Effects of two composts and two grasses on microbial biomass and biological activity in a salt-affected soil

Ecological Engineering 60 (2013) 363–369

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Effects of two composts and two grasses on microbial biomass and biological activity in a salt-affected soil Youssef Ouni a,∗ , Abdelbasset Lakhdar a , Rosalia Scelza b , Riccardo Scotti b , Chedly Abdelly a , Zouhaier Barhoumi a , Maria A. Rao b a b

Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj Cédria, B.P. 901, 2050 Hammam-Lif, Tunisia Department of Agriculture, University of Naples Federico II, via Università 100, 80055 Portici, Italy

a r t i c l e

i n f o

Article history: Received 4 April 2013 Received in revised form 11 July 2013 Accepted 6 September 2013 Available online 10 October 2013 Keywords: Composts MSW compost PW compost Microbial biomass Soil enzymes Soil remediation Saline soil

a b s t r a c t The effectiveness of compost supply at several doses (0, 50, 100, and 150 t/ha) to a saline soil was studied using municipal solid waste (MSW) and palm waste (PW) composts. The experiment was carried out in pots under cultivation of Polypogon monspeliensis (halophyte forage species) and Hordeum vulgare (common forage species) and lasted three months. The investigation focused on some selected soil physico-chemical properties, soil microbial biomass, and ten soil enzymatic activities; Arylsulfatase (ARY), dehydrogenase (DEH), ␤-glycosidase (␤-GLU), protease (PRO), urease (URE), invertase (INV), Fluorescein diacetate hydrolase (FDAH), catalase (CAT), acid and alkaline phosphatases (PHO). Both amendments improve markedly the saline soil quality. They ameliorate the physico-chemical properties. The increase of soil pH is regarded as an interesting fact and is usually proportional to the compost application rate. Electrical conductivity increased proportionally to the applied rates. Soil carbon and nitrogen amounts were also improved and the highest raise (7.5-folds) was noted for carbon. According to the substantial increase of the organic matter, levels of measured microbial biomass and several enzyme activities in saline soil were improved. DEH activity which proposed as a measure of overall microbial activity exhibited a significant increase only at dose 2 (100 t/ha). Consequently, One hundred tones of composts per hectare, under which some enzymes exhibited an optimal of activity and metal accumulation can be minimized, appeared an interesting rate for saline soil amendment. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Salt toxicity is one of three main effects of salt excess in the soil: osmotic effect, nutritional effect, and toxic (or specific) effect (Rafael, 2009). Apart from the natural salinization, human-induced secondary salinization occurs frequently mainly as a consequence of over irrigation caused by improper management of irrigation facilities, poor soil internal drainage condition. In general, two major approaches are used in reclaiming salinized soils: (i) accelerating soil desalinization process by leaching salts down the profiles, and (ii) enhancing the tolerance of the existing crop cultivars to salt stress coupled with breeding new salt-tolerant crop species (Liang et al., 1996). These measures are especially crucial to the sustainable agriculture in Tunisia. The influence of salt as a major stress to soil microorganisms has been the subject of several studies (Mamilov et al., 2004; Pankhurst et al., 2001; Sardinha et al., 2003; Sarig and

∗ Corresponding author. Tel.: +216 79412948; fax: +216 79412948. E-mail address: ouni [email protected] (Y. Ouni). 0925-8574/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ecoleng.2013.09.002

Steinberger, 1994). A decrease in carbon dioxide (CO2 ) production, enzyme activities, or microbial biomass in soil has often been observed in the field (Pathak and Rao, 1998) and under laboratory incubations (Ghollarata and Raiesi, 2007; Rietz and Haynes, 2003; Wichern et al., 2006). Soil enzyme activities were found to decrease with increasing salinity but the degree of inhibition varied among the enzymes assayed and the amount of salt added (Frankenberger and Bingham, 1982; Sardinha et al., 2003; Wichern et al., 2006; Yuan et al., 2007). The same authors observed that dehydrogenase (oxydoreductase) activity was severely inhibited by salinity, whereas the hydrolases (amidase, urease, acid and alkaline phosphatase, phosphodiesterase, inorganic pyrophosphatase, rhodanase, ␣-glucosidase, and ␣-galactosidase) showed lower inhibition. In contrast, García and Hernández (1996) reported that the activity of hydrolases, such as protease, ␤-glucosidase, and phosphatase, were more negatively affected by salinity than oxidoreductases (dehydrogenase and catalase). Increasing salinity thus has detrimental effects on biologically mediated processes in the soil, such as soil respiration (Ghollarata and Raiesi, 2007; Pathak and Rao, 1998). Despite, soil microorganisms have the ability to adapt or tolerate osmotic stress caused

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by salinity (Sparling et al., 1989; Wichern et al., 2006; Yuan et al., 2007). Numerous physical, chemical, and biological approaches were established to reclaim salt-affected soils (Qadir et al., 2007; Wong et al., 2009; Rabhi et al., 2010; Feizi et al., 2010; Mokoi and Verplancke, 2010). The application of organic matter increases soil microbial biomass and some soil enzymatic activities such as urease, alkaline phosphatase and ␤-glucosidase (Lakhdar et al., 2008). Tejada and Gonzalez (2005) demonstrated that an increase in the organic matter content of saline soils increases soil microbial biomass. The role of compost in salt-affected soils is very vital because the organic source is ultimate opportunity to improve the physical properties of such soils which have been deteriorated to the extent that water and air passage become extremely difficult in such soils. Resultantly, the water stands on the surface of these soils for weeks long. The plants when grown under these conditions often die due to deficiency of root respiration. The compost can be a very good organic amendment in saline agriculture as well as for reclamation of salt-affected soils (Zaka et al., 2003). The aim of this work was to study the effects of two different composts (municipal solid waste compost and palm waste compost) on saline soil reclamation. Soil physical, chemical and biological properties during a period of three months under cultivation of Polypogon monspeliensis (halophyte forage species) and Hordeum vulgaris (common forage species) were emphasized. 2. Materials and methods 2.1. Saline soil, and municipal solid waste (MSW) and palm waste (PW) composts sources The current investigation was conducted in pots and under green house conditions. The used saline soil is a loam-silt one (20% clay, 58% silt, and 22% sand), collected from salt-affected soil of Soliman (North-East Tunisia, 36◦ 41 16 ), dried and sieved at 2 mm. Palm waste compost (PW) was obtained from composting station of Gabes (South Tunisia). Municipal solid waste (MSW) compost was collected from composting station of Beja (North Tunisia). It was mechanically produced by mixing weekly the waste heap under aerobic conditions by fast fermentation and aged 8 months before use. The main analytical characterization of the saline soil, PW and MSW were initially determined (Table 1). 2.2. Soil amendment and culture conditions The saline soil was prior amended with different doses of MSW and PW compost (0, 50, 100 and 150 t/ha), and putted in 5 kg pots. After that, P. monspeliensis and H. vulgare seeds were sown. The pots were placed in a randomized complete block design with four treatments and three replicates, with minimum–maximum temperatures of 21–25 ◦ C, 40–60% relative humidity and natural daylight with minimum–maximum light flux of 200–1000 ␮mol m−2 s−1 . All pots were irrigated when necessary with tap water to saturation and then drained freely to field capacity. Hand weeding was done to manage the weeds and no pesticides were applied. After 90 days, plants were harvested and fresh soil samples were collected for biochemical assays. Physico-chemical parameters were determined on an oven dried soil. 2.3. Physico-chemical properties determination Physico-chemical analyses were performed on air-dried and sieved (<2 mm) soil samples according to standard techniques (Sparks, 1996), and they are shown in Table 1. According to USDA

