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Quality characteristics of Burley tobacco irrigated with saline water
Field Crops Research 92 (2005) 75–84 www.elsevier.com/locate/fcr
Quality characteristics of Burley tobacco irrigated with saline water Maria Isabella Sifola* Department of Agricultural Engineering and Agronomy, University of Naples Federico II, Via Universita` 100, 80055 Portici (Naples), Italy Received 10 January 2004; accepted 1 September 2004
Abstract The effect of irrigation with saline water on quality of Burley tobacco (cv. C 104) was investigated in Southern Italy over four consecutive years. A rainfed control (RC) was compared with treatments irrigated with volumes equal to crop evapotranspiration of saline waters at 0.5 (NW), 2.5 (SW1), 5 (SW2) and 10 (SW3) dS m1 electrical conductivity (ECw). In 2000 and 2001 an additional salinity treatment (15 dS m1 ECw) was included (SW4). The amounts of Cl added to the soil by irrigation ranged from 36.3 kg ha1 (good quality water in 1999) to 16.2 Mg ha1 (saline water at 15 dS m1 ECw in 2000). Saline irrigation did not affect yield and yield components of cured leaves. In 1998 and 1999 the filling power of Burley tobacco did not change significantly with increasing salinity of the irrigation water. In 2000 and 2001 the filling power of SW2, SW3 and SW4 treatments was significantly less than that of NW. The Cl content of tobacco grown with SW2 was significantly greater than that grown with NW and there were no differences between SW1 through SW4 treatments. The filling power and the leaf Cl content were inversely related to the amount of Cl applied in the range between 40.3 kg ha1 and 5.1 Mg ha1. The filling power decreased and Cl increased up to the SW2 treatment; beyond that level neither Cl nor filling power changed in response to increasing amounts of Cl applied. The leaf alkaloid content was unaffected by salinity. Total N was unaffected by either the growing season or the saline treatments. Cigarettes obtained from saline treatments did not burn during the smoking test in 1998. In 1999 cigarettes made from SW1 and SW2 did burn, but those from SW3 did not. In 2000 and 2001 the smoking test was performed only on commercial blends containing 10 or 30% of cut tobacco from saline treatments and both blends burned similarly to cigarettes made entirely from tobacco grown under non-saline conditions. In conclusion, quality of Burley tobacco was unaffected by irrigation with saline water at 2.5 dS m1 and the inhibitory effect of salinity on burning properties could be overcome by appropriate mixture in commercial blends. # 2004 Elsevier B.V. All rights reserved. Keywords: Alkaloids; Burning capacity; Filling power; Leaf chloride; Nicotiana tabacum L.; Tar
1. Introduction * Tel.: +39 081 2539125; fax: +39 081 7755129. E-mail address: [email protected].
Tobacco is cultivated in Southern Italy in areas prone to incipient soil salinization due to incorrect
0378-4290/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2004.09.007
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irrigation management (Sifola, 2002). Physiological and yield responses of Burley tobacco to salinity of the irrigation water was recently studied (Sifola and Postiglione, 2002a). Salinity reduces plant dry weight, height and yield at harvest, and decreases the number of leaves per plant (Kannan and Ramani, 1988; Sifola and Postiglione, 2002a). Previous studies also focused on the accumulation of chlorine (Cl) in leaf tissue and the negative effects on the burning capacity of cigarettes. Excessive Cl reduced tobacco quality because it changed leaf texture and depressed burning. Mulchi (1982) reported that soil applications of Cl above 44 kg ha1 reduced leaf quality and leaf burn of cured Maryland tobacco. An excess of Cl resulted in thick, brittle leaves with both colour and aroma altered (McCants and Woltz, 1967). Nevertheless, soil applications of less than 40 kg ha1 Cl were considered beneficial as they stimulated growth without negative effects on burning of flue-cured tobacco (Neas, 1957; McCants and Woltz, 1967). The level at which Cl is detrimental depends on factors other than mere leaf concentration (King, 1990). When present at high concentrations within the plant tissue, Cl may inhibit enzyme action and protein synthesis (Greenway and Munns, 1980). It has also been found to alter plasma membrane permeability and membrane lipid composition (Leopold and Willing, 1984). It is well known that the nitrogen (N) form in the soil plays an important role in the relationship between leaf Cl concentrations and leaf toxicity symptoms. In particular, nitrate N decreases the Cl concentration in the leaf of Burley tobacco (Fuqua et al., 1976) and prevents the expression of Cl toxicity (McCants and Woltz, 1967; King, 1990; Sweby et al., 1994). McCants and Woltz (1967) reported that Cl as high as 8.9% of leaf dry weight did not cause any apparent abnormality if nitrate was the dominant form of N, but leaf Cl content as low as 0.95% induced symptoms (colour and texture) usually associated with Cl toxicity if ammonium was the main form of N. McCants and Woltz (1967) also reported that pH less than 5.4 or greater than 7.4 reduced the uptake of Cl. Moreover, it has been reported in Burley tobacco that nicotine is negatively related to leaf Cl because of the decreasing amounts of N compounds caused by high Cl (Fuqua et al., 1976). However, other authors
did not report an effect of Cl on nicotine in flue-cured tobacco (Peele et al., 1960; McCants and Woltz, 1967). In particular, Peele et al. (1960) compared four concentrations of Cl in the irrigation water (from 5 to 225 mg L1) and found that the nicotine content of flue-cured tobacco ranged between 1.89 and 1.60% (at 25 and 75 mg L1 Cl, respectively) and was not correlated with Cl. Despite these studies, there is little information on the effect of salinity, and Cl in particular, on aircured leaf quality of Burley tobacco. For instance, hardly anything is known about the effect on filling power or other marketable properties. The main objective of this work was to determine the response of quality traits (leaf chloride content, burning capacity, filling power, alkaloid and N contents of the cured leaves) of field-grown Burley tobacco to irrigation with water at different concentrations of NaCl.
2. Materials and methods 2.1. Plant material and irrigation Field experiments were conducted in the Sele River Plain (408370 N; 148580 E) in Southern Italy over four years (1998–2001). Seedlings of Burley tobacco cv. C 104 were transplanted at a density of two plants m2 (1 m 0.5 m distance) in the third week of May in 1998, the second week of May in 1999 and 2001, and the second week of June in 2000. Plot size was 120 m2 in all years except in 2001 (150 m2). Fertilization, topping, control of sprouting, and other cultural practices were performed as previously reported (Sifola and Postiglione, 2002a). Physical and chemical characteristics of soils are reported in Table 1. Five drip irrigation treatments were compared as follows: (a) a rainfed control (RC) irrigated only twice at transplanting (average of 22 mm seasonal volume) to ensure seedling establishment; (b) irrigated with good quality water (NW) of 0.5 dS m1 electrical conductivity; (c) irrigated with saline water of 2.5 dS m1 ECw (SW1); (d) irrigated with saline water of 5 dS m1 ECw (SW2); and (e) irrigated with saline water of 10 dS m1 ECw (SW3). In 2000 and 2001, an additional level (SW4) of salinity (15 dS m1 ECw) was included. Saline solutions were obtained by
M.I. Sifola / Field Crops Research 92 (2005) 75–84 Table 1 Physical and chemical properties of soils in 1998, 1999, 2000 and 2001
Sand (%) Silt (%) Clay (%) Lime (%) pH Organic matter (%) N (Kjeldahl) (%) NO3–N (ppm) NH4–N (ppm) ECe (dS m1) Field capacity (% d.w.) Wilting point (% d.w.)
