sw—soil and water: effect of water salinity and irrigation technology on yield and quality of...

Biosystems Engineering (2002) 81 (2), 237}247doi:10.1006/bioe.2001.0038, available online at http://www.idealibrary.com onSW*Soil and Water

E!ect of Water Salinity and Irrigation Technology on Yield and Quality of Pears

Gideon Oron��; Yoel DeMalach�; Leonid Gillerman��; Itsik David�; Susan Lurie�

�The Institute for Desert Research, Ben-Gurion University of the Negev, Kiryat Sde-Boker 84990, Israel�Department for Industrial Engineering and Management, Beer-Sheva 84105, Israel; e-mail of corresponding author: [email protected]

�Ramat Negev Agricultural Field Station, Doar-Naa Chalutza 85415, Israel; e-mail: [email protected]�Agricultural Research Organization, The Volcani Center, The Institute for Technology and Storage of Agricultural Products,

Bet-Dagan 50250, Israel; e-mail: [email protected]

(Received 8 November 2000; accepted in revised form 9 November 2001; published online 28 January 2002)

The scarcity of fresh water in arid regions makes saline water a valuable alternative water source for irrigation.Saline water has an agricultural potential but it is necessary to develop special management procedures toobtain maximum yield and high product quality.Field experiments, which were carried out in a pear orchard, demonstrate that the choice of irrigation method

is very important for saline water irrigation. It was shown that by using saline water through subsurface dripirrigation (SDI) reasonable yields can be obtained. Moisture distribution under SDI is better adjusted to theroot pattern in order to counteract osmotic e!ects of the soil salinity in comparison to conventional dripirrigation. Saline water use, particularly through SDI, tends to increase sugar content and acidity of the fruitssimultaneously, along with decreasing fouling phases.

� 2002 Silsoe Research Institute

1. Introduction

Most areas in the state of Israel, which is located in anarid zone, are characterized by scarce water resources.High-quality water resources available for use in agricul-ture are decreasing due to growth of population andincreasing of living standards. It has led to use low-quality waters (e.g. treated wastewater or saline water) inagriculture simultaneously with implementation of themost e$cient application technologies.In the Northern Negev of Israel, there is an aquifer that

contains several hundred billion m� of saline water (Issar&Nativ, 1988). The salinity of the water varies in the rangeof electrical conductivity (EC) between 4 and 7dSm��

(Tscheschke et al., 1974; Twersky et al., 1975) while freshwater is commonly below 2dSm��. Until recently, thiswater was not actually used for agricultural irrigation inIsrael. However, fresh water resources are becoming scarceand have to be replaced with unconventional water sour-ces, in particular with saline water (Oron, 1993).Utilization of saline water for irrigation is associated

with salt accumulation in the soil, which might be harm-ful to plants, and diminishing yields. The salt e!ects on

1537-5110/02/020237#11 $35.00/0 23

physiological process result from lowering of the soilwater potential and the toxicity of speci"c ions (Bresleret al., 1982). On the other hand, it has been repeatedlyreported that non-toxic highly saline water has an agri-cultural potential. If irrigation can be managed in a waywhich provides a high soil moisture content and, conse-quently, high soil water potential within the whole rootzone, the osmotic e!ects will be damped (Bernstein& Fancois, 1973; Tsheschke et al., 1974; Michelakis et al.,1993). Moreover, when saline water is skillfully used forirrigation, it can be bene"cial for agricultural production,particularly in orchards (Ho!man et al., 1986). Salinewater use for agricultural production o!ers several addi-tional bene"ts:

(1) re-use (instead of disposal as with fresh water) duringthe entire year, with minimal environmental risk ofgroundwater deterioration (Oron, 1993); and

(2) a premium market price for the fruits and vegetableproducts because of a high content of total solublesolids and an extended shelf life, due to the adapta-tion of the plant to the stressful growing conditions(Mizrahi & Pasternak, 1985).

