Application of municipal solid waste compost reduces the negative effects of saline water in Hordeum maritimum L

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Application of municipal solid waste compost reduces the negative effects of saline water in Hordeum maritimum L
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  Application of municipal solid waste compost reduces thenegative effects of saline water in  Hordeum maritimum  L. Abdelbasset Lakhdar a,b,* , Chokri Hafsi b , Mokded Rabhi b , Ahmed Debez b,1 ,Francesco Montemurro c , Chedly Abdelly b , Naceur Jedidi a , Zeineb Ouerghi d a Centre de Recherches et Technologies des Eaux, Technopole Borj Cedria, BP 273, Soliman 8020, Tunisia b Laboratoire d’Adaptation des Plantes aux Stress Abiotiques, Centre de Biotechnologies, Technopole Borj Cedria, BP 901, Hammam Lif 2050, Tunisia c C.R.A, Istituto Sperimentale Agronomico, Via C. Ulpiani 5, 70125 Bari, Italy d Unite´  de Physiologie et de Biochimie de la Tole´ rance au Sel chez les Plantes, Faculte´  des Sciences de Tunis, Campus Universitaire, 1060 Tunis, Tunisia Received 16 May 2007; received in revised form 21 December 2007; accepted 21 December 2007Available online 4 March 2008 Abstract The efficiency of composted municipal solid wastes (MSW) to reduce the adverse effects of salinity was investigated in  Hordeum mari-timum  under greenhouse conditions. Plants were cultivated in pots filled with soil added with 0 and 40 t ha  1 of MSW compost, andirrigated twice a week with tap water at two salinities (0 and 4 g l  1 NaCl). Harvests were achieved at 70 (shoots) and 130 (shootsand roots) days after sowing. At each cutting, dry weight (DW), NPK nutrition, chlorophyll, leaf protein content, Rubisco (ribulose-bisphosphate carboxylase/oxygenase) capacity, and contents of potential toxic elements were determined. Results showed that compostsupply increased significantly the biomass production of non salt-treated plants (+80%). This was associated with higher N and P uptakein both shoots (+61% and +80%, respectively) and roots (+48% and +25%, respectively), while lesser impact was observed for K + . Inaddition, chlorophyll and protein contents as well as Rubisco capacity were significantly improved by the organic amendment. MSWcompost mitigated the deleterious effect of salt stress on the plant growth, partly due to improved chlorophyll and protein contentsand Rubisco capacity (  15%,   27% and   14%, respectively, in combined treatment, against   45%,   84% and   25%, respectively,in salt-stressed plants without compost addition), which presumably favoured photosynthesis and alleviated salt affect on biomass pro-duction by 21%. In addition, plants grown on amended soil showed a general improvement in their heavy metals contents Cu 2+ , Pb 2+ ,Cd 2+ , and Zn 2+ (in combined treatment: 190%, 53%, 168% and 174% in shoots and 183%, 42%, 42% and 114% in roots, respectively) butremained lower than phytotoxic values. Taken together, these findings suggest that municipal waste compost may be safely applied tosalt-affected soils without adverse effects on plant physiology.   