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Tobacco Nicotiana tabacum L. - Industrial plants - Herbaceous crops

Tobacco Nicotiana tabacum L. - Industrial plants - Herbaceous crops

Class: Dicotyledonae
Subclass: Gamopetalae
Order: Tubiflorae
Family: Solanaceae
Species: Nicotiana tabacum L.

French: tabac; English: tobacco; Spanish: tobaco; German: Tobak

Origin and diffusion

The Nicotiana genus belongs to the Solanaceae family and includes the N. tabacum species (the most widespread in the world) and the N. rustic (little used because very strong; it was once used as an insecticide).
There are several varieties of tobacco, which differ in characteristics, climatic needs, cultivation technique and care of the leaves after harvest. According to the method of treatment and the type of goods it is classified into:
- light tobacco (cured in the air, in the sun or with indirect fire)
- dark tobacco (cured in the air or with indirect fire)
In Italy different varieties are grown, such as: Virginia, Burley, Kentucky, Herzegovina, Havanna, Maryland, Paraguay, Perustiza, Badischer, Xanthi Yakà.
Christopher Columbus was the first European to know tobacco when he landed on the Bahamas in 1492. The roll of dry leaves of tobacco that the natives smoked was called tabaco. Over time there has been a profound evolution in the type of use: from cigars and shredded for the pipe has passed to a predominant use of cigarettes. Until 1971 in Italy the cultivation of tobacco was done under the strictest monopoly of the state; subsequently cultivation and sale were liberalized. In order to encourage European production, the European Union has established measures to support the prices of leaf tobacco: target price (ensures the farmer a sufficient remuneration) and intervention price (90% of the intervention price for tobacco which is not found buyers).
The largest producers in the world are: China, U.S.A, India, Brazil, Turkey, Zimbabwe, Indonesia, Greece, Italy.

Tobacco flowers - Nicotiana tabacum L. (photo Elena Nelli)

Botanical characters

Leaves - They are the most nicotine-rich organs. The plant has a determined development whose cauline apex differentiates leaves up to a certain moment, after which it differs in inflorescence. The number of leaves ranges from 25 to 35 and are slightly petiolate or sessile, sometimes with almost amplessicauli appendages similar to stipules. They have whole margins, penninervic veins, slightly wavy edges and on the whole surface they have glandular hairs that secrete a viscous liquid.
The shape of the leaves is ovate-lanceolate the ratio between length and maximum width varies from 1.5 to 3.5 however the size is very variable according to the variety, environmental conditions, breeding techniques and position on the stem.
With ripening the leaves change color towards yellowish-green and take on a hanging shape and then reflex.
Stem - It is robust, erect, unbranched, tomentose and viscous due to the resinous substances emitted by the glandular hairs. The development in height varies greatly according to the number and length of the internodes; generally it is around 1.5-2 m.
Roots - Tobacco has a very branching root system, but since it is transplanted, the taproot breaks during transplantation and the plant in the open field is anchored to the soil by an extensive system of rather superficial fibrous roots.
Flowers - Large and showy, they have gamesepalo calyx with 5 unequal teeth, pedunculated and gathered in apical inflorescence in panniculus. The corolla is white in the tube, while in the lobes it varies from pink to red to yellow to white. It is longer than the calyx and has 5 lobes. Landroceo is composed of 5 stamens. The gynaeceum is composed of a pistil with a bilocular supero ovary very rich in ova, surmounted by a long stylus, with a bilobed stigma.
Fertilization is autogamous, but occasional allogamy may occur, due to wind or insects.
Fruits - Each fertilized flower produces an ovate-conical capsule, which opens when ripe for 3-4 valves, leaving thousands of seeds to come out.
Seeds - They are extremely small (10,000 gram to 12,000 gram in 1 gram), kidney-shaped, brown in color, roughly cross-linked on the surface.

