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Agriculture, Ecosystems and Environment 140 (2011) 454–461

Contents lists available at ScienceDirect

Agriculture, Ecosystems and Environment

journa l homepage: www.e lsev ier .com/ locate /agee

live orchard irrigation with reclaimed wastewater: Agronomic andnvironmental considerations

ran Segala, Arnon Daga, Alon Ben-Gala, Isaac Ziporia, Ran Erela, Shoshana Suryanob, Uri Yermiyahua,∗

Gilat Research Center, Agricultural Research Organization, M.P. Negev 85280, IsraelInstitute of Soil, Water and Environmental Sciences, Agricultural Research Organization, P.O.B. 6, Bet-Dagan, Israel

r t i c l e i n f o

rticle history:eceived 12 August 2010eceived in revised form 12 January 2011ccepted 14 January 2011

eywords:eclaimed wastewaterlive treealinityitrate

a b s t r a c t

The olive (Olea europaea) oil industry is experiencing a transition from traditional rain-fed to intensivelymanaged irrigated orchards. Moreover, since fresh water resources in typical olive cultivation regions areoften scarce, alternative water sources, often marginal in quality, are increasingly used for the irrigationof olives. Utilization of reclaimed wastewater (RWW) increases the susceptibility of olive trees to osmoticstress and augments the potential of groundwater contamination by nutrients and salts. The objectiveof this study was to evaluate tree growth and productivity and to quantify nitrate and chloride (Cl)losses in an olive orchard irrigated with RWW. A four year field study compared two olive tree varieties,‘Barnea’ and ‘Leccino’, and three treatments: (i) fresh water application with commercial fertilizer atrecommended rates (Fr), (ii) RWW application with commercial fertilizer at recommended rates (Re) and(iii) RWW application with commercial fertilizer reduced according to the amounts of the nutritionalconstituents in the wastewater itself (Re−). No significant difference was found in nutrient and mineralaccumulation in diagnostic leaves and no differences in trunk growth, fruit production or oil yields wereobserved between treatments. In spite of this, lower measured Cl concentration in diagnostic leaves of‘Barnea’ and higher Cl concentrations in its root zone relative to ‘Leccino’ suggested that ‘Barnea’ treesbetter controlled Cl uptake. While similar amounts of water were applied, the Re and Re− treatments

loaded the soil profile with 1.75 times more Cl then the Fr treatment. Additionally, significantly morenitrates were transported out of the root zone in the Re treatment compared to Fr and Re− for bothcultivars. We conclude that RWW used for irrigating olive oil orchards had no effect on vegetative growthand productivity but increased salt loads into and beyond the root zone. The nutritional constituents in theRWW used to irrigate olives should be accounted for in order to increase fertilizer application efficiency

rt of

and minimize the transpo

. Introduction

Fresh water scarcity in semi-arid environments and lack ofptions for disposal of domestic liquid waste have inspired a globalgricultural move towards utilization of treated domestic wastew-ter (reclaimed wastewater – RWW) for the irrigation of cropsPedrero et al., 2010). In Israel, for instance, 32.7% of the irrigationater in 2007 originated from RWW (Statistical abstract of Israel,

009). Similar trends of RWW replacing fresh water for irrigationre occurring in the USA and other countries (Hamilton et al., 2007).

he olive oil industry is particularly relevant and important regard-ng RWW utilization for a number of reasons: (i) it has concurrentlyxperienced a transition from traditional rain-fed to modernizedntensive cultivation practices, where water and fertilizer appli-

∗ Corresponding author. Tel.: +972 8 9928649; fax: +972 8 9926485.E-mail address: uri4@volcani.agri.gov.il (U. Yermiyahu).

167-8809/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.agee.2011.01.009

nutrients into groundwater.© 2011 Elsevier B.V. All rights reserved.

cation have become inherent to olive oil production (Connor andFereres, 2005); (ii) the olive tree is considered relatively tolerantto salinity (Chartzoulakis, 2005) and (iii) olive fruits are not eatenfresh but only consumed after processing, thus decreasing the riskfrom direct exposure to pathogenic microorganisms presented inRWW (Palese et al., 2009). Additionally, fresh water scarcity in theMediterranean region, where olive oil production is concentrated(Vossen, 2007), has promoted the utilization of RWW to irrigateolive orchards (Bedbabis et al., 2009; Charfi et al., 1999; Al-Abasiet al., 2009).