7 � 2002 Silsoe Research Institute

G. ORON E¹ A¸ .238

Applying saline water continuously through drip irri-gation systems might result in salt accumulation close tothe soil surface (Bresler et al., 1982; Ayers & Westcot,1985; Pasternak & DeMalach, 1987; DeMalach &Pasternak, 1993; Oron et al., 1995). Under conventionalsurface drip irrigation (DI), during precipitation and uni-form distribution on the soil surface, the salts that areaccumulated close to the soil surface can migrate down-wards and reach the main root zone. This process mayinhibit water and nutrient uptake, consequently causingadverse e!ects on the crop growth and yield (Hanson& Bendixen, 1995). In order to o!-set the osmotic shockimposed on the crop by the leached salts (surface dripirrigation systems during precipitation), a practical solu-tion was proposed. It is a common practice in arid regionsto maintain equilibrium conditions in the soil, and to keepthe salt front in a permanent position in the periphery ofthe root zone by continuing drip irrigation during theperiods of precipitation (Hanson, 1995). The water in"l-trating into the soil during precipitation is not shifting thesalt front due to the opposing e!ect of the water emittingfrom the subsurface water source (the emitter).Alternatively, Oron et al. (1990, 1991) and Phene

(1993) have suggested that this problem can be overcomeby applying saline water through a subsurface drip irriga-tion (SDI) system. It is anticipated that under SDI, thesalt front is driven deeper into the soil bulk medium andto the periphery of the root zone, thus minimizing therisk of damaging the plants. Likewise, Phene & Phene(1987) reported that since the SDI is installed below thesoil surface, a properly managed system (primarily byfrequent irrigation) is advantageous in comparison withconventional DI systems, especially with regard to e$-cient water and nutrient utilization, salinity managementand deep percolation.The purpose of this study was to evaluate the e!ect of

di!erent water qualities and drip irrigation systems (DIand SDI with emitters located at variable depths in thesoil) use on the yield and fruit quality. The possibility ofusing saline water through SDI for fruit tree irrigation isbeing examined in the "eld in a pear orchard.

2. Materials and methods

2.1. ¹he experimental site

The experiment was being conducted at the RamatNegev Agro-Research Centre, located about 35 kmsouth-west of the City of Beer-Sheva, Israel (longitude34341�03�� and latitude 31305�00��). The mean annual rain-fall in the region is about 102mm spread over four rainymonths (November through February). Mean maximalambient temperature reaches about 34)93C during July

and August and mean minimal temperature is close to5)43C during January. The relative humidity during sum-mer months varies from 20% to 30%. Annual class &A'pan evaporation is about 2294mm. The experimentalsoil is a light loess (sandy loam), consisting of 51)4% silt,8)8% clay and 39)8% sand. The moisture content at "eldcapacity is approximately 24% by volume.

2.2. ¹he experimental layout

The possibility of using SDI for saline water applica-tion was examined in a pear orchard. Spadona pear(Pyrus spp.) trees, arranged in six rows, were planted in1982 at a row spacing of 5m and inter-row spacing of2)5m. One drip lateral served every pear row with emit-ters spaced 75 cm apart and having a discharge of 4 lh��.Prior to commencement of the experiment (from 1982until 1992) the trees were irrigated by a conventionalonsurface DI system. Current research began in March1993 with the following treatments:

(1) three rows were irrigated with saline water having anEC of about 4)4 dSm��; and

(2) three control rows were irrigated with fresh high-quality tap water with an electrical conductivity of1)2 dSm��.

Each row consisted of three treatments with two repli-cations: (i) surface DI; (ii) SDI with emitters located ata soil depth of 30 cm; and, (iii) SDI with emitters locatedat 60 cm soil depth. Only the central row out of the threewas examined in each replication. Although a "eldexperiment consisting of two replications only might leadto false interpretation of the results, it was decided toconduct the research in an available pear plantationdespite the reduced number of replications, in order toobtain preparatory information which would lead toa more detailed and well organized experiment.The SDI was maintained by connecting small diameter

(4mm diameter) microtubes (&spaghetti') to the on-lineemitters and inserting them into the soil up to the desig-nated depths of 30 and 60 cm. This arrangement wasimplemented in order to avoid a signi"cant intrusion intothe tree root zone and, consequently, to minimize poten-tial damage to the crop by converting the conventionalsurface DI system to a SDI system. Special attention waspaid during the initial research phases in order to preventwater up-#ow in the &chimney' into which each &spaghetti'tube was inserted.

