Impaginato 295 Adv. Hort. Sci., 2019 33(2): 295-298 DOI: 10.13128/ahs-23986 Tobacco dust waste as an alternative medium to grow geranium (Pelargonium x hortorum) plants S. Tzavara, A.I. Darras (*), A. Assimakopoulou Department of Agriculture, University of Peloponnese, 24100 Kalamata, Greece. Key words: agricultural waste, EC, ornamentals, peat, pH. Abstract: Tobacco dust (TD) waste is the typical lignocellosic agricultural residue of cigarette processing. In the region of Peloponnese, cigarette produc- tion is carried out by the leading company of Karelias S.A. The production of TD waste of approx. 2-3 tons/month is a major problem for the company. Plant growth media containing peat (P) + 0, 5, 10, 25 or 50% TD were prepared and tested on geranium plant growth and development. The use of TD increased EC and pH of the final medium. Plants of the cvs “ML Diego” and “ML Sailing ‘12” grown in P+5% or in P+10% TD had similar height, number of leaves, number of flowers, photosynthetic activity and transpiration rates to the P alone (control) indicating that solid agro-industrial waste of tobacco could be used to partially substitute peat in growing medium for floricultural crop production. 1. Introduction Pelargonium x hortorum or ‘‘zonal geranium’’ is an ornamental species that originate from South Africa, perfectly adapted to the Mediterranean region. It is propagated by cuttings and it is a hybrid between P. inquisaus (L.) L’Herit and P. zonale (L.) L’Herit (Dole and Wilkins, 2005). Zonal gera- niums attract an increased commercial interest as they are extensively used in landscape designs and terrace gardens (Berninger, 1993). Flowering is strongly dependent on growth stage (i.e. juvenility), temper- ature (i.e. cold requirement) and sunlight (i.e. intensity and duration), but zonal geraniums are not described as long- or short-day plants (Fonteno, 1992; Dole and Wilkins, 2005). Agricultural waste such as cotton gin trash, olive mill and green waste have been used in combination with peat for cultivation of ornamental plants (Papafotiou et al., 2004; 2005; Grigatti et al., 2007). The residue from tobacco processing (i.e. the tobacco dust; TD) is buried to landfields, but in high w/w concentrations can be toxic due to its high tannin and alkaloid content (Briski et al., 2003). Compared to other waste material, TD contains higher N and K and has pH values ranging between 5.0 and 6.0 (Aderidan et al., 2003). The application of TD waste in soil cultivated with lettuce increased yield compared to control plants (Okur et al., (*) Corresponding author: tassosdarras@yahoo.co.uk Citation: TZAVARA S., DARRAS A.I., ASSIMAKOPOULOU A., 2019 - Tobacco dust waste as an alternative medium to grow geranium (Pelargonium x horto- rum) plants. - Adv. Hort. Sci., 33(2): 295-298 Copyright: © 2019 Tzavara S., Darras A.I., Assimakopoulou A. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 22 September 2018 Accepted for publication 20 March 2019 AHS Advances in Horticultural Science Short note http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2019 33(2): 295-298 296 2008). It was suggested that incorporation of TD waste as an alternative organic amendment might improve soil chemical and biological parameters, as well as crop yield in soils containing low organic mat- ter content. Apparently, no previous research has been con- ducted on utilization of tobacco byproducts as alter- natives to grow ornamental plants. In the present study, we tested growing mediums of peat + increas- ing concentrations of TD on growth and flowering response of zonal geraniums. 