Nursery Laboratory Development and Operation.")



Managing a Soluble Salts Problem

There are three general steps that can be taken to deal with high soluble
salts:
1. Desalination or dilution of saline water
2. Cultural management to minimize accumulation of soluble salts
3. Growing salt-tolerant species
Desalination or Dilution
Desalination is the least practical method. While it is possible to pur-
chase tanks of deionizing resins that will remove salts, the deionizing
resins are extremely expensive when considering the large volumes of
water used in the nursery. The use of water softeners does not solve a solu-
ble salts problem. Water softeners remove calcium and magnesium from
water but they replace these salts with sodium which is still a salt that
will cause problems.
On the other hand, diluting poor quality water with good quality water
or alternating water sources is usually much more feasible. For example, if
a nursery had access to city water, the city water could be mixed with poor
quality water to obtain an acceptable concentration of salts. An alternative
is to use city water (or a blend with city water) for salt-sensitive species and
poor quality water for salt-tolerant crops. Another option is to alternate









Table 2. Interpretation of soluble salts levels in irrigation
water.

Classification of Electrical Conductivity
Irrigation Water (dS/m or mmhos/cm)

Excellent <0.25
Good 0.25-0.75
Permissible 0.75-2.00
Doubtful 2.00-3.00
Unsuitable >3.00

a Adapted from Kidder and Rhue, 1983.

the use of good and poor quality water according to availability and plant
needs. A final choice would be to use good quality water during critical
stages of growth (during flushes of growth, for example) and use poor
quality water at other times. These alternatives would not be as
expensive as converting completely to city water.
Which option to choose depends on the degree of salinity of the various
water sources, the salt tolerance of the crops at different stages of growth,
the use of cultural management techniques to control soluble salts levels,
and the cost of each of the options (Shalhevet, 1984). On the whole,
desalination or dilution is not as practicable as the remaining two alter-
natives.
Cultural Management
Irrigation management and potting soil management are practical
management techniques, depending on the salinity of the irrigation water.
Cultural management to avoid soluble salts buildup involves proper fer-
tilizer selection, irrigation management, and potting medium selection.
Fertilization. Since fertilizers are salts, fertilization will increase the
osmotic effect of the soil solution. To minimize this osmotic effect,
growers should avoid using high rates of fertilizers or fertilization pro-
grams providing sudden release of nutrients. The "salt index" was
developed to rank fertilizers on the basis of their osmotic effect relative to
sodium nitrate (Jurinak and Wagenet, 1981). The higher the salt index, the
greater is the osmotic effect. A list of common fertilizers and their salt
indices is given in Table 3.
Use of continuous liquid fertilization or slow-release fertilizers may not
cause sudden, high concentrations of soluble salts, although over time
their use can result in soluble salts problems. However, electrical conduc-
tivity of irrigation water (ECw) after fertilizer injection should not exceed









Table 3. Salt indices ofselected fertilizers."

Material Salt Indexb

Nitrogen sources:
Ammonium nitrate 104.7
Ammonium sulfate 69.0
Calcium nitrate 52.5
Diammonium phosphate 34.2
Monoammonium phosphate 29.9
Potassium nitrate 73.6
Sodium nitrate 100.0
Urea 75.4
Phosphorous sources:
Diammonium phosphate 34.2
Monoammonium phosphate 29.9
Superphosphate 7.8
Triple superphosphate 10.1
Potassium sources:
Potassium chloride 114.3
Potassium nitrate 73.6
Potassium sulfate 46.1
Others:
Calcium carbonate (limestone) 4.7
Calcium sulfate (gypsum) 8.1
Sodium sulfate 74.2

aAdapted from Rader et al., 1943.
Relative osmotic effect as compared to an equivalent weight of sodium nitrate (= 100).