2.3. =ater application

During 3 years of experimentation, the crop receivedequal volumes of irrigation water amounting to

Fig. 1. Monthly amounts of water applied for irrigation of thepear orchard

00 10 20 30 40

00 000

Soil moisture content, % v/v0 10 20 30 40

Soil moisture content, % v/v

239EFFECT OF WATER SALINITY AND IRRIGATION TECHNOLOGY ON PEARS

approximately 900mm (Fig. 1). Water application com-menced towards the end of February and continued upto October. During the peak consumption period (Mayto July), the irrigation interval was 3}4 days in order tomaintain adequate soil moisture in the e!ective crop rootzone. During the remaining months, the irrigation inter-val was seven days. Irrigation scheduling was based onClass &A' pan evaporation measurements, multiplied bythe locally developed crop coe$cients for pear planta-tions (Table 1; DeMalach & Pasternak, 1993).

2.4. Moisture and salinity monitoring in the soil

Soil moisture and salinity distribution in the soil atdi!erent depths in every treatment was monitored peri-odically, following standard procedures. Soil moisturecontent was measured by a standard gravimetericmethod. Soil salinity was determined by a commonmethod of measuring the electrical conductivity (EC) ofthe saturated extracts. During the peak consumptionperiod (June to August) soil moisture and salinity weremeasured once a month.Soil samples for moisture and salinity assessment were

taken at 0, 20, 40, 60 and 80 cm radially from the lateral

Table 1Crop coe7cient Kc used for pear orchard irrigation

Month K�

February 0)20March 0)20April 0)35May 0)55June 0)65July 0)70August 0)50September 0)35October 0)20

on both sides near emitter and in the middle between twoadjacent emitters. The corresponding depths were 0}10,20}30, 60}70 and 90}100 cm. A similar monitoringlayout was used for the soil sampling at half the distancebetween the emitters.

2.5. Pear yield and fruit quality monitoring

The pears were hand harvested for the yield assessmentduring July of the years 1993, 1994 and 1995. The pearyields were measured by weighing the fruits immediatelyafter harvest in the "eld. The signi"cance of the yielddi!erences was determined by one-tailed &t'-test at 95%signi"cance level. The quality of the fruits was furthermonitored for the harvests of 28, 26 and 23 July of 1994,1995 and 1996, respectively (the pear quality was notassessed for the 1993 harvest since the testing equipmentbecame available only for the 1994 harvest; the 1996harvest was towards the end of the experiment withrelatively poor results, hence it was decided not to in-clude the yield in the analysis, to characterize the fruitquality).For fruit quality parameters determination, three

samples of ten fruits per treatment were sampled at eachobservation time for the 1994 and 1995 harvest (only onesample of 15 fruits was taken for the 1996 harvest). Pear"rmness was measured on two peeled sides of each fruitusing a penetrometer with an 8 mm tip. Soluble solidscontent (SSC) (a measure for sugar content) and titrat-able acidity (TA) were measured by pooling a slice fromeach fruit in the replicate and juicing them. The solublesolids were measured with refractometer. The TA wasdetermined by taking 2 ml of the juice, titrating it to pH

(b)(a) (b)

DI DI

(a)

SDI 60 cmdeep

SDI 30 cmdeep

SDI 60 cmdeep

SDI 30 cmdeep

200

20

40

60

180

100

80

120

140

160

Soil

dept

h, c

m

200

20

40

60

180

100

80

120

140

160

Soil

dept

h, c

m

Fig. 2. Soil Moisture proxles below the emitter for on-surface(DI) and subsurface drip irrigation (SDI) for: (a) fresh waterirrigation; and (b) saline water; ( ), anticipated optimum range

of soil moisture content

Fig. 3. Soil moisture (% v/v) distribution in the pear orchard subject to diwerent depths of emitter location and saline water application,18 June 1994, 10 h after irrigation termination; (a) onsurface drip irrigation; (b) subsurface drip irrigation (emitter depth 30 cm);