2. Materials and Methods Plant material, media preparation and experimental lay-outs Zonal geranium (Pelargonium x hortorum) rooted cuttings (3-5 leaves; up to 12 cm height) of cvs ‘ML Diego’ (red inflorescences) and ‘ML Sailing’12’ (white inflorescences) were provided by Selecta-one ltd (Kavala, Greece). Single rooted cuttings were trans- planted in plastic 2.5 L pots filled with growing medi- ums of peat + TD. TD was provided by Karelias S.A. (Kalamata, Greece) and samples were analyzed in a continuous flow analyzer (CFA ΑΑ3; Seal-Analytical Ltd., Germany) (Table 1). Peat (Hawita, Germany) was mixed with 0, 5, 10, 25 and 50% (w/w) TD (Table 2). Six-replicate pots per treatment with geranium plants were placed on the ground of a non-heated greenhouse at the premises of the University of Peloponnese (lat. 37° 2’ 20’’ N, long. 22° 6’ 51’’ E) in a completely randomized design. Two individual exper- iments were carried out (one for each cultivar) from November 2017 to February 2018. Medium properties, plant assessments and statistical analysis Medium pH and EC (mS/cm) were measured using a pH/mV Meter (Delta OHM HD 2105.2, Padova, Italy) and a Conductivity Handheld Meter (Eutech Instruments, EcoScan CON 5, Singapore), respective- ly. Plant height (cm), number of leaves and number of inflorescences were recorded weekly over the entire cultivation period of nine weeks. Chlorophyll fluorescence, net CO2 assimilation (As; μmol m-2 sec) and transpiration (E; mmol m-2 sec) were recorded using a handheld fluorimeter (OS-30p, Opti-Sciences, Inc. U.S.A.) and a LCpro+ portable photosynthesis system (ADC Bioscientific ltd. Great Amwell, Herts, UK), respectively, on the 5th, 6th, 7th and the 8th week from transplanting (i.e. week-1). Data means were separated using Duncan’s multiple range test at P = 0.05. Statistical analysis was performed in SPSS v. 21. 3. Results Tobacco dust contained nicotine, TSS and small amounts of nitrates and ammonia (Table 1). EC and p H v a l u e s r a n g e d b e t w e e n 8 . 9 2 a n d 9 . 4 6 , a n d between 5.3 and 5.6, respectively. After mixing peat with 0 - 50% TD, pH and EC of the final growing medi- um increased linearly to reach the values of 5.42 and 6.18 mS/cm, respectively (Table 2). Table 1 - Means and range values of tobacco dust content Tobacco dust samples were analyzed in a continuous flow analy- zer Tobacco dust content Means Range Nicotine (mg/L) 158.18 157.84 -160.14 TSS (mg/L) 583.12 581.36 -584.04 Nitrates (mg/L) 32.06 30.15-33.02 Ammonia (mg/L) 6.38 6.25 - 6.52 EC (mS/cm) 9.17 8.92-9.46 pH 5.5 5.3-5.6 Table 2 - pH and EC (mS/cm) values of growing media after mixing peat with tobacco dust at 0 (control), 5, 10, 25 and 50% (w/w) Growing media pH EC (mS/cm) Mixing peat 4.00 0.06 Mixing peat + 5% Tobacco dust 4.51 1.30 Mixing peat + 10% Tobacco dust 4.85 3.22 Mixing peat + 25% Tobacco dust 5.09 4.84 Mixing peat + 50% Tobacco dust 5.42 6.18 Peat replacement with 5 or 10% TD in the grow- ing medium positively affected growth and flowering of cvs. “ML Diego” and “ML Sailing’12” geraniums (Table 3). Plants of cv. “ML Diego” grown in P+5% or P+10% TD maintained similar or higher height, num- ber of leaves, number of inflorescences, net CO2 assimilation and transpiration rates to the control plants (i.e. P+0% TD) (Table 3). However, plants grown in P+25 or P+50% TD suffered reductions in growth and flowering compared to the controls. Plants grown in P+25 or P+50% TD showed reduced number of inflorescences and transpiration rates, compared to the plants grown in P+5 or P+10% TD (Table 3). Stunting growth and reduced flowering of plants cultivated in P+25 or P+50% TD were justified Tzavara et al. - Tobacco dust an alternative medium to grow geranium 297 by decreases in chlorophyll fluorescence (Fv/Fm) ratios (Table 3). The Fv/Fm ratios ranged between 0.571 and 0.893 for plants grown in P+25% TD and between 0.538 and 0.835 for plants grown in P+50% TD indicating damage in plants’ photosystem (PS II) that induced stress responses. Plants of cv. “ML Sailing’12” grown in P+5, P+10 or P+25% TD, showed similar or higher number of leaves, number of inflorescences, net CO2 assimila- tion and transpiration rates to the control plants (Table 3). However, plants grown in P+50% TD showed reduced height, number of leaves, number of inflorescences, indicating damage in plants’ photo- system (PS II) recorded as low Fv/Fm ratio ranging between 0.538 and 0.773 (Table 3). Plants in P+50% TD failed to reach minimum growth requirements and standard commercial size. 4. Discussion and Conclusions TD successfully replaced part of peat in growth