POTENTIAL USE OF SALINE WATER FOR IRRIGATING SHELTERBELT PLANTS IN THE ARID REGION

IRRIGATION AND DRAINAGE

Irrig. and Drain. 61: 107–115 (2012)

Published online 16 March 2011 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ird.619

POTENTIAL USE OF SALINE WATER FOR IRRIGATING SHELTERBELT PLANTS INTHE ARID REGION†

MENG HU1, SHAOZHONG KANG1*, JIANHUA ZHANG2, FUSHENG LI3, TAISHENG DU1 AND LING TONG1

1Centre for Agricultural Water Research in China, China Agricultural University, Beijing, China2Department of Biology, Hong Kong Baptist University, Hong Kong, China

3Agricultural College, Guangxi University, Nanning, Guangxi, China

ABSTRACT

In water‐scarcity areas fresh water is allocated with priority to urban areas and agriculture, and ecosystem function benefits areobtained from marginal quality water. Meanwhile the scientific use of saline water needs to quantify the effect of quality andquantity of water on plant growth. A saline irrigation experiment was carried out for two shelterbelt plants, Haloxylonammodendron Bunge and Caragana karshiskii Kom, during 2007–08 in the arid region of northwest China. Three saltconcentrations (3, 7 and 12 g l−1) were considered and irrigation was controlled when soil moisture reached an enacted criticalvalue. Based on the quadratic regressions fitted to the experimental data, the befitting irrigation with the three saltconcentrations for H. ammodendron and C. karshiskii respectively were 381 and 295mm, 290 and 248mm, 213 and 188mm,averaged for two years. Two kinds of plant–water–salinity production functions, quadratic and square root functions wereemployed to describe the relationship between plant biomass increment and quality and quantity of applied saline water. Thefunctions performed well with experimental data and showed a positive marginal productivity with water and a negativemarginal productivity with salt for the frontal area. That could be useful for evaluating low‐quality water exploitation andestimating the growth and yield of shelterbelt plants in connection with forest planning. Copyright © 2011 John Wiley &Sons, Ltd.

key words: saline irrigation; shelterbelt plants; biomass production; Haloxylon ammodendron Bunge; Caragana karshiskii Kom

Received 17 January 2010; Revised 9 November 2010; Accepted 10 November 2010

RÉSUMÉ

Dans les zones où l’eau est rare, l’eau douce est allouée en priorité aux villes et à l’agriculture pendant que les bénéfices issusdes écosystèmes sont obtenus avec de l’eau de qualité médiocre. Alors que l’utilisation de l’eau salée à des fins agricolesrequiert encore d’un point de vue scientifique des besoins de quantifier l’effet de la qualité et la quantité d’eau sur la croissancedes plantes, une expérience d’irrigation avec des eaux saumâtres a été réalisée pour deux plantes utilisées pour faire des brise‐vent, respectivement ammodendron Haloxylon Bunge et Caragana karshiskii Kom. Ce travail a été conduit en 2007–08 dans larégion aride du nord‐ouest de la Chine. Trois concentrations en sels (3, 7 et 12 g l−1) ont été examinées et l’irrigation a étédéclenchée pour une humidité du sol atteignant une valeur critique donnée. Sur la base des régressions quadratiques ajustéesaux données expérimentales, l’irrigation ajustée aux besoins avec les trois concentrations de sel pour ammodendron H. et C.karshiskii étaient respectivement 381 et 295mm, 290 et 248mm, 213 et 188mm, en moyenne pendant deux ans. Deux typesde fonctions de production végétale ont été employés pour décrire la relation entre l’accroissement de la biomasse végétale, ladose d’eau salée et sa qualité. Ces fonctions ont donné un bon ajustement aux données expérimentales et élucidé les valeurstrouvées pour la zone frontale (I.E. les zones directement exposées aux vents dominants). Cela pourrait être utile àl’exploitation des eaux de qualité médiocre et à l’estimation de la croissance et du rendement des plantes brise‐vent dans lecadre de la planification forestière. Copyright © 2011 John Wiley & Sons, Ltd.

mots clés: irrigation saline; plantes brise‐vent; production de biomasse; ammodendron Haloxylon Bunge; Caragana karshiskii Kom

* Correspondence to: Dr. Shaozhong Kang, Centre for Agricultural Water Research in China, China Agricultural University, Beijing 100083, China,Tel: +86‐10‐62737611; Fax: +86‐10‐62737611. E‐mail: [email protected]†L’utilisation de l’eau saumâtre pour irriguer les plantes brise‐vent dans les régions arides.