Environmental needs

Tobacco is an originally sub-tropical and therefore short-day plant, but with the extension of its cultivation it has adapted to the different photoperiodic regime becoming neutral-day.
Temperature: needs 15 ° C to germinate and 25-30 ° C to flower. Therefore in temperate climates it carries out the cycle in the spring-summer period.
Environments: very adaptable, from equatorial to continental ones, thanks to its great genetics and the variability of the product types.
Soil: high adaptability in soils with different pH, texture, nutrient richness. It avoids those rich in salts, especially chlorides.
- Dark tobaccos treated with direct heat require clayey, heavy and fertile soils, high temperatures and moderate rainfall.
- Air-cured dark tobaccos require heavy, fertile and rich in organic matter soils that others shy away from.
- Oriental tobaccos treated in the sun require low fertility and pebbly soils, often shallow, and a xerophytic environment that generates small plants with small leaves. It is essential then the absence of rain during the collection and care period.
- Light tobaccos treated with indirect heat require loose soils with low organic fertility, in order to prevent the plant from finding nitrogen to be absorbed in the final phase of the cycle. Rainfall or irrigation must be abundant and regular.
- Air-cured clear tobaccos require deep, fertile, medium-textured, well-aerated soils.

Variety

The requisites sought in the tobacco varieties are productivity and good product quality, generic objectives that can be pursued by improvers following different approaches. The latter can be resistance or tolerance to adversity (enhancing those already found or finding new sources of resistance), earliness of ripeness (because the harvests do not go on too long in the autumn, with inconveniences and damage to quality), suitability for mechanical harvesting (drums robust, well spaced internodes, non-erect bearing leaves), nicotine content suited to market needs, low tar potential.

Field of Tobacco - Nicotiana tabacum L. (photo Elena Nelli)

Cultivation technique and care

Plant Nursery:
Given the small size of the seed, the extreme delicacy of the seedling and the high temperatures necessary to germinate and grow, tobacco cannot be sown directly on the field. The sowing is then done in seedbeds when the average daily temperature reaches 6-8 ° C, (end of February in the South of Italy, March in the Center-North) with a density of 600-800 square meter sowing 1 gr. every square meter. The sowing is broadcast by performing a good mixing of the seed or with suspension in water through a watering can. The seed is buried with a slight compression of the soil or by covering it with a layer of sterilized soil. The seedbeds can be of different types: hot bed, greenhouse-tunnels, float system. In the latter, the density of the seed is determined by the distance between the alveoli.
- Hotbed seedbed
It was developed from the beginning by Italian tobacco growing. It can be all above ground or partially underground. It consists of drawers delimited with materials that are easy to disinfect and which do not give shelter to parasites (concrete slabs, masonry, etc.) with a width of around 1.30-1.50 m, so as to make crop care possible and easier. lestirpamento.
The hotbed seedbed is made up of several elements which are: the drainage layer, the thermogenic layer (consisting of manure), the seed bed and the cover.
- Serre-tunnel
For their simplicity and cost-effectiveness they have supplanted traditional seedbeds almost everywhere.
They consist of a plastic film covering, supported by metal arches, which ensures a good greenhouse effect. Thanks to the covering, there is no need for the drainage layer or for the hot bed and therefore the seed bed does not need to go beyond the countryside level requiring the box structure. Therefore, the seed beds are made in the open ground, instead of in caissons, by spreading a sterile layer of sand or better, of pozzolana, with a thickness of approximately 0.10 m to be removed every year.
The most used plastic film is polyethylene, cheaper and more ecological than other plastics, even if the greenhouse effect it produces is partial, in the sense that it does not completely trap the infrared radiation emitted by the soil.
- Float system
It is the most recent evolution of tobacco seedbed.
It creates inside the tunnel greenhouse waterproof basins with plastic film spread on perfectly level ground and with raised edges so as to contain a layer of water 0.2 m high. Other basic elements of the system are cellular containers of expanded polyurethane that float on the water. The alveoli of the containers are filled with a sterile peat-based substrate and a tobacco seed is deposited in the center of each one (all mechanized operations). The newly seeded alveolar containers are placed to float in the basins filled with an appropriate nutrient solution; from it the seedlings draw water and nutrients. The length and the width of the basins are exact multiples of the dimensions of the containers, so that they turn out to form a compact floating surface covering the entire surface of the tank. In this way, more robust seedlings are obtained, transplanting seedlings with earthen bread, less competition between the plants thanks to the regularity of their arrangement and therefore greater number of plants valid per square meter, elimination of any phytosanitary problem related to the substrate, ease of management of the greenhouse as irrigation is not required, reduction of temperature drops thanks to the thermal flywheel made up of the liquid mass.
Field:
Rotation: renewal crop follows or precedes wheat, the improving power is different according to the type and cultivation technique adopted. It can happen to itself but there may be problems due to parasites that require the return to rotation.
Soil preparation: plow in the previous summer or autumn at about 0.30-0.40 m and finish it for transplanting with harrowing.
Transplant: carry it out with temperatures higher than 15 °. Transplanting with machines has entered current practice because it allows you to reduce the use of labor. After transplanting, it is advisable to irrigate to ensure engraftment. If some plants do not take root, it is advisable to replace them early with others from seedbeds.
Fight against weeds: tobacco must be defended against weeds because it is very sensitive to this type of damage. This can be achieved with weeding-tamping or with chemical weeding that can be carried out pre-transplant with or without burying or post-transplant.
Topping: with this operation the stem is popped to accumulate the reserve substances, nicotine, on a limited number of leaves so that they grow large, heavy and strong. It is practiced only on a limited number of varieties destined to produce strong and substantial tobaccos (Kentucky, Virginia). Normally the topping is done by hand (40-60 hours of work), but also with topping machines mounted on «stilts» to be able to pass over the crop (2-3 hours of work). The effect of the topping on the leaves is all the more marked the lower and earlier the operation. With the elimination of the apical part of the plant, an auxin imbalance is caused in the plant whereby the buds existing in the axil of the leaves, normally dormant, germinate forming the so-called "cacchi" which, if left to grow, would cancel the effect of the topping. In order to eliminate these axillary shoots, chopping is necessary after trimming; which can be avoided by preventing the sprouting of the axillary buds with suitable "anti-bud" chemical products.
Sbranciatura: it was once a mandatory practice. It consists in removing the 2-3 basal leaves by hand, dirty and small, allowing the airing of the crown and the development of the plant. Lately the basal leaves are also collected and therefore this practice is no longer carried out.
Anti-cryptogamic fight: fungicide treatments against blue mold.