2008 Elsevier Ltd. All rights reserved. Keywords:  Municipal solid waste compost; Heavy metals; Rubisco; Salt; Soluble proteins 1. Introduction Irrigation with poor quality water is one of the main fac-tors resulting in salt accumulation and decreasing agricul-tural productivity. The accumulation of Na + in tissues of plants growing in saline media restricts the uptake of essen-tial nutrients (mainly N, P, K + and Ca 2+ ) (Ghoulam et al.,2002), thereby reducing the plant biomass production. Inaddition, the excessive salt amounts adversely affect soilphysical and chemical properties, as well as the microbio-logical processes. Tejada and Gonzalez (2006) showed thatincreasing electrical conductivity decreases soil permeabil-ity, structural stability, and bulk density. The mechanismsof growth inhibition also include the disturbance of plantwater uptake, due to the high osmotic potential of the 0960-8524/$ - see front matter    2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.biortech.2007.12.071 * Corresponding author. Address: Centre de Recherches et Technologiesdes Eaux, Technopole Borj Cedria, BP 273, Soliman 8020, Tunisia. Tel./fax: +216 71410740. E-mail address:  abdelbassetlak@yahoo.fr (A. Lakhdar). 1 Current address: Institut fu¨r Botanik, Leibniz Universita¨t Hannover,Herrenha¨user Str. 2, D-30419 Hannover, Germany.  Available online at www.sciencedirect.com Bioresource Technology 99 (2008) 7160–7167  external medium and the impairment of both photosynthe-sis and protein synthesis (Romero-Aranda et al., 2001).However, the negative effect of soil salinity depends onthe plant tolerance aptitude and the salinity level (Munns,2002). Halophytes, which are plants naturally adapted tosaline environments, exhibit wide differences in toleratingthis stress (Tester and Davenport, 2003). Among these spe-cies, the facultative halophyte  Hordeum maritimum  is animportant annual fodder crop common in the Mediterra-nean ecosystems (Cue´nod et al., 1954). In Tunisia, it isoften observed on the borders of saline depressions, inclose association with strict halophytes (Abdelly et al.,1995).Recently, several biological methods were establishedfor reclamation of salt-affected soils, including the use of organic amendments (Hanay et al., 2004). In this context,animal manures and composts have been investigated fortheir effectiveness in soil remediation and plant yieldimprovement (Tejada et al., 2006; Walker and Bernal,2008). Their utilization may promote nutrient availabilityand plant growth (Alburquerque et al., 2007), and stimu-late respiration, photosynthesis (Gurrero et al., 2001),and chlorophyll content (Tejada and Gonzalez, 2006).Arena et al. (2005) reported more efficient carbon fixationby Rubisco in compost grown plant at high CO 2  concentra-tion. Indeed, excessive application of composts and/ortheir low quality can result in an accumulation of pollu-tants (mainly heavy metals) in the soil (Weber et al.,2007), which affects the metabolism of living organisms(Watanabe and Suzuki, 2002; Lin et al., 2007). Therefore,non-conventional techniques of soil remediation uses, espe-cially non-selective collect of municipal wastes, couldinduce an accumulation of heavy metals in plants, leadingto a decrease in their biomass and chlorophyll contents(Sinha and Gupta, 2005) and impairment of the photosyn-thetic efficiency (Bertrand and Poirier, 2005). The beneficialeffects of compost utilization should be assessed togetherwith the potentially detrimental ones. Changes of plantphysiological activities after amendment with MSW com-post have to be well recognized, since knowledge of allaspects of compost application is essential to sustain agri-cultural practice.The aim of this survey was to study the possibility of using MSW compost to reduce salt-induced damage in H. maritimum  plants. The effects of this amendment wereinvestigated on growth, chlorophyll and soluble proteincontents, and Rubisco capacity. 