Reclaimed wastewaters are domestic liquid wastes typicallytreated by screening, oxidation, sedimentation and biologicaldigestion at designated plants. The composition of RWW includes

soluble minerals and organic matter which depend quantitativelyand qualitatively on the original source of the water and the typesand levels of treatment (Pescod, 1992; Pedrero et al., 2010). Typi-cally, RWW is defined as brackish water (Na and Cl as major ions)containing major plant nutritional constituents such as nitrogen

s and Environment 140 (2011) 454–461 455

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E. Segal et al. / Agriculture, Ecosystem

N), phosphorous (P) and potassium (K). On one hand, RWW appli-ation can positively affect plant growth conditions by increasinglant water availability and soil fertility (Da Fonseca et al., 2007).n the other hand, excess amounts of these minerals as well asther dissolved salts can adversely affect plant development as aesult of salt accumulation in the root zone (Biggs and Jiang, 2009)nd can also increase the potential for groundwater contaminationy salts and nutrients due to leaching below the root zone (Kasst al., 2005).

Although the olive tree is defined as a crop “moderately tolerant”o salinity (Maas and Hoffman, 1977; Aragues et al., 2004), high soilalinity has a negative effect on its photosynthetic activity, vegeta-ive growth, and fruit and oil production (Chartzoulakis, 2005). Inrinciple, the effects of irrigation water salinity can be minimizedy maintaining a leached root zone by frequent water applicationsnd by applying quantities in excess of plant consumption. Practi-ally, such water management is not always feasible or desired foreasons of controlling tree growth and oil quality.

The mineral nutrition of olive trees has mainly been studiedn rain fed orchards. Recommended N application amounts forraditional orchards range between 0.45 and 2 kg tree−1 year−1

Freeman et al., 2005; López-Villalta, 1996; Jasrotia et al., 1999).imilar amounts, 0.5–1 kg tree−1 year−1 were recommended forpplication of K by Hussein (2008) and Morales-Sillero et al. (2007,009). Due to its extensive root system and the symbiosis withycorrhizal fungi, the olive tree takes up P very efficiently (López-illalta, 1996; Therois, 2009; Freeman et al., 2005). Therefore, Peficiency in olives is rare and P fertilization is often not rec-mmended or practiced (López-Villalta, 1996; Fernández-Escobart al., 1999; Freeman et al., 2005; Therois, 2009). As olive cultiva-ion moves to more arid environments and nutrient poor soils, ands intensive management leads to significantly increased yields,fertilization is becoming more necessary and common. Erel et al.

2008) showed that fruit yield can be severely limited by P availabil-ty as flowering intensity and fruit set of ‘Barnea’ olives increaseds a function of P in irrigation water. On the other hand, the inten-ive management might result in over application of N, which wasound to have a negative effect on olive oil quality indices, includingolyphenol and free fatty acid contents (Fernández-Escobar et al.,006; Dag et al., 2009).

The agronomic importance of considering the nutritional con-tituents of RWW in fertilizer management has been studiedn several crops including bermudagrass (Adeli et al., 2003),rapevines (Paranychianakis et al., 2006) and cotton (Mandal etl., 2008). Regarding olives, Al-Abasi et al. (2009) found no sta-istical differences in leaf mineral concentrations between treesrrigated with RWW and fresh water. However, the N concentra-ion of the two water sources in those studies was alike and muchower than recommended application amounts (20% for RWW and4% for fresh water). In spite of findings that indicate nutrients inWW are available for crop mineral nutrition in most forms, it istill common practice for growers of crops including olives to followhe standard fertilizing recommendations, without considering theutrients arriving with the RWW.

Application of RWW has potential substantial environmentalmplications as the water and its constituents are transported outf the root zone into ground and surface waters. Such transportan lead to the salinization of groundwater (Kass et al., 2005), con-amination of drinking water with nitrates (Duan et al., 2010) orathogens (Bradford and Segal, 2009), and loading of surface watersith nutrients (Bond, 1998).

We hypothesized that when irrigating olive orchards withWW, subtracting the content of the major nutritional constituents

n the RWW from the recommended nutrient application ratesould not affect tree growth and yield. Moreover, reduction in

pplied fertilizers would minimize the potential contamination Tab

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4 ms and Environment 140 (2011) 454–461

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Table 2Composition of fresh water and of reclaimed wastewater. Values represent the fouryear average and standard deviation (2006–2009; n = 18).

