Comparing Application Methods for Boron Fertilizer on the Yield and Quality of Tobacco (Nicotiana tabacum L.)

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Comparing Application Methods for Boron Fertilizer on the Yield andQuality of Tobacco (Nicotiana tabacum L.)Muhammad Tariqa; Ali Akbarb; Lataf-ul-Haqb; Amanullah Khanc

a Department of Soil and Environmental Sciences, Northwest Frontier Province AgriculturalUniversity, Peshawar, Pakistan b Pakistan Tobacco Company, Mansehra, Pakistan c Department ofAgronomy, Northwest Frontier Province Agricultural University, Peshawar, Pakistan

Online publication date: 05 July 2010

To cite this Article Tariq, Muhammad , Akbar, Ali , Lataf-ul-Haq and Khan, Amanullah(2010) 'Comparing ApplicationMethods for Boron Fertilizer on the Yield and Quality of Tobacco (Nicotiana tabacum L.)', Communications in SoilScience and Plant Analysis, 41: 13, 1525 — 1537To link to this Article: DOI: 10.1080/00103624.2010.485234URL: http://dx.doi.org/10.1080/00103624.2010.485234

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Communications in Soil Science and Plant Analysis, 41:1525–1537, 2010Copyright © Taylor & Francis Group, LLCISSN: 0010-3624 print / 1532-2416 onlineDOI: 10.1080/00103624.2010.485234

Comparing Application Methods for BoronFertilizer on the Yield and Quality of Tobacco

(Nicotiana tabacum L.)

MUHAMMAD TARIQ,1 ALI AKBAR,2 LATAF-UL-HAQ,2

AND AMANULLAH KHAN3

1Department of Soil and Environmental Sciences, Northwest Frontier ProvinceAgricultural University, Peshawar, Pakistan2Pakistan Tobacco Company, Mansehra, Pakistan3Department of Agronomy, Northwest Frontier Province Agricultural University,Peshawar, Pakistan

The present study is based on the hypothesis that different methods of supplying boron(B) may have different effects on the yield and quality performance of tobacco crop. Afield experiment was conducted to study the effect of different methods of B fertilizationon the yield, quality, and leaf composition of flue-cured Virginia tobacco (cv. K-399) in2007 at the Pakistan Tobacco Research Station, Mansehra. Three different methods (i.e.,foliar spray, soil application, and root dipping at the rates of 0.25 kg ha–1, 1 kg ha–1,and 0.5 mg B L–1, respectively) in the form of boric acid along with a control (where noB was applied) were used in a randomized complete block design and replicated fourtimes. Results revealed that different methods of B application significantly affectedtobacco yield, quality, and nutrient uptake compared to the control. Maximum leaf areaof 707 cm2, green leaf yield of 18553 kg ha–1, cured leaf yield of 2314 kg ha–1, gradeindex of 79%, nicotine content of 2.54%, and sugar content of 18.35% were noted inthe treatment plot where B was applied as a foliar spray; however, in a few cases, therewas no significant difference found among different methods of B application. Chlorideand potassium contents were not significantly affected by any method of B fertilization.The B fertilization increased the concentration of this element in tobacco leaf, and amaximum concentration of B 48.55 mg kg–1 was noted in the foliar spray treatment.Moreover, fertilizer-use efficiency for different methods of B application revealed thatfoliar spray is more efficient as compared to soil application and root-dipping methods.Nutrient ratios to B such as potassium (K) / B and chloride (Cl) / B considerablydecreased in tobacco leaf with increases in the concentration of B in leaves. Theseratios provided some indication of the interrelationship of B with these nutrients intobacco plants. Results also revealed that K/B and Cl/B ratios closely correlated withthe grade index of tobacco leaf, and good grades of tobacco were found to be at a K/Bratio of 682 and a Cl/B ratio of 148 under the experimental conditions. The overallresults indicated that the B foliar spray at the rate of 0.25 kg ha–1 significantly increasedthe yield, quality, and the nutrient uptake by the tobacco crop under the prevailingconditions and was more effective than other methods of B application.