1998
1999
2000
2001
47.0 20.8 32.2 Traces 6.9 1.33 0.11 – – 1.81 22.7 14.7
47.3 24.6 28.1 2.2 6.7 1.39 0.12 5.0 11.2 3.76 26.4 14.9
45.3 22.2 32.8 0.6 6.9 0.83 0.11 4.2 11.8 1.24 29.0 17.8
54.6 17.6 27.8 4.1 7.9 0.56 0.07 8.8 12.8 1.55 29.9 18.0
Field capacity and wilting point were determined at 0.03 and 1.5 MPa, respectively.
adding commercial NaCl (51% Cl) to the irrigation water to reach the desired ECw levels. The amount of water needed for irrigation was calculated as reported in Sifola and Postiglione (2002a). In brief, irrigated treatments received an amount of water equal to crop evapotranspiration (ETc), estimated from Class A pan evaporation rate measured on site (pan coefficient = 0.8) multiplied by crop coefficients (kc). Irrigation was applied when water depletion in the soil profile exceeded 40% of available water, which was calculated for the 0– 0.15 m depth at transplanting and 0–0.50 m at maximum plant development. Monthly distribution of the number of irrigations, irrigation volumes and rainfall in the four years of study is reported in Table 2. Considering both the amount of water applied with irrigation during the growing season and the concentration of Cl in the commercial NaCl used, the
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following amounts of Cl were added to the soil by irrigation yearly: 2.7 2.3 2.7 2.4
(SW1)–10.8 (SW3) Mg ha1 in 1998; (SW1)–9.2 (SW3) Mg ha1 in 1999; (SW1)–16.2 (SW4) Mg ha1 in 2000; (SW1)–14.4 (SW4) Mg ha1 in 2001.
For the NW treatment (water containing 13 mg L1 Cl ) amounts of 42.8, 36.3, 42.8 and 37.8 kg Cl ha1 were added by irrigation in 1998, 1999, 2000 and 2001, respectively. The electrical conductivity of the soil (ECe) was determined by sampling the soil at two depths (0–0.3 and 0.3–0.6 m) on 21 May, 15 July, 31 July, 1 September 1998, 7 July and 8 September 1999, 3 July, 21 August, 4 September 2000, 26 June, 20 July, 7 August and 7 September 2001. The mean weighted conductivity of the soil was calculated by dividing the ECe at 25 8C by the number of days between two successive samplings (Sifola and Postiglione, 2002a). The dilution effect of rainfall on ECw was calculated according to the equation reported in Sifola and Postiglione (2002a) assuming an electrical conductivity of the rainfall of 0.05 dS m1. Mean temperatures (min and max) and rainfall were recorded during the growing seasons using a weather station on site (Fig. 1). In 1998 maximum values were greater than 30 8C in the mid of June, in the mid and late July and in the early August while in 1999, maximum values were greater than 30 8C only in early June and August (Fig. 1a). Average daily maximum temperatures were greater than 30 8C in early and late parts of July and in August 2000, whereas in 2001 from late June through late August (Fig. 1b). During the 1998 growing season rainfall was
Table 2 Monthly distribution of the number of irrigations, irrigation volumes and rainfall in the four years of study Month
May June July August Septembera
No. of irrigations
Volume (mm)
Rainfall (mm)
1998
1999
2000
2001
1998
1999
2000
2001
1998
1999
2000
2001
– 4 5 2 –
– 2 5 2 –
– – 5 6 1
– 1 5 3 –
– 83 165 81 –
– 63 138 78 –
– – 129 164 36
– 20 170 101 –
11 1 1 10 21
90 60 30 3 42
3 16 12 8 14
25 16 10 0 40
Irrigation water supplied at transplanting (average of 22 mm) was not included. a In 2000 plots were harvested in the second week of September.
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M.I. Sifola / Field Crops Research 92 (2005) 75–84
Fig. 1. Rainfall (bars) and air temperatures (minimum and maximum) in 1998 and 1999 (a), 2000 and 2001 (b). Symbols are sums (rainfall) and means (temperatures) calculated over 10-day periods. Open symbols represent data for 1998 and 2000, filled symbols for 1999 and 2001. (& and &) minimum temperature; (* and *) maximum temperature.
only 43.8 mm, prevalently in May. In 1999 rainfall was high from the late May through July and totalled 225 mm from May through September. In 2000 and 2001 rainfall during the tobacco-growing season was well distributed except for August 2001, which was dry, and amounted to 53 and 91 mm, respectively (Fig. 1). 2.2. Leaf curing, filling power and smoking test Leaf yield was determined from an average of 68 (1998, 1999 and 2000) and 84 (2001) plants per plots harvested from the central part of each plot about 30 days after topping. Leaves from basal, middle-lower, middle-upper and apical (tips) stalk positions were collected separately (Sifola and Postiglione, 2002b). Harvesting was performed on 20 August, 24 August, 10 September and 23 August in 1998, 1999, 2000 and 2001, respectively. Details of leaf curing, yield determination and cigarette manufacturing were previously reported
(Sifola and Postiglione, 2002b). Curing was performed by desiccating whole plants in indoor open rooms at ambient air temperature and humidity for about 45 days. Yield of cured leaves was determined at standard moisture content of 19% for each of the four stalk positions. Cigarettes of standard sizes (70 mm length, 7.9 mm diameter and 0.9 g mean weight) and 13% moisture content were manufactured from cut tobacco of leaf laminas after removing midribs from the middle part (middle-lower and middle-upper positions) of plants using a Molins Mark 8 machine (Barton Tobacco Machinery, Brinklow, UK). Samples of 20 cigarettes from each plot were selected homogeneous in weight and draft resistance for the smoking test. In addition to the cigarettes made from each saline treatment, the cut tobacco resulting from each saline treatment was blended at a rate of 10 and 30% to produce standard commercial cigarettes in 2000 and 2001. The 10 and 30% proportions of Burley tobacco
M.I. Sifola / Field Crops Research 92 (2005) 75–84
were selected because they are the rates currently used for commercial cigarette production. The filling power (cm3 g1) was measured on cut tobacco from each plot using a densimeter DD60/A (Borgwaldt, Hamburg, Germany). A sample of 20 g of cut tobacco at standard moisture content of 12.5% was put in a cylinder and then subjected to a pressure of 2 kg. The volume occupied by the sample was the filling power expressed as specific volume (cm3 g1) at a reference temperature of 22 8C. The smoking test was made according to the ISO 3308 protocol (2000) at the following standard conditions: 2 s puff duration, 35 0.3 ml puff volume (at 20 8C), 60 s puff frequency. Determinations of nicotine and tar content of smoke were made according to the ISO 4387 (2000).
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Yield and yield components (number of leaves per plant and leaf mean weight), filling power and alkaloid, chloride and total N contents of cured leaves were subjected to analysis of variance (ANOVA). The mean values of each year were tested for homogeneity of variance before data of the four years were pooled together in the ANOVA model.
3. Results The ECe within the 0.6 m topsoil profile increased with increasing salinity of the irrigation water according to a linear relationship in all four years (Fig. 2). The increase of ECe was significantly greater in 1998 (when June, July and August were dry, Fig. 1a) than in 1999, 2000 and 2001.
2.3. Analytical determinations Kjeldahl N of cured leaves was determined in 2000 and 2001 (Sifola and Postiglione, 2003). Alkaloids and chloride concentrations were measured on ground lamina of cured leaves from the middle part of plants (middle-lower and middle-upper positions), in 2000 and 2001. Twenty-five cubic centimeters of distilled water were added to a sample of 250 mg, the flask shaken for 30 min, then the extract filtered through a Whatman no. 40 paper and the filtrate collected in an analyser cup after discarding the first few cubic centimeters. Samples were run together with standards through a continuous flow analyser (Flowsys Systea, Rome, Italy). Total alkaloids were determined by reaction with sulphanilic acid and cyanogen chloride. Cyanogen chloride was generated in situ by the reaction of potassium cyanide and chloramine T solution (N-chloro-4-methyl benzenesulphonamide sodium salt) and absorbance was read at 460 nm according to a standard procedure (CORESTA 35, 1994). The chloride concentration was determined by mixing the leaf sample with nitric acid and then adding mercuric thiocyanate, and absorbance was read at 480–490 nm. 2.4. Experimental design and statistical analysis The experimental design was a randomised complete block with three replications. To avoid contamination between treatments, each plot was isolated from adjacent plots by guard rows (2 m 10 m).