Copyright © 2011 John Wiley & Sons, Ltd.

108 M. HU ET AL.

INTRODUCTION (37 °50′49″ N, 102 °51′01″ E) of China Agriculture

In arid regions, wind erosion and dust storms do lots of harmto agricultural production and human health. Some winderosion control methods, such as mulching and shelterbelts,have been tested to prevent soil loss, sand dune movementand burial of farmland (Bielders et al., 2000; Kang et al.,2004). Haloxylon ammodendron Bunge (H. ammodendron)and Caragana karshiskii Kom (C. karshiskii) are nativedominant shrubs in northwest China and have beencommonly used for controlling desertification. In manyareas there, rainfall is so limited that the newly plantedshelterbelts cannot work effectively unless supplied withsome saline groundwater. However, indiscriminate exploi-tation of marginal quality water for irrigation in the absenceof proper salt–water–vegetation management practices posesgrave risks to soil health. Because of the scarce precipitationand considerable evapotranspiration, a moderate accumula-tion of salt in shallow soil is unavoidable when saline wateris used for irrigation (Kang et al., 2004; Singh et al., 2009).

To tackle the salt accumulation problem, we shouldestimate the plant yield in response to salinity and waterstress at the same time and find an appropriate irrigationstrategy. There are many studies that have attempted toestimate the separate or combined effect of water andsalinity on plant production functions. Some agriculturalpractices showed that the salinity and amount of salinewater used for irrigation generally exceeded experimentallevels but could result in good agricultural income (Knappand Sadorsky, 2000; Wang et al., 2007). Nevertheless, untilrecently there was little information available in theliterature about the quantitative relationship between annualbiomass increment of shelterbelt plants and the quantity andsalinity of applied water.

The objective of the study was to quantify the effects of saltconcentration and amount of irrigation water on the annualbiomass increment and to develop a plant–water–salinityproduction model that could be used for supplementaryirrigation with poor quality water. And we focused on theplant–water–salinity production functions of plant height,branch length, canopy diameter and frontal area in response tosaline water irrigation for H. ammodendron and C. karshiskiion the basis of experimental data. With the establishment ofsome quantitative relationships, it was possible to determinethe separate and interactive effects of the quantity and salinityof applied water on particular items of growth of the plants.

MATERIALS AND METHODS

Experimental site and design

The experiment was conducted at the Shiyanghe Experi-mental Station for Water‐Saving in Agriculture and Ecology


University, located in the Shiyang River Basin, northwestChina. The area is characterized by a continental temperateclimate with mean annual precipitation of 160mm and openwater evaporation of 2000mm. The mean annual temper-ature is 8 °C and annual accumulated temperature (>0 °C) is3550 °C. Duration of average annual sunshine is over3000 h with 150 frost‐free days.

The experiment started on 1 May 2007 and ended on 21October 2008.Haloxylon ammodendronBungeandCaraganakarshiskiiKomplants that were 2–3 years oldwere used for theexperiment; the one‐year‐old saplings were cultivated in theusual manner, with sufficient soil water and no salt stress. Theexperimental soil was irrigated desert soil (siltigic‐orthicanthrosols), soil texture was loamy sand (sand (2 ~ 0.05mm) –90.1%, silt (0.05 ~ 0.002mm) – 9.1% and clay (≤0.002mm) –0.8%). Soil electrical conductivity was 0.113 dS m−1, organicmatter content 2.1 g kg−1 and pH 7.8. Mean bulk density was1.41 g cm−3, the field capacity (θf) 0.20 cm

3 cm−3 and theinitial salt content 2.3 g kg−1. The concentrations of K+, Na+,Ca2+, Mg2+, Cl‐, CO3

2‐ and SO42‐ were 12, 290, 254, 80, 180,

97 and 1201mg kg−1, respectively.Three salt concentrations were considered, i.e. 3 , 7, 12 g

l−1 or electrical conductivity (ECw) of 3.2, 7.1 and 11.2 dSm−1, respectively. Irrigation was based on soil water deficit,and two kinds of critical soil moisture were considered,0.10 cm3 cm−3 (50%θf) and 0.05 cm3 cm−3 (25%θf). Foreach salt treatment, irrigation started when soil watercontent reached the critical soil moisture, which is shownin Table I for different growing stages, and four replicateswere taken. Soil water content was determined using aportable soil moisture monitoring system (Diviner 2000,Sentek Pty Ltd, Australia), emendated by a gravimetricmethod. The saline water was obtained from a 2 : 2 : 1weight mixture of NaCl, MgSO4 and CaSO4, to representlocal groundwater chemical composition; the main concen-trations of ions in groundwater were Na+ + K+ 129.76mgl−1, Mg2+ 45.71mg l−1, Ca2+ 31.92mg l−1, SO4

2‐ 296.22mgl−1, Cl‐ 150.19mg l−1, HCO3

‐ 41.19mg l−1.