Keywords Fertilizer-use efficiency, foliar spray, quality, ratio, root dipping, soilapplication, tobacco, yield

Received 3 September 2008; accepted 26 August 2009.Address correspondence to Muhammad Tariq, Department of Soil and Environmental Sciences,

NWFP Agricultural University, Peshawar, 2500 Pakistan. E-mail: [email protected]

1525

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1526 M. Tariq et al.

Introduction

Tobacco (Nicotiana tabacum L.) is widely grown throughout the world for the manufac-turing of cigarettes, cigars, and bids, whereas Nicotiana rustica L. is utilized for snuff,hokka, and chewing purposes (Poustini and Shamel 2000). In addition, tobacco possessesnot only insecticidal value (Hussain, Haq, and Ilahi 1983) but also medicinal value (Larsonand Silvette 1975). Among various species of tobacco, flue-cured Virginia tobacco is one ofthe most productive species in Pakistan, and the growers get a greater net return from it thanfrom other cash crops. Specifically, in Northwest Frontier Province (NWFP), tobacco con-tributes more than 50% of the total production. According to recent information, the areaunder tobacco cultivation in Pakistan was 56.4 m ha, and in NWFP it was 36.5 m ha. Theyields are 1996 kg ha–1 and 2408 kg ha–1, respectively (MINFAL 2005–6). These statisticsindicate that the agroclimatic conditions of NWFP are highly suitable for tobacco cultiva-tion, and therefore it is the major source of farmers’ incomes. The chemical composition[such as nicotine, sugar, chloride (Cl), and potassium (K) contents] of tobacco leaf playsan important role in the evaluation of tobacco quality. The absolute and relative amounts ofthese constituents depend not only on crop varieties, maturity, soil and climatic conditions,and curing processes (Dell 1991) but also on the method and amount of fertilizers such asboron (B), which is one of the deficient micronutrients in Pakistan (Rashid 1996). Becauseof its high mobility in soil, B is not readily retained in light-textured soils and is unavailablebecause of the calcareous nature and alkaline reaction of soils. Therefore, B must be addedannually, using a method suitable for tobacco, which is sensitive to B deficiency. However,there are several opinions regarding B application methods for tobacco crop. Silberbush(2002) stated that foliar fertilization of B is a widely used practice to correct nutritionaldeficiencies in plants caused by improper supply of nutrients to roots. Moreover, foliarapplication is used to supply B to a crop when B demands are greater than can be suppliedvia the soil (Asad, Edwards, and Blamey 2003). Others reported that no significant differ-ences were found between yields obtained with foliar or soil B applications (Dunn, Stevens,and Kendig 2005). Furthermore, Marsh (1992) argued that the requirements of dicotyle-donous plants were greater than those of monocotyledonous plants, because of more Badsorption on the surface of roots (Tanaka 1967). This was proved in the various stud-ies, specifically on tobacco crops (Patel and Mehta 1966). However, an extensive literaturesurvey indicated that very little or no work has been conducted in this region to comparedifferent methods of B application on tobacco. Therefore, the present experiment was car-ried out to evaluate the relative efficiency of different methods of B application and todetermine the most effective, viable, and economical method for achieving the maximumprofitable yield and good-quality tobacco. Keeping in view these objectives, we tested ahypothesis that different methods of B supply may have similar effects on the yield andquality of tobacco crops.

Materials and Methods

Experimental Layout and Sowing

A field experiment was carried out to study the effect of different methods of B applica-tion on the yield and quality of flue-cured Virgina tobacco (Nicotiana tabacum L.) varietyK-399 at the Tobacco Research Farm in Mansehra during 2007. The experiment was laidout in a randomized complete block design. There were four treatments, and each treatmentplot was replicated four times. The tobacco seeds were sown in the first week of December,and healthy seedlings were transplanted to the experimental plots in the first week of