2. Methods  2.1. Culture conditions and sampling  Table 1 shows the main characteristics of the soil, com-post, and irrigation water used in the present study.Clayey–loamy soil was obtained from the INAT-Mornegfarm, close to Tunis. Three selected soil samples (20 cmdepth each) were randomly removed, air-dried, sieved at2 mm, and then analyzed. The compost was mechanicallyproduced by mixing weekly the waste heap under aerobicconditions by fast fermentation and the compost usedwas eight month old. In a completely randomized experi-mental design with ten replications,  H. maritimum  seedswere sown in pots (20 cm diameter and 30 cm height) con-taining 2 kg of clayey–loamy soil in a glass house withmean (night–day) temperatures of 18–25   C and relativehumidity 80–70%. Once germination occurred, seedlings(7 per pot) were irrigated twice a week at 2/3 of the soilfield capacity (with no leaching). The following treatmentswere applied: (1) C = soil without MSW compost and irri-gation with tap water (control treatment); (2) S = soil with-out MSW compost and irrigation with tap watercontaining 4 g l  1 NaCl; (3) C + A = soil amended with40 t ha  1 of MSW compost and irrigation with tap water;(4) S + A = soil amended with 40 t ha  1 of MSW compostand irrigation with tap water added of 4 g l  1 of NaCl.  H.maritimum  shoots were harvested either at 70 (C1) and 130days after sowing (C2), while roots were sampled only atC2.  2.2. Plant analysis Shoot and root samples were dried at 60   C until con-stant weight, ground with a porcelain grinder, and thenused for nutrient and heavy metal analyzes. For Na + ,K + , and heavy metals (Cu 2+ , Zn 2+ , Cd 2+ , and Pb 2+ ), sam-ples were digested in 4/1 (v/v) HNO 3 /HClO 4  mixture andthe element concentrations were determined by flame pho-tometry (case of Na + and K + ) atomic absorption spec-trometry (Perkin–Elmer Analyzer) (case of heavy metals).Nitrogen and phosphate contents were assayed followingrespectively Kjeldahl’s and vanado-molybdate (Fleuryand Lecler, 1943) methods.  2.3. Chlorophyll and protein content and Rubisco activity Chlorophyll concentration, protein content and Rubiscoactivity were assayed on the 4th leaf (from the shoot base) Table 1Soil, compost and irrigation water characteristics (mean ± standarddeviation calculated on three replications basis)Soil Compost Irrigation waterpH 8.8 ± 0.08 8.1 ± 0.04 8.7 ± 0.5CE( l S) 404 ± 36 8 10 3 ± 40 2.1 ± 0.08C (%) 0.72 ± 0.44 13 ± 2.0N (%) 0.11 ± 0.01 1.14 ± 0.06C/N 7 ± 1.13 11 ± 1.8Cu (mg kg  1 ) 57.48 ± 3.7 91.63 ± 13Pb (mg kg  1 ) 24.01 ± 1.2 251.63 ± 12Cd (mg kg  1 ) 1.04 ± 0.2 3.37 ± 0.3Zn (mg kg  1 ) 158.9 ± 15 290.19 ± 11K + (mmol l  1 ) 0.36 ± 0.09Na + (mmol l  1 ) 0.27 ± 0. 