2.0 dS/m (mmhos/cm) (Hanan, 1982). Also, release rates of slow-release
fertilizers vary considerably; and those with more rapid release rates
should be avoided or used at lower application rates.
Irrigation. Plants subject to high concentrations of soluble salts
should never be kept "on the dry side." As the potting medium in a con-
tainer dries, the salts in the soil solution become more concentrated,
thereby intensifying the effects of the soluble salts on roots. Frequent
irrigation can prevent dry/wet cycles and avoid the concentrations of salts
between irrigations. Because of their efficiency, it is more practical to
irrigate frequently with drip irrigation systems than by sprinkler irriga-
tion. Another advantage of drip irrigation is that saline water never comes
in contact with foliage. Sprinkler irrigation can deposit salts on leaves that
may cause leaf injury.
Potting Medium. Potting medium characteristics affect the efficiency
of leaching and can indirectly affect the concentration of salts in the soil










solution. Leaching, or excess watering, will be an important part of every
program to manage soluble salts. Research has shown that leaching is
more effective if the container medium is fine-textured with small pores,
as opposed to a coarse, porous mixture (Kerr and Hanan, 1985). In a
medium with large pores, water runs through too quickly to adequately
flush the salts. Thus, the higher the percolation rate of the soil', the less effi-
cient is the leaching process.
A potting medium with a high water-holding capacity won't dry out as
quickly, making it easier to keep the medium moist and prevent the con-
centration of soluble salts. Fortunately, high water-holding capacity and
small pore size are compatible traits in a potting medium. (For information
on determining water-holding capacity, see University of Florida Exten-
sion Circular 556, "Nursery Laboratory Development and Operation.")
Leaching. Leaching is probably the most important management tool
for salinity control. Pots should be leached whenever soluble salts reach a
critical level (dependent on the crop; see Table 4). Leaching requirements
can be estimated by determining the electrical conductivity of the irriga-
tion water and the leachate and using the following formula (U.S. Salinity
Laboratory Staff, 1954):

LR = ECw/ECdw x 100 = percentage of water to be applied
greater than crop requirements

where ECwis the electrical conductivity of irrigation water and ECdwis the
electrical conductivity of leachate.
Recent research has found that, as a general rule, pots should be leached
with a quantity of water equal to two container-capacities of water (Kerr
and Hanan, 1985). "Container-capacity" refers to the amount of water a
container-full of potting medium will hold after it is thoroughly saturated
and allowed to drain. Leaching with more than two container-capacities
wastes water. In addition, leaching is more efficient when the leach water
is distributed evenly across the soil surface. Leaching is another reason to
use a liquid or slow-release fertilization program: regular leaching also
washes out nutrients.
Salt-tolerant Plants
A final way to handle a salinity problem is to grow salt-tolerant species.
This is not as drastic as it may sound. Many ornamental plants have a
degree of salt tolerance. Salt tolerance of a number of woody ornamentals
is given in Tables 4 and 5. More information can be found in University of
Florida fact sheets on salt tolerance of landscape plants and in "Salt
Tolerant Plants for Florida Landscapes," by William Barrick (Report
Number 28, Florida Sea Grant College, August, 1979). Unfortunately,
most evaluations of salt tolerance in these publications and in Table 4 are










from observations in the landscape and may only indicate survival, rather
than an acceptable growth rate for the nursery. However, the relative
degree of tolerance should still hold true in the nursery.
Nursery growers should be aware that a plant may not have a uniform
level of salt tolerance throughout its entire life cycle. Young or actively-
growing plants may not have the same degree of salt tolerance as older
plants or those with mature growth. Unfortunately, no generalities can be
made as to the stages of growth when all species are sensitive to soluble
salts. Also, salt tolerance may vary with cultivar or rootstock as well as
with species and growth stage. Finally, the foliage of some species may be
damaged by salts deposited by overhead irrigation.


Summary

Management of a soluble salts problem can include desalination or dilu-
tion of saline irrigation water, cultural management to prevent soluble
salts buildup, and growth of salt-tolerant species. Cultural management
involves the following:
Use fertilizers or fertilization methods that minimize soluble salts
accumulation in the potting medium.
Keep the potting medium moist.
Use a fine-textured potting medium with a high water-holding
capacity.
Leach the potting medium as needed as determined by soluble salts
measurements.
Monitor soluble salts in irrigation water and medium at least month-
ly and twice each week if fertilizer is injected through the irrigation
system.











Table 4. Salt tolerances of selected species.