Effects of B on Quality of Tobacco 1527

March. The plot size was kept at 6 × 4 m, with a row-to-row distance of 90 cm anda plant-to-plant distance of 60 cm. Three different methods were used for B application(foliar spray, soil application, and root dipping in solution), and one control plot (whereno B was applied) was included. Boric acid (H3BO3, 17% B) was used as a source of Bfertilizer along with a basal dose of 50 kg nitrogen (N), 60 kg phosphorus (P), and 80 kgK ha–1 in the form of compound fertilizer, that is, NPK (12:15:20). Foliar spray at the rateof 0.25 kg B ha–1, soil application at 1 kg B ha–1 (banding after transplantation), and rootdipping in 0.5 mg B L–1 suspension (for 60 s) at the time of transplantation were used. Thetobacco plants were topped on 22 leaves. Before conducting the experiment, a compositesoil sample from a depth of 0–20 cm was collected and analyzed for various physicochem-ical characteristics of the experimental site. Representative leaves from each treatment plotwere collected after curing for the required qualitative and quantitative determination oftobacco.

Estimation of Yield and Yield Attributes

Length and breadth of the 5th, 10th, and 15th leaves were measured in centimeters fromeach selected plant, and the leaf area was determined in square centimeters according tothe method suggested by Elings (2000).

For green leaf yield plot–1, mature leaves were harvested in four subsequent pickingand weighed separately for each treatment plot in kg ha–1. Similarly, the cured leaf weightwas recorded on the already-weighed green leaves after curing. Grade index is the per-centage of top grades that was recorded by observing the color of cured leaves of eachtreatment plot in all pickings. The leaves already cured were counted, and percentage ofelected top grades were calculated by the following formula:

Grade index = Number of leaves of upper grades in a treatment

Total number of leaves in a treatment× 100

Determination of Leaf Quality

Nicotine content of the cured leaves was determined by the method of nicotine in envi-ronmental tobacco smoke using the gas chromatographic method (AOAC 2000). Chloridecontent in the same cured leaves was estimated by method of Chapman and Pratt (AOAC2000), whereas reducing and nonreducing sugar contents were calculated by the methodof Stellenbosch (2002).

Determination of Leaf Nutrients

Cured leaves were dried, ground by Wiley mill, and ashed (Gaines and Mitchell 1979).The B concentrations in the digests were determined by spectrophotometry using theAzomethine-H method (Bingham 1982), whereas K in the same digests was determinedby flame photometry.

Statistical Analysis

The data collected during field and laboratory investigations were analyzed statisticallyusing the analysis of variance (ANOVA) technique, and means were compared by the



least significant difference (LSD) according to the procedures described by Steel, Torrie,and Dickey (1997). In addition, multiple regression analysis was used to determine therelationships of leaf B with yield, quality, and mineral content of tobacco leaves.

Results and Discussion

The physicochemical properties of the experimental site are presented in Table 1, whichshows that the soil was silty loam in texture, almost neutral in reaction, nonsaline in nature,moderately calcareous, low in organic-matter content, and slightly deficient in hot-water-extractable B (Sillanpaa 1982) and available K (Bajawa and Rehman 1996). Soluble Cl(Katyal and Randhawa 1983) was in the suitable range.

Yield and Yield Attributes

Leaf Area. Results showed that leaf area was significantly affected by different methods ofB fertilization (Table 2). The maximum leaf area of 707 cm2 was recorded in the treatmentplot where B was applied as a foliar spray, the next greatest leaf area was in the plot with thesoil application method, and the smallest (678 cm2) leaf area was recorded in the controlplot. This increase in leaf area may be due to the synergistic effect of B on N and P, whichare mostly responsible for vegetative growth of plants. Lopez-Lefebre et al. (2002) statedthat the positive effect that increased B application exerted on dry material productionin the roots and leaves could be explained by the general improvement in the nutritionalstate, particularly N and P. Similarly, Ruiz et al. (2001) also reported that increase in foliarbiomass in B treatment was due to the stimulation of nitrate (NO3) assimilation, whichresulted in vigorous growth of tobacco leaves.