Constituent Units Reclaimed wastewater Fresh water

pH 7.7 (0.3) 7.5 (0.2)ECa dS m−1 1.65 (0.13) 0.9 (0.2)NH4–N

mg L−1

4.8 (6.8) 0.0 (0.0)NO3–N 15.2 (3.9) 3.4 (2.2)Total N 19.9 (6.0) 3.4 (2.2)K 29.6 (2.2) 4.4 (2.8)P 5.8 (1.8) 0.0 (0.0)Mg 39 (6) 28 (13)Ca 67 (11) 50 (15)B 0.22 (0.04) 0.10 (0.05)Cl 323 (30) 168 (56)Na 198 (25) 81 (28)SARb (meq L−1)1/2 4.9 (0.8) 4.2 (1.9)

TAs

56 E. Segal et al. / Agriculture, Ecosyste

f groundwater due to leaching. Our objective was to study theffects of RWW used for irrigation on olive growth and yield and touantify the nitrate (NO3) loss and salt load from a RWW irrigatedrchard.

. Materials and methods

A four year field study compared two olive tree varieties,Barnea’ and ‘Leccino’, and two water sources combined with twoertilization treatments. The experiment was conducted within

20 ha commercial high-density olive orchard, designed forully mechanized fruit removal with a continuous straddle overhe canopy harvester. For both cultivars planting density was00 trees ha−1 with 4.5 m spacing between rows and 2.5 m betweenrees. The experimental treatments commenced when the treesere four years old, and were conducted for four consecutive years

2006–2009). 2006 was the first commercial harvest of the orchard.The orchard was located in the coastal plain of central Israel

31◦4′50′′N, 34◦46′32′′E), represented by a Mediterranean climate.aily average maximum air temperature at the site varies between1.1 ◦C during summer to 17.2 ◦C during winter. Average annualrecipitation is 47.8 cm falling exclusively between October andpril. Average annual evaporation rate of a Class-A pan is 172.3 cm.he soil profile was sampled at three locations within the exper-mental plot prior to treatment initiation and analyzed for somehysical and chemical properties. Particle size distribution wasetermined by the hydrometer method (Gee and Or, 2002). Elec-rical conductivity (EC) (Cyberscan 500, Eutech Instruments), pH420A, Orion), soluble K, Na, Ca and Mg (atomic absorption – AAn-lyst 200, PerkinElmer) were determined from saturated pasteolution. Calcium carbonate (CaCO3) was analyzed by calcimeterP1.85, Eijkelkamp). Total N and C were analyzed by the combustion

ethod (Flash EA 1112, Thermo). Phosphorus (P) was extractedollowing the Olsen bicarbonate extractable P method (Pierzynski,000). Average values and standard deviations of the soil proper-ies are given in Table 1. The soil texture was clayey with 58 mm ofvailable water in the upper 60 cm (estimated by ROSSETA – Schaapt al., 2001). The soil was characterized by high pH due to abundantarbonate (CO3), with sodium (Na), and therefore sodium absorp-ion ratio (SAR), increasing with depth. On the contrary, organic

atter and total P in the soil decreased with depth.Two water sources were utilized throughout the experiment. A

econdary-treated domestic wastewater from the city of JerusalemRWW) and well water originated from the local coastal aquiferfresh). Water samples of each source were collected 4–5 timesuring the irrigation season and analyzed for EC, pH, soluble K, Na,a and Mg. Chloride (Cl) was quantified by chloridometer (Chloride

able 3nnual precipitation, irrigation, potential evapotranspiration, actual crop factor, and apptudy.

Year 2006 2007

Treatment Fra Reb Re−c Fr Re

Precipitation (mm) 507 480Irrigation (mm) 360 500ETp

d (mm) 1085 1083Kc

f 0.47 0.44Applied N (kg ha−1) 268 245 + 72g 308 190 194 + 100Applied P (kg ha−1) 0 0 + 21 21 0 0 + 29Applied K (kg ha−1) 295 301 + 106 334 317 324 + 148Applied Cl (kg ha−1) 873 1436 1466 1108 1889

a Fr is fresh water application with commercial fertilizer.b Re is reclaimed wastewater application with commercial fertilizer.c Re− is reclaimed wastewater application with reduced commercial fertilizer.d ETp is the potential evapotranspiration (Penman–Monteith) during the irrigation seasf Kc is the actual crop factor (I × ETp

−1).g Recommended amount (left) and over application amount (right).

a EC is the electrical conductivity of the water.b SAR is sodium absorption ratio.

926, Sherwood Scientific). Mineral concentration of NO3–N, NH4–Nand P was determined by a colorimetric system (QuickChem 8500,Lachat Instruments). Average values of major constituents and theirstandard deviations over the four years of the study are presentedin Table 2. The higher EC of the RWW was due to enhanced concen-trations of minerals, including major plant nutritional constituents(N, P and K) and salts, especially Na and Cl.