Fig. 2. The relationship between the amount of Cl applied and the electrical conductivity of the soil (ECe) in 1998 and 1999 (a), and 2000 and 2001 (b). The ECe was calculated as the mean weighted conductivity in the 0–0.6 m top soil. Equations, r and standard error (S.E.) of slope: y = 1.844 + 0.395x, r = 0.919**, S.E. = 0.053 (1998); y = 2.969 + 0.208x, r = 0.765**, S.E. = 0.055 (1999); y = 2.944 + 0.138x, r = 0.710**, S.E. = 0.041 (2000); y = 3.810 + 0.176x, r = 0.642*, S.E. = 0.058 (2001). 1998 (open circles); 1999 (filled circles); 2000 (open squares); 2001 (filled squares); * significant at P < 0.05 and ** at P < 0.01.
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Table 3 The effects of irrigation with saline water on yield and yield components of Burley tobacco over four growing seasons
Year (Y) 1998 1999 2000 2001
Yield of cured leaves (Mg ha1)
Number of leaves (per plant)
Mean leaf weight (g)
0.948 1.503 1.169 1.707
13.9 14.4 13.3 16.4
3.6 5.3 4.7 5.4
b a ab a
Irrigation with saline water (I) RC 1.144 b NW 1.308 ab 1.435 a SW1 SW2 1.402 a SW3 1.370 a ANOVA Y I YI
b b b a
13.5 14.9 15.2 15.0 13.9
4.3 4.6 4.9 4.9 5.0
**
**
**
**
n.s. n.s.
n.s. n.s.
n.s.
b a a a
The significance of treatment effects was determined after subjecting data to the analysis of variance (ANOVA). Different letters within columns indicate least significant differences at P < 0.01 within year or irrigation. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2, and SW3, irrigated with saline water of 2.5, 5 or 10 dS m1 ECw, respectively; ** significant at P < 0.01; n.s., not significant.
The interaction between the effect of irrigation with saline water and the growing season was not significant for yield of cured leaves, the number of leaves per plant and the mean leaf weight (Table 3). Therefore, the effect of saline water and year on yield and yield components is discussed separately. The yield of cured leaves was significantly greater in 1999 and 2001 than in 1998. In 2001 the number of leaves per plant was significantly more than that of the other three years. The mean leaf weight was significantly less in 1998 than in the other years (Table 3). Saline irrigation did not affect yield and yield components of cured leaves. SW1, SW2 and SW3 treatments yielded significantly greater than RC, while the yield of NW did not differ from the rainfed treatment. The average yield of SW4 treatment across 2000 and 2001 was 1.60 Mg ha1, not significantly different from other saline treatments (data not shown). On the other hand, irrigation with saline waters had a market effect on growth in three out of four years. Total plant dry matter at harvest was decreased by
Fig. 3. The effect of irrigation with saline water on the filling power of cut Burley tobacco in 1998, 1999, 2000 and 2001. The line represents the least significant differences at P < 0.01. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2 and SW3, irrigated with saline water of 2.5, 5, or 10 dS m1 ECw, respectively.
26.7, 15.8 and 28.3% in 1998, 2000 and 2001, respectively (data not shown), when salinity of the irrigation water was increased from NW to SW3 (1998) and to SW4 (2000 and 2001). In 1998 and 1999 the filling power of Burley tobacco did not change significantly with increasing salinity of the irrigation water (Fig. 3). In the two following years (2000 and 2001) the filling power of SW2, SW3 and SW4 treatments were significantly less than that of NW (Fig. 3). Average values of filling power across all treatments were less in 2000–2001 than 1998–1999. As for the comparison between irrigated and non-irrigated plots, the filling power of NW was significantly greater than that of RC in 1998, 1999 and 2000, but not in 2001. The interaction between years and salinity of water was not significant for the content in Cl, alkaloids or total N of cured leaves. Leaf Cl contents were high since they ranged between 4.0 (NW) and 6.1% (SW3) (Fig. 4). Irrigating with saline water had a significant effect on Cl content. The Cl content of SW2 and SW3 were significantly greater than that of NW (6.0 and 6.1% versus 4.0%, respectively), but there were no differences between treatments SW1 through SW4 (5.2 through 5.5%) The average content of Cl across irrigation treatments was not significantly different between years (5.2% versus 5.4% in 2000 and 2001, respectively). The filling power and the leaf Cl content showed an inverse response to the amount of Cl applied in the
M.I. Sifola / Field Crops Research 92 (2005) 75–84
Fig. 4. The relationship between the amount of Cl applied and the filling power or leaf Cl content of cured leaves of Burley tobacco. The lines represent the least significant differences at P < 0.05 (filling power) or P < 0.01 (chloride). FP, filling power.
range of Cl applied between 40.3 kg ha1 and 5.1 Mg ha1 (Fig. 4). The filling power decreased and Cl increased up to salinity levels of the SW2 treatment; beyond that level either Cl or filling power did not change in response to increasing amounts of Cl applied. Leaf alkaloid content was unaffected by salinity; values in 2001 were numerically different from 2000 values (average of 2.1% versus 2.7 % of dry weight), but the difference was not significant. Total N was unaffected by either the growing season (2.9% of dry weight in both years) or the saline treatments (2.8– 3.0% of dry weight for all treatments). Cigarettes made with tobacco obtained from saline treatments in 1998 did not burn during the smoking
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test. In 1999 cigarettes made from SW1 and SW2 did burn, but those from SW3 did not. In both years cigarettes from NW or RC treatments burned normally. In 1998 and 1999 the nicotine delivery in smoke of cigarettes made with tobacco from rainfed plants was significantly greater than that of NW plants; the tar from the cured leaves of the RC treatment was greater than that of NW treatment in 1998 but not in 1999 (Table 4). Moreover, there was no difference in nicotine or tar content between NW, SW1 and SW2 treatments in 1999 (Table 4). Because of the inhibition of the burning capacity of cigarettes from saline treatments in both previous years, in 2000 and 2001 the smoking test was performed only on commercial blends containing 10 or 30% of cut tobacco from saline treatments. Both types of blends burned normally and were similar to cigarettes made entirely from tobacco grown under non-saline conditions (data not shown).
4. Discussion In this four-year experiment irrigation with saline waters did not influence yield and yield components. Previous experiments conducted on field-grown Burley tobacco under saline conditions showed that saline water at 10 dS m1 decreased yield by 30% resulting in classification as a moderately tolerant species (Sifola and Postiglione, 2002a). In that work, the maximum value of ECe in the 0–0.6 m top soil was 9 dS m1, whereas in the current experiment ECe did not exceed 6.2 dS m1 (SW3 treatment in 1998) which may explain the lack of any quantitative effect in the
Table 4 The effects of irrigation with saline water on the smoking test in 1998 and 1999 Irrigation with saline water
Aspiration (no. per cigarette)
Nicotine (mg per cigarette)
Tar (mg per cigarette)
1998 RC NW
10.47 (0.09) 12.80 (1.40)
4.44 (0.30) 1.89 (0.12)
32.49 (0.69) 23.96 (1.24)
1999 RC NW SW1 SW2
9.40 8.55 11.52 13.20
4.43 2.68 2.68 2.62
25.44 22.21 20.34 21.29
(0.29) (0.33) (0.46) (0.00)
(0.19) (0.14) (0.21) (0.00)
(0.65) (1.32) (0.96) (0.00)
Standard errors of means (n = 3) are reported in parenthesis. In 1998 SW1 and in 1999 SW3 did not burn and data are not available here. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2, irrigated with saline water of 2.5 or 5 dS m1 ECw, respectively.