Green Leaf. Results showed a significant increase in green leaf yield in the treatmentplots where B was applied as foliar spray and with soil application as compared to con-trol (Table 2), but differences in the results were statistically nonsignificant among foliar

Table 1Physicochemical properties of experimental soil

Property Unit Value

Sand % 07.0Silt % 81.0Clay % 12.0Textural class — Silt loampHs (1:5) % 7.20E.Cs (1:5) dS m–1 0.38Lime % 5.62Organic matter % 1.12Hot-water-extractable B µg g–1 0.46Soluble Cl µg g–1 24.0Available K mg kg–1 123.0



Table 2Effect of different methods of B application on the yield and yield attributes of tobacco

TreatmentsLeaf area

(cm2)Green leaf(kg ha–1)

Cured leaf(kg ha–1)

Grade index(%)

Control 678 b 17501 b 2213 b 72 bFoliar spray 707 a 18553 a 2314 a 79 aSoil application 688 ab 18272 a 2265 ab 78 aRoot dipping 683 b 17823 b 2238 b 74 ab

LSD (P < 0.05) 19 754 68 5CV (%) 1.77 2.61 1.87 4.26

Note. Means followed by similar letters do not differ significantly from one another at the 5% levelof probability.

and soil application methods. Dunn, Stevens, and Kendig (2005) also observed a simi-lar nonsignificant difference between these two methods. However, a maximum yield of18553 kg ha–1 was obtained from the treatment plot, where B was applied as a foliar sprayfollowed by soil application. These findings are in agreement with the previous work ofDiggs, Ratto de Miguez, and Shorrocks (1992), who reported an increase in yield due to Bfoliar spray, and this improved growth was due to direct absorption of B from aerial partsof plants. In the present study, among different methods of B application, the minimumyield of 17823 kg ha–1 was given by the root-dipping method, which is statistically non-significant with control, indicating that B was not properly absorbed by the roots, perhapsbecause of the short time of root dipping in B solution, which lowered the green leaf yield.

Cured Leaf. Results showed that a maximum cured leaf yield of 2314 kg ha–1 was recordedin the treatment plot where B was applied as a foliar spray, followed by the yield fromthe soil application method (Table 2). Any differences between these two treatments arestatistically nonsignificant, but the lowest yield of 2213 kg ha–1 was given by the control(where no B was applied). In cash crops like tobacco, this improvement in yield givesa prominent increase in net return to the growers. Asad, Blamey, and Edwards (2002)reported similar results when they applied B as foliar spray on sunflowers and found anincrease in dry mass of mature parts, that is, stems, mature leaf blades, and petioles.

Grade Index. Grade index is the percentage of top grades, where grades relate to theripeness, color line, aroma, damage to, and physical appearance of leaf. Results showedthat the different methods of B have significant effects on the grade index (Table 2), butall the three methods showed nonsignificant differences among themselves. The maximumgrade index was given by the treatment plot with foliar spray of B, which provided 79% ofupper grades of total production, followed by soil and root-dipping methods of B applica-tion with 78% and 74% good grades, respectively. The lowest grade index was recorded inthe control, which was 72%. This improvement in the tobacco quality seems to be mainlythe synergetic effect of B on other essential elements during uptake. Similar conclusionswere also drawn by Li et al. (2005), who stated that B content in base fertilizer resulted ingreater content of other essential elements, which could improve the nutrition and qualityof tobacco leaf.



Leaf Quality

Nicotine. Results indicated that there is an increase in the nicotine content due to applied B(Table 3). The greatest nicotine content (2.54%) was recorded in the treatment plot whereB was used as a foliar spray, followed by the nicotine in the plot using the root-dippingmethod (2.49%). Generally, the nicotine content of tobacco varies area to area and mostlydepends on the physicochemical properties of soil and climatic conditions. Nicotine is aN-base compound, and in the present study, this increase might be due to the high uptakeof N and other essential nutrients due to B fertilization. These results are supported bythe recent findings of Li et al. (2005), who reported that adding B with base fertilizersincreased content of the other elements. Results further showed that with increasing the Bconcentration in tobacco leaves, the nicotine content linearly increased, which showed apositive but nonsignificant correlation (Figure 1). This relationship indicates that B has aneffect on nicotine content of tobacco. Nicotine content is the most important component oftobacco, provoking a physiological effect on the smoker. Our assumption is that nicotineis an N-base compound, and in the present study, this increase might be due to the greaterN uptake. These observations are in line with the previous work of Ruiz et al. (2001), whoconcluded that NO3-N assimilation in tobacco leaf has a negative effect on tobacco qualityand augmented the nicotine content; both effects are harmful for human consumption.