The experimental site included 36 plots (3 treatments × 6 repli-cates × 2 cultivars) organized in a randomized block design for eachcultivar. Each plot included 12 trees (3 rows × 4 trees in a row) withthe two middle trees used for measurements and the other ten asborder trees. The treatments (water source–fertilization combina-tions) were: (i) fresh water application with commercial fertilizerat recommended rates (Fr), (ii) RWW with commercial fertilizer atrecommended rates (Re) and (iii) RWW application with reducedamount of commercial fertilizer after subtracting the amounts of Nand K in the RWW (Re−). The irrigation seasons started in March orApril each year depending on precipitation events and amountsand ended in October or November according to fruit ripening.Deficit irrigation strategy was implemented to control the size ofthe trees and facilitate their training and harvest. Some conse-quences of the deficit irrigation levels were apparent in: (i) the lowactual crop factor (Table 3) compared to that found to be optimal(0.75) by Grattan et al. (2006) under similar growing conditions,

(ii) low fruit water content (Table 5) and (iii) relative low stemwater potential values (−27 to −36 bar) measured in July for alltreatments using the Scholander pressure chamber (Arimad 3000,MRC, Israel) technique. A single drip line per row (UniRam, Netafim)

lication of nitrogen, phosphorus, potassium and chloride over the four years of the

2008 2009

Re− Fr Re Re− Fr Re Re−325 349655 370

1116 11090.29 0.31

247 190 194 + 130 277 190 194 + 74 22129 0 0 + 38 38 0 0 + 22 22392 317 324 + 194 438 317 324 + 90 3341957 1369 2390 2500 890 1478 1477

on (April–October).

E. Segal et al. / Agriculture, Ecosystems and Environment 140 (2011) 454–461 457

Table 4Mineral concentration in leaves. Values represent average and standard deviation of the three treatments in 2006–2008 and each individual treatment in 2009.

Constituent/treatment N (% of dry weight) P (% of dry weight) K (% of dry weight) Na (% of dry weight) Cl (% of dry weight)

Leccino2006 1.48 (0.02) 0.12 (0.01) 1.19 (0.03) NAe 0.23 (0.01)2007 1.89 (0.02) 0.13 (0.01) 1.37 (0.04) 0.027 (0.003) 0.24 (0.01)2008 1.82 (0.10) 0.13 (0.01) 1.47 (0.05) 0.024 (0.007) 0.30 (0.04)2009

Fra 1.92 (0.10) Ad 0.12 (0.01) A 1.55 (0.07) A 0.015 (0.002) A 0.26 (0.04) AReb 1.92 (0.12) A 0.13 (0.01) B 1.53 (0.08) A 0.016 (0.007) A 0.25 (0.03) ARe−c 1.89 (0.13) A 0.13 (0.01) B 1.54 (0.08) A 0.018 (0.003) A 0.26 (0.03) A

Barnea2006 1.28 (0.01) 0.10 (0.01) 0.78 (0.04) NA 0.15 (0.01)2007 1.84 (0.08) 0.11 (0.01) 0.96 (0.01) 0.024 (0.005) 0.20 (0.02)2008 1.62 (0.23) 0.12 (0.01) 0.93 (0.06) 0.025 (0.004) 0.21 (0.02)2009

Fr 1.59 (0.14) A 0.11 (0.02) A 1.10 (0.11) A 0.017 (0.007) A 0.19 (0.03) ARe 1.58 (0.10) A 0.11 (0.01) A 1.10 (0.09) A 0.016 (0.001) A 0.18 (0.03) ARe− 1.66 (0.15) A 0.11 (0.01) A 1.10 (0.11) A 0.017 (0.002) A 0.19 (0.02) A

a Fr is fresh water application with commercial fertilizer.b Re is reclaimed wastewater application with commercial fertilizer.

wftmoatbnmNtdatawer

tsbdfpscNlodofawmieIFab

c Re− is reclaimed wastewater application with reduced commercial fertilizer.d Letters represent statistical groups (P < 0.05).e NA, not available.

ith 2.3 L h−1 emitters spaced every 50 cm distributed water andertilizer twice a week (April–June and September–November) andhree times a week (July–August). Fertilization followed the com-

on recommended local commercial practice and supplied 180 kgf N ha−1 year−1 and 290 kg of K ha−1 year−1 (Therois, 2009). Andditional single N application of 191 kg of N ha−1 was appliedo the trees at the beginning of the growing season, prior to theeginning of the study. Ready mixed liquid fertilizer of macro-utrients was injected into the irrigation water. A 6:0:12 N–P–Kixture was used to fertilize the Fr and Re treatments, and a 4:0:8–P–K mixture to the Re− treatment. Annual precipitation, irriga-

ion quantities, potential evapotranspiration and actual plant factoruring the irrigation season (March–September), macro-nutrientsnd Cl application for each year are given in Table 3. Chloride hadwo sources: fertilizer and wastewater. In practice, while the targetmounts of N and K were supplied to the Fr treatment, N, P and Kere supplied in excess to the Re treatment and P was supplied in

xcess to the Re− treatment. Less Cl was applied to the Fr treatmentelative to the Re and Re− treatments.