11Cl  (mmol l  1 ) 4.5 ± 0.71Ca 2+ (mmol l  1 ) 1.42 ± 0.3 A. Lakhdar et al./Bioresource Technology 99 (2008) 7160–7167   7161  of 63- and 123-day old plants. For the latter, three leavesfrom each elementary plot were sampled and immediatelyground in pre-chilled mortar with 2 ml 100 mM Tris–bis-cine (pH 8) containing 5% glycerol (v/v), 5 mM MgCl 2 ,and 1%  b -mercaptoethanol (v/v), and centrifuged for10 min at 12,000  g   at 4   C.After the crude extract (5  l l) was added to the reactionmedium, the activity (as  l mol h  1 g  1 DW) was assayedspectrophotometrically at 340 nm and 30   C for 10 min(Ouerghi et al., 2000). The reaction medium contained100 mM Tris–bicine (pH 8.0), 10 mM MgCl 2 , 0.2 mMEDTA, 5 mM dithiothreitol (DTT), 40 mM NaHCO 3 ,4 mM ATP, 0.2 mM NADH, 0.2 mM ribulose 1,5-biphos-phate (RuBP) and one enzyme unit of 3-phosphoglyceratekinase (PGK) and glyceraldehydes 3-phosphate dehydro-genase (3-PGADH).Leaf soluble protein content was determined on thecrude extract according to Bradford (1976), using bovineserum albumin (BSA) as standard. Chlorophyll contentwas determined in 80% acetone extract. After centrifuga-tion (12,000  g  , 20 min) absorbance of clear supernatantwas measured spectrophotometrically at 663 and645 nm. Total chlorophyll as well as chlorophyll a andb concentrations were calculated according to Arnon(1949).  2.4. Statistical analysis The statistical analysis was achieved using the SPSS 10.0software. Data were subjected to One-Way ANOVA testand means were compared using Duncan’s Multiple RangeTest at 5% significance level. 3. Results 3.1. Plant growth and Na + accumulation Fig. 1A shows the effect of salt, compost and combinedtreatments on  H. maritimum  shoot DW (dry weight) atthe first cut (C1) and on shoot and root ones at the finalharvest (C2). In S treatment, sodium accumulation in salt-stressed leaves (Fig. 1B) was concomitant to a decrease of biomass production (19%) at C1 cut. This growth diminu-tion was significantly accentuated reaching 70% and wasassociated with symptoms of necrosis and chlorosis atC2 cut. Under non saline conditions, the presence of com-post improved shoot dry matter production at both C1(52%) and C2 (81%) cuts with respect to the correspond-ing control treatment. However, no variation wasobserved in biomass production in plants subjected tothe interactive effects of salt and compost (S + A) at C1cut as compared to the control, although they accumu-lated higher Na + ions (0.84 mmol g  1 ). The prolongationof treatment duration (C2) decreased growth of (S + A)-treated plants by 47%. Nevertheless, the decline of bio-mass production in S-treated plants was much morepronounced. 3.2. NPK uptake At C1 cut, no significant change in nitrogen and phos-phorus concentrations was observed in  H. maritimum plants in S treatment in comparison to the control (Table2), whereas K + uptake showed a 22% decrease. Onamended soil (C + A), nutrient uptake was improved by37% and 80% for N and P concentrations, respectively.Whereas for potassium, the beneficial effect of compostapplication resulted only in a slight enhancement (+4%).Under saline conditions, this MSW compost amendmentincreased N and P uptake despite the high Na + accumula-tion in plants (Fig. 1B), while K + nutrition showed no sig-nificant improvement. At the final harvest (C2), the shootsof all treatments displayed the same behavior as at C1 cutfor N, P and K + uptake. In plants subjected to the combi-nation of salt and compost (S + A), N and P uptake weresignificantly higher than the control, while K + uptakewas reduced. In roots, the organic amendment improvedN concentration but had no effect on P and K + one. 3.3. Chlorophyll content At C1 harvest, the total chlorophyll content was 9.74and 6.20 mg g  1 DW for C and S treatments, respectively,showing a reduction of 36% by salt exposure (Table 3). 01.01.52.02.5    D   W .  