Chloride. Results revealed that nonsignificant differences were observed among the treat-ments, indicating Cl could not change with B application (Table 3). These results are in

Table 3Effect of different methods of B application on the quality of tobacco

TreatmentsNicotine

(%)Chloride

(%)Reducingsugar (%)

Potassium(g kg–1)

Control 2.39 c 0.73 17.09 b 25.79Foliar spray 2.54 a 0.72 18.35 a 33.11Soil application 2.43 bc 0.69 17.50 ab 27.96Root dipping 2.49 ab 0.75 17.28 b 29.89

LSD (P < 0.05) 0.09 NS 0.75 NSCV (%) 2.33 15.53 2.98 13.68

Note. Means followed by similar letters do not differs significantly from one another at the 5%level of probability. NS, nonsignificant.

y = 0.0088x + 2.0747R2

= 0.3957

2.4

2.4

2.5

2.5

2.6

B mg kg–1

Nic

otin

e %

37.5 40.5 43.5 46.5 49.5

Figure 1. Relationship between B concentration and nicotine content of tobacco leaf.



agreement with the findings of Lopez-Lefebre et al. (2002), who detected no change in theCl content of tobacco leaf due to applied B. In the present study, Cl contents showed non-significant differences in all the treatments, and they were less than the permissible limitof 1.5% for tobacco. Chari (1995) suggested the threshold value for Cl content should beless than 1.5% in a good and acceptable tobacco leaf. Moreover, Akehurst (1981) reportedthat if the Cl content rises above 2.5%, the resulting tobacco is nearly incombustible. Thepresent study further revealed that with increasing the B concentration in tobacco leaf,the Cl content linearly decreases, which showed negative and nonsignificant correlation(Figure 2). This relationship suggests that if a tobacco leaf contains more B, that reducesCl content, which is a good index of its quality because more Cl is not good for smok-ing tobacco as it decreases the burning and glowing properties of cigarettes. Moreover, Clcontent in tobacco leaf is of vital importance as its appropriate balance with K determinesquality such as color, smell, and burning qualities.

Sugar. Results showed that reducing sugar is significantly affected by various methods ofB application (Table 3). A maximum reducing sugar content of 18.35% was recorded in thetreatment plot where B was applied as foliar spray, followed by the plot with soil-applied B(17.50%), but no significant differences were found among themselves. However, amongdifferent methods of B application, the minimum reducing sugar content (17.28%) wasgiven by the root-dipping method, which was statistically at par with control but has a sig-nificant difference from the foliar spray treatment, indicating that B was directly absorbedby leaves and helped in the synthesis of sugar. These results are in line with the early workof Valmis and Ulrich (1971) and Katyal and Randhawa (1983), who suggested that B playsa significant role in the synthesis of sugar. Moreover, the present study suggests that there issome relationship between B and sugar in tobacco (Figure 3). Results further revealed thatwith increasing the B concentration in leaf the sugar content of tobacco linearly increases.Although the relationship is statistically nonsignificant, it indicates that B plays a role inthe synthesis of sugar. In tobacco, reducing sugar exercises the most favorable influence onthe aroma and taste during smoking and thus is one of the important constituents for theevaluation of tobacco quality. Moreover, its higher content imparts sweetness to aroma butdeteriorates the burning quality.

Potassium. The results of K concentration in tobacco leaves revealed that a maximum Kconcentration was observed (33.11 g kg–1) in the foliar spray treatment plot, whereas thelowest K concentration (19.62 g kg–1) was found in the control (Table 3). Results furthershowed that different methods of B application did not affect K concentration significantly,but the correlation studies indicate that there is an increasing pattern of K concentration

y = –0.0033x + 0.8677R2

= 0.3868

0.67

0.70

0.73

0.76

Chl

orid

e %

B mg kg–137.5 40.5 43.5 46.5 49.5

Figure 2. Relationship between B concentration and Cl content of tobacco leaf.



y = 0.0409x + 17.392R2

= 0.3433

19

19

20

20

21

Suga

r %

B mg kg–137.5 40.5 43.5 46.5 49.5

Figure 3. Relationship between B concentration and sugar content of tobacco leaf.