Soil sampling was conducted twice a year, at the beginning ofhe irrigation period (March) and prior to harvest and rainy sea-on (September). Soil samples were collected under the drip lineetween the two measured trees in each replicate plot from threeepths, 0–30, 30–60 and 60–90 cm. Air dried 200 g of ground soilrom each sample was used to prepare a saturated paste. Subsam-le from the paste was oven dried (105 ◦C) and used to calculate theaturation percentage. Similar to the water analysis, the electricalonductivity of the soil extract (ECe) and major concentration ofO3, K, Na and Cl were determined. Trunk diameter and diagnostic

eaves (youngest mature) were sampled from each measured treence a year in July (Freeman et al., 2005). Chloride in the leaf wasetermined based on water extraction (0.1 g dry matter in 10 mLf deionized water). Powdered leaf material was digested with sul-uric acid and hydrogen peroxide, and then analyzed for N, P, Knd Na concentration (Snell and Snell, 1949). Total N in the leavesas considered as ammonium and analyzed with the other ele-ents as described above. Trunk diameter was measured annually

n May, 50 cm above the ground level. Yield was determined for

ach monitored tree, harvested at the appropriate ripeness level.ndividual fruit weight was determined from a sample of 100 fruits.ruit number per tree was calculated by dividing total fruit yield byverage single fruit weight. Water content in fruit was determiney crushing the fruit with an Abencor (MC2, Ingenieria y Sistems,

Spain) hammer crusher, weighing and drying the paste for 72 h at105 ◦C. Mineral concentration of the paste was measured follow-ing the same protocols as leaves. Oil percentage was measured bychemical extraction of the dry paste by Soxhlet extraction usinghexane.

Annual mass balances of Cl and NO3 in the upper soil profile thatwere used to estimate their leaching below the root zone were:

Clirrigation − Cldrainage − Clplant − �Clsoil = 0 (1)

NO3irrigation + NO3

nitrification − NO3drainage − NO3

plant − �NO3soil = 0

(2)

The mass balances were calculated on a yearly basis in kg ha−1

units for the upper 60 cm of the soil profile, where roots were vis-ibly concentrated and assumed to be most active regarding waterand nutrient uptake under irrigated conditions. Soil storage wascalculated based on measured concentrations in the soil paste andmeasured saturation percentage from the beginning of the irriga-tion season (March), estimated soil bulk density (1250 kg m3) andactive root zone volume (1500 m3 ha−1, based on a wet strip ofabout 1 m × 0.6 m below the drip line). Irrigation inputs are statedin Table 3. The estimation of plant uptake was calculated as com-bined removal by the fruits and canopy. Fruits and pruning materialwere assumed to be the dominant sinks for Cl and N while storagein the tree from year to year was negligible. Removal by the fruitswas based on measured concentration in fruits and fruit biomass.Upmost removal by the canopy was calculated from estimated dryweight of the pruned biomass and measured leaf concentrations(assuming that Cl and N content in the woody parts were smallerthan leaf – Therois, 2009). Nitrification was assumed to terminatedue to the long time lag between measuring and last application ofN (5–6 months) and the typical rapid nitrification found in irrigatedsoils (Strong et al., 1999). Statistical analyses were conducted withSigma-plot software (v. 11, Systat Inc.). The Student’s T-test wasused to determine the probability (P) for significant differences.

3. Results and discussion

3.1. Mineral in leaves

Concentrations of N, P, K, Na and Cl in the diagnostic leaves eval-uated throughout the experiment are presented in Table 4. There

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58 E. Segal et al. / Agriculture, Ecosyste

ere no significant differences between treatments for each min-ral throughout the four years of the study as demonstrated by the009 data set (besides minor increase of P in the ‘Leccino’ 2009).herefore, only averages of the three treatments and standard devi-tions are presented for 2006–2008. The additional amounts of N,, K, Na and Cl due to RWW application did not result in accu-ulation in the leaves. Mineral concentrations in diagnostic leaves

erve as a bench mark for salinity and nutritional status of oliveree (López-Villalta, 1996). Therefore, the measured concentrationsf N, P and K within a range considered normal (Therois, 2009)ndicated an adequate nutritional status for the cultivars in all 3reatments. However, Fernández-Escobar et al. (2006) and Dag et al.2009) reported decreases in oil quality due to over application of N,hich were not associated with increases in N detected in diagnos-