(Soil Survey Staff, 1975), the soil was classified as a sandy clay loam soil (clay 20%, sand 45%, and silt 58%). Soil and organic residues pH were determined with a glass electrode pH meter in 1:2.5 soils to water ratio. Total nitrogen was determined by the Kjeldahl method as recommended by Brookes et al. (1985). Organic C content was determined by dry combustion (Walkley and Black, 1934). Heavy metal contents (Cu, Zn, Pb, and Cd) were determined by atomic absorption spectrophotometer after acid digestion (nitric acid and chloridric acid, 3:1 ratio) according to Pauwels et al. (1992). Three independent replicates were performed for each sample and blanks were measured in parallel.

2.4. Biological activity assays Microbial biomass (MB) was determined by the chloroform fumigation-extraction method (Vance et al., 1987). The enzyme activities were determined on fresh, moist and sieved (<2 mm) soil. Substrates: p-nitrophenyl-␤-deglucoside and p-nitrophenylphosphate were used for determination of ␤-glucosidase (E.C. 3.2.1.21 [␤-GLU]) and phosphatase (E.C.3.1.3.2 [PHO]), respectively. An aliquot (1 g) of soil was incubated with 5 ml of buffered substrate in reaction flasks for 1 h at 30 ◦ C, under continuous stirring. Specific buffers and pH were used as reported in Sannino and Gianfreda (2001) and Eivazi and Tabatabai (1990). Enzymatic reactions were stopped by rapidly transferring the mixtures to a freezer and holding them there for 10 min. Concentrations of pnitrophenol were determined at 400 nm after addition of NaOH and CaCl2 for PHO and Tris/NaOH buffer (pH 10.0) and CaCl2 for ␤-GLU. For the determination of protease (E.C. 3.2.1.26 [PRO]) activity, 1 g of soil was treated with 1 ml Tris buffer (pH 8.0) and 0.5 ml toluene for 15 min, then 2 ml 1% (w/v) casein were added to, and the soil was placed in an incubator at 37 ◦ C for 24 h. The aromatic amino acids (product) released were extracted with 3 ml trichloroacetic acid 15% (w/v). Five milliliters 0.4 M NaCO3 and 1 ml Folin–Ciocalteu reagent were added to 1 ml filtrate. After incubation at 37 ◦ C for 15 min, the products were measured calorimetrically at 680 nm (Institute of Soil Science, Chinese Academy of Science, 1985; Xu and Zheng, 1986). Catalase (E.C. 1.11.1.6 [CAT]) activity was measured using the titration method. Fresh soil (5 g) was placed at 0–4 ◦ C for 30 min, with 25 ml 3% H2 O2 added, the samples were placed at 0–4 ◦ C for 30 min again, before terminating the reaction with the addition of 25 ml (1 M) H2 SO4 . After filtration, 4 ml (0.5 M) H2 SO4 was added to 1 ml filtrate, using 20 mM KMnO4 to measure the O2 absorbed (Institute of Soil Science, Chinese Academy of Science, 1985; Xu and Zheng, 1986). Urease (E.C. 3.5.1.5 [URE]) activity was measured using urea, and the ammonium released from soil was assayed calorimetrically at 460 nm (Kandeler and Gerber, 1988). Arylsulfatase (E.C. 3.1.6.1 [ARY]) activity was determined by the method of Tabatabai and Bremner (1970). Dehydrogenase (E.C. 1.1 [DEH]) activity was measured by mixing 1 g of soil with 1 ml of buffered tetrazolium salts (TTC) solution, according to Trevors (1984). Invertase (INV) (E.C. 3.2.1.26) activity was determined using the Stemmer et al. (1999) method. Fluorescein diacetate hydrolase (FDAH) was measured by the method of Greena et al., 2006. A fumigation–extraction method was used to estimate microbial biomass C (MB-C) with extractable C converted to microbial C using standard factor (Vance et al., 1987). Soil was fumigated with ethanol-free chloroform for 24 h. Fumigated and non-fumigated soil samples were then extracted with 0.5 M K2 SO4 for 30 min in an oscillating plane at room temperature, after filtration soil extracts were stored at 2 ◦ C prior to analysis. Sub-samples of filtrates from both fumigated and non-fumigated

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Table 1 Characteristics of the used saline soil and municipal solid waste (MSW) and palm waste (PW) composts (data are means ± SD, n = 3).

pH EC (dS m−1 ) N (g kg−1 ) C (g kg−1 ) C/N K+ (meq/100 g) Na+ (meq/100 g) Ca2+ (meq/100 g) Mg2+ (meq/100 g) CEC Cu2+ (mg kg−1 ) Pb2+ (mg kg−1 ) Zn2+ (mg kg−1 ) Cd2+ (mg kg−1 )

MSW compost

PW compost

Saline soil

8.00 ± 0.02 8.09 ± 0.10 11.13 ± 0.03 144.50 ± 11.50 12.98 ± 1.06 1.83 ± 0.06 1.02 ± 0.01 20.14 ± 0.03 5.11 ± 0.00 27.47 ± 2.67 89.40 ± 0.63 254.00 ± 0.75 290.65 ± 1.30 2.88 ± 0.14

7.72 ± 0.02 5.90 ± 0.003 15.19 ± 1.02 259.33 ± 3.06 17.07 ± 1.01 10.80 ± 0.01 0.05 ± 0.01 55.02 ± 0.08 5.04 ± 0.01 30.53 ± 2.26 2.05 ± 0.05 2.23 ± 0.15 4.37 ± 0.25 <0.10