g  p  o   t  -    1 cbab C1  ShR C2 cbacdbaa01.01.52.02.5    N  a   + .  m  m  o   l  g   -   1    D   W 0.30.60.91.2abbababac bca Treatments S+AC S C+A 0 S+AC S C+A  00.30.60.91.20.50.5 Fig. 1. (A) Shoot and root dry matter of   H. maritimum  plants. (B) Na + concentrations in shoot and root. (C): Control treatment without salt norcompost. S: control irrigated with tap water added with 4 g l  1 NaCl.C + A: soil amended of 40 T ha  1 of compost and irrigated with tapwater. S + A: soil amended by 40 t ha  1 of compost and irrigated with tapwater added 4 g l  1 NaCl. The first harvest (C1) was carried out on shoots,after 70 days of sowing. Final harvest (C2) was carried out 60 days afterthe first. Data are the mean of 10 replicates ± SE. Means followed by thesame letters are not significantly different according to the Duncan’sMultiple Range Test at  P  6 0.05.7162  A. Lakhdar et al./Bioresource Technology 99 (2008) 7160–7167   This reduction was observed in both chlorophyll a and bcontents, but was less marked for the former. As a conse-quence, chl a/b ratio significantly increased in salt-treatedplants as compared to the control. Compost supply undernon saline conditions (C + A treatment) had no impacton total chlorophyll content. Whereas, in S + A treatmenttotal chlorophyll and chl a content showed to be lessaffected by salt stress (  16% and   10%, respectively), ascompared to S treatment (  47% and   42%, respectively).Total chlorophyll was lower at C2 than at C1 harvest,this decrease being particularly higher in S treatment(5.19 mg g  1 DW). As for C1, the compost amendmentshowed to be efficient in reducing saline constraint. Indeed,salt-treated plants (S), for which, a strong decline in totalchlorophyll content was observed on non-amended soil incomparison to the control (  45%), showed a much lowerdiminution when supplied with compost in S + A treat-ment (  15%). 3.4. Protein content and Rubisco capacity At the first cut (C1), a strong decline of total solubleprotein content and Rubisco capacity was recorded for Splants, while changes were not significant under C + Atreatment (Table 4). The positive effect of compost wasmore marked under saline (S + A) than non-saline condi-tions (C + A). Indeed, total soluble protein content wasmore than 4 fold-higher in S + A (50 mg g  1 DW) thanin S plants (11,3 mg g  1 DW). Nevertheless, this valueremained lower than that of the control (76 mg g  1 DW).The capacity of Rubisco in control plants (C) was about370  l mol h  1 g DW at the first cut (Table 4). It decreasedby 15% in S treatment. On amended soil, this parameterwas considerably enhanced, reaching and even exceedingthe control value in S + A and C + A plants, respectively.At the second harvest (C2), the reduction of Rubiscocapacity was more pronounced in S plants in comparisonto the control (25%). It was however less affected inS + A treatment than in S one (14%). 3.5. Heavy metal accumulation At the first cut (C1), Cu 2+ concentrations were 14 and13  l g g  1 DW in C and S plants, respectively, and17  l g g  1 DW in both C + A and S + A treatments (Table5). At the second cut (C2), shoots of both control and non-amended salt-treated plants showed comparable concentra-tions (20  l g g  1 DW). Compost application associated Table 2Nitrogen, phosphorus and potassium contents of   H. maritimum  at the first (C1) and second cut (C2)C S C + A S + AN (mmol g  1 ) C1 Sh1 2.43 ± 0.12c 2.40 ± 0.13c 3.33 ± 0.09a 3.07 ± 0.13bC2 Sh2 1.83 ± 0.82c 1.54 ± 0.34c 2.95 ± 0.13a 2.23 ± 0.02bR 1.31 ± 0.07c 1.24 ± 0.12c 1.95 ± 0.11a 1.68 ± 0.11bP (mmol g  1 ) C1 Sh1 0.05 ± 0.001b 0.05 ± 0.005b 0.09 ± 0.003a 0.09 ± 0.014aC2 Sh2 0.10 ± 0.003a 0.07 ± 0.005b 0.10 ± 0.008a 0.12 ± 0.003aR 0.04 ± 0.008a 0.04 ± 0.005a 0.05 ± 0.002a 0.04 ± 0.006aK + (mmol g  1 ) C1 Sh1 1.25 ± 0.03a 1.00 ± 0.15b 1.30 ± 0.12a 0.96 ± 0.07bC2 Sh2 0.91 ± 0.19a 0.69 ± 0.10b 0.96 ± 0.11a 0.66 ± 0.18bR 0.52 ± 0.02a 0.40 ± 0.06b 0.55 ± 0.025a 0.36 ± 0.14bC: control treatment without salt nor compost. S: control irrigated with tap water added with 4 g l  1 NaCl. C + A: soil amended of 40 t ha  1 of compostand irrigated with tap water. S + A: soil amended by 40 t ha  1 of compost and irrigated with tap water added 4 g l  1 NaCl. Data are the means of 10replicates. Mean values followed by the same letter are not significantly different at  P  6 0.05.Table 3Total chlorophyll (chl a + b), chlorophyll a (chl a), chlorophyll b (chl b) and chlorophyll a/b ratio (chl a/b) of   H. maritimum  shoots, at the two cuts (C1and C2)C S C + A S + Achl (a + b) C1 9.74 ± 0.46a 6.20 ± 0.47c 9.66 ± 0.23a 8.16 ± 0.30b(mg g  1 DW) C2 9.16 ± 0.19a 5.19 ± 0.57d 8.60 ± 0.69ab 7.70 ± 0.21bcchl a C1 6.49 ± 0.38a 4.42 ± 0.26c 6.23 ± 0.50ab 5.82 ± 0.29b(mg g  1 DW) C2 6.25 ± 0.18a 3.81 ± 0.19c 5.74 ± 0.36b 5.64 ± 0.10bchl b C1 3.25 ± 0.22a 1.78 ± 0.27c 3.43 ± 0.50a 2.34 ± 0.17b(mg g  1 DW) C2 2.91 ± 0.30a 1.38 ± 0.30c 2.86 ± 0.43a 2.06 ± 0.13bchl a/b C1 2.03 ± 0.12b 2.51 ± 0.29a 1.85 ± 0.38b 2.50 ± 0.22aC2 2.15 ± 0.23b 2.76 ± 0.14a 2.03 ± 0.24b 2.74 ± 0.14aC: control treatment without salt nor compost. S: control irrigated with tap water added with 4 g l  1 NaCl. C + A: soil amended of 40 t ha  1 of compostand irrigated with tap water. S + A: soil amended by 40 t ha  1 of compost and irrigated with tap water added 4 g l  1 NaCl Data are the means of fourreplicates. Means followed by the same letters are not significantly different according to the Duncan’s Multiple Range Test at  P  6 0.05. A. Lakhdar et al./Bioresource Technology 99 (2008) 7160–7167   7163  (S + A) or not (C + A) with salt treatment increased Cu 2+ concentrations to 58 and 55  l g g  1 DW, respectively. Irre-spective of salinity level, higher values were found in rootsin the presence of organic amendment (113,8–139,4  l g g  1 DW).Shoot Zn 2+ concentrations showed close values inde-pendently of the treatment at the first cut (C1), whileextending treatment duration (C2) increased shoot accu-mulation in C + A and S + A treatments (+45 and+53%, respectively). The highest values were recorded inroots of plants cultivated on amended soil (C + A andS + A treatments: 112,2 and 144,7  l g g  1 DW,respectively).In both C and S treatments, shoot Cd 2+ and Pb 2+ con-centrations measured at C1 did not exceed 1 and 1.2  l g g  1 DW, respectively. Plants cultivated on amended soil(C + A and S + A) showed significantly higher values(1.5  l g g  1 for Cd 2+ and 2  l g g  1 for Pb 2+ ). At C2, shootaccumulation for the tow metals was enhanced, especiallyin C + A and S + A treatments (+150% and +168% forCd 2+ , and +130% and +174% for Pb 2+ , respectively). Asfor Cu 2+ and Zn 2+ , Pb 2+ and Cd 2+ concentrations werehigher in roots than in shoots, mainly in the case of Pb 2+ (Table 5). 