Measurements and methods

Growth parameters were measured every two weeks. Plantheight (H), from ground surface to tip, and annual branchlength (B) were measured using a tape with the accuracy of1mm. Canopy area (Ca) was calculated from digital photos(Guevara‐Escobar et al., 2005; Boese et al., 2008). Thencanopy diameter (Cd) was calculated as follows:

Cd ¼ 2

ffiffiffiffiffiffiCa

π

r(1)

The frontal area (Fa) was calculated as a product of plantheight and canopy diameter (Wolfe and Nickling, 1993):

Irrig. and Drain. 61: 107–115 (2012)

Table I. The minimum critical soil moistures (cm3 cm−3) atdifferent growing stages of H. ammodendron and C. karshiskii in2007 and 2008. Irrigation started when soil moisture reached thesecritical values

Growingstage

Sproutingstage

Twigstage

Vigorousstage

Deciduousstage

Period 22/4 ~ 20/5 21/5 ~ 19/6 20/6 ~ 10/9 11/9 ~ 20/10

Tr0 0.10 0.10 0.10 0.10Tr1 0.05 0.10 0.10 0.10Tr2 0.10 0.05 0.10 0.10Tr3 0.10 0.10 0.05 0.10Tr4 0.10 0.10 0.10 0.05

Each treatment contained three saline concentrations: 3, 7 and 12 g l−1.

Tablebranc

Plant

H. am2007

2008

C. ka2007

2008

In eac

109USE OF SALINE WATER FOR IRRIGATING SHELTERBELT PLANTS

Copy

Fa =H ×Cd (2)

The annual increment was calculated as the differencebetween the beginning and the end of the growing period ina year. Table II shows the quality and quantity of appliedwater, annual increment of plant height, branch length,canopy diameter and frontal area for the Tr0 soil moisturetreatment in the two years.

Plant–water–‐salinity production functions

In this study, the annual increment of plant height, branchlength, canopy diameter and frontal area forH. ammodendronand C. karshiskii were related to two human‐controlledvariables – quantity and quality of the irrigation water (hereonly the salinity component of quality is considered). Other

II. The salinity and amount of irrigation water (Ir), and the annuh length (B), canopy diameter (Cd) and frontal area (Fa) for Tr0 i

Salinity (g l−1) Ir (mm)

modendron3 337 a7 305 a12 250 b3 389 a7 295 b12 190 c

rshiskii3 280 a7 216 b12 195 b3 293 a7 284 a12 187 b

h year, treatments with the same letter were not significantly different at P

right © 2011 John Wiley & Sons, Ltd.

factors that may affect biomass increment were consideredconstant.

Based on previous studies (Dinar et al., 1991; Kaushalet al., 1985; Singh et al., 2009) on the development of salt–water production functions, the analysis here was undertakenusing quadratic and square root functional forms. Thequadratic forms imply that (while holding all other variablesconstant) an increase in the level of one of the human‐controlled variables results in a change (increase or decrease –depending on the relationship) in the level of the dependentvariable up to a certain point. Any further increase in its levelresults in an opposite response (decrease or increase,respectively) in the dependent variable level. The square rootfunction is similar to the quadratic. It imposes nonzeroelasticity of substitution among factors with no growth plateauand diminishing marginal productivity, but allows for sharpercurvature near the maximum and a less rapid decrease in totalproduct than the quadratic (Llewelyn and Featherstone, 1997).

The implicit relationships to be estimated were:

al incn 200

H (cm

57.7550.1745.4968.0558.6661.86

62.6534.3328.5079.3953.7531.52

< 0.05

Bio= a0 + a1Ir + a2Ir2 + a3C+ a4C

2 + a5IrC (3)

Bio= b0 + b1Ir + b2Ir0.5 + b3C+ b4C

0.5 + b5Ir0.5C0.5 (4)

where the annual biomass increment (Bio) was detailed byplant height (H), branch length (B), canopy diameter (Cd)and frontal area (Fa). The amount of irrigation water (Ir)and its salt concentration (C) were indicated in millimeters(mm) and grams per liter (g l−1).