7.97 ± 0.08 5.13 ± 0.06 1.28 ± 0.08 2.58 ± 0.10 2.02 ± 0.19 1.05 ± 0.00 0.89 ± 0.00 5.08 ± 0.00 1.37 ± 0.00 8.39 ± 0.41 11.20 ± 0.03 82.09 ± 0.09 79.37 ± 0.31 1.07 ± 0.06

soils were analyzed for extractable C. Triplicates were performed for each activity assay. 2.5. Statistical analysis Statistical analysis was carried out using statistica version 6.0 (Statsoft Inc.). Pearson’s correlation coefficients were calculated to assess the correlation between different variables. Data were analyzed using a one-way ANOVA (F-test). Data were first tested for normality with the Kolmogorov–Smirnov test and for homogeneity of variance with the Brown–Forsythe test. Significant test results were followed by Tukey tests for identification of important contrasts (Day and Quinn, 1989). Differences between measurements of fluorescence at dawn and mid-day were compared using Student’s test (t-test). 3. Results 3.1. Physico-chemical properties of the amended saline soil after P. monspeliensis and H. vulgare harvests MSW compost and PW compost application increased generally the values of all measured physico-chemical properties, when compared to the unamended saline-soil. Different patterns were observed according to the species, doses and type of amendment used. In this study, the increase of soil pH is regarded as a major fact when MSW and PW compost is used. Such increase was usually proportional to the application rate, under cultivation species (Table 2). Electrical conductivity (EC) of the soil solution is related to the dissolved solutes content of soil and is often used as a measurement of soil salt content. MSW compost and PW compost applied at rates ranging from 50 to 150 t/ha increased proportionally the EC of salt affected soil. In MSW compost amendment case, the EC levels increased from 512.67 to 764.33 ␮S cm−1 in P. monspeliensis cultivated soil, and from 512.67 to 750.71 ␮S cm−1 in H. vulgare cultivated one. While a high increase was recorded with PW compost amendment, and EC values rose up to 839 and 887 ␮S cm−1 in P. monspeliensis and H. vulgare cultivated soils, respectively (Table 2). Application of 50, 100 and 150 t/ha MSW and PW composts increased soil nitrogen and carbon contents as compared to control (Table 2). Under MSW compost, nitrogen concentrations were ranged between 1.28 and 2.63 g kg−1 for H. vulgare cultivated soil, and between 1.25 and 1.69 g kg−1 for P. monspeliensis cultivated soil. The highest value was observed in H. vulgare cultivated and PW compost amended soil (Table 2). Furthermore, carbon concentration increased from 2.51 to 15.97 g kg−1 for H. vulgare and 2.51 to 16.32 g kg−1 for P. monspeliensis cultivated soils, following MSW compost application at rate 3 (150 t/ha) (Table 2). The highest

increase was noted for the PW compost application, and values can reach 7.5-folds of those of the unamended P. monspeliensis and H. vulgare cultivated soil, at rate 3 (150 t/ha) (Table 2). In addition, application of both compost increased C and N ratio, and the highest values were noted in P. monspeliensis cultivated soil, especially at rate 3 (150 t/ha) (Table 2). The MSW and PW composts amendment increased almost all exchangeable cations compared to the control. In fact, Potassium contents increased following soil amendment, and the highest values were noted for both species at rates 2 (100 t/ha) for the PW, and at rate 3 (150 t/ha) for the MSW compost (Table 3). Such increase was observed also for calcium, and the highest amounts were observed at rate 3 for PW compost and at rate 2 for MSW compost amended soils (Table 3). Exchangeable Ca2+ represents the main part of the cation exchange capacity (CEC), and in both amendment cases the proportion exceeds more than 70% (Table 3). In contrast, K+ and Mg2+ amounts declined with higher rates in amended saline soils, despite the fact that cation exchange capacity increased markedly with the addition of MSW compost and PW compost (Table 3). Heavy metal concentration at some extent increased or did not change in concomitance with MSW compost and PW supply (Table 4). At the highest dose of MSW compost (150 t/ha), Cu2+ concentration increased by 55% in H. vulgare cultivated soil and by 40% in P. monspeliensis cultivated one. Equally, Pb2+ concentrations increased by 24% and 16% in H. vulgaris and P. monspeliensis cultivated soils, respectively (Table 4). In addition, MSW compost tended to increase total soil Zn and Cd concentrations when compared to control. Its application at the highest rate (150 t/ha) resulted in slightly increase of Zn2+ by approximately 19% and 30% in P. monspeliensis and H. vulgare cultivated soils, respectively, and of Cd by 19% and 25% in P. monspeliensis and H. vulgare cultivated soils, respectively (Table 4). No change of total soil Zn2+ , Cd, Pb2+ and Cu2+ were observed in PW compost amended soil (Table 4). 3.2. Soil microbial biomass and enzymatic activities According to the substantial increase of C and N biomass, previously mentioned, the levels of measured microbial biomass and enzyme activities in saline soil were generally enhanced by the application of 50, 100 and 150 t/ha of MSW and PW amendments when compared to control. In fact, the soil microbial biomass increased during the experimental period in amended soil, and the greatest increase was observed in P. monspeliensis cultivated soil amended by 150 t/ha MSW compost (20.67 mg C/100 g dry soil) and in H. vulgare cultivated soil amended with 100 t/ha of MSW compost (23.28 mg C/100 g dry soil). Whereas, the highest amounts of microbial biomass was observed in H. vulgare cultivated

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Table 2 Some characteristics of municipal solid waste (MSW) and palm waste (PW) composts amended saline-soil, after H. vulgare and P. monspeliensis harvest (data are means ± SD, n = 3). EC1/5 (dS m−1 )

pH Soil cultivated with H. vulgare PW 0 50 100 150 MSW

0 50 100 150

Soil cultivated with P. monspeliensis PW 0 50 100 150 MSW

a,b,c,d,e,f,g,h

0 50 100 150

N (g kg−1 )

C (g kg−1 )