Species


Good Salt Tolerance


Cortaderia selloana
Euonymusfortunei
Ficus pumila
Ilex vomitoria
Juniperus conferta
Juniperus silicicola
Liriope spp.
Myrica cerifera
Pinus clausa
Quercus virginiana
Sabal palmetto
Serenoa repens


Bambusa spp.
Eriobotryajaponica
Eucalyptus cinerea
Fatsiajaponica
Ficus benjamin
Ligustrum spp.
Platanus occidentalis
Pyracantha spp.
Quercus laurifolia
Quercus nigra
Trachycarpusfortunei


Acer rubrum
Berberis spp.
Camellia spp.
Gardenia jasminoides
Ilex opaca
Rhododendron cvs.
Rosa spp.
Spiraea spp.
Taxodium distichum
Ulmus spp.
Viburnum spp.


Common Name


Pampas grass
Wintercreeper
Creeping fig
Yaupon holly
Shore juniper
Southern red cedar
Lilyturf
Wax myrtle
Sand pine
Live oak
Cabbage palm
Saw palmetto


Moderate Salt Tolerance


Poor Salt Tolerance


Bamboo
Loquat
Eucalyptus
Fatsia
Weeping fig
Privet
Sycamore
Firethorn
Laurel oak
Water oak
Windmill palm


Red maple
Barberry
Camellia
Gardenia
American holly
Azalea
Rose
Spirea
Baldcypress
Elm
Viburnum










Table 5. Salt tolerances ofselected species based on soluble salts


levels in soil.



Species

Abelia grandiflora
Glossy abelia
Bauhinia purpurea
Orchid tree
Bougainvillea spectabilis
Bougainvillea
Buxus microphylla
Boxwood
Callistemon viminalis
Bottlebrush
Carissa grandiflora
Natal plum
Chamaerops humilis
European fan palm
Cotoneaster congestus
Cotoneaster
Dracaena endivisa
Dracaena
Elaeagnus pungens
Silverberry
Euonymusjaponica
Euonymus
Feijoa sellowiana
Pineapple guava
Hedera canariensis
Algerian ivy
Hibiscus rosa-sinensis
Hibiscus
Ilex cornuta 'Burfordii'
Burford holly
Juniperus chinensis
Spreading juniper
Lagerstroemia indica
Crape myrtle
Lantana camera
Lantana
Leucophyllumfrutescens
Texas sage


Salt
Tolerance
Rating

Very Poor

Poor

High

Moderate

Good

High

Good

Very Poor

Good

Moderate

Good

Very Poor

Poor

Poor

Very Poor

Moderate

Very Poor

Moderate

High


dS/ma FOI
Growth
Reduction
>25%

2.3

4-5

>10


LD50b Ref.c

4 1

NAd 3

>10 2


3.6 >10 2

4.0 >15 2


>10

6.5

1.9


>10 2

9 1

4 1


6.0 >10 2

3.8 >10 2

7.5 >10 2


4 2

5 2


2.0 >10 2


2.1

4.0

<4

3.6

>13


6 2

12 2

<4 3

11 2

>15 1


(continued)
a DeciSiemens per meter (dS/m) have the same value as mmhos/cm; values are for
b saturated paste extract.
Level at which half of exposed plants would die.
1) Francois, L.E. and R.A. Clark. 1978.
2) Bernstein, L., L.E. Francois and R.A. Clark. 1972.
d 3) Francois, L.E. 1982.
NA not available.











Table 5. (continued)




Species


Salt
Tolerance
Rating


Ligustrum lucidum Moder
Glossy privet
Liquidambar styraciflua Good
Sweet gum
Liriodendron tulipifera Very P
Tulip poplar
Magnolia grandiflora Poor
Magnolia
Mahonia aquifolium Very P
Oregon grape holly
Nandina domestic Poor
Heavenly bamboo
Nerium oleander Good
Oleander
Photinia x fraseri Very P
Redtop
Pinus halepensis Good
Aleppo pine
Pinus thunbergiana Moder
Japanese black pine
Pittosporum tobira Poor
Pittosporum
Podocarpus macrophyllus Very P
Yew podocarpus
Prunus cerasifera Moder
Cherry plum
Pyracanthafortuneana Moder:
Pyracantha
Raphiolepis indica Moder;
India hawthorn
Rosa var. Grenoble Very P4
Rose
Syzygium paniculatum High
Brush cherry
Thuja orientalis Moder
Oriental arborvitae
Trachelospermumjasminoides High
Confederate jasmine
Viburnum tinus Poor
Laurestinus


ate


dS/ma FOR:

Growth
Reduction


>25%

3.6


b


LD0 b

12


7-8 NA 3


oor



oor


<4 3


4-5 NA 3


4 1

9 2

>15 2

4 1


oor



ate



oor

ate

ate

ate

oor



ate


6.0 >11 1


9 1


2.2 >15 2


2.2

5-6

4.0

4.7

2.2

>13

3.6

>15

3.2


6 1

NA 3

12 2

9 1

4 2


>15

>15


>15 1

9 2


DeciSiemens per meter (dS/m) have the same value as mmhos/cm; values are for
b saturated paste extract.
Level at which half of exposed plants would die.
1) Francois, L.E. and R.A. Clark. 1978.
2) Bernstein, L., L.E. Francois and R.A. Clark. 1972.
3) Francois, L.E. 1982.
NA not available.


Ref.

2











References

Ayers, R.S. and D.W. Westcot. 1976. Water quality for agriculture. Irrigation and
Drainage Paper 29. Food and Agriculture Organization of the United Nations,
Rome, 97 pp.
Barrick, W.E. 1979. Salt tolerant plants for Florida landscapes. Sea Grant
College Program, Report Number 28.
Bernstein, L., L.E. Francois, and R.A. Clark. 1972. Salt tolerance of
ornamental shrubs and ground covers. J. Amer. Soc. Hort. Sci. 97:550-556.
Farnham, D.S., R.F. Hasek, and J.L. Paul. 1985. Water Quality. Its effects on
ornamental plants. Leaflet 2995. Cooperative Extension, Univ. of Calif., Div.
of Agric. and Nat. Res.
Francois, L.E. and R.A. Clark. 1978. Salt tolerance of ornamental shrubs,
trees, and iceplant. J. Amer. Soc. Hort. Sci. 103:280-283.
Francois, L.E, 1982. Salt tolerance of eight ornamental tree species.J. Amer. Soc.
Hort. Sci. 107:66-68.
Hanan, J.J. 1981. Bulk density, porosity, percolation and salinity control in
shallow, freely draining, potting soils. J. Amer. Soc. Hort. Sci. 106:742-746.
Hanan, J. 1982. Salinity III: Handling water supplies to minimize salinity
problems. Research Bulletin 384. Colo. Greenhouse Growers Assn.
Ingram, D.L. and R.W. Henley. 1983. Nursery laboratory development and
operation. Univ. of Fla. Extension Circular 556.
Knox, G.W. and R.J. Black. 1984. Series of Univ. of Fla. fact sheets on salt-
tolerant plants for Florida.
Jurinak, J.J. and R.J. Wagenet. 1981. Fertilization and salinity. In Salinity in
irrigation and water resources, D. Yaron, ed., Marcel Dekker, Inc., New York,
pp. 103-119.
Kerr, G.P. and J.J. Hanan. 1985. Leaching of container media. J. Amer. Soc.
Hort. Sci. 110:474-480.
Kidder, G. and R.D. Rhue. 1983. Interpretation of IFAS water tests. Notes
in Soil Science, No. 10, May 1983. Fla. Coop. Ext. Serv.
Rader, L.F., L.M. White, and C.W. Whittaker. 1943. The salt-index A
measure of the effect of fertilizers on the concentration of the soil solution.
Soil Sci. 55:201-208.
Rhue, R.D., D.L. Ingram, G. Kidder, and J.T. Midcap. 1980. The
greenhouse and potting media test. Notes in Soil Science, No. 3, June 1980.
Fla. Coop. Ext. Serv.
Shalhevet, J. 1984. Management of irrigation with brackish water. In Soil
salinity under irrigation, I. Shainberg andJ. Shalhevet, eds., Springer-Verlag,
Berlin, pp. 298-318
U.S. Salinity Laboratory Staff. 1954. Diagnosis and improvement of saline
and alkali soils. U.S. Dept. Agric. Handbook No. 60, U.S. Govt. Printing
Office, Washington, D.C., 160 pp.




















































This publication was produced at a cost of $1,524.28, or 24 cents per copy, to
inform commercial nursery operators about techniques for managing saline
irrigation water. 8-6. 3M-86



COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE
OF FOOD AND AGRICULTURAL SCIENCES, K.R. Tefertiller, director, in coopera-
tion with the United States Department of Agriculture, publishes this information
to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and is
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is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida,
Gainesville, Florida 32611. Before publicizing this publication, editors should contact this address to
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