(c) subsurface drip irrigation (emitter depth 60 cm); ( ), emitter location

020406080

100120140160180200

0 2 4 6 10 11 12 14Soil electrical conductivity, dS m−1

020406080

100120140160180200

Soil

dept

h, c

m

Soil

dept

h, c

m

Soil electrical conductivity, dS m−1

(a) (b)

DISDI 30 cm

deep

SDI 60 cmdeep

DI

SDI 30 cmdeep

SDI 60 cmdeep

0 1 2 3 4 5 6

Fig. 4. Soil salinity proxles below the emitter subject to diwerentwater qualities and depths of emitter locations: (a) fresh water;and (b) saline water; DI, surface drip irrigation; SDI 30, subsur-face drip irrigation at a depth of 30 cm; SDI 60, subsurface drip

irrigation at a depth of 60 cm

G. ORON E¹ A¸ .240

8)2 with 0)1 NaOH and expressing the result as malicacid. The fruits were measured at harvest and sub-sequently after 5 months storage at !13C air temper-ature, and later following 7 days shelf life at 203C. Rotsand the internal #esh disorder, core#ush, were deter-mined visually after halving each fruit at the end ofshel#ife. The signi"cance of the results, at 95% con"-dence level, for the di!erent treatments was determinedwith the Duncan multi-range test.

3. Results

3.1. Moisture distribution in the soil

The "eld data provided information characterizing themoisture distribution in the soil (Figs 2 and 3). Accordingto results, SDI with the emitter installed at a depthof 30 cm, consistently ensures favourable soil moistureconditions for the pear trees both in terms of amount anduniformity. The soil moisture content varies in the rangeof 18% (approximately 25% below the "eld capacity soilmoisture content) to 24% ("eld capacity moisturecontent). On the other hand, conventional DI facilitatesoptimal moisture content primarily in the upper soillayer. The lower part of the root zone, which is com-monly considered to be up to a depth of 100 cm (Stegmanet al., 1983) is subject to inadequate moisture conditions.For example, the moisture distribution pattern underconventional DI is probably inferior for pear treesgrowth in comparison with SDI system that is installedat a depth of 30 cm.Likewise, the soil moisture distribution under SDI

with emitters located at a depth of 60 cm was neitheruniform nor did it induce good crop growth, since it is

associated with increased deep percolation losses. Thus,the active root zone remains relatively dry and the lowerlayers of the root zone contain high moisture resulting inine$cient use of the applied irrigation water.

3.2. Salinity distribution in the soil

Salinity in the soil as expressed by electrical conductiv-ity distribution also exhibits trends similar to that of thesoil moisture irrespective of the water quality used forirrigation (Figs 4 and 5). For the emitters located 30 cmdeep, extremely high salinity (16}20dSm��) wasrecorded only in the "rst few centimetres close to thesoil surface, similar to the previous "ndings (Hanson &

Fig. 5. Salinity distribution contours for electrical conductivity in dS m!1 in a pear orchard as a function of emitter location depth,June 1993 (one day after irrigation termination) for: (a) tap water irrigation; and (b) saline water irrigation; each for (i) surfacedrip irrigation; (ii) subsurface drip irrigation at a depth of 30 cm; (iii) subsurface drip irrigation at a depth of 60 cm; ( ),

emitter location


Bendixen, 1995; Or, 1996). On the other hand, in theimmediate vicinity of the emitter, i.e., in the active rootzone depth of the crop, the salinity (expressed by the EC)varies within a narrow range from 3 to 5 dSm��. It isanticipated that SDI maintains continuous soil leachingphases not only downwards, but also upwards andradially. Therefore, for emitters located at a depth of30 cm the salts in the irrigation water and those initiallycontained in the soil were displaced to the periphery ofthe root zone. Therefore, the soil salinity in the mainactive zone was approximately equivalent to the salinityof the applied water. On the other hand, as expected, theconventional DI facilitated su$cient leaching just belowthe emitter in the top soil layer, contributing to extraaccumulation of salts in the active root zone of the crop.Thus, the soil salinity level remained fairly high in deep

soil layers (more than 80 cm deep) under the conven-tional DI system.Likewise, the leaching process was more e!ective

downwards towards the lower soil layers while the upperones remained relatively dry, for the emitter located ata depth of 60 cm (Fig. 4). For emitters at a depth of 60 cm,salt accumulated in the top layers, leading to a salinityhigher than in the water applied for irrigation.