C/N

8.00 8.03 8.12 8.17

± ± ± ±

0.11a 0.02ab 0.02cd 0.02d

5.23 6.12 7.551 8.87

± ± ± ±

0.005a 0.012b 0.013c 0.008d

1.18 2.22 2.91 3.32

± ± ± ±

0.08a 0.09e 0.04f 0.09g

2.53 12.97 17.90 18.36

± ± ± ±

0.12a 0.58d 2.08g 0.58h

2.16 5.85 6.14 5.53

± ± ± ±

0.23a 0.41b 0.55c 0.20b

8.02 7.98 8.08 8.13

± ± ± ±

0.03a 0.02ab 0.02bc 0.01cd

5.15 5.02 6.63 7.50

± ± ± ±

0.004a 0.056a 0.047b 0.015c

1.25 1.83 2.20 2.63

± ± ± ±

0.09a 0.01d 0.01e 0.01f

2.51 9.17 13.24 16.32

± ± ± ±

0.09a 0.02c 1.01e 1.02f

2.01 5.02 6.03 6.20

± ± ± ±

1.05a 1.40b 0.47c 0.38c

8.00 8.15 8.23 8.27

± ± ± ±

0.10a 0.03d 0.01e 0.01e

5.16 6.64 8.07 8.39

± ± ± ±

0.004a 0.025b 0.004c 0.011d

1.27 1.62 1.98 2.23

± ± ± ±

0.08a 0.00b 0.04d 0.10e

2.53 12.41 17.79 19.45

± ± ± ±

0.04a 0.06b 0.06g 0.70h

1.98 7.66 8.96 8.74

± ± ± ±

0.49a 0.03d 1.37e 6.93d

7.99 8.22 8.29 8.37

± ± ± ±

0.10a 0.03e 0.04e 0.01f

5.13 6.19 7.28 7.64

± ± ± ±

0.006a 0.006b 0.005c 0.008c

1.25 1.67 1.74 1.69

± ± ± ±

0.04a 0.00b 0.00c 0.00b

2.51 8.43 12.29 15.97

± ± ± ±

0.09a 0.01b 0.02d 0.98f

2.01 5.02 7.07 9.45

± ± ± ±

2.14a 0.01b 0.11d 0.58f

Means followed by the same letters are not significantly different according to Duncan’s test, P < 0.05.

soil amended by 50 t/ha PW compost (18.074 mg C/100 g dry soil) and 100 t/ha PW compost for soil cultivated with P. monspeliensis (18.074 mg C/100 g dry soil) (Table 5). ARY activity increased with increasing application rates mainly at 50 and 100 t/ha of PW and MSW composts, respectively (Table 5). Furthermore, the addition of MSW compost at 150 t/ha slightly increased the activity of ARY compared to the unamended soil. There was no significant difference between the types of compost for the all treatment. The difference of ARY activity was remarked only between species and doses (Table 5). Significantly detectable increases were also occurred for ␤-GLU activity in the presence of two composts (Table 5). For PW, the highest increase was recorded at 150 t/ha amended soil cultivated by H. vulgare (180% as compared to control) and at 50 t/ha amended soil cultivated by P. monspeliensis (123% as compared to control). For MSW compost, substantial rises were detected at 100 t/ha amended soil and cultivated by H. vulgare and P. monspeliensis (280% and 133%, respectively) as compared to controls (Table 5).

ACID PHO and ALK PHO showed an increase with amendments reaching a maximum at 100 t/ha PW and both species cultivated soils (Table 5). Under MSW amendment, the highest amounts of ACID PHO and ALK PHO activities were noted, respectively, at 100 and 50 t/ha H. vulgare cultivated soil, and vice versa for P. monspeliensis cultivated one (Table 5). DEH activity exhibited a significant increase only at 100 t/ha PW and MSW composts, reaching at least 14% and 60% for H. vulgare and P. monspeliensis cultivated soils, respectively (Table 5). At 150 t/ha of PW compost, DEH activity showed a slight decrease compared to rate 0 t/ha for H. vulgare (Table 5). CAT, FAD, INV, URE and PRO activities were also increased with soil amendments. There were a rise of 19% of CAT activity at 100 t/ha MSW and H. vulgare cultivated soil. Equally, an increase was putted out for FAD activity at 100 t/ha MSW amended soils reaching 56% and 23% in H. vulgare and P. monspeliensis case, respectively (Table 5). MSW rate 2 (100 t/ha) seemed to enhance URE activity by more than 82% in P. monspeliensis cultivated soil (Table 5).

Table 3 Cation concentrations of the municipal solid waste (MSW) and palm waste (PW) composts amended saline-soil, after H. vulgare and P. monspeliensis harvest (data are means ± SD, n = 3). K+

Na+

Ca2+

Mg2+

CEC

(meq/100 g) Soil cultivated with H. vulgare PW 0 50 100 150 MSW

0 50 100 150

Soil cultivated with P. monspeliensis PW 0 50 100 150 MSW

a,b,c,d,e

0 50 100 150

1.03 1.46 1.46 1.36

± ± ± ±

0.10a 0.04d 0.24d 0.54c

0.92 1.12 1.13 1.12

± ± ± ±

0.01a 0.01b 0.01b 0.02b

5.50 8.66 9.14 9.18

± ± ± ±

0.05a 0.16b 0.50c 0.11c

1.47 1.72 1.54 1.43

± ± ± ±

0.09a 0.16d 0.27c 0.10bc

8.90 12.66 13.28 12.70

± ± ± ±

0.09a 0.36b 0.66b,c 0.15b

1.09 1.05 1.04 1.29

± ± ± ±

0.02a 0.07a 0.13a 0.02c

1.01 0.92 1.13 1.19

± ± ± ±

0.01a 0.02a 0.00b 0.01c

5.73 8.70 10.50 8.29

± ± ± ±

0.15a 0.14b 0.14d 0.12b

1.33 1.41 1.59 1.37

± ± ± ±

0.01a 0.02bc 0.27cd 0.04b

8.89 12.09 14.26 12.07

± ± ± ±

0.1a 0.07b 0.04c 0.12b

1.00 1.04 1.34 1.08

± ± ± ±

0.00a 0.04a 0.18c 0.13a

0.90 1.12 1.13 0.93

± ± ± ±

0.00a 0.02b 0.00b 0.01a

5.49 8.91 9.01 9.59

± ± ± ±

0.12a 0.08b 0.07c 0.31c

1.31 1.40 1.55 1.48

± ± ± ±

0.00a 0.01b 0.18c 0.05d

8.78 12.48 13.01 13.07

± ± ± ±

0.12a 0.12b 0.07bc 0.12bc

1.04 1.02 1.24 1.48

± ± ± ±

0.00a 0.04a 0.21b 0.16d

0.89 0.98 1.13 1.11

± ± ± ±

0.00a 0.01a 0.02b 0.01b

5.54 8.46 11.52 7.94

± ± ± ±

0.12a 0.00b 0.58e 0.04b

1.38 1.56 1.52 1.40

± ± ± ±

0.00b 0.01b 0.58c 0.00b

8.85 12.03 15.75 11.91

± ± ± ±

0.12a 0.04b 0.63d 0.20d

Means followed by the same letters are not significantly different according to Duncan’s test, P < 0.05.