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current study. Irrigation at 2.5 or 5 dS m1 did not have negative effects on yield (SW1 and SW2 produced similarly to NW and more than RC treatment). When the salinity of water reached 10 dS m1 or greater concentrations, the plant dry matter was reduced by 18% (mean of four years) with respect to NW. This reduction was less than that previously reported by Sifola and Postiglione (2002a). Considering that the commercial yield of saline treatments was not less than that of the irrigated control this response could be explained by more dry matter allocated to leaves than to stems under saline conditions (Sifola and Postiglione, 2002a). The effect of irrigation with saline water on the filling power of cured leaves was not consistent. Salinity reduced the filling power in 2000 and 2001, but not in 1998 and 1999. In 2000 and 2001 the reduction in filling power was significant up to SW2 (5.1 Mg Cl ha1) without any further decrease at greater salinity levels (SW3 and SW4). Interestingly, the Cl content of cured leaves increased significantly up to SW2, showing an inverse trend with the filling power when plotted against the amount of Cl applied with saline irrigation (Fig. 4). Although there is no conclusive evidence about the reason for the reduction in filling power due to salinity, it is likely that salinity (and Cl applications in particular) determined changes in leaf structure, i.e. leaf thickening resulting by looser arrangement of both palisade and mesophyll cells caused by chloride as reported for tobacco and other species (Longstreth and Nobel, 1979; Bongi and Loreto, 1989; King, 1990). McCants and Woltz (1967) attributed the poor burning capacity of tobacco leaves grown under high Cl levels to anatomical factors such as leaf thickness and hygroscopicity. Both Cl uptake and accumulation are often reported to increase linearly over a wide range of Cl concentration in the medium. For instance in fluecured tobacco, Orphanos (1987) reported Cl accumulation when Cl was applied at rates from 1.7 and 5.1 mM L1, and Peedin (1990) that Cl accumulation increased linearly within the range from 8 to 112 kg Cl applied per hectare. In the present study leaf Cl accumulated linearly with the amount of Cl applied only within the range 40.3–5100 kg ha1 (Fig. 4). Beyond those levels there was no further effect of Cl applied on leaf Cl content, indicating that saturation had been reached.
In the current experiment leaf Cl content ranged between 4.0 and 6.1% dry weight. These values are greater than 2%, the threshold value hypothesized by many authors for inhibiting the burning properties of tobacco (Akehurst, 1981; Juan and del Castillo, 1986; Guardiola et al., 1987; King, 1990). Other authors indicated an even less threshold value (1%) above which tobacco did not burn well or at all (Fless, 1990; King, 1990). Chloride contents as high as 1.0 and 2.1% were reported by Peedin (1990) in lower and upper leaves, respectively, of flue-cured tobacco. Either Cl applications exceeding 44 kg ha1 or Cl concentration in cured leaves greater than 53 g kg1 were reported to reduce significantly duration of leaf burn, the quality index and the average price of Maryland tobacco (Mulchi, 1982; Sims, 1985). In the present study, Cl applied with saline irrigation were substantially greater ranging from a minimum of 2.3 (SW1 in 1999) to a maximum of 16.2 (SW4 in 2000) Mg ha1. Therefore, it is not surprising that burning was completely inhibited. Interestingly, mixing 10 or 30% tobacco from saline plots produced cigarettes with normal burning capacity (10 and 30% are the proportions of Burley tobacco commonly used in commercial blends), which implies that it is possible to use Burley tobacco grown under saline conditions. In the current study the problems of storage or fermentation of the cured product reported by Sims (1985) were not found. In this experiment there was no effect of NaCl on total N content of cured leaves and the leaf N content measured was consistent with that reported for Burley tobacco in the literature (Akehurst, 1981). Even though there is an interaction between Cl and NO3 accumulation (McCants and Woltz, 1967; Fixen, 1993), that depends on levels of Cl and NO3 applied. The external concentrations of Cl and inorganic N (NH4+ and NO3) apparently affected both Cl fluxes and compartmentation in barley (Britto et al., 2004). Britto et al. (2004) reported that when NO3 was the N source there was a suppression of Cl fluxes and accumulation and, in particular, of the flux to the vacuole. Liu and Shelp (1996) indicated that NO3 absorption of broccoli was not inhibited by the presence of Cl in the growing medium and that the decrease in NO3 accumulation in the shoot resulted by the stimulation of organic-N formation from adsorbed NO3.
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Alkaloids did not vary with salinity of the irrigation water similarly to what previously reported by Peele et al. (1960), who showed that Cl did not influence synthesis of alkaloids in flue-cured tobacco. On the contrary, Fuqua et al. (1976) found Cl affecting nicotine of Burley tobacco by decreasing the amounts of N compounds. As for nicotine in the smoke of cigarettes, in 1998 and 1999 the nicotine content values for RC grown tobacco were about two-fold greater than that of NW, in agreement with results reported for Burley (Franklin et al., 1964; Sifola et al., 1998; Sifola and Postiglione, 2002b), Maryland (Brown et al., 1970) and oriental tobaccos (Sficas, 1970). In conclusion, this study confirmed the relatively high tolerance of tobacco to salinity (growth and yield), but also showed that quality was markedly affected since the filling power was decreased in two years, the leaf chloride content was increased and cured leaves did not burn. Nevertheless, cured leaves from tobacco grown under saline conditions could be used successfully to manufacture cigarettes when blended at rates less than 30% even though both the salinity of water and amounts of chloride applied with irrigation were very high. Although tobacco is moderately tolerant to salinity and the inhibitory effect on burning properties of Burley type obtained from saline plots can be overcome by appropriate mixtures, growers should be aware of the potential risks for soil properties associated with the use of saline waters for irrigation.
Acknowledgements This research work was carried out with the financial support of the Commission of The European Community – Community Fund for Tobacco Research and Information – Commission Regulament (EEC) n. 2427/93. It does not necessarily reflect the views of the Commission and in no way anticipates its future in this area.
References Akehurst, B.C., 1981. Tobacco, second ed. Tropical Agricultural Series, Longman Inc., New York. Bongi, G., Loreto, F., 1989. Gas-exchange properties of salt-stressed olive (Olea europaea L.) leaves. Plant Physiol. 90, 533–545.
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Britto, D.T., Ruth, T.J., Lapi, S., 2004. Cellular and whole-plant chloride dynamics in barley: insights into chloride–nitrogen interactions and salinity responses. Planta 218, 615–622. Brown, G.W., Street, O.E., McKee, C.G., 1970. Effect of irrigation, nitrogen fertilization, plant population and variety on the physico–chemical properties of Maryland tobacco. I. Agronomic effect. CORESTA Bulletin Information, n. A202. CORESTA 35, 1994. Determination of total alkaloids (as nicotine) in tobacco by continuous flow analysis. www.coresta.org/ recommendedmethod. Fixen, P.E., 1993. Crop response to chloride. Adv. Agron. 50, 107– 150. Fless, K.C., 1990. Field practices. In: Davis, D.L., Nielsen, M.T. (Eds.), Tobacco: Production, Chemistry and Technology, Blackwell Science, University Press Cambridge, UK, pp. 76–103. Franklin, R.E., Teater, R.W., Curry, R.E., Schwab, G.O., 1964. Nitrogen-irrigation interaction in Burley tobacco production. Agron. J. 56, 361–362. Fuqua, B.D., Sims, J.L., Leggett, J.E., Benner, J.F., Atkinson, W.O., 1976. Nitrate and chloride fertilization effects on yield and chemical composition of burley tobacco leaves and smoke. Can. J. Plant Sci. 56, 893–899. Greenway, H., Munns, R., 1980. Mechanisms of salt tolerance in nonhalophytes. Annu. Rev. Plant Physiol. 31, 149–190. Guardiola, J.M., Perez, O., Diaz, L., 1987. Effect of chlorine and potassium on combustibility from fine plantations. Tabaco 10, 29–43. ISO 3308, 2000. Routine analytical cigarette-smoking machine. Definitions and standard conditions. www.iso.ch/iso/en/ISOONLINE.frontpage. ISO 4387, 2000. Cigarettes. Determination of total and nicotine-free dry particulate matter using a routine analytical smoking machine. www.iso.ch/iso/en/ISOONLINE.frontpage. Juan, R., del Castillo, N., 1986. Irrigation water management and chemical and physical characteristics of covered dark tobacco. Riego y Drenaje 9, 71–83. Kannan, S., Ramani, S., 1988. Evaluation of salt tolerance in cowpea and tobacco: effects of NaCl on growth, relative turgidity and photosynthesis. J. Plant Nutr. 11, 435–448. King, M.J., 1990. Tobacco. In: Stewart, B.A., Nielsen, D.R. (Eds.), Irrigation of Agricultural Crops, Agronomy Series, vol. 30. American Society of Agronomy Inc., Madison, WI, USA, pp. 811–833. Leopold, A.C., Willing, R.P., 1984. Evidence for toxicity effects of salts on membranes. In: Staples, R.C. (Ed.), Salinity Tolerance in Plants: Strategies for Crop Improvement, Wiley, New York, pp. 67–76. Liu, L., Shelp, B.J., 1996. Impact of chloride on nitrate absorption and accumulation by broccoli (Brassica oleracea var. italica). Can. J. Plant Sci. 76, 367–377. Longstreth, D.J., Nobel, P.S., 1979. Salinity effects on leaf anatomy. Plant Physiol. 63, 700–703. McCants, C.B., Woltz, W.G., 1967. Growth and mineral nutrition of tobacco. Adv. Agron. 19, 211–269. Mulchi, C.L., 1982. Chloride effects on agronomic, chemical and physical properties of Maryland tobacco. I. Response to chloride applied to the soil. Tob. Sci. 26, 113–116.