ic leaves. Therefore, the over application of N in the Re treatmentill likely result in inferior oil quality. Normal leaf concentration

f salinity indicators, Cl and Na (Freeman et al., 2005) indicatedo effect of salinity stress or toxicity (>0.2% for Na and >0.5% forl). Cultivar related differences were apparent in mineral accumu-

ation in leaves. Higher values of N, P, K and Cl were measured inLeccino’ compared to ‘Barnea’. Specifically, the lower Cl concentra-ion in the leaves of the ‘Barnea’ relative to ‘Leccino’ correspond toormer publications that claimed ‘Barnea’ is more salt tolerant thanLeccino’ (Demiral, 2005).

.2. Tree growth, fruit and oil yields

Vegetative and reproductive measurements of the trees are pre-ented in Table 5. For both cultivars in each year, no significantifferences were found between treatments for all parameters:runk diameter, fruit number, average fruit weight, oil content,ater content, fruit yield and oil yield. The average annual growth

n trunk diameter (July–July) of both cultivars decreased over theears from 17.5% for 2006–2007 to 12.25% for 2007–2008 and 5%or 2008–2009. The ‘Leccino’ trees carried medium yields in 2006nd 2007, high yields in 2008 and no yield in 2009 (due to nat-ral biennial bearing cycle exasperated by a relatively hot winter

n 2008–2009 which didn’t provide satisfactory chilling hours forood flowering induction). The ‘Barnea’ trees had high yields in006 and 2008, medium yields in 2007, and, similar to ‘Lechino’,ery low yields in 2009. Average individual fruit weight rangedetween 2.21 g (2008) and 2.86 g for ‘Lechino’ and 2.15 and 4.12 g2007) for ‘Barnea’. Fruit number per tree ranged from 0 to 9900 inhe ‘Off’ and high yields years, respectively, for ‘Leccino’ and from48 to 10930 fruits per tree in the low and high years, respec-ively, for ‘Barnea’. Fruit size was generally negatively correlatedo fruit number. The ‘Barnea’ trees had higher oil content in theirruits (ranging from 19.2 to 26.6%) than the ‘Leccino’ (ranging from7.8 to 20.5%). Multiplying olive fruit yield by oil content pro-ided oil yield per tree, which ranged from 2.1 to 4.2 kg tree−1

1890–3780 kg ha−1) in the ‘On’ years (2006, 2008) in ‘Leccino’. TheBarnea’ trees had similar oil yields, ranging from 2.0 to 4.4 kg tree−1

1800–3960 kg ha−1).

.3. Soil

Soil salinity measured as ECe was linearly related to the concen-ration of the most frequently occurring anion, Cl (Fig. 1). The datauggest a single linear relation between Cl and ECe throughout thexperiment. This relationship was consequentially used to aid cal-ulation of the salt load to the soil as a result of the transition from

resh water to RWW. Fig. 2 presents the soil profiles of Cl (A and B)nd NO3–N (C and D) at the beginning and end of the 2008–2009ainy season (349 mm) for each treatment. The large standard devi-tions were due to the variability of water and nutrient distributionnder drip lines and to soil heterogeneity. Higher concentrations of Ta

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ig. 1. Chloride (Cl) concentration versus electrical conductivity of the soil saturatedaste extraction (ECe), during the four years of the study.

l were measured in the upper 60 cm of the soil profile at the begin-ing of the rainy season relative to measured values following theainy season (Fig. 2A and B). In contrast, similar values were mea-ured at the lowest depth (60–90 cm) at both sampling dates. Noignificant difference was found between treatments (P = 0.12), yetverage Cl concentrations in the soil samples from the ‘Barnea’ plotsere higher than those in the ‘Leccino’ (P = 5E−04). These observa-

ions were valid for the other experimental years, as well (data notresented).

The combined lower Cl concentration in the leaves of theBarnea’ (Table 4) and higher concentrations in the soil (Fig. 2) sup-ort previous findings that ‘Barnea’ controls the entrance of Cl to

lant tissues better than other varieties (Weissbein et al., 2008).

Barnea’ therefore may be preferred agronomically for utilizationf high salinity RWW. In contrast, ‘Leccino’ would become the pre-erred variety when environmental considerations dominate dueo the higher tissue concentrations of N, P, K and Cl, indicating that

ig. 2. Soil profile distribution of chloride (Cl, A and B) and nitrate (NO3–N, C and D) mhe 2008–2009 rainy season. Horizontal bars represent standard deviations. Fresh waterommercial fertilizer (Re) and reclaimed wastewater application with reduced commerci

Environment 140 (2011) 454–461 459

the cultivar can more efficiently deplete minerals from the soil.Under the assumption that the two varieties had similar growthrates, more minerals were removed from the soil due to pruningand harvesting of ‘Leccino’ trees, thus lowering the potential fortheir transport out of the root zone.