3.3. >ield

According to the "eld results, relatively high pearyields for both water qualities were obtained when theemitters were located at a depth of 30 cm below the soilsurface (Fig. 6). The yield with fresh water for the

Fig. 6. Ewect of emitter location and water quality on pear trees yield for: (a) tap water application; and (b) saline water application;( ), surface drip irrigation; ( ), subsurface drip irrigation at a depth of 30 cm and, ( ), subsurface drip irrigation at a depth

of 60 cm

G. ORON E¹ A¸ .242

treatment with emitters 30 cm deep is higher by 11}19%than for conventional on-surface DI. Similarly, the yieldwith saline water and emitters at a depth of 30 cm washigher by 32}40% than for on-surface DI. However, thecrop under conventional surface drip system performedbetter in terms of yield (9}11% for fresh water and36}40% for saline water irrigation) in comparison to theyields obtained for SDI with emitters located 60 cm deep.The di!erences in yields obtained in the present study aresomewhat inconsistent, primarily due to the diversemoisture content and salinity in the root zone (Ayers &Westcot, 1985).The di!erences with the yields of various treatments

were further analysed by the one-tailed &t'-test for 95%signi"cance level (Tables 2}4). Four samples were used forassessing the pear yield for every treatment and for calcu-lating the &t' values. The calculated &t' was compared with

the tabulated &t' for six degree of freedoms [two treatmentswith four replications each namely, t

��(6)"1)94]. The

results indicate the advantage of SDI at a depth of 30 cm,both for the fresh and saline water. There is a clearevidence that saline water application at a depth of 30 cmis much better than on-surface application.Based on the conventional approach which concerns

the mean amount of water stored in the crop root zoneand the mean salinity level (Maas & Ho!man, 1977;Stegman et al., 1983; Shalhevet, 1994), presented inTable 5, the large di!erences in the yields obtained inpresent experiment (Fig. 6) are somewhat perplexing.Analyzing the data regarding mean soil moisture contentand average soil salinity in the root zone during theactive growing season found negligible di!erences be-tween the treatments (Table 5). This observation, there-fore, gave rise to the speculation that the observed yield

Table 2The pear yields for the 1993 harvest and 95% signi5cance level implementing one-tailed 9t ’-test analysis for assessing the

di4erences between the treatments

Treatment* Yield $SD*,Mgha!1

Yield $SD*,Mg ha!1

Calculated*t+

Non-signixcant andsignixcant diwerences

at t0)95(6)"1)94

30 fresh}0 fresh 86)4$14)8 72)0$10)2 1)60 Non-signi"cant0 fresh}60 fresh 72)0$10)2 65)6$9)1 0)94 Non-signi"cant30 fresh}60 fresh 86)4$14)0 65)9$6)1 2)56 Signi"cant

30 sal}0 sal 74)9$11)8 55)0$8)6 2)73 Signi"cant0sal}60 sal 55)0$8)6 49)0$7)9 1)03 Non-signi"cant30sal}60 sal 74)9$11)8 49)0$7)9 3)65 Signi"cant

0 fresh}0 sal 72)0$10)2 55)0$8)6 2)55 Signi"cant30 fresh}30 sal 86)4$14)8 74)9$11)8 1)22 Non-signi"cant60 fresh}60 sal 65)6$9)1 49)0$7)9 2)76 Signi"cant

30 sal}0 fresh 74)9$11)8 72)0$10)2 0)37 Non-signi"cant

*Fresh, fresh water; sal, saline water; 0, surface drip irrigation; 30, 60, Subsurface drip irrigation at 30 and 60 cm depths,respectively; SD, standard deviation.


di!erences might be due to variations in the soil moisturedistribution pattern (which can also counteract the os-motic e!ects) and might a!ect the salt distribution ratherthan the amount per se.