Care

It is a slow and controlled drying, during which the leaves undergo deep and decisive biochemical and organoleptic transformations. With care, the qualitative product characteristics on which the realization price depends to a large extent are developed or strengthened.
Indirectly cured tobaccos: tobaccos that enter the blends of the most common blonde cigarettes. Their characteristic is a color varying from lemon yellow to orange, of light to medium strength, with a high content of sugars, mostly little marked aroma.
The most famous in the world is Virginia produced in North Carolina (USA), strong, substantial, relatively aromatic. Italy is the largest European country of direct fire tobacco production with two distinct types of product: the first, traditional, exclusive of Italy called Bright Italy (or Bright) in a phase of strong regression, the other relatively recent called Virginia, which is taking over among Italian tobacconists because they are more accepted on world markets.
- Stages of indirect fire treatment
1) Yellowing. The cell is hermetically loaded and closed so as to ensure a high relative humidity (80-85%), the temperature reaches 30 ° C and remains there until the leaves have taken on a yellowish tint; then saumenta of about 1 ° C then, with another stop at 35 ° for the beginning of the actual yellowing; after which it rises to about 38 °: at this temperature the leaves remain until a strong lemon yellow color appears. This is the most difficult phase of the treatment because with an incorrect maneuver the typical yellow color of Bright Italia could be compromised.
2) Fixation of the yellow color. Once the desired yellow color is obtained, the oxidative processes are stopped, which would lead to the formation of the brown color, the opening of the air vents, so as to eliminate excess humidity.
3) Drying of the foil. From 38 ° C to 50 ° increasing the temperature by 1 ° then, always keeping the air vents open to the maximum. Stop at 50 ° until the leaf edges are completely dry.
4) Drying of the rib. From 50 ° the cell is brought to 65 ° (increase of 1 ° -1.5 ° then) by gradually closing the extractors and air intakes. At 65 ° it is expected that the ribs have become perfectly friable: at this point the cure is finished, but it is necessary to proceed with the next phase to guarantee the conservation of the product.
5) Sterilization of the product. The temperature is raised again: from 65 ° to 85 °, increasing by 2-3 ° then. In the latter phase, tobacco acquires the characteristic odor and also the necessary preservation and color stabilization, due to the activation of the enzymes.
A well done cure lasts from 5 to 7 days depending on the state of the leaves.
Air-cured light tobaccos: cured (even the dark ones) by hanging the strings of leaves in shady and airy structures where, without any intervention of any kind, they perform the cure in a rather long time: from 3 to 4 weeks. It requires inexpensive but voluminous structures and reduced manipulations but is rudimentary because it does not allow to regulate environmental conditions. This is why it is long, and leads to the decomposition of sugars (which are absent or scarce). The most important tobacco is Burley.
Air-cured dark tobaccos: dark tobaccos are used in cigars, shredded and dark cigarettes. In Italy in the past two types were important: the Beneventano, in the provinces of Benevento and Avellino, and the Nostrano del Brenta, in the Veneto.
Today these tobaccos have practically disappeared because their taste finds less and less appreciators. In their replacement, fairly new tobaccos for Italy have spread, among which Havanna and Badischer Geudertheimer are the ones that have met the greatest success spreading very quickly in replacement of Nostrano del Brenta and Beneventano. The cured leaves have a nicotine content of 2%. These tobaccos are used as a filling for cigars and dark cigarettes.
Dark tobacco cured by direct fire:
They are the least important tobaccos in the world tobacconist scene, but in Italy they have a far from negligible importance: Italy is in 4th place for production, after the USA, Poland and Malaysia.
The only representative of this category is Kentucky tobacco.
Pressing
Once the treatment is completed, the tobacco is subjected to reinvigoration, that is, it is slightly moistened so that it can be pressed without the leaves shattering. It is of the utmost importance that the tobacco is pressed with the right degree of humidity. If the tobacco is put in too wet bales it loses the brightness of its color with devaluation of the product. As previously mentioned, the farmer generally sells his leaf tobacco, that is, cured and packaged in bales.
The assessment of the quality of the tobacco is made by an expert report made by expert technicians who estimate by eye the percentages of the various classes (A, B, C and out of grade) present in the consignment.