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Neas, I., 1957. Sulphur nutrition in flue-cured tobacco. Agron. J. 45, 472–477. Orphanos, P.I., 1987. Distribution of chloride in tobacco laminae and midribs as influenced by the chloride content of the irrigation water. Plant Soil 102, 287–290. Peedin, G.F., 1990. Production practices: flue-cured tobacco. In: Davis, D.L., Nielsen, M.T. (Eds.), Tobacco: Production, Chemistry and Technology. Blackwell Science, University Press Cambridge, UK, pp. 104–142. Peele, T.C., Webb, H.J., Bullock, J.F., 1960. Chemical composition of irrigation waters in the South Carolina coastal plain and effects of chlorides in irrigation water on the quality of fluecured tobacco. Agron. J. 52, 464–467. Sficas, A.G., 1970. Irrigation experiments on oriental tobacco. In: Proceedings of the Fifth International Tobacco Science Congress, Hamburg, Germany, p. 175. Sifola, M.I., Cuocolo, B., Postiglione, L., 1998. Effect of increasing nitrogen fertilization rate on yield and quality of Burley tobacco (Nicotiana tabacum L.) grown under stressed and well-watered conditions. Ital. J. Agron. 2, 117–125.
Sifola, M.I., 2002. Assessment of water quality used for irrigation of tobacco (Nicotiana tabacum L.) in the Campania region, Italy. Book of Abstract, Environnement et identite´ en Mediterrane´ e, , pp. 504–505. Sifola, M.I., Postiglione, L., 2002a. The effect of increasing NaCl in irrigation water on growth, gas exchange and yield of tobacco Burley type. Field Crops Res. 74, 81–91. Sifola, M.I., Postiglione, L., 2002b. The effect of nitrogen fertilization and irrigation on dry matter partitioning, yield and quality of tobacco (Nicotiana tabacum L.) Burley type. Agricoltura Mediterranea 132, 33–43. Sifola, M.I., Postiglione, L., 2003. The effect of nitrogen fertilization on nitrogen use efficiency of irrigated and non-irrigated tobacco (Nicotiana tabacum L.). Plant Soil 252, 313–323. Sims, J.L., 1985. Potassium nutrition of tobacco. In: Munson, R.D. (Ed.), Potassium in Agriculture. ASA, CSA, and SSSA, Madison, WI, USA, pp. 1023–1044. Sweby, D.L., Huckett, B.I., Watt, M.P., 1994. Effects of nitrogen nutrition on salt-stressed Nicotiana tabacum var. Samsun in vitro plantlets. J. Exp. Bot. 45, 995–1008.
Quality characteristics of Burley tobacco irrigated with saline water Maria Isabella Sifola* Department of Agricultural Engineering and Agronomy, University of Naples Federico II, Via Universita` 100, 80055 Portici (Naples), Italy Received 10 January 2004; accepted 1 September 2004
Abstract The effect of irrigation with saline water on quality of Burley tobacco (cv. C 104) was investigated in Southern Italy over four consecutive years. A rainfed control (RC) was compared with treatments irrigated with volumes equal to crop evapotranspiration of saline waters at 0.5 (NW), 2.5 (SW1), 5 (SW2) and 10 (SW3) dS m1 electrical conductivity (ECw). In 2000 and 2001 an additional salinity treatment (15 dS m1 ECw) was included (SW4). The amounts of Cl added to the soil by irrigation ranged from 36.3 kg ha1 (good quality water in 1999) to 16.2 Mg ha1 (saline water at 15 dS m1 ECw in 2000). Saline irrigation did not affect yield and yield components of cured leaves. In 1998 and 1999 the filling power of Burley tobacco did not change significantly with increasing salinity of the irrigation water. In 2000 and 2001 the filling power of SW2, SW3 and SW4 treatments was significantly less than that of NW. The Cl content of tobacco grown with SW2 was significantly greater than that grown with NW and there were no differences between SW1 through SW4 treatments. The filling power and the leaf Cl content were inversely related to the amount of Cl applied in the range between 40.3 kg ha1 and 5.1 Mg ha1. The filling power decreased and Cl increased up to the SW2 treatment; beyond that level neither Cl nor filling power changed in response to increasing amounts of Cl applied. The leaf alkaloid content was unaffected by salinity. Total N was unaffected by either the growing season or the saline treatments. Cigarettes obtained from saline treatments did not burn during the smoking test in 1998. In 1999 cigarettes made from SW1 and SW2 did burn, but those from SW3 did not. In 2000 and 2001 the smoking test was performed only on commercial blends containing 10 or 30% of cut tobacco from saline treatments and both blends burned similarly to cigarettes made entirely from tobacco grown under non-saline conditions. In conclusion, quality of Burley tobacco was unaffected by irrigation with saline water at 2.5 dS m1 and the inhibitory effect of salinity on burning properties could be overcome by appropriate mixture in commercial blends. # 2004 Elsevier B.V. All rights reserved. Keywords: Alkaloids; Burning capacity; Filling power; Leaf chloride; Nicotiana tabacum L.; Tar
1. Introduction * Tel.: +39 081 2539125; fax: +39 081 7755129. E-mail address: [email protected].
Tobacco is cultivated in Southern Italy in areas prone to incipient soil salinization due to incorrect
0378-4290/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2004.09.007
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irrigation management (Sifola, 2002). Physiological and yield responses of Burley tobacco to salinity of the irrigation water was recently studied (Sifola and Postiglione, 2002a). Salinity reduces plant dry weight, height and yield at harvest, and decreases the number of leaves per plant (Kannan and Ramani, 1988; Sifola and Postiglione, 2002a). Previous studies also focused on the accumulation of chlorine (Cl) in leaf tissue and the negative effects on the burning capacity of cigarettes. Excessive Cl reduced tobacco quality because it changed leaf texture and depressed burning. Mulchi (1982) reported that soil applications of Cl above 44 kg ha1 reduced leaf quality and leaf burn of cured Maryland tobacco. An excess of Cl resulted in thick, brittle leaves with both colour and aroma altered (McCants and Woltz, 1967). Nevertheless, soil applications of less than 40 kg ha1 Cl were considered beneficial as they stimulated growth without negative effects on burning of flue-cured tobacco (Neas, 1957; McCants and Woltz, 1967). The level at which Cl is detrimental depends on factors other than mere leaf concentration (King, 1990). When present at high concentrations within the plant tissue, Cl may inhibit enzyme action and protein synthesis (Greenway and Munns, 1980). It has also been found to alter plasma membrane permeability and membrane lipid composition (Leopold and Willing, 1984). It is well known that the nitrogen (N) form in the soil plays an important role in the relationship between leaf Cl concentrations and leaf toxicity symptoms. In particular, nitrate N decreases the Cl concentration in the leaf of Burley tobacco (Fuqua et al., 1976) and prevents the expression of Cl toxicity (McCants and Woltz, 1967; King, 1990; Sweby et al., 1994). McCants and Woltz (1967) reported that Cl as high as 8.9% of leaf dry weight did not cause any apparent abnormality if nitrate was the dominant form of N, but leaf Cl content as low as 0.95% induced symptoms (colour and texture) usually associated with Cl toxicity if ammonium was the main form of N. McCants and Woltz (1967) also reported that pH less than 5.4 or greater than 7.4 reduced the uptake of Cl. Moreover, it has been reported in Burley tobacco that nicotine is negatively related to leaf Cl because of the decreasing amounts of N compounds caused by high Cl (Fuqua et al., 1976). However, other authors
did not report an effect of Cl on nicotine in flue-cured tobacco (Peele et al., 1960; McCants and Woltz, 1967). In particular, Peele et al. (1960) compared four concentrations of Cl in the irrigation water (from 5 to 225 mg L1) and found that the nicotine content of flue-cured tobacco ranged between 1.89 and 1.60% (at 25 and 75 mg L1 Cl, respectively) and was not correlated with Cl. Despite these studies, there is little information on the effect of salinity, and Cl in particular, on aircured leaf quality of Burley tobacco. For instance, hardly anything is known about the effect on filling power or other marketable properties. The main objective of this work was to determine the response of quality traits (leaf chloride content, burning capacity, filling power, alkaloid and N contents of the cured leaves) of field-grown Burley tobacco to irrigation with water at different concentrations of NaCl.