3.4. Fruit quality

According to the results (Tables 6}9) applying salinewater has several advantages in regards to the fruit qual-

TabThe pear yields for the 1994 harvest and 95% signi5cance le

di4erences betwee

Treatments* Yield $SD*,Mg ha!1

Yield $

Mg h

30 fresh}0 fresh 62)6$13)9 55)8$

0 fresh}60 fresh 55)8$8)4 36)3$

30 fresh}60 fresh 62)6$13)9 36)3$

30 sal}0 sal 56)9$3)2 43)4$

0 sal}60 sal 43)4$8)9 24)9$

30 sal}60 sal 56)9$3)2 24)9$

0 fresh}0 sal 55)8$8)4 43)4$

30 fresh}30 sal 62)6$13)9 56)9$

60 fresh}60 sal 36)3$8)4 24)9$

30 sal}0 fresh 56)9$3)2 55)8$

*Fresh, fresh water; sal, saline water; 0, surface drip irrigatirespectively; SD, standard deviation.

ity parameters. Applying saline water under SDI evenimproves the fruit quality.

3.4.1. Firmness of fruits No signi"cant di!erence in"rmness of the fruits can be identi"ed for the threeharvesting years (Tables 6}9). That is also the case forfruits after 5 months of storage under temperature condi-tions of !13C.

le 3vel implementing one-tailed 9t :-test analysis for assessing then the treatments

SD*,a!1

Calculated*t+

Non-signixcant andsignixcant diwerences

at t0)95(6)"1)94

8)4 0)84 Non-signi"cant8)4 3)28 Signi"cant8)4 3)24 Signi"cant

8)9 2)85 Signi"cant2)7 3)98 Signi"cant2)7 15)29 Signi"cant

8)9 2)03 Signi"cant3)2 0)80 Non-signi"cant2)7 2)58 Signi"cant

8)4 0)24 Non-signi"cant

on; 30, 60, subsurface drip irrigation at 30 and 60 cm depths,

Table 4The pear yields for the 1995 harvest and 95% signi5cance level implementing one-tailed 9t :-test analysis for assessing the

di4erences between the treatments

Treatments* Yield $SD*,Mg ha!1

Yield $SD*,Mg ha!1

Calculated&t'

Non-signixcantandsignixcant diwerences

at t0)95(6)"1)94

0 fresh}60 fresh 55)2$8)1 38)5$6)3 3)25 Signi"cant30 fresh}0 fresh 68)4$7)1 55)2$8)1 2)45 Signi"cant30 fresh}60 fresh 68)4$7)1 38)5$6)3 6)30 Signi"cant0 sal}60 sal 33)4$2)2 30)2$12)4 0)51 Non-signi"cant30 sal}0 sal 57)2$7)3 33)4$2)2 6)24 Signi"cant

0 fresh}0 sal 55)2$8)1 33)4$2)2 5)19 Signi"cant30 sal}60 sal 57)2$7)3 30)2$12)4 3)75 Signi"cant30 fresh}30 sal 68)4$7)1 57)2$7)3 2)20 Signi"cant60 fresh}60 sal 38)5$6)3 30)2$12)4 1)19 Non-signi"cant30 sal}0 fresh 57)2$7)3 55)2$8)1 0)37 Non-signi"cant

*Fresh, fresh water; sal, saline water; 0, surface drip irrigation; 30, 60, subsurface drip irrigation at 30 and 60 cm depths,respectively; SD, standard deviation.

G. ORON E¹ A¸ .244

3.4.2. Soluble solids content Similarly, no signi"cantdi!erences could be detected for the soluble solids ex-pressed by the sugar content in the fruits (Tables 6}9).This holds both at the time of harvest and after a 5 monthstorage period.

3.4.3. ¹itratable acidity A higher level of titratableacidity (TA) content can be identi"ed for all saline watertreatments (Tables 6}9). That "nding persists aftera 5 month storage. The highest TA content was encoun-tered in the saline water application under the SDI treat-ment at the depths of 30 and 60 cm.