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Table 4 Heavy metal concentrations of municipal solid waste (MSW) and palm waste (PW) composts amended saline-soil, after H. vulgare and P. monspeliensis harvest (data are means ± SD, n = 3). Cu2+

Pb2+ −1

)

± ± ± ±

0.07a 0.29bc 0.28bc 0.09c

(mg kg Soil cultivated with H. vulgare PW

MSW

a,b,c,d,e,f,g,h

± ± ± ±

0.08b 0.23a 0.23a 0.08a

79.21 79.01 79.01 78.97

± ± ± ±

0.11bc 0.02b 0.02b 0.05a

1.01 0.96 0.96 0.92

± ± ± ±

0.01b 0.04b 0.07b 0.04a

11.15 ± 0.05a 14.73 ± 0.29e 16.49 ± 0.36g

82.04 88.42 96.53 107.07

± ± ± ±

0.06a 0.60de 1.43f 5.27d

79.35 86.30 98.65 103.24

± ± ± ±

0.23bc 0.65e 1.52h 1.10i

1.01 1.23 1.28 1.34

± ± ± ±

0.02b 0.04d 0.04d 0.07d

11.16 11.35 11.46 11.52

± ± ± ±

0.05a 0.03b 0.03bc 0.04bc

82.00 80.55 81.31 81.40

± ± ± ±

0.10b 0.09a 0.02b 0.01a

79.37 78.29 80.02 80.12

± ± ± ±

0.31bc 0.06a 0.35c 0.51c

1.02 1.03 1.10 1.14

± ± ± ±

0.03b 0.58b 0.00c 0.03b

11.19 13.45 14.23 15.63

± ± ± ±

0.06a 0.01d 0.01e 0.11f

82.09 86.34 94.53 97.31

± ± ± ±

0.08b 1.21c 0.65e 1.07g

79.36 84.73 92.69 96.85

± ± ± ±

0.30bc 1.5d 0.27f 0.67g

1.07 1.11 1.21 1.31

± ± ± ±

0.06bc 0.01c 0.02d 0.02d

11.06 11.44 11.49 11.74

0 50 100 150

0 50 100 150

MSW

Cd2+

82.07 81.62 81.62 81.73

0 50 100 150

Soil cultivated with P. monspeliensis PW 0 50 100 150

Zn2+

Means followed by the same letters are not significantly different according to Duncan’s test, P < 0.05.

4. Discussion 4.1. Effects of MSW and PW composts on physico-chemical properties of salt affected soil As expected, the added organic amendment improved properties of salt-affected soil. Soil pH increased following MSW compost and PW compost application. Such result was accordance with several studies (Mkhabela and Warman, 2005). The pH increase was usually proportional to the application rate and nature of composts, and may be due to the mineralization of carbon and the subsequent production of OH− ions by ligand exchange as well as the introduction of basic cations, such as K+ , Ca2+ , and Mg2+ (Mkhabela and Warman, 2005). The EC which often used as a parameter for estimation of soil salinity since it gives idea on total dissolved salts content which increased with amendments application. Such result was in agreement with those found by Walter et al. (2006), and Lakhdar et al. (2008). The highest increase of EC being seen following PW application may be due to the important amounts of K+ and Ca2+ in such compost. Concerning exchangeable cations, the application rates of composts seemed to be slightly increased it. Minor increase of Na+ concentration depending on the application rate of compost was observed. In general, Na+ concentrations in unamended soil showed change during three months of P. monspeliensis and H. vulgare cultivated soils. There are several possible explanations for the observed effect. Firstly, Na+ may have been taken up by plants as a substitute by K+ as the soil and compost were low in compost (Havlin et al., 1999; Quintero et al., 2007). Ameliorative effects of calcium, particularly for soil structure and pH are widely known and gypsum (CaSO4 H2 O) is often used to reclaim sodic soils (Chorom and Rengasamy, 1997; Qadir et al., 2002). Additionally, both compost amendments showed low exchangeable Mg2+ and K+ . These deficiencies in Mg2+ and K+ can occur when either Ca2+ is present in high amounts. These results are in agreement with the findings of other authors (Aitken et al., 1998; Havlin et al., 1999). MSW and PW composts amendment improved soil C and N contents which in consistence with the findings of Madejon et al. (2001), Marschner et al. (2003) and Lakhdar et al. (2008). Use of

PW compost induced a high increase of C and N contents in saline soil compared to MSW, which certainly due to its high initial concentration of C and N. The soil enrichment of organic amendment favors the development of P. monspeliensis and H. vulgaris, which will protect the soil and will contribute to its remediation. Consequently, the addition of these organic materials may be considered a good strategy for saline soil remediation. These results seem to be dependent on compost types and their nutrient status as well as the plant species (Crecchio et al., 2001). For both organic amendments, the large increase of C content compared to the N one explained in some way the raise up of C/N ratio. In addition, MSW compost tended to increase total soil Cu, Pb and Zn concentrations when compared to PW compost. The difference was remarked only between the species and the doses. These results are in agreement with the findings of other authors (Walter et al., 2006). 4.2. Effects of MSW and PW composts on soil biological activities Soil biological property is increasingly being used to evaluate soil quality, and such parameter appeared most sensitive to changes in the soil environment. In the current investigation and following both organic amendments, microbial biomass and several enzymatic activities were significantly stimulated. The increase of soil microbial biomass which depends largely on readily metabolizable C in the organic waste (Tejada and Gonzalez, 2005) was in agreement with previous findings (Molero et al., 2006; Tejada et al., 2006; Mondini et al., 2008). Concerning enzymes activities, Oxidative enzymes, especially DEH, were proposed as a measure of overall microbial activity being an intracellular enzyme related to oxidative phosphorylation processes that occurs in all intact and viable microbial cells (Tejada et al., 2006). Incorporation of both PW and MSW composts increased dehydrogenase activity because the added material may contain intra and extracellular enzymes and may also stimulate microbial activity in the soil (Liang et al., 2005). In the greenhouse experimental, the control soil showed values of enzymatic activities lower than those observed with treatment compost. These results are in agreement with the findings of other authors (Lakhdar et al., 2008; Tejada et al.,

0.11c 0.08d 0.06b 0.09f ± ± ± ± 0.83 0.97 0.77 1.20 0.00a 0.00a 0.00e 0.00d ± ± ± ± 0.01 0.01 0.06 0.05 0.08b 0.08a 0.11h 0.22i ± ± ± ± 0.67 0.58 1.09 1.15 0.01bc 0.01a 0.02e 0.01bc ± ± ± ± 0.07 0.05 0.09 0.07 0.88b 1.04a 0.22b 0.53c ± ± ± ± 14.25 11.45 14.91 18.82 0.00c 0.02c 0.00d 0.01c ± ± ± ± a,b,c,d,e,f,g,h

Means followed by the same letters are not significantly different according to Duncan’s test, P < 0.05.