Patterns of NO3 distribution in the soil profile were similar tothose of Cl. Higher concentrations were measured in the upper60 cm, especially in the ‘Leccino’ and similar values at the lowestdepth in ‘Barnea’ plots (Fig. 2C and D). No significant difference wasfound between treatments in the ‘Leccino’ plots (P = 0.11) and simi-larly, NO3 concentrations in the soil samples from the ‘Barnea’ plotswere higher than those in the ‘Leccino’ (P = 1E−06). These trendscontinued to be measured in each of the additional three years ofthe experiment (data not presented).

In our experiment, Cl served as an indicator to estimate saltload due to its (i) having a strong correlation to ECe under the cur-rent experimental conditions, (ii) low relative uptake rate (ratiobetween uptake and supplied), (iii) being an anion with low adsorp-tion rate and high mobility in the soil and (iv) being the mostfrequently occurring anion in the wastewater (Table 2). The accu-mulation of Cl in the upper 60 cm of the soil profile during theirrigation season (Fig. 2) implied intensive root water uptake indi-cating the active root zone. Since irrigation was applied at deficitlevels, excessive Cl was subsequently transported below this zonemainly following precipitation events during the winter. Quantify-ing the exact amount of Cl leached below the root zone requires anestimation of the plant uptake rates (Eq. (1)). This was establishedfrom measured Cl concentration in the olive paste (0.19%) and in theleaves (Table 4), measured fruit yield (Table 5) and dry weight of thepruned branches, estimated at 5 kg tree−1. Leaching of Cl (Eq. (1))

from the root zone for each treatment is presented in Table 6. Calcu-lated Cl leached is presented for each year and the total of the fouryears of the study, for both cultivars. The transition from fresh waterto RWW for irrigation resulted in significantly increased Cl drainedfrom the root zone (∼4000 kg Cl ha−1 for Fr and ∼6900 kg Cl ha−1

easured in saturated paste solution at the beginning (Beg.) and the end (End) ofapplication with commercial fertilizer (Fr), reclaimed wastewater application withal fertilizer (Re−).

460 E. Segal et al. / Agriculture, Ecosystems and Environment 140 (2011) 454–461

Table 6Chloride (Cl) and nitrate (NO3–N) depletion from the root zone. Values are annual average and standard deviation.

Treatment Fra Reb Re−c

Constituent Cl (kg ha−1) NO3–N (kg ha−1) Cl (kg ha−1) NO3–N (kg ha−1) Cl (kg ha−1) NO3–N (kg ha−1)

Year Leccino2006–2007 933 (59) 6 (19) 1491 (93) 19 (4) 1478 (154) 2 (2)2007–2008 1081 (63) 6 (5) 1857 (144) 112 (8) 1891 (73) 45 (11)2008–2009 1175 (169) 16 (5) 2203 (161) 73 (6) 2378 (48) 39 (15)2009–2010 864 (267) 106 (6) 1392 (265) 186 (12) 1344 (205) 130 (12)Total 4053 Ad (558) 134 ae (70) 6943 B (663) 390 b (30) 7091 B (480) 216 a (40)Year Barnea2006–2007 730 (155) 101 (40) 1353 (157) 114 (40) 1346 (126) 93 (57)2007–2008 1248 (145) 105 (48) 2002 (155) 188 (34) 2086 (147) 162 (30)2008–2009 1131 (148) 45 (7) 2071 (182) 77 (17) 2024 (289) 18 (35)2009–2010 773 (141) 99 (6) 1362 (236) 192 (23) 1250 (692) 116 (48)Total 3882 A (589) 350 a (101) 6788 B (730) 571 b (114) 6706 B (1254) 389 a (170)

a Fr is fresh water application with commercial fertilizer.b Re is reclaimed wastewater application with commercial fertilizer.c Re− is reclaimed wastewater application with reduced commercial fertilizer.

fpyzsata9bidiitisrhlbal

a(miiouNltmcfmetlRs‘

d Uppercase letters represent statistical groups for Cl (P < 0.05).e Lowercase letters represent statistical groups for NO3–N (P < 0.05).