TabMean soil moisture content and soil salinity given by the electricasubject to emitter location (120 samples soil samples were taken 3 t

the lateral on both sides near emitter and at

Mean soil moisture conte%v/v

Water Yearquality DI* SDI30*

Freshwaterirrigation

199419951996

17)2$1)215)1$1)311)6$0)7

20)2$0)815)1$0)911)6$0)7

Salinewaterirrigation

199419951996

19)0$1)319)0$1)215)5$0)8

20)2$0)919)1$0)715)0$0)6

*DI, SDI30 and SDI60, surface drip irrigation, subsurface drideviation.

3.4.4. Core-ush The core#ush analysis conducted onlyfor the 1995 harvest emphasizes the advantage of salinewater use (Tables 8 and 9). A relatively high core#ushpercentage can be identi"ed for tap water applicationand a signi"cantly low one for the saline water treat-ments.

3.4.5. Healthiness The healthiness analysis refers to dis-ease free and overall fruit quality. Similar, to the coref-lush parameter, more healthy fruits, in terms of diseasefree and overall quality, were obtained under the salinewater application (Tables 8 and 9). The di!erence

le 5l conductivity in dSm!1 in the root zone for two water qualitiesimes during active growing period at 0, 20 and 40 cm radially from0+10, 20+30, 60+70 and 90+100 cm depths)

nt$SD*, Mean soil electricalconductivity$SD*, dS m!1

SDI60* DI* SDI30* SDI60*

16)8$1)113)7$1)09)7$0)8

1)4$0)23)6$0)53)8$0)6

1)8$0)34)3$0)54)2$0)4

2)0$0)20)5$0)44)5$0)5

18)9$1)217)5$0)614)0$0)8

6)1$0)98)0$1)27)0$1)1

4)8$0)87)2$0)88)0$1)0

6)4$0)78)3$1)08)2$1)2

p irrigation at 30 and 60 cm depths, respectively; SD, standard

Table 6Pear quality criteria of the 1994 year harvest (three replications)*

Water andemitter

Harvest, 28 July 1994 Removal after storage,19 December 1994

depth, cm**Firmness,

NSolublesolids

content, %

Titratableacidity, %

Firmness,N

Solublesolids

content, %


Tap}0 54)2� 14)4�� 0)28�� 27)1� 15)5� 0)17�Tap}30 60)4� 13)8� 0)25� 24)5� 15)2� 0)18��Tap}60 59)2� 14)5�� 0)30� 29)2�� 15)4� 0)21��

Sal}0 62)5� 14)1�� 0)30� 30)6�� 15)1� 0)23�Sal}30 61)4� 14)7� 0)36� 32)2� 15)3� 0)22�Sal}60 67)2� 14)7� 0)36� 33)1� 15)7� 0)24�

*Results with same letter (in column) are not signi"cantly di!erent at 5% level according to Duncan multi-range test.-Tap, irrigation with tap water; Sal, irrigation with saline water; 0, surface drip irrigation; 30, 60, subsurface drip irrigation at

30 and 60 cm depths, respectively.


between the tap and saline water is signi"cant (accordingto Duncan multi-range test) where the 30 cm deep SDItreatment was the superior one.

4. Conclusions

Field experiments were conducted in order to con"rmthe hypothesis that saline water application under sub-surface drip irrigation (SDI) is advantageous in compari-son to conventional surface drip irrigation. The resultsobtained in the study con"rm the assumption that salinewater application has a great potential in irrigation,primarily in regard to the agricultural products quality.Saline water application can signi"cantly improve thefruit quality. When shifting from tap to saline water