2. Materials and methods 2.1. Plant material and irrigation Field experiments were conducted in the Sele River Plain (408370 N; 148580 E) in Southern Italy over four years (1998–2001). Seedlings of Burley tobacco cv. C 104 were transplanted at a density of two plants m2 (1 m 0.5 m distance) in the third week of May in 1998, the second week of May in 1999 and 2001, and the second week of June in 2000. Plot size was 120 m2 in all years except in 2001 (150 m2). Fertilization, topping, control of sprouting, and other cultural practices were performed as previously reported (Sifola and Postiglione, 2002a). Physical and chemical characteristics of soils are reported in Table 1. Five drip irrigation treatments were compared as follows: (a) a rainfed control (RC) irrigated only twice at transplanting (average of 22 mm seasonal volume) to ensure seedling establishment; (b) irrigated with good quality water (NW) of 0.5 dS m1 electrical conductivity; (c) irrigated with saline water of 2.5 dS m1 ECw (SW1); (d) irrigated with saline water of 5 dS m1 ECw (SW2); and (e) irrigated with saline water of 10 dS m1 ECw (SW3). In 2000 and 2001, an additional level (SW4) of salinity (15 dS m1 ECw) was included. Saline solutions were obtained by
M.I. Sifola / Field Crops Research 92 (2005) 75–84 Table 1 Physical and chemical properties of soils in 1998, 1999, 2000 and 2001
Sand (%) Silt (%) Clay (%) Lime (%) pH Organic matter (%) N (Kjeldahl) (%) NO3–N (ppm) NH4–N (ppm) ECe (dS m1) Field capacity (% d.w.) Wilting point (% d.w.)
1998
1999
2000
2001
47.0 20.8 32.2 Traces 6.9 1.33 0.11 – – 1.81 22.7 14.7
47.3 24.6 28.1 2.2 6.7 1.39 0.12 5.0 11.2 3.76 26.4 14.9
45.3 22.2 32.8 0.6 6.9 0.83 0.11 4.2 11.8 1.24 29.0 17.8
54.6 17.6 27.8 4.1 7.9 0.56 0.07 8.8 12.8 1.55 29.9 18.0
Field capacity and wilting point were determined at 0.03 and 1.5 MPa, respectively.
adding commercial NaCl (51% Cl) to the irrigation water to reach the desired ECw levels. The amount of water needed for irrigation was calculated as reported in Sifola and Postiglione (2002a). In brief, irrigated treatments received an amount of water equal to crop evapotranspiration (ETc), estimated from Class A pan evaporation rate measured on site (pan coefficient = 0.8) multiplied by crop coefficients (kc). Irrigation was applied when water depletion in the soil profile exceeded 40% of available water, which was calculated for the 0– 0.15 m depth at transplanting and 0–0.50 m at maximum plant development. Monthly distribution of the number of irrigations, irrigation volumes and rainfall in the four years of study is reported in Table 2. Considering both the amount of water applied with irrigation during the growing season and the concentration of Cl in the commercial NaCl used, the
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following amounts of Cl were added to the soil by irrigation yearly: 2.7 2.3 2.7 2.4
(SW1)–10.8 (SW3) Mg ha1 in 1998; (SW1)–9.2 (SW3) Mg ha1 in 1999; (SW1)–16.2 (SW4) Mg ha1 in 2000; (SW1)–14.4 (SW4) Mg ha1 in 2001.
For the NW treatment (water containing 13 mg L1 Cl ) amounts of 42.8, 36.3, 42.8 and 37.8 kg Cl ha1 were added by irrigation in 1998, 1999, 2000 and 2001, respectively. The electrical conductivity of the soil (ECe) was determined by sampling the soil at two depths (0–0.3 and 0.3–0.6 m) on 21 May, 15 July, 31 July, 1 September 1998, 7 July and 8 September 1999, 3 July, 21 August, 4 September 2000, 26 June, 20 July, 7 August and 7 September 2001. The mean weighted conductivity of the soil was calculated by dividing the ECe at 25 8C by the number of days between two successive samplings (Sifola and Postiglione, 2002a). The dilution effect of rainfall on ECw was calculated according to the equation reported in Sifola and Postiglione (2002a) assuming an electrical conductivity of the rainfall of 0.05 dS m1. Mean temperatures (min and max) and rainfall were recorded during the growing seasons using a weather station on site (Fig. 1). In 1998 maximum values were greater than 30 8C in the mid of June, in the mid and late July and in the early August while in 1999, maximum values were greater than 30 8C only in early June and August (Fig. 1a). Average daily maximum temperatures were greater than 30 8C in early and late parts of July and in August 2000, whereas in 2001 from late June through late August (Fig. 1b). During the 1998 growing season rainfall was
Table 2 Monthly distribution of the number of irrigations, irrigation volumes and rainfall in the four years of study Month
May June July August Septembera
No. of irrigations
Volume (mm)
Rainfall (mm)
1998
1999
2000
2001
1998
1999
2000
2001
1998
1999
2000
2001
– 4 5 2 –
– 2 5 2 –
– – 5 6 1
– 1 5 3 –
– 83 165 81 –
– 63 138 78 –
– – 129 164 36
– 20 170 101 –
11 1 1 10 21
90 60 30 3 42
3 16 12 8 14
25 16 10 0 40
Irrigation water supplied at transplanting (average of 22 mm) was not included. a In 2000 plots were harvested in the second week of September.
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Fig. 1. Rainfall (bars) and air temperatures (minimum and maximum) in 1998 and 1999 (a), 2000 and 2001 (b). Symbols are sums (rainfall) and means (temperatures) calculated over 10-day periods. Open symbols represent data for 1998 and 2000, filled symbols for 1999 and 2001. (& and &) minimum temperature; (* and *) maximum temperature.
only 43.8 mm, prevalently in May. In 1999 rainfall was high from the late May through July and totalled 225 mm from May through September. In 2000 and 2001 rainfall during the tobacco-growing season was well distributed except for August 2001, which was dry, and amounted to 53 and 91 mm, respectively (Fig. 1). 2.2. Leaf curing, filling power and smoking test Leaf yield was determined from an average of 68 (1998, 1999 and 2000) and 84 (2001) plants per plots harvested from the central part of each plot about 30 days after topping. Leaves from basal, middle-lower, middle-upper and apical (tips) stalk positions were collected separately (Sifola and Postiglione, 2002b). Harvesting was performed on 20 August, 24 August, 10 September and 23 August in 1998, 1999, 2000 and 2001, respectively. Details of leaf curing, yield determination and cigarette manufacturing were previously reported
(Sifola and Postiglione, 2002b). Curing was performed by desiccating whole plants in indoor open rooms at ambient air temperature and humidity for about 45 days. Yield of cured leaves was determined at standard moisture content of 19% for each of the four stalk positions. Cigarettes of standard sizes (70 mm length, 7.9 mm diameter and 0.9 g mean weight) and 13% moisture content were manufactured from cut tobacco of leaf laminas after removing midribs from the middle part (middle-lower and middle-upper positions) of plants using a Molins Mark 8 machine (Barton Tobacco Machinery, Brinklow, UK). Samples of 20 cigarettes from each plot were selected homogeneous in weight and draft resistance for the smoking test. In addition to the cigarettes made from each saline treatment, the cut tobacco resulting from each saline treatment was blended at a rate of 10 and 30% to produce standard commercial cigarettes in 2000 and 2001. The 10 and 30% proportions of Burley tobacco
M.I. Sifola / Field Crops Research 92 (2005) 75–84
were selected because they are the rates currently used for commercial cigarette production. The filling power (cm3 g1) was measured on cut tobacco from each plot using a densimeter DD60/A (Borgwaldt, Hamburg, Germany). A sample of 20 g of cut tobacco at standard moisture content of 12.5% was put in a cylinder and then subjected to a pressure of 2 kg. The volume occupied by the sample was the filling power expressed as specific volume (cm3 g1) at a reference temperature of 22 8C. The smoking test was made according to the ISO 3308 protocol (2000) at the following standard conditions: 2 s puff duration, 35 0.3 ml puff volume (at 20 8C), 60 s puff frequency. Determinations of nicotine and tar content of smoke were made according to the ISO 4387 (2000).