All data were statistically analyzed and ANOVA analyseswere performed using the SAS System for Windows V8(SAS Institute Inc., USA).

rement of H. ammodendron and C. karshiskii in height (H),7 and 2008

) B (cm) Cd (cm) Fa (cm2)

a 49.48 a 61.42 a 6 890 ab 44.60 ab 55.09 ab 5 587 bb 41.60 b 47.38 b 6 317 aa 68.10 a 97.78 a 13 944 ab 57.30 b 94.57 a 12 456 abb 50.65 b 85.20 b 11 632 b

a 39.10 a 36.86 a 2 167 ab 26.00 b 24.44 b 1 619 abb 24.70 b 22.95 b 1 368 ba 65.45 a 73.99 a 9 674 ab 35.65 b 45.28 b 5 016 bc 22.20 c 44.10 b 3 000 c

.

Irrig. and Drain. 61: 107–115 (2012)

110 M. HU ET AL.

RESULTS AND DISCUSSION

Annual biomass under different saline irrigation

The annual growth of H. ammodendron and C. karshiskiiin plant height, branch length, canopy diameter and frontalarea during the two years (Table II, Tr0 presented) reflectedthe effects of various amounts of irrigation water and theirsalt concentration. Response of their annual growth wassimilar for various qualities and quantities of irrigationwater. Compared to the plants irrigated with salt concen-tration of 3 g l−1, the amount of irrigation water with saltconcentration of 12 g l−1 applied to H. ammodendron and C.karshiskii reduced the annual growth by 26 and 30%(2007), 51 and 36% (2008), respectively. Meanwhile thereductions for the annual growth of H. ammodendron andC. karshiskii irrigated with salt concentration of 12 g l−1inplant height, branch length, canopy diameter and frontalarea were 21 and 55, 16 and 37, 23 and 38, 8 and 37% in2007, 9 and 60, 26 and 66, 13 and 40, 17 and 69% in 2008,respectively. From the aforementioned statistical data, thegrowth reduction of C. karshiskii was significantly greaterthan that of H. ammodendron when the salinity of irrigationwater increased from 3 to 12 g l−1, and it could be concludedthat the annual growth of C. karshiskii was more sensitive tosalt stress than H. ammodendron. And moreover, thepercentages of reduction for both H. ammodendron andC. karshiskii were greater in 2008 than in 2007, with theimpact of quite different precipitation in the growing seasonof the two years, 177mm in 2007 and 89mm in 2008. Themonsoon rains concentrated in a shorter period (June–September) not only displaced the surface salts, but thebetter quality rainwater carried over in the soil profile wasbeneficially utilized by plants. Thus Minhas (1996) declaredthat the concept of leaching requirements might hold forarid but not for semiarid monsoonal climates. Recently,Letey and Feng (2007) and Singh et al. (2009) haveindicated that predictions assuming steady‐state conditionsgenerally overestimate the negative consequences ofirrigating with saline waters. Thus, it was advocated thatthe irrigation guideline for saline water be revised toaccount for the dynamic interactions between the soil–water–plant matrix and also the possible contributions ofrainfall in decreasing the impact of saline irrigation. Theseanalytical procedures were also undertaken for othertreatments (Tr1, Tr2, Tr3, Tr4), and they had similarresponses (results not shown).

Table II shows that water application declined with highersalt concentration. From earlier work in salinity managementand salinity economics for crops, befitting water applicationgenerally increased at first with the increase of saltconcentration, expecting higher leaching fractions tocounteract the salt effects, and then started to decrease dueto reduced evapotranspiration (ET) from salt stress (Letey


and Feng, 2007; Minhas, 1996). However, H. ammodendronand C. karshiskii were perennial shrubs, which can endurecertain levels of salt stress without a need for leaching incontrast to nonhalophyte crops, and our results were acombination of the moisture‐deficit only irrigation rule andreduced ET.

The annual growth response functions with irrigationwater (Ir) for three salt concentrations for the two years areplotted in Figure 1. The maximum annual biomasses werehigher with salt concentration of 3 g/l than 7 g/l and 12 g/l.And the slope of the line, which described the biomassesincreased with quantities of irrigation water, were higher withsalt concentration of 3 g/l than 7 g/l and 12 g/l. From thequadratic regressions fitted to the experimental data for eachyear, the estimated amount of irrigation water reflected thepotential of water consumption when the annual incrementreached the maximum (Table III). Averaged for plant height,branch length, canopy diameter and frontal area, the befittingamount of 3, 7 and 12 g l−1 saline irrigation water for2‐year‐old H. ammodendron and C. karshiskii was 357and 269, 304 and 213, 227 and 191mm, respectively.Meanwhile, for 3‐year‐oldH. ammodendron andC. karshiskiiwith saline concentration of 3, 7 and 12 g l−1, the befittingamount of irrigation water was 405 and 320, 276 and 283, 199and 185mm, respectively. Thus there was an average decreaseof 36 and 29% in the befitting amounts of irrigation water for2‐year‐old H. ammodendron and C. karshiskii when saltconcentration increased from 3 to 12 g l−1, and the decreasesfor 3‐year‐oldH. ammodendron andC. karshiskiiwere 51 and42%, respectively.