TabPear quality criteria of the 1995

Water and Harvest, 26 July 1995emitterdepth,cm�*

Firmness,N

Solublesolids

content, %

Ta

Tap}0 55)2�� 14)6�Tap}30 59)9� 14)0�Tap}60 56)2�� 14)0�

Sal}0 54)6�� 14)5�Sal}30 52)7� 14)9�Sal}60 54)3�� 15)4�

*Results with same letter (in column) are not signi"cantly di!�Tap, irrigation with tap water; Sal, irrigation with saline wat


application it is recommended, in order to minimize yieldlosses, to use SDI systems. Saline water application un-der subsurface drip irrigation will provide the most fa-vourable conditions for plant development, subject tosoil characteristics and environmental factors. UnderSDI, the salts that are contained in the irrigation waterand in the soil will be shifted to the periphery of theirrigated root zone domain, including towards the soilsurface. Extra precautions are required in order to pre-vent excessive salts accumulation close to the soil surfaceduring SDI saline water application. That can be main-tained by seasonal leaching and irrigation during precipi-tation. Furthermore, SDI o!ers speci"c advantages likedecreased demand due to minimizing evaporation andruno!, better weed control and convenient agriculturalmachinery manoeuvre. Major considerations will be

le 7year harvest (three replications)*

Removal after storage, 1January, 1996

itratablecidity, %

Firmness,N

Solublesolids

content, %


0)32� 37)0� 14)9� 0)13�0)34� 35)7� 15)1� 0)18��0)33� 37)9� 14)8� 0)14�

0)45� 39)4� 14)8� 0)24�0)51� 35)0� 15)5� 0)22��0)44� 41)7� 15)6� 0)20��

erent at 5% level according to Duncan multi-range test.er; 0, surface drip irrigation; 30, 60, subsurface drip irrigation at

Table 8Removal criteria for the pears 1995 harvest (three replications)*

Water andRemoval after storage: 7 days shelf

time, 7 January 1996Removal after storage: 7 days shelf

time, 7 January 1996emitterdepth,cm�

Firmness,N

Solublesolids

content, %


Firmness,N

Solublesolids

content, %


Tap}0 25)8�� 14)6� 0)16�� 26)7�� 76)7� 23)3�Tap}30 24)5� 15)3� 0)14� 6)7� 93)3� 6)7�Tap}60 27)5� 14)2� 0)15� 49)3� 96)7� 3)3�

Sal}0 26)3�� 14)7� 0)21� 12)3� 31)7� 68)3�Sal}30 25)1�� 14)6� 0)18�� 13)3� 26)7� 73)3�Sal}60 27)1�� 14)7� 0)21� 9)0� 43)3� 56)7�

*Results with same letter (in column) are not signi"cantly di!erent at 5% level according to Duncan multi-range test.�Tap, irrigation with tap water; Sal, irrigation with saline water; 0, surface drip irrigation; 30, 60, subsurface drip irrigation at


Table 9Pear quality criteria of 1996 year harvest (15 fruits per sample)*

Water and Harvest, 23 July 1996 Removal after storage, December 1996emitterdepth,cm�*

Firmness,N

Solublesolids

content, %


Firmness,N

Solublesolids

content, %


Tap}0 44)6� 14)0�� 0)13� 16)9� 15)0�� 0)17�Tap}30 45)4� 14)5� 0)06� 16)1� 14)6� 0)17�Tap}60 39)6� 14)2�� 0)18� 17)3� 15)1�� 0)17�

Sal}0 38)8� 13)9� 0)16� 19)4� 14)6� 0)16�Sal}30 43)0� 15)4� 0)20� 17)3� 15)4� 0)19�Sal}60 45)4� 15)4� 0)18� 15)7� 15)6� 0)18�

*Results with same letter (in column) are not signi"cantly di!erent at 5% level according to Duncan multi-range test.�Tap, irrigation with tap water; and Sal, irrigation with saline water; 0, surface drip irrigation; 30, 60, subsurface drip irrigation at


G. ORON E¹ A¸ .246

adequate lateral location and depths. Larger scale de-monstrative experiments and "eld monitoring in com-mercial orchards are required in order to strengthenthese "ndings.

Acknowledgements

The study was partially supported by RASHI Founda-tion project No. 2438 on &&Development of subsurfaceporous emitters for improved irrigation management''and BARD research fund No. IS2552-95 on &&Optimiza-tion of secondary wastewater reuse to minimize environ-mental risks''. The authors appreciate the contributivecomments and suggestions made by the editors andanonymous referees.

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