medium for zonal geranium plant production. Plants of cvs. “ML Diego” and “ML Sailing 12” responded well when grown in P+5, P+10 and in few cases in P+25% TD and, therefore, could potentially replace part of peat in the growth medium. The concept of peat replacement with agricultural waste material for the cultivation of ornamental plants has been exam- ined the past 20 years. Papafotiou et al. (2004) showed that olive-mill waste composts (OWC) could partially replace peat for the production of Euphorbia pulcherrima (poinsettia), although, at concentration of >12.5% delayed growth compared to plants culti- vated in peat/perlite medium. Tropical potted plants such as Syngonium podophyllum, Ficus benjamina and Codiaeum variegatum could be successfully grown in 75% OWC without showing symptoms of toxicity or other negative effects on growth and development (Papafotiou et al., 2005). Cotton gin trash compost (CGTC) and rice hulls (RH) were tested as peat replacements for the production of Nerium oleander, Pelargonium zonale, Dedranthema grandi- flora and Lantana camara (Papafotiou et al., 2001). Replacing peat with 60% of GCTC resulted in plant height decrease of all species, except those of P. zonale and increase in number of flowers to all species, except those of D. grandiflora. The use of green waste and sewage sludge compost (WSSC) at 80% - 20% (v:v) as a 25%-replacement of white peat, had positive effects on growth and flowering of Begonia semperflorens, Mimulus hybridus, Tagetes patula x erecta and Salvia splendens (Grigatti et al., 2007). All species grown in 25% WSSC showed greater height, number of flowers and plant dry weight compared to plants grown in 100% white peat. TD is a potent agricultural byproduct that could be used in concentrations of <25% without affecting growth and quality of ornamentals. Replacing peat with byproducts of the agricultural sector, merits an eco-biological prospect of environmental-friendly ornamental production. Further research is needed to test TD as peat replacement for cultivation of other ornamental species. Data are means ± SE of 9-week recordings and letters indicate the statistical differences according to Duncan’s multiple range test at P = 0.05. - not measured. Plants failed to reach minimum growth requirements. Table 3 - Effect of growing medium of peat amended with 0, 5, 10, 25 and 50% TD on number of leaves, plant height, number of inflore- scences, chlorophyll fluorescence, net CO2 assimilation and transpiration of P. x hortorum plants of cvs "ML Diego" and "ML Sailing'12" Treatments Plant height (cm) Range (cm) Number of leaves Range Number of inflorescences Range Net CO 2 assimilation (μmol m-2.sec) Range (μmol m-2.sec) Transpiration (mmol m-2.sec) Range (mmol m-2.sec) Chlorophyll fluorescence (F v /F m ) Range (F v /F m ) ML Diego' 0 8.83±0.25 ab 4-16 11.82±0.41 c 4-24 0.85±0.07 a 0-3 2.18±0.26 a 0.34-6.11 1.00±0.087 a 0.61-1.92 0.805±0.001 a 0.778-0.834 5 8.89±0.27 ab 2-18 13.50±0.66 b 4-33 0.86±0.09 a 0-6 3.01±0.34 a 0.24-7.14 1.36±0.170 a 0.71-2.57 0.801±0.002 a 0.685-0.828 10 9.12±0.24 a 5-17 15.12±0.68 a 2-36 0.93±0.10 a 0-5 2.40±0.29 a 0.22-5.32 1.28±0.184 a 0.42-2.34 0.802±0.002 a 0.753-0.878 25 8.39±0.23 b 4-15 12.11±0.55 bc 4-28 0.60±0.08 b 0-3 2.08±0.20 a 0.28-4.00 0.65±0.060 b 0.33-1.06 0.786±0.004 b 0.571-0.893 50 7.01±0.19 c 4-18 5.79±0.32 d 2-20 0.31±0.05 c 0-2 2.23±0.68 a 0.14-4.90 0.37±0.082 c 0.13-0.61 0.731±0.006 c 0.538-0.835 ML Sailing'12' 0 9.70±0.33 a 5-16 14.11±0.62 bc 5-24 0.83±0.10 ab 0-3 2.07±0.32 b 0.34-4.07 0.89±0.096 a 0.29-1.40 0.801±0.001 a 0.778-0.819 5 9.53±0.38 a 2-18 15.79±1.00 ab 4-33 0.76±0.11 ab 0-3 3.40±0.52 a 0.24-7.14 1.04±0.161 a 0.30-2.72 0.793±0.003 a 0.685-0.818 10 9.07±0.34 a 5-17 16.68±1.01 a 4-36 0.98±0.16 a 0-5 2.40±0.62 ab 0.22-5.32 1.17±0.232 a 0.32-2.27 0.799±0.001 a 0.777-0.824 25 7.64±0.30 b 4-14 12.94±0.83 c 4-28 0.53±0.11 b 0-3 1.77±0.40 b 0.28-3.69 0.48±0.057 b 0.26-0.71 0.779±0.005 a 0.668-0.893 50 6.25±0.14 c 4-9 5.01±0.16 d 3-7 0.20±0.06 c 0-1 - - - - 0.678±0.008 b 0.538-0.773 Adv. 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