y = 0.4706x + 8.5569R2

= 0.5062

25

28

31

34

K g

kg–1

B mg kg–137.5 40.5 43.5 46.5 49.5

Figure 4. Relationship between B concentration and K content of tobacco leaf.

with B concentration in leaf (Figure 4), which suggests a positive relationship between Band K in tobacco plant. This is good evidence to suggest that B enhances the K uptakein tobacco, because K improves the smoking quality of tobacco (increasing the burningquality of cigarettes). From these results, it can be concluded that B has positive effects onthe utilization of K. Lopez-Lefebre et al. (2002) observed a positive response of B on Kconcentration in tobacco crop. Similarly, Tariq and Mott (2006) also observed a positiveinfluence of B on the concentration of K in a radish crop in a sand culture study. In general,K is an essential component of tobacco plant and is needed in an amount sufficient fornormal growth and development. In tobacco, K improves the burning quality of the leaf,helps in the synthesis of sugar and starch, improves the aroma and taste of the smoke,and minimizes the deleterious effects of other elements, specifically Cl (Hashmi et al.1990).

Nutrient Ratio

Potassium/B Ratio. Results showed that with increasing concentration of B, the K/B rationonsignificantly decreases in tobacco leaves (r = –0.40). It is evident from the results thatthe maximum K/B ratio was found in the treatment plot, where B was applied as a foliarspray, whereas the minimum K/B ratio was recorded in the treatment receiving B in soil(banding method). Singh and Sinha (1976) also reported a similar decreasing trend of K/Bratio in plant due to increasing levels of B for cauliflower; Carpena-Artes and Carpena-Ruiz (1987) found similar results for tomato and Tariq and Mott (2006) did also for radish.In the present study, K/B ratios were also plotted against the grade index of tobacco leaf(Figure 5). Though it showed a nonsignificant correlation, as the K/B ratio increases, the



y = 0.0001x2 – 0.1969x + 148.94

R2 = 0.1823

69

72

75

78

81

K/B Ratio in leafG

rade

inde

x %

550 600 650 700 750

Figure 5. Relationship between K/B ratio and leaf grade index of tobacco.

leaf grade decreases, which indicates that leaf grades not only depend on B but also dependon the concentration of K in leaf. However, a good grade was found to be at a K/B ratio of682 in tobacco leaf under our experimental conditions.

Chloride/B Ratio. Results showed that the concentration of B in leaf led to a significantdecrease in the Cl/B ratio, which resulted in a negative relationship in tobacco (r = –0.98).Results further revealed that the decreasing Cl/B ratio correlated with increasing concen-tration of B, perhaps due to the competition between these two anions on the uptake site.Similar decreasing trends of Cl with B have been reported by Supanjani and Lee (2006)and Ben-Gal and Shani (2002) for hot pepper and tomato plants, respectively. In the case oftobacco, Lopez-Lefebre et al. (2002) reported no change in the Cl content due to increasinglevels of B. In the present study, Cl/B ratios were also regressed against the grade indexof tobacco leaf, which resulted in a significantly negative relationship (Figure 6). This isgood evidence that as Cl/B ratio increases the leaf grades linearly decrease, indicating thatCl detoriates the leaf quality of tobacco. However, a good leaf grade was found at a Cl/Bratio of 148 in tobacco leaf under our experimental conditions.

Boron Concentration. Results showed that the B concentrations in plants was significantlyaffected by different methods of B application (Figure 7), which ranged from 38.5 to 48.55mg kg–1. The maximum (48.55 mg kg–1) concentration of B was recorded in the treatment

y = –24.328Ln(x) + 200.02R2

= 0.9689

69

72

75

78

81

125 145 165 185 205Cl/B Ratio in leaf

Gra

de in

dex

%

Figure 6. Relationship between Cl/B ratio and leaf grade index of tobacco.