0.14 0.15 0.16 0.13 0.02a 0.04b 0.07e 0.05c ± ± ± ± 0.30 0.47 1.00 0.83 0.01b 0.04f 0.02ef 0.03d ± ± ± ± 0.20 0.33 0.31 0.27 0.00d 0.01d 0.01g 0.00f ± ± ± ± 0.01a 0.00a 0.01c 0.01b MSW

0 50 100 150

5.82 10.62 12.87 20.68

± ± ± ±

0.00a 0.02d 0.01e 1.08h

0.06 0.07 0.12 0.10

± ± ± ±

0.21 0.22 0.28 0.26

0.11c 0.09a 0.02e 0.02g ± ± ± ± 0.83 0.64 1.10 1.32 0.00a 0.00a 0.00c 0.00c ± ± ± ± 0.01 0.01 0.03 0.04 0.08b 0.07d 0.03bc 0.02b ± ± ± ± 0.67 0.82 0.71 0.68 0.07 ± 0.01bc 0.06 ± 0.02b 0.08 ± 0.02c 0.10 ± 0.02e 0.88b 1.21a 0.36e 0.63ef ± ± ± ± 14.25 10.89 23.41 24.64 0.00c 0.01c 0.01f 0.00c ± ± ± ± 0.14 0.14 0.35 0.15 0.03a 0.02a 0.06e 0.04e ± ± ± ± 0.30 0.27 1.00 0.96 0.01b 0.02a 0.03e 0.02e ± ± ± ± 0.20 0.15 0.30 0.30 0.00d 0.01e 0.00e 0.00d ± ± ± ± 0.01a 0.01d 0.01bc 0.00b Soil cultivated with P. monspeliensis 0 5.82 ± 0.00a PW 6.34 ± 2.11b 50 100 12.96 ± 0.00e 150 6.58 ± 0.05b

0.06 0.14 0.11 0.10

± ± ± ±

0.21 0.26 0.24 0.20

± ± ± ± 0.83 1.46 1.39 1.33 0.00a 0.00b 0.00a 0.00a ± ± ± ± 0.01 0.02 0.01 0.01 0.02a 0.02b 0.02c 0.02d ± ± ± ± 0.58 0.68 0.74 0.81 0.02a 0.00b 0.01d 0.02b ± ± ± ± 0.04 0.06 0.09 0.06 0.63d 0.39ef 2.02g 0.00e ± ± ± ± 21.48 24.30 26.55 22.88 0.02b 0.01b 0.02d 0.01bc ± ± ± ± 0.10 0.11 0.16 0.11 0.02a 0.01d 0.02c 0.01c ± ± ± ± 0.29 0.89 0.77 0.78 0.02e 0.01f 0.01h 0.02c ± ± ± ± 0.29 0.35 0.46 0.24 0.01a 0.01g 0.01e 0.01e ± ± ± ± 0.00b 0.01bc 0.01bc 0.00b MSW

0 50 100 150

5.97 9.48 23.28 16.90

± ± ± ±

0.54a 2.10c 1.10i 1.63f

0.09 0.11 0.11 0.10

± ± ± ±

0.10 0.28 0.25 0.24

± ± ± ± 0.83 1.17 1.22 1.38 0.00b 0.01e 0.01bc 0.01a 0.09 0.20 0.11 0.06

± ± ± ±

0.10 0.14 0.12 0.18

± ± ± ±

0.01a 0.01bc 0.01b 0.00c

0.29 0.41 0.46 0.39

± ± ± ±

0.02e 0.01g 0.02h 0.01g

0.29 0.84 1.41 0.81

± ± ± ±

0.02a 0.01c 0.02f 0.03c

0.10 0.07 0.32 0.09

± ± ± ±

0.00b 0.01a 0.00e 0.00a

21.48 24.98 23.73 25.29

± ± ± ±

0.63d 1.40f 0.39e 0.62fg

0.04 0.08 0.10 0.09

± ± ± ±

0.02a 0.02c 0.02e 0.02d

0.58 0.89 0.92 0.90

± ± ± ±

0.02a 0.01f 0.02g 0.03fg

0.01 0.02 0.02 0.01

± ± ± ±

0.00a 0.00b 0.00b 0.00a

PRO URE INV FAD CAT DEH ALK.PHO ACID PHO ␤-GLU ARY MB

Soil cultivated with H. vulgare 0 5.97 ± 0.54a PW 18.07 ± 1.06g 50 100 12.94 ± 0.00e 150 9.22c ± 1.02

Table 5 Microbial biomass and some enzyme activities in saline-soil amended with municipal solid waste (MSW) and palm waste (PW) composts, after H. vulgare and P. monspeliensis harvest (data are means ± SD, n = 3).

0.13c 0.02i 0.00h 0.03g

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0.13c 0.01e 0.05f 0.00h

368

2006) reporting negative effect of salt on biochemical process. This may be due to a ‘salting-out’ effect which involves a decrease in enzyme solubility through dehydration, thus altering the enzyme ‘catalytic site’. The effect depends on the concentration of the salts and on the chemical composition of the enzyme itself (Garcia-Gil et al., 2000). Moreover, soil salinity disperses the clays contained therein, the extracellular enzymes would be less protected and perhaps denatured by proteolysis (Garcia-Gil et al., 2000). In our study, this seems the most likely cause of the decrease in enzymatic activities observed in the saline soils. During the experiment, the enzyme activities of URE, PRO, CAT, FAD and INV were increased with composts treatment. The observed stimulation of URE and PRO activity (related to the N cycle) is appreciable even with high doses of organic amendments, probably due to the higher microbial biomass produced in response. On the other hand, some studies indicated that high doses of some organic materials could introduce into the soil toxic compounds such as heavy metals which could have a negative effect on enzyme activities (Garcia-Gil et al., 2000; Crecchio et al., 2004). Our materials do not have high quantities of heavy metals compared to the norme AFNOR, and consequently high doses of these materials will not present toxicity of this type. In addition, Garcia et al. (1994) indicated that the positive effect of the organic amendments on soil biological quality is due to the stimulation of microbial growth and/or to the addition of microbial cells or enzymes with the amendment, which can counteract the negative effect produced by some toxic compounds. Pathak and Rao (1998), found a steady evolution of CO2 throughout 3 months of high salinity treatment showing a high activity of the heterotrophic microflora. Increases in these enzyme activities above baseline levels persisted for 3 months after application (Perucci, 1990). Furthermore, it was found that the addition of MSW compost at 150 t/ha reduced some activity compared to 100 t/ha dose. This decrease is likely attributed to the potential toxic effects exerted by trace elements in this particular compost (Garcia-Gil et al., 2000; Crecchio et al., 2004). Some authors suggested that the effect of metals on soil enzyme activities seems to be dependent on the time of application, their concentration, and soil characteristics (Crecchio et al., 2001). On the other hand, soil ARY and PHO activities were stimulated at high doses of organic amendment during this experiment. The demand for P by plants and soil microorganisms may be responsible for the stimulation in the synthesis of this enzyme (Garcia et al., 1994). According to Rao and Tarafdar (1992), increases in PHO activity indicate changes in the quantity and quality of soil phosphoryl substrates. The supply of readily metabolizable C in the organic byproduct is likely to have been the most influential factor contributing to the increased soil ARY and PHO activities.