or the Re and Re− treatments). Due to low uptake of Cl by thelant and minor changes of Cl in the root zone between consecutiveears, most of the applied Cl was transported below the active rootone during the rainy season. The average increase in Cl load to theoil under RWW application was 1.75 times that of the fresh waterpplication, similar to the ratio between the Cl concentrations of thewo water sources over the four years of the study. Presenting thesebsolute values relative to the supplied amount revealed that about7% of the Cl in the fresh water and 98% in the RWW were leachedelow the root zone. Salt leaching is an essential practice to avoid

mpairment of soil structure and fertility and inhibition of plantevelopment due to the osmotic potential and specific ion toxic-

ty (Chartzoulakis, 2005). Yet, leached salts have the potential toncrease the salinity of groundwater, where time scale and magni-ude of the process depends on the water table depth, water fluxesn the vadose zone, and its mineral composition (Bond, 1998). In thistudy, deep mineral transport took place mainly as a result of spo-adic winter rainfall, when precipitation/infiltration rates becameigher than actual evapotranspiration rates. In more arid climates

acking significant precipitation, water application in excess woulde required to manage leaching and the irrigation-season deficitpplication strategy practiced in the experimental case would beess feasible.

Accurate quantification of NO3 leaching below the root zone ischallenging task due the complexity of the N cycle in the soil

Bar-Tal, 2011). For example, lack of information on N transfor-ation rates (i.e. mineralization, nitrification, denitrification and

mmobilization) disallows calculating the concentrations of thenorganic forms of N (ammonium and nitrate) in the soil solutionver time. However, comparison between treatments enables eval-ation of the effect of N application on the potential leaching ofO3 below the root zone (Eq. (2)). Similarly to Cl, quantifying the

eaching amounts of NO3 below the root zone requires an estima-ion of plant uptake rates. The estimation was established from

easured total N concentration in the olive paste (0.8% for ‘Lec-ino’ and 0.5% for ‘Barnea’) and in the leaves (Table 4), measuredruit yield (Table 5) and dry weight of the pruned branches, esti-

ated at 5 kg tree−1. Leaching of NO3–N from the root zone forach treatment is presented in Table 6. The Re treatment, charac-

erized by greater application of N, resulted in significant highereached amounts (about 480 kg of NO3–N ha−1) than for the Fr ande− (about 270 kg of NO3–N ha−1). These differences were mea-ured throughout the three years of the study for both ‘Leccino’ andBarnea’ cultivars. Similar to Cl, NO3 is an anion with high mobility

in the soil and therefore, under the current experimental setup, thetiming and magnitude of leaching was mainly during the winterrainy season.

4. Conclusions

The current transition towards RWW for irrigation of intensiveolive orchards was investigated from agronomical and environ-mental perspectives. The two water sources combined with twofertilization strategies created variable N, P, K and Cl applicationto two cultivars, characterized by different sensitivities to salini-ties. No significant differences were found between treatments foreither cultivar from agronomic perspectives, measured in termsof mineral concentrations in leaves, trunk diameter, fruit size andyield, and oil yield. Consideration of the plant available nutrients inthe RWW allowed the reduction of applied fertilizer. From an envi-ronmental perspective, the greater application of Cl from RWWresulted in greater transport below the root zone. Specifically,‘Barnea’ trees had better control over Cl uptake, while ‘Leccino’trees were found to have the potential to deplete minerals moreefficiently from the soil. Similarly, enhanced application of N, whenits content in the RWW was not considered in the fertilization strat-egy, resulted in greater transport of NO3 below the active root zone.The occurrence of the Cl and NO3 losses was mainly during the win-ter rainy season when precipitation rates were higher than actualevapotranspiration rates. Long-term transport of salts and NO3 intothe hydrological system might negatively affect the quality of thelocal groundwater. In summary, the transition to RWW did not havean effect on olive tree growth and productivity, but did have envi-ronmental repercussions as the transport of salts below the rootzone was enhanced. Consideration of nutrients in RWW allows thereduction of applied fertilizer and facilitates the minimization oftransport of nutrients below the root zone during the rainy sea-son. Optimization between the reduced nutrient and increased salttransport requires continued long term evaluation of crop produc-tion and environmental aspects of irrigation with RWW.

Acknowledgments

This research was supported by grant M26-062 of the USAIDMiddle East Regional Cooperation Program, as well as by grant 203-0620 from the Chief Scientist of the Israeli Ministry of Agricultureand Rural Development. The first author was supported by a return-ing scientist scholarship from the Israeli Ministry of Immigration.

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E. Segal et al. / Agriculture, Ecosystem

e thank Inna Feingold, Eugene Presnov, Talal Alhwashla, Yuliaubbotin and Lyudmila Yusupov for technical support in the fieldnd laboratory.

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