0

10

20

30

40

50

Lea

f B

(m

g kg

–1)

Applied B

LSD(P < 0.05) = 5.02

C Fs Sa Rd

Figure 7. Effect of different methods of B application on leaf B content of tobacco. C, control; Fs,foliar spray; Sa, soil Application; and Rd, root dipping in suspension.

plot where B was applied as a foliar spray, followed by the plot receiving the soil applica-tion method, and the minimum B concentration was found in the control. These results arein agreement with the findings of Lopez-Lefebre et al. (2002), who reported that the con-centration of B increased with the application of B as compared to the control in tobaccoleaves. In the present study, the greatest B concentration in leaf was found in the foliarspray treatment, which may be due to the direct absorption of foliar plus root uptake fromthe soil by the tobacco plants. Ruiz et al. (2001) reported the same idea. However, leavesare the main organ for B accumulation, and the amount of B accumulated in the leavescould not be redistributed to other organs under these conditions. Tariq and Mott (2006)made also similar observations in radish crop. Results further revealed that in the presentstudy no treatment except the control showed either B deficiency or toxicity when com-pared with the threshold values for tobacco crop as reported by Shorrocks (1984). He notedthat levels in leaves of < 10 µg B g–1 are considered to be deficient, 10–40 µg B g–1 islow, 40–100 µg B g–1 is normal, and >360 µg B g–1 is toxic.

Fertilizer-Use Efficiency. In the present study, B-fertilizer-use efficiency was calculatedaccording to the procedure of Craswell (1987) to find out which one application methodfor B fertilizer is most efficient under the prevailing conditions (Figure 8). However, resultsclearly showed that the foliar spray treatment gave the most recovery of B accumulation,greater yield, and good-quality tobacco as compared to other methods of B fertilization.The reason is that foliar spray of B directly absorbed on the tobacco leaves, which resultedin better performance. Ruiz et al. (2001) drew similar conclusions. Second, losses of Bdue to erosion, leaching, precipitation, and adsorption in soil were minimized as well.Finally, the foliar spray is more effective, viable, and economical than other methodsfor B fertilization on the experimental soil of Mansehra. Furthermore, we agree with therecent findings of Roberts (2008) that fertilizer-use efficiency can be optimized by fer-tilizer best-management practices that apply nutrients at the right rate, time, and place.Therefore, the efficiency of foliar spray proved better than other methods because of theright rate, time, and place, and these sprays should be applied before B deficiency occursas the tobacco crop unable to adequately recover from the morphological or physiologicalchanges resulting from low-B status.



0

2

4

6

8

10

12

14

App

aren

t B r

ecov

ery

(%)

C Fs Sa RdApplied B

Figure 8. Effect of different methods of B application on B efficiency in tobacco. C, control; Fs,foliar spray; Sa, soil Application; amd Rd, root dipping in suspension.

Conclusions

Among different methods of B application, the foliar spray at the rate of 0.25 kg ha–1 alongwith basal dose of NPK (12:15:20) significantly increased yield and yield attributes such asleaf area, green leaf yield, cured leaf yield, and grade index as compared to other methodsof B application and control.

The quality parameters such as nicotine and sugar contents of tobacco were signifi-cantly increased, while Cl decreased where B was applied as a foliar spray, a better resultthan other methods of B application.

Increasing B concentrations in tobacco leaf enhanced the concentration of K andshowed positive correlation, whereas Cl concentrations were decreased, which resultedin a negative relationship. The decrease of Cl was perhaps due to increase of K in leaf.

Nutrient ratios to B such as K/B and Cl/B considerably decreased in tobacco leafwith increasing concentrations of B in leaf. These ratios provided some indication for theinterrelationship of B with these nutrients. The present study suggests that the applicationof B not only affects the relative values of individual element but also affects the balanceamong nutrients to B in tobacco crop. Results also revealed that K/B and Cl/B ratiosclosely correlated with the grade index of tobacco leaf, and good grades of tobacco werefound at K/B ratio of 682 and Cl/B ratio of 148 under the experimental conditions.

The determined fertilizer-use efficiency showed that foliar spray of B at the rate of0.25 kg ha–1 is the most effective, viable, and economical method for achieving themaximum profitable yield and good-quality tobacco under prevailing conditions.

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Comparing Application Methods for Boron Fertilizer on the Yield and Quality of Tobacco (Nicotiana tabacum L.)

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