5. Conclusions In conclusion, unamended saline soil showed lower values of microbial biomass and enzymatic activities, which indicates that biochemical quality was negatively affected by salt. The application of MSW and PW at the doses studied under climatic conditions improved the soil enzymatic and microbial activities closely related to the nutrient cycling and bioavailability, and thus plant adaptation to salt stress. These organic treatments also favor the development of P. monspeliensis and H. vulgare, under deleterious conditions. Consequently, the addition of these organic materials may be considered a good strategy to improve plant productivity on saline soils, but, care should be taken from risks related to its use (trace elements and salinity level).

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Acknowledgments This work has been done as apart of a National Research Project and financially supported by Ministry of Higher Education, Scientific Research and Technology. Part of this work was carried out at the Dipartimento di Scienze del Suolo, della Pianta, dell’Ambiente e delle Produzioni Animali, Università di Napoli Federico II, Portici, Italy. The authors gratefully acknowledge the personnel of the Laboratories. References Aitken, R.L., Moody, P.W., Dickson, T., 1998. Field amelioration of acidic soils in south-east Queensland. I. Effects of amendments on soil properties. Aust. J. Soil Res. 49, 627–637. Brookes, P.C., Landman, A., Pruden, G., Jenkinson, D.S., 1985. Chloroform fumigation and the release of soil nitrogen: a rapid direct extraction method to measure microbial biomass nitrogen in soil. Soil Biol. Biochem. 17, 837–842. Chorom, M., Rengasamy, P., 1997. Carbonate chemistry, pH and physical properties of an alkaline sodic soil as affected by various amendments. Aust. J. Soil Res. 35, 149–161. Crecchio, C., Curci, M., Mininni, R., Ricciuti, P., Ruggiero, P., 2001. Shortterm effects of municipal solid waste compost amendments on soil carbon and nitrogen content, some enzyme activities and genetic diversity. Biol. Fertil. Soils 34, 311–318. Crecchio, C., Curci, M., Mininni, R., Ricciuti, P., Ruggiero, P., 2004. Effects of municipal solid waste compost amendments on soil enzyme activities and bacterial genetic diversity. Soil Biol. Biochem. 36, 1595–1605. Day, R.W., Quinn, G.P., 1989. Comparisons of treatment after an analysis of variance in Ecology. Ecol. Monogr. 59, 433–463. Eivazi, F., Tabatabai, M.A., 1990. Factors affecting glucosidase and galactosidase activities in soils. Soil Biol. Biochem. 22, 891–897. Feizi, M., Hajabbasi, M.A., Mostafazadeh-Fard, B., 2010. Saline irrigation water management strategies for better yield of safflower (Carthamus tinctorius L.) in an arid region. Aust. J. Crop Sci. 4, 408–414. Frankenberger, W.T., Bingham, F.T., 1982. Influence of salinity on soil enzyme activities. Soil Sci. Soc. Am. J. 46, 1173–1177. García, C., Hernández, T., 1996. Influence of salinity on the biological and biochemical activity of a calciorthid soil. Plant Soil 178, 255–263. Garcia, C., Hernandez, T., Costa, F., Ceccanti, B., 1994. Biochemical parameters in soils regenerated by the addition of organic wastes. Waste Manage. Res. 12, 457–466. Garcia-Gil, J.C., Plaza, C., Soler-Rovira, P., Polo, A., 2000. Long-term effects of municipal solid waste compost application on soil enzyme activities and microbial biomass. Soil Biol. Biochem. 32, 1907–1913. Ghollarata, M., Raiesi, F., 2007. The adverse effects of soil salinization on the growth of Trifolium alexandrinum L. and associated microbial and biochemical properties in a soil from Iran. Soil Biol. Biochem. 39, 1699–1702. Greena, V.S., Stottb, D.E., Diack, M., 2006. Assay for fluorescein diacetate hydrolytic activity: optimization for soil samples. Soil Biol. Biochem. 38, 693–701. Havlin, J.L., Beatone, J.D., Tisdale, S.L., Nelson, L.W., 1999. Soil Fertility and Fertilizers: An Introduction to Nutrient Management, 6th ed. Prentice Hall, Inc., USA. Institute of Soil Science, Chinese Academy of Science, 1985. Methods on Soil Microorganisms Study (in Chinese). Science Press, Beijing, pp. 260–275. Kandeler, E., Gerber, H., 1988. Short-term assay of soil urease activity using colorimetric determination of ammonium. Biol. Fertil. Soils 6, 68–72. Lakhdar, A., Hafsi, C., Rabhi, M., Debez, A., Montemurro, F., Abdelly, C., Jedidi, N., Ouerghi, Z., 2008. Application of municipal solid waste compost reduces the negative effects of saline water in Hordeum maritimum L. Bioresour. Technol. 99, 7160–7167. Liang, Y., Nikolic, M., Peng, Y., Chen, W., Jiang, Y., 2005. Organic manure stimulates biological activity and barley growth in soil subject to secondary salinization. Soil Biol. Biochem. 37, 1185–1195. Liang, Y.C., Shen, Q.R., Shen, Z.G., Ma, T.S., 1996. Effects of silicon on salinity tolerance of two barley cultivars. J. Plant Nutr. 19, 173–183. Madejon, E., Burgos, P., Lopez, R., Cabrera, F., 2001. Soil enzymatic response to addition of heavy metals with organic residues. Biol. Fertil. Soils 34, 144–150. Mamilov, A., Dilly, O.M., Mamilov, S., Inubushi, K., 2004. Microbial eco-physiology of degrading aral sea wetlands: consequences for C-cycling. Soil Sci. Plant Nutr. 50, 839L 842. Marschner, P., Kandeler, E., Marschner, B., 2003. Structure and function of the soil microbial community in a long-term fertilizer experiment. Soil Biol. Biochem. 35, 453–461. Mkhabela, M., Warman, P.R., 2005. The influence of municipal solid waste compost on yield, soil phosphorus availability and uptake by two vegetable crops, grown in a Pugwash sandy loam soil in Nova Scotia. Agr. Ecosyst. Environ. 106, 57–67. Rabhi, M., Ferchichi, S., Jouini, J., Hamrouni, M.H., Koyroc, H.W., Ranieri, A.D., Abdelly, C., Smaoui, A., 2010. Phytodesalination of a salt-affected soil with the halophyte Sesuvium portulacastrum L. to arrange in advance the requirements for the successful growth of a glycophytic crop. Bioresour. Technol. 101, 6822–6828. Molero, S., Porras, J.C.R., Herencia, J.F., Madejon, E., 2006. Chemical and biochemical property in a silty loam soil under conventional and organic management. Soil Tillage Res. 90, 162–170.