Quadratic and square root model as functions ofwater quantity and quality

To be more comparable and to eliminate the influence ofclimate and soil, the annual biomass increments weregeneralized on a relative basis (ReH, Reb, ReCd, ReFa) witha value of 1 representing maximum biomass from Tr0‐3 g l−1

treatment in the two years, respectively; and irrigation water(Ir) had been scaled to E601‐open pan evaporation (OPE) inthe growing periods (709mm in 2007 and 966mm in 2008).

The results of the regression analyses for theH. ammodendron and C. karshiskii annual increments arepresented in Table IV. The regressions explained a largepercentage (more than 90%) of the observed variations inthe annual biomass increment. Levels of the F‐statistic(a test for the overall significance of a multiple regression;Greene, 2003) indicated that the estimated regressionssignificantly (p < 0.01) explained the variations in the levelsof the various dependent variables.

These functions (Table IV) also indicated that the annualbiomass increment (plant height, branch length, canopydiameter and frontal area) of H. ammodendron and

Irrig. and Drain. 61: 107–115 (2012)

H3= -0.0017Ir 2 + 1.32Ir - 185 R2= 0.892

H7= -0.008Ir 2 + 4.37Ir - 533 R2= 0.906

H12= -0.0088Ir 2 + 3.35Ir - 256 R2= 0.657

0 100 200 300 400B3= -0.0007Ir 2 + 0.62Ir - 76.04 R2= 0.962

B7= -0.009Ir 2 + 4.95Ir - 620 R2= 0.767

B12= -0.0044Ir 2 + 1.80Ir - 129 R2= 0.664

0 100 200 300 400

H3= -0.0050Ir 2 + 3.46Ir - 539 R2= 0.915

H7= -0.0023Ir 2 + 1.46Ir - 187 R2= 0.667

H12= -0.0046Ir 2 + 2.11Ir - 197 R2= 0.784

0

20

40

60

80

100

0 100 200 300

Hei

ght

(cm

)3g/L

7g/L

12g/L

B3= -0.0019Ir 2 + 1.46Ir - 231 R2= 0.737

B7= -0.0038Ir 2 + 2.34Ir - 315 R2= 0.765

B12= -0.0078Ir 2 + 3.43Ir - 327 R2= 0.848

0

20

40

60

80

0 100 200 300

Bra

nch

len

gth

(cm

)

Cd3= -0.0028Ir 2 + 1.96Ir - 280 R2= 0.823

Cd7= -0.0063Ir 2 + 3.76Ir - 505 R2= 0.905

Cd12= -0.0061Ir 2 + 2.73Ir - 252 R2= 0.872

0

20

40

60

80

100

0 100 200 300

Can

opy

dia

met

er (c

m)

Fa12= -0.60Ir 2 + 284Ir - 27531 R2= 0.786

Fa7= -0.66Ir 2 + 384Ir - 50790 R2= 0.909

Fa3= -0.54Ir 2 + 377Ir - 58777 R2= 0.861

0

2000

4000

6000

8000

10000

12000

14000

0

Fro

nta

l are

a (c

m2 )

Irrigation (mm)

2007

2007

2007

2007

2008

2008

2008

2008

Cd3= -0.0017Ir 2 + 1.28Ir - 142 R2= 0.928

Cd7= -0.0095Ir 2 + 5.33Ir - 655 R2= 0.611

Cd12= -0.0059Ir 2 + 2.38Ir - 151 R2= 0.700

0 100 200 300 400

Fa3= -0.14Ir 2 + 116Ir - 10574 R2= 0.970

Fa7= -1.48Ir 2 + 820Ir - 100751 R2= 0.958

Fa12= -1.02Ir 2 + 406Ir - 28730 R2= 0.802

0 400

( )

300200100 300200100

Figure 1. The annual increment of height (Hi, i = 3, 7, 12, represented salt concentrations), branch length (Bi), canopy diameter (Cdi) and frontal area (Fai) asfunctions of irrigation water (Ir) for H. ammodendron (I) and C. karshiskii (II) under three salt concentrations of irrigation water in 2007 and 2008