4. Discussion 4.1. Plant growth and nutrition The present study showed that salt treatment induced amarked reduction of biomass production in  H. maritimum plants grown on non-amended soil, especially at the secondcut (Fig. 1A). This likely resulted from the prolonged expo-sure to salinity, which may have caused plant cell and tis-sue. The mechanisms explaining such a growth inhibitioninclude, among other factors, the disturbance of plantnutrition (Table 3). Shoots and roots of plants subjectedto S treatment exhibited a strong accumulation of Na + which caused an inhibition of mineral nutrient uptake, inparticular for nitrogen, potassium, and phosphorus (Kayaet al., 2001). Under non-saline conditions, the compostamendment significantly improved plant growth(Fig. 1A). This result is in agreement with the findings of Alburquerque et al. (2007), pointing out the positiveimpact of urban waste compost application on the growthof Ryegrass plants. Growth is often positively correlatedwith nutrient uptake as reported by several studies. Verlin-den and McDonald (2007) showed that compost amend-ment increased  Limonium sinuatum  and  Celosia argentea Table 4Soluble protein content and Rubisco capacity of   H. maritimum  shoots, at the first (C1) and the second (C2) cutsC S C + A S + ATotal protein C1 79.91 ± 5.88a 18.45 ± 4.20c 86.79 ± 7.88a 60.30 ± 3.55b(mg g  1 ) C2 69.53 ± 6.22a 11.35 ± 3.70c 76.07 ± 0.13a 50.60 ± 2.90bRubisco capacity C1 369.75 ± 15b 314.39 ± 11c 389.54 ± 5a 361.74 ± 17b( l mol h  1 g  1 ) C2 322.58 ± 10b 247.49 ± 9d 364.36 ± 8a 275.29 ± 12cC: control treatment without salt nor compost. S: control irrigated with tap water added with 4 g l  1 NaCl. C + A: soil amended of 40 t ha  1 of compostand irrigated with tap water. S + A: soil amended by 40 t ha  1 of compost and irrigated with tap water added 4 g l  1 NaCl. Data are the means of fourreplicates ± SE. Means followed by the same letters are not significantly different according to the Duncan’s Multiple Range Test  P  6 0.05.Table 5Heavy metal concentrations ( l g g  1 DW) of   H. maritimum  at the first (C1) and second cut (C2)C S C + A S + ACu 2+ ( l g g  1 ) C1 Sh1 14.91 ± 3.01b 13.72 ± 2.68b 17.05 ± 2.70a 17.77 ± 3.61aC2 Sh2 20.00 ± 2.44b 23.08 ± 3.72b 55.04 ± 6.80a 58.70 ± 5.37aR 76.08 ± 12.10b 65.07 ± 17.03b 113.87 ± 17.0a 139.45 ± 20.80aZn 2+ ( l g g  1 ) C1 Sh1 67.98 ± 3.31a 64.22 ± 12.26a 54.78 ± 12.61ab 62.08 ± 12.69aC2 Sh2 77.08 ± 2.82b 66.62 ± 8.51b 111.81 ± 13.55a 118.06 ± 14.19aR 101.50 ± 12.04b 106.86 ± 14.21b 112.20 ± 15.41b 144.71 ± 40.10aCd 2+ ( l g g  1 ) C1 Sh1 1.08 ± 0.16b 1.01 ± 0.17b 1.52 ± 0.28a 1.52 ± 0.18 ª C2 Sh2 1.20 ± 0.17b 1.50 ± 0.15b 3.02 ± 0.27a 3.22 ± 0.26 ª R 2.65 ± 0.40b 2.85 ± b 3.00 ± 0.70ab 3.78 ± 0.95 ª Pb 2+ ( l g g  1 ) C1 Sh1 1.01 ± 0.21b 1.27 ± 0.16b 1.97 ± 0.29a 2.07 ± 0.24aC2 Sh2 5.51 ± 1.30b 5.35 ± 2.07b 12.69 ± 2.37a 15.12 ± 2.35aR 10.58 ± 0.87b 13.36 ± 3.70b 22.86 ± 3.21a 22.74 ± 1.48aC: control treatment without salt nor compost. S: control irrigated with tap water added with 4 g l  1 NaCl. C + A: soil amended of 40 t ha  1 of compostand irrigated with tap water. S + A: soil amended by 40 t ha  1 of compost and irrigated with tap water added 4 g l  1 NaCl. (Sh1; shoot first cut, Sh2;shoot second cut, R: root). Data are the means of 10 replicates. Means followed by the same letters are not significantly different according to the Duncan’sMultiple Range Test  P  6 0.05.7164  A. Lakhdar et al./Bioresource Technology 99 (2008) 7160–7167 
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