369

Mondini, C., Cayuela, M.L., Sinicco, T., Sanchez-Montedero, M.A., Bertolone, E., Bardi, L., 2008. Soil application of meat and bone meal. Short-term effect on mineralization dynamic and soil biochemical and microbiological properties. Soil Biol. Biochem. 40, 462–474. Mokoi, J.H.J.R., Verplancke, H., 2010. Effect of gypsum placement on the physical properties of a saline sandy loam soil. Aust. J. Crop Sci. 4, 556–563. Pankhurst, C.E., Yu, S.B., Hawke, G., Harch, B.D., 2001. Capacity of fatty acid profiles and substrate utilization patterns to describe differences in soil microbial communities associated with increased salinity or alkalinity at three locations in South Australia. Biol. Fertil. Soils 33, 204–217. Pathak, H., Rao, D.L.N., 1998. Carbon and nitrogen mineralization from added organic matter in saline and alkali soils. Soil Biol. Biochem. 30, 695–702. Pauwels, J.M., Van Ranst, E., Verloo, M., Mvondo Ze, A., 1992. Méthodes d’analyses de sols et de plantes, équipement, gestion de stocks de verrerie et de produits chimiques. A.G. Building, Bruxelles. Perucci, P., 1990. Effect of the addition of municipal soild-waste compost on microbial biomass and enzyme activities in soil. Biol. Fertil. Soils 10, 221–226. Qadir, M., Qureshi, R.H., Ahmad, N., 2002. Amelioration of calcareous saline sodic soils through phytoremediation and chemical strategies. Soil Use Manage. 18, 381–385. Qadir, M., Oster, J.D., Schubert, S., Noble, A.D., Sahrawat, K.L., 2007. Phytoremediation of sodic and saline-sodic soils. Adv. Agron. 96, 197–247. Quintero, J.M., Fournier, J.M., Benlloch, M., 2007. Na+ accumulation in shoot is related to water transport in K+ starved sunflower plants but not in plants with a normal K+ status. J. Plant Physiol. 164, 60–67. Leal, R.M.P., Herpin, U., da Fonseca, A.F., 2009. Sodicity and salinity in a Brazilian oxisol cultivated with sugarcane irrigated with wastewater. Agr Water Manage. 96, 307–316. Rao, A.V., Tarafdar, J.C., 1992. Seasonal changes in available phosphorus and different enzyme activities in arid soils. Ann. Arid Zone 31, 185–189. Rietz, D.N., Haynes, R.J., 2003. Effects of irrigation-induced salinity and sodicity on soil microbial activity. Biol. Fertil. Soils 35, 845–854. Sannino, F., Gianfreda, L., 2001. Pesticide influence on soil enzymatic activities. Chemosphere 22, 1–9. Sardinha, M., Müller, T., Schmeisky, H., Joergensen, R.G., 2003. Microbial performance in soils along a salinity gradient under acidic conditions. Appl. Soil Ecol. 23., 237–244. Sarig, S., Steinberger, Y., 1994. Microbial biomass response to seasonal fluctuations in soil salinity under canopy of desert halophytes. Biol. Fertil. Soils 26, 1405–1408. Soil Survey Staff, 1975. Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys. USDA-SCS Agricultural Handbook 436. U.S. Department of Agriculture, Washington, DC. Sparks, D.L., 1996. Methods of Soil Analysis, Chemical Methods. Part 3. SSSA Book Series No. 5. Soil Science Society of America, American Society of Agronomy, Madison, WI, USA. Sparling, G.P., West, A.W., Reynolds, J., 1989. Influence of soil moisture regime on the respiration response of soils subjected to osmotic stress. Aust. J. Soil Res. 27, 161–168. Stemmer, M., Gerzabek, M.H., Kandeler, E., 1999. Invertase and xylanase activity of bulk soil and particle-size fraction during maize straw decomposition. Soil Biol. Biochem. 31, 9–18. Tabatabai, M.A., Bremner, J.M., 1970. Arylsulphatase activity of soils. Soil Sci. Soc. Am. Proc. 34, 427–429. Tejada, M., Garcia, C., Gonzalez, J.L., Hernandez, M.T., 2006. Use of organic amendment as a strategy for saline soil remediation: influence on the physical, chemical and biological properties of soil. Soil Biol. Biochem. 38, 1413–1421. Tejada, M., Gonzalez, J.L., 2005. Beet vinasse applied to wheat under dryland conditions affects soil properties and yield. Eur. J. Agron. 23, 336–347. Trevors, J.T., 1984. Dehydrogenase activity in soil. A comparison between the INT and TTC assay. Biol. Fertil. Soils 16, 673–674. Vance, E.D., Brookes, P.C., Jenkinson, D.S., 1987. An extraction method for measuring soil microbial biomass C. Soil Biol. Biochem. 19, 703–707. Walter, I., Martinez, F., Cuevas, G., 2006. Plant and soil responses to the application of composted MSW in a degraded, semiarid shrubland in central Spain. Compost Sci. Util. 14 (2), 147–154. Wichern, J.F., Wichern, F., Joergensen, G.R., 2006. Impact of salinity on soil microbial communities and the decomposition of maize in acidic soils. Geoderma 137, 100–108. Wong, V.N.L., Dalal, R.C., Greene, R.S.B., 2009. Carbon dynamics of sodic and saline soil following gypsum and organic material additions: a laboratory incubation. Appl. Soil Ecol. 41, 29–40. Xu, G.H., Zheng, H.Y., 1986. Handbook of Analysis of Soil Microorganism. Agriculture Press, Beijing, pp. 249–291 (in Chinese). Yuan, B.C., Li, Z.Z., Liu, H., Gao, M., Zhang, Y.Y., 2007. Microbial biomass and activity in salt affected soils under arid conditions. Appl. Soil Ecol. 35, 319–328. Walkley, A., Black, I.A., 1934. An Examination of Degtjareff Method for Determining Soil Organic Matter and a Proposed Modification of the Chromic Acid Titration Method. Soil Sci. 37, 29–37. Zaka, M.A., Mujeeb, F., Sarwar, G., Hassan, N.M., Hassan, G., 2003. Agromelioration of saline sodic soils. J. Biol. Sci. 3 (3), 329–334.