C. karshiskii increased asymptotically with water applied upto critical values defined by the salt concentration.Moreover, the rate of their increases with Ir/OPE andthe maximum possible biomasses were also defined bysalt concentration of irrigation water. Since the higherquantities of saline water mean more input of salts, theiraddition resulted in higher salts in the root zone. Thus, thesimultaneous build‐up of salinity seemed to have obscured

Copyright © 2011 John Wiley & Sons, Ltd. Irrig. and Drain. 61: 107–115 (2012

the possible benefits accruing with higher quantities ofsaline waters (Singh et al., 2009).

To our knowledge about the soil–water–plant relation,while holding other variables constant, plant yield increasedas water quantity increase beyond some minimum value,and the yield decreased as the initial level of soil salinity inthe root zone and as the increased salt concentration in theirrigation water went beyond some minimum values. In the

)

H3= -0.013Ir 2 + 6.94Ir - 843 R2= 0.867

H7= -0.0023Ir 2 + 1.05Ir - 85.96 R2= 0.893

H12= -0.006Ir 2 + 2.30Ir - 191 R2= 0.920

0

20

40

60

80

100

0 100 200

Hei

ght

(cm

)3g/L

7g/L

12g/L

H3= -0.002Ir 2 + 1.47Ir - 184 R2= 0.945

H7= -0.0028Ir 2 + 1.64Ir - 186 R2= 0.893

H12= -0.0018Ir 2 + 0.73Ir - 43.08

R2= 0.875

0 100 200 300B3= -0.0045Ir 2 + 2.75Ir - 352 R2= 0.866

B7= -0.0033Ir 2 + 1.82Ir - 217 R2= 0.833

B12= -0.0052Ir 2 + 1.68Ir - 111

R2= 0.886

0 100 200 300

B3= -0.0058Ir 2 + 3.01Ir - 3527 R2= 0.887

B7= -0.0027Ir 2 + 1.08Ir - 81.98 R2= 0.914

B12= -0.0071Ir 2 + 2.67Ir - 227 R2= 0.950

0

20

40

60

80

0 100 200

Bra

nch

leng

th (

cm)

Cd3= -0.010Ir 2 + 5.22Ir - 635 R2= 0.895

Cd7= -0.0045Ir 2 + 1.86Ir - 166 R2= 0.979

Cd12= -0.0047Ir 2 + 1.86Ir - 161 R2= 0.909

0

20

40

60

80

0 100 200

Can

opy

dia

met

er (

cm) Cd3= -0.0049Ir 2 + 2.98Ir - 381 R2= 0.947

Cd7= -0.0037Ir 2 + 2.02Ir - 232 R2= 0.848

Cd12= -0.0022Ir 2 + 0.90Ir - 48.29

R2= 0.948

0 100 200 300

2007

2007

20072008

2008

2008

Fa3= -0.23Ir 2 + 133Ir - 16797 R2= 0.826

Fa7= -0.19Ir 2 + 82.64Ir - 7156 R2= 0.935

Fa12= -0.70Ir 2 + 259Ir - 22516 R2= 0.949

0

2000

4000

6000

8000

0 200

Fro

nta

l are

a (c

m2 )

Irrigation (mm)

2007

( )

Fa3= -0.88Ir 2 + 534Ir - 70854

R2= 0.916

Fa7= -0.31Ir 2 + 179Ir - 20955

R2 = 0.871

Fa12= -0.34Ir 2 + 116Ir - 7068

R2= 0.848

0 300

2008

100 200100

Figure 1. Continued

112 M. HU ET AL.

same way, the final level of root zone soil salinity decreasedwith increasing irrigation water quantities (except for apossible increase where relatively insufficient water quan-tities were applied), decreasing initial level of soil salinityand salt concentration of the irrigation water. For the case ofplant biomass and water application, there was a positiveeffect of further increases in water application on biomassproduction after some minimum application, but its effectbecame smaller as more water was applied, which was


usually defined as the positive‐diminishing marginal‐productivity zone on the production surface.