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Yield and yield components (number of leaves per plant and leaf mean weight), filling power and alkaloid, chloride and total N contents of cured leaves were subjected to analysis of variance (ANOVA). The mean values of each year were tested for homogeneity of variance before data of the four years were pooled together in the ANOVA model.
3. Results The ECe within the 0.6 m topsoil profile increased with increasing salinity of the irrigation water according to a linear relationship in all four years (Fig. 2). The increase of ECe was significantly greater in 1998 (when June, July and August were dry, Fig. 1a) than in 1999, 2000 and 2001.
2.3. Analytical determinations Kjeldahl N of cured leaves was determined in 2000 and 2001 (Sifola and Postiglione, 2003). Alkaloids and chloride concentrations were measured on ground lamina of cured leaves from the middle part of plants (middle-lower and middle-upper positions), in 2000 and 2001. Twenty-five cubic centimeters of distilled water were added to a sample of 250 mg, the flask shaken for 30 min, then the extract filtered through a Whatman no. 40 paper and the filtrate collected in an analyser cup after discarding the first few cubic centimeters. Samples were run together with standards through a continuous flow analyser (Flowsys Systea, Rome, Italy). Total alkaloids were determined by reaction with sulphanilic acid and cyanogen chloride. Cyanogen chloride was generated in situ by the reaction of potassium cyanide and chloramine T solution (N-chloro-4-methyl benzenesulphonamide sodium salt) and absorbance was read at 460 nm according to a standard procedure (CORESTA 35, 1994). The chloride concentration was determined by mixing the leaf sample with nitric acid and then adding mercuric thiocyanate, and absorbance was read at 480–490 nm. 2.4. Experimental design and statistical analysis The experimental design was a randomised complete block with three replications. To avoid contamination between treatments, each plot was isolated from adjacent plots by guard rows (2 m 10 m).
Fig. 2. The relationship between the amount of Cl applied and the electrical conductivity of the soil (ECe) in 1998 and 1999 (a), and 2000 and 2001 (b). The ECe was calculated as the mean weighted conductivity in the 0–0.6 m top soil. Equations, r and standard error (S.E.) of slope: y = 1.844 + 0.395x, r = 0.919**, S.E. = 0.053 (1998); y = 2.969 + 0.208x, r = 0.765**, S.E. = 0.055 (1999); y = 2.944 + 0.138x, r = 0.710**, S.E. = 0.041 (2000); y = 3.810 + 0.176x, r = 0.642*, S.E. = 0.058 (2001). 1998 (open circles); 1999 (filled circles); 2000 (open squares); 2001 (filled squares); * significant at P < 0.05 and ** at P < 0.01.
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Table 3 The effects of irrigation with saline water on yield and yield components of Burley tobacco over four growing seasons
Year (Y) 1998 1999 2000 2001
Yield of cured leaves (Mg ha1)
Number of leaves (per plant)
Mean leaf weight (g)
0.948 1.503 1.169 1.707
13.9 14.4 13.3 16.4
3.6 5.3 4.7 5.4
b a ab a
Irrigation with saline water (I) RC 1.144 b NW 1.308 ab 1.435 a SW1 SW2 1.402 a SW3 1.370 a ANOVA Y I YI
b b b a
13.5 14.9 15.2 15.0 13.9
4.3 4.6 4.9 4.9 5.0
**
**
**
**
n.s. n.s.
n.s. n.s.
n.s.
b a a a
The significance of treatment effects was determined after subjecting data to the analysis of variance (ANOVA). Different letters within columns indicate least significant differences at P < 0.01 within year or irrigation. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2, and SW3, irrigated with saline water of 2.5, 5 or 10 dS m1 ECw, respectively; ** significant at P < 0.01; n.s., not significant.
The interaction between the effect of irrigation with saline water and the growing season was not significant for yield of cured leaves, the number of leaves per plant and the mean leaf weight (Table 3). Therefore, the effect of saline water and year on yield and yield components is discussed separately. The yield of cured leaves was significantly greater in 1999 and 2001 than in 1998. In 2001 the number of leaves per plant was significantly more than that of the other three years. The mean leaf weight was significantly less in 1998 than in the other years (Table 3). Saline irrigation did not affect yield and yield components of cured leaves. SW1, SW2 and SW3 treatments yielded significantly greater than RC, while the yield of NW did not differ from the rainfed treatment. The average yield of SW4 treatment across 2000 and 2001 was 1.60 Mg ha1, not significantly different from other saline treatments (data not shown). On the other hand, irrigation with saline waters had a market effect on growth in three out of four years. Total plant dry matter at harvest was decreased by
Fig. 3. The effect of irrigation with saline water on the filling power of cut Burley tobacco in 1998, 1999, 2000 and 2001. The line represents the least significant differences at P < 0.01. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2 and SW3, irrigated with saline water of 2.5, 5, or 10 dS m1 ECw, respectively.
26.7, 15.8 and 28.3% in 1998, 2000 and 2001, respectively (data not shown), when salinity of the irrigation water was increased from NW to SW3 (1998) and to SW4 (2000 and 2001). In 1998 and 1999 the filling power of Burley tobacco did not change significantly with increasing salinity of the irrigation water (Fig. 3). In the two following years (2000 and 2001) the filling power of SW2, SW3 and SW4 treatments were significantly less than that of NW (Fig. 3). Average values of filling power across all treatments were less in 2000–2001 than 1998–1999. As for the comparison between irrigated and non-irrigated plots, the filling power of NW was significantly greater than that of RC in 1998, 1999 and 2000, but not in 2001. The interaction between years and salinity of water was not significant for the content in Cl, alkaloids or total N of cured leaves. Leaf Cl contents were high since they ranged between 4.0 (NW) and 6.1% (SW3) (Fig. 4). Irrigating with saline water had a significant effect on Cl content. The Cl content of SW2 and SW3 were significantly greater than that of NW (6.0 and 6.1% versus 4.0%, respectively), but there were no differences between treatments SW1 through SW4 (5.2 through 5.5%) The average content of Cl across irrigation treatments was not significantly different between years (5.2% versus 5.4% in 2000 and 2001, respectively). The filling power and the leaf Cl content showed an inverse response to the amount of Cl applied in the
M.I. Sifola / Field Crops Research 92 (2005) 75–84
Fig. 4. The relationship between the amount of Cl applied and the filling power or leaf Cl content of cured leaves of Burley tobacco. The lines represent the least significant differences at P < 0.05 (filling power) or P < 0.01 (chloride). FP, filling power.
range of Cl applied between 40.3 kg ha1 and 5.1 Mg ha1 (Fig. 4). The filling power decreased and Cl increased up to salinity levels of the SW2 treatment; beyond that level either Cl or filling power did not change in response to increasing amounts of Cl applied. Leaf alkaloid content was unaffected by salinity; values in 2001 were numerically different from 2000 values (average of 2.1% versus 2.7 % of dry weight), but the difference was not significant. Total N was unaffected by either the growing season (2.9% of dry weight in both years) or the saline treatments (2.8– 3.0% of dry weight for all treatments). Cigarettes made with tobacco obtained from saline treatments in 1998 did not burn during the smoking
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test. In 1999 cigarettes made from SW1 and SW2 did burn, but those from SW3 did not. In both years cigarettes from NW or RC treatments burned normally. In 1998 and 1999 the nicotine delivery in smoke of cigarettes made with tobacco from rainfed plants was significantly greater than that of NW plants; the tar from the cured leaves of the RC treatment was greater than that of NW treatment in 1998 but not in 1999 (Table 4). Moreover, there was no difference in nicotine or tar content between NW, SW1 and SW2 treatments in 1999 (Table 4). Because of the inhibition of the burning capacity of cigarettes from saline treatments in both previous years, in 2000 and 2001 the smoking test was performed only on commercial blends containing 10 or 30% of cut tobacco from saline treatments. Both types of blends burned normally and were similar to cigarettes made entirely from tobacco grown under non-saline conditions (data not shown).