Eventually, however, as more water was irrigated it maycause aeration and salinity problems (in the case of over‐irrigation and if drainage was restricted) and loss of yield (thezone where this occurs was characterized by a negativemarginal productivity). The more Na+ ions were adsorbed,the higher the sodium adsorption ratio (SAR) of irrigationwater (van de Graaff and Patterson, 2001). If continually

Irrig. and Drain. 61: 107–115 (2012)

able III. The quantity of irrigation water (Ir mm) calculated whene annual increment of H. ammodendron and C. karshiskii ineight (H cm), branch length (B cm), canopy diameter (Cd cm) androntal area (Fa cm2) reached the maximum under three salineoncentrations based on the quadratic regressions fitted to thexperimental data in 2007 and 2008

Salinity(g l−1)

H B Cd Fa

. ammodendron007 3 346 384 350 349

7 317 308 298 29112 229 220 224 237

008 3 388 443 376 4147 273 275 281 27712 190 205 202 199

. karshiskii007 3 267 259 261 289

7 228 200 207 21712 192 188 198 185

008 3 368 306 304 3037 293 276 273 28912 203 162 205 171


Tthhfce

H2

2

C2

2

irrigated with water rich in Na+ ions, the adsorbedmultivalent ions (such as Ca2+, Al3+, Fe3+) in the soil wouldgradually be replaced by adsorbed Na+. When this happened,the exchangeable sodium percentage (ESP), and hence thesodicity, increased. Monovalent ions like sodium were lesseffective in neutralizing the charge on the colloid andpreventing swelling and dispersion than bivalent or trivalentions, thus individual colloid particles continued to repel eachother and stay in solution, causing deterioration of the soilhydraulic properties (Brady, 1990; Bronick and Lal, 2005).

Table IV. The quadratic and square root functions of relative annual ibranch length (ReB), canopy diameter (ReCd) and frontal area (ReFa) u

Plant Functions

H. ammodendron ReH= 1.63Ir/OPE‐0.22(Ir/OPE)2+ 0.094C‐0.ReB= 2.22Ir/OPE‐1.29(Ir/OPE)2+ 0.029C‐0.ReCd= 2.97Ir/OPE‐1.96(Ir/OPE)2+ 0.068C‐0ReFa= 3.04Ir/OPE‐2.72(Ir/OPE)2+ 0.035C‐0ReH= 1.99Ir/OPE‐0.85(Ir/OPE)0.5‐0.083C+ 0ReB= 0.43Ir/OPE + 0.76(Ir/OPE)0.5 + 0.0017CReCd= 0.92Ir/OPE+ 0.73(Ir/OPE)0.5‐0.035CReFa= ‐0.49Ir/OPE+1.59(Ir/OPE)0.5‐0.003C+

C. karshiskii ReH= 3.45Ir/OPE‐3.16(Ir/OPE)2‐0.021C + 0.ReB= 4.23Ir/OPE‐3.58(Ir/OPE)2‐0.070C+ 0.ReCd= 2.87Ir/OPE‐0.71(Ir/OPE)2‐0.027C+ 0ReFa= 2.75Ir/OPE‐2.32(Ir/OPE)2‐0.022C+ 0ReH= 0.08Ir/OPE+ 1.56(Ir/OPE)0.5+ 0.010CReB= ‐0.39Ir/OPE+ 2.91(Ir/OPE)0.5+ 0.098CReCd= 1.34Ir/OPE+ 1.47(Ir/OPE)0.5+ 0.081CReFa= 0.0031Ir/OPE + 0.85(Ir/OPE)0.5‐0.008

Notes: 1. ** significance level P< 0.01. 2. The unit of salt concentration (C) wa


Such behavior had been observed in many biologicalexperiments (Dinar et al., 1991; Singh et al., 2009) and wasalso explained by the classical theory of production (Russelland Wilkinson, 1979). This relationship had also beenfound by Letey and Dinar (1986) and Dinar and Knapp(1986) to work well for relating yield and water quality andquantity, and for relating the final level of soil salinity andwater quality and quantity. Economic theory assumed thatthe rational producer, if free to choose, would not producein the zone of negative marginal productivity.

Frontal area

The frontal area was the above‐ground barrier againststraightforward wind blow, and was influenced by theinteraction of quantity and quality of irrigation water(Table IV). The Ir/OPE derivative of quadratic functionsin Table IV indicated that ReFa of H. ammodendron andC. karshiskii increased asymptotically with applied water upto the Ir/OPE ratio of 0.56 and 0.59, respectively. However,the rate of increase in ReFa with Ir/OPE and the maximumpossible frontal area were defined by the salt concentration(C) of the irrigation water, the symmetry for Ir/OPE had anegative correlation with C, and the symmetry ofH. ammodendron decreased more quickly with the increaseof C than that of C. karshiskii, which was consistent with theforegoing data (Table III). Similarly, the C derivative of thequadratic function reflected the reducing rate of ReFa withC. Caragana karshiskii had a negative derivative, and itsfrontal area decreased absolutely with the increase of C;meanwhile the derivative of H. ammodendron was close tozero in the experimental levels of C and Ir/OPE ratio, and its

ncrement of H. ammodendron and C. karshiskii in height (ReH)nder saline water irrigation in 2007 and 2008

R2 F‐value

0039C2‐0.11(Ir/OPE)C 0.925 57.10**0006C2‐0.03(Ir/OPE)C 0.931 62.42**.0017C2‐0.18(Ir/OPE)C 0.944 77.05**.0005C2‐0.10(Ir/OPE)C 0.922 54.49**.57C0.5‐0.26(Ir/OPE)0.5C0.5 0.927 58.15**+ 0.04C0.5‐0.02(Ir/OPE)0.5C0.5 0.932 63.44**

+ 0.39C0.5‐0.52(Ir/OPE)0.5C0.5 0.947 81.35**0.10C0.5‐0.20(Ir/OPE)0.5C0.5 0.926 57.18**0009C2‐0.04(Ir/OPE)C 0.945 78.94**0042C2‐0.03(Ir/OPE)C 0.965 126.79**.0031C2‐0.074(Ir/OPE)C 0.928 58.84**.0017C2‐0.074(Ir/OPE)C 0.919 52.25**‐0.12C0.5‐0.05(Ir/OPE)0.5C0.5 0.945 79.34**‐0.52C0.5‐0.12(Ir/OPE)0.5C0.5 0.965 126.82**‐0.24C0.5‐0.39(Ir/OPE)0.5C0.5 0.928 58.81**C‐0.15C0.5+ 0.39(Ir/OPE)0.5C0.5 0.919 51.83**

s g l−1.

Irrig. and Drain. 61: 107–115 (2012

,

)

114 M. HU ET AL.

frontal area decreased insignificantly with C (Table II).Salinity slightly affected the growth of H. ammodendron

compared to that of C. karshiskii when irrigated with salinewater, indicating that H. ammodendron had stronger saltresistance. Some studies also indicated thatH. ammodendronexhibited halophyte characteristics, stem succulence andhaving a salt gland (Dong et al., 2003; Xu et al., 1999).Leaf or stem succulence (i.e. high water content) for theregulation of internal ion concentrations and accumulatingions for osmoregulation was an adaptative feature to adaptto saline environments for many halophytes in the familyChenopodiaceae, allowing them have optimal growth inthe presence of salt (Song et al., 2006; Tester andDavenport, 2003). Short and Colmer (1999) reported thatsucculence in Halosarcia pergranulata subsp. pergranulataincreased slightly as the NaCl concentration rose from 10 to400mol m−3. Patel and Pandey (2007) reported the growth ofCassia montana was stimulated by salt and optimum growthwas at 7.9 dS m−1 of salinity, due to its osmotic adjustmentand increased leaf area. That was good news for theestablishment of a shelterbelt which held some marginalquality water.

CONCLUSIONS

During the two‐year experiments with the twomost prominentshelterbelt shrubs, H. ammodendron and C. karshiskii, wefound that H. ammodendron had a stronger salt tolerance thanC. karshiskii. The possible maximum biomasses as well as therate of increase with increased quantities of applied water wereclearly defined by the salinity. Rainfall with less saltconcentration was likely to obviate the disadvantageouseffects of salt input along with irrigation water.

The quadratic and square root functions can describe thestatistically significant separate and interactive effects of inputwater quality and quantity on plant height, branch length,canopy diameter and frontal area of bothH. ammodendron andC. karshiskii. The frontal area of C. karshiskii increased withamount of irrigation water but decreased with amount of saltresulting from irrigation water; however, H. ammodendrondid not significantly decrease with salt concentration when itwas less than 12 g l−1. Based on the quadratic regressions fittedto the experimental data, the befitting quantities of irrigationwater with different salt concentrations for the two shrubs canbe generated. These values should provide some guidelines inthe management of wind shelterbelt vegetation and salinewater resources.

ACKNOWLEDGEMENTS

We are grateful for the research grants from the NationalNatural Science Foundation of China (40771034,50809072), the National High Technology Research and


Development Program of China (863 Program,2006AA100203), Program 200801104‐2 supported by theMinistry of Water Resources of China and the Hong KongResearch Grants Council (HKBU 262708).

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POTENTIAL USE OF SALINE WATER FOR IRRIGATING SHELTERBELT PLANTS IN THE ARID REGION