4. Discussion In this four-year experiment irrigation with saline waters did not influence yield and yield components. Previous experiments conducted on field-grown Burley tobacco under saline conditions showed that saline water at 10 dS m1 decreased yield by 30% resulting in classification as a moderately tolerant species (Sifola and Postiglione, 2002a). In that work, the maximum value of ECe in the 0–0.6 m top soil was 9 dS m1, whereas in the current experiment ECe did not exceed 6.2 dS m1 (SW3 treatment in 1998) which may explain the lack of any quantitative effect in the
Table 4 The effects of irrigation with saline water on the smoking test in 1998 and 1999 Irrigation with saline water
Aspiration (no. per cigarette)
Nicotine (mg per cigarette)
Tar (mg per cigarette)
1998 RC NW
10.47 (0.09) 12.80 (1.40)
4.44 (0.30) 1.89 (0.12)
32.49 (0.69) 23.96 (1.24)
1999 RC NW SW1 SW2
9.40 8.55 11.52 13.20
4.43 2.68 2.68 2.62
25.44 22.21 20.34 21.29
(0.29) (0.33) (0.46) (0.00)
(0.19) (0.14) (0.21) (0.00)
(0.65) (1.32) (0.96) (0.00)
Standard errors of means (n = 3) are reported in parenthesis. In 1998 SW1 and in 1999 SW3 did not burn and data are not available here. RC, rainfed control; NW, irrigated with water of 0.5 dS m1 ECw; SW1, SW2, irrigated with saline water of 2.5 or 5 dS m1 ECw, respectively.
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current study. Irrigation at 2.5 or 5 dS m1 did not have negative effects on yield (SW1 and SW2 produced similarly to NW and more than RC treatment). When the salinity of water reached 10 dS m1 or greater concentrations, the plant dry matter was reduced by 18% (mean of four years) with respect to NW. This reduction was less than that previously reported by Sifola and Postiglione (2002a). Considering that the commercial yield of saline treatments was not less than that of the irrigated control this response could be explained by more dry matter allocated to leaves than to stems under saline conditions (Sifola and Postiglione, 2002a). The effect of irrigation with saline water on the filling power of cured leaves was not consistent. Salinity reduced the filling power in 2000 and 2001, but not in 1998 and 1999. In 2000 and 2001 the reduction in filling power was significant up to SW2 (5.1 Mg Cl ha1) without any further decrease at greater salinity levels (SW3 and SW4). Interestingly, the Cl content of cured leaves increased significantly up to SW2, showing an inverse trend with the filling power when plotted against the amount of Cl applied with saline irrigation (Fig. 4). Although there is no conclusive evidence about the reason for the reduction in filling power due to salinity, it is likely that salinity (and Cl applications in particular) determined changes in leaf structure, i.e. leaf thickening resulting by looser arrangement of both palisade and mesophyll cells caused by chloride as reported for tobacco and other species (Longstreth and Nobel, 1979; Bongi and Loreto, 1989; King, 1990). McCants and Woltz (1967) attributed the poor burning capacity of tobacco leaves grown under high Cl levels to anatomical factors such as leaf thickness and hygroscopicity. Both Cl uptake and accumulation are often reported to increase linearly over a wide range of Cl concentration in the medium. For instance in fluecured tobacco, Orphanos (1987) reported Cl accumulation when Cl was applied at rates from 1.7 and 5.1 mM L1, and Peedin (1990) that Cl accumulation increased linearly within the range from 8 to 112 kg Cl applied per hectare. In the present study leaf Cl accumulated linearly with the amount of Cl applied only within the range 40.3–5100 kg ha1 (Fig. 4). Beyond those levels there was no further effect of Cl applied on leaf Cl content, indicating that saturation had been reached.
In the current experiment leaf Cl content ranged between 4.0 and 6.1% dry weight. These values are greater than 2%, the threshold value hypothesized by many authors for inhibiting the burning properties of tobacco (Akehurst, 1981; Juan and del Castillo, 1986; Guardiola et al., 1987; King, 1990). Other authors indicated an even less threshold value (1%) above which tobacco did not burn well or at all (Fless, 1990; King, 1990). Chloride contents as high as 1.0 and 2.1% were reported by Peedin (1990) in lower and upper leaves, respectively, of flue-cured tobacco. Either Cl applications exceeding 44 kg ha1 or Cl concentration in cured leaves greater than 53 g kg1 were reported to reduce significantly duration of leaf burn, the quality index and the average price of Maryland tobacco (Mulchi, 1982; Sims, 1985). In the present study, Cl applied with saline irrigation were substantially greater ranging from a minimum of 2.3 (SW1 in 1999) to a maximum of 16.2 (SW4 in 2000) Mg ha1. Therefore, it is not surprising that burning was completely inhibited. Interestingly, mixing 10 or 30% tobacco from saline plots produced cigarettes with normal burning capacity (10 and 30% are the proportions of Burley tobacco commonly used in commercial blends), which implies that it is possible to use Burley tobacco grown under saline conditions. In the current study the problems of storage or fermentation of the cured product reported by Sims (1985) were not found. In this experiment there was no effect of NaCl on total N content of cured leaves and the leaf N content measured was consistent with that reported for Burley tobacco in the literature (Akehurst, 1981). Even though there is an interaction between Cl and NO3 accumulation (McCants and Woltz, 1967; Fixen, 1993), that depends on levels of Cl and NO3 applied. The external concentrations of Cl and inorganic N (NH4+ and NO3) apparently affected both Cl fluxes and compartmentation in barley (Britto et al., 2004). Britto et al. (2004) reported that when NO3 was the N source there was a suppression of Cl fluxes and accumulation and, in particular, of the flux to the vacuole. Liu and Shelp (1996) indicated that NO3 absorption of broccoli was not inhibited by the presence of Cl in the growing medium and that the decrease in NO3 accumulation in the shoot resulted by the stimulation of organic-N formation from adsorbed NO3.
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Alkaloids did not vary with salinity of the irrigation water similarly to what previously reported by Peele et al. (1960), who showed that Cl did not influence synthesis of alkaloids in flue-cured tobacco. On the contrary, Fuqua et al. (1976) found Cl affecting nicotine of Burley tobacco by decreasing the amounts of N compounds. As for nicotine in the smoke of cigarettes, in 1998 and 1999 the nicotine content values for RC grown tobacco were about two-fold greater than that of NW, in agreement with results reported for Burley (Franklin et al., 1964; Sifola et al., 1998; Sifola and Postiglione, 2002b), Maryland (Brown et al., 1970) and oriental tobaccos (Sficas, 1970). In conclusion, this study confirmed the relatively high tolerance of tobacco to salinity (growth and yield), but also showed that quality was markedly affected since the filling power was decreased in two years, the leaf chloride content was increased and cured leaves did not burn. Nevertheless, cured leaves from tobacco grown under saline conditions could be used successfully to manufacture cigarettes when blended at rates less than 30% even though both the salinity of water and amounts of chloride applied with irrigation were very high. Although tobacco is moderately tolerant to salinity and the inhibitory effect on burning properties of Burley type obtained from saline plots can be overcome by appropriate mixtures, growers should be aware of the potential risks for soil properties associated with the use of saline waters for irrigation.
Acknowledgements This research work was carried out with the financial support of the Commission of The European Community – Community Fund for Tobacco Research and Information – Commission Regulament (EEC) n. 2427/93. It does not necessarily reflect the views of the Commission and in no way anticipates its future in this area.
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