Collection and use

Tobacco leaves are typically harvested in subsequent passes. The leaves, a useful product of tobacco, must be harvested at the right degree of technical ripeness. The signs of this ripening, which starts from the lowest leaves and proceeds upwards, are as follows:
- Light green coloring of the flap to decrease the chlorophyll content
- Yellowish internal marbling, starting from the tip and from the edges of the leaf, which extend towards the center.
- Downward curvature of the apex and leaf margins.
- The leaves synergize due to the accumulation of starch and, when folded, they break with a clear and rectilinear fracture.
- The leaf detaches easily from the stem.
- For the break-up of epidermal glandular hairs, resinous materials are released, which make the leaf sticky to the touch, with the emission of a strong odor.
Dark tobaccos, in which strength, taste and aroma are of great importance, must be harvested when fully ripe; the light ones, on the other hand, at the first signs of maturity (with a little early harvest they see improved combustibility and increased lightness).
The harvest is done by machine or by hand, of this there are three methods:
Whole plant harvest. It is done by cutting the plants at the base of the stem and laying them in the inter-row, with every care to avoid lacerations, and leaving them to dry for a few hours.
Leaf collection. The technical maturation of the leaves is scaled from the bottom, upwards so the leaf collection, made in successive steps, is rational in that the various leaf crowns are harvested at the right degree of ripeness. In the most accurate systems, hand picking is done by picking 3-4 leaves at a time which allows you to keep the various crowns of leaves distinct: basal, first median, second median, subapical and apical. To reduce costs, especially with mechanized harvesting, there is a tendency to reduce the number of harvests by picking several leaves at a time so only three crowns are distinguished: basal, median and apical.
Mixed collection. The low and middle ones are collected leaf by leaf, while the apical ones, when ripe, are gathered together by cutting the stem. It is a suitable system for varieties with many leaves.
The best time to harvest tobacco is in the morning, as soon as the leaves have dried from the dew. The leaves must be immediately transported with great care and caution to the place of care where they are packaged on strings in strings of a given number of leaves, by hand skewering or through the use of skewing, stapling or killing machines; the strings of leaves are tied on special poles that allow them to be spread in the treatment rooms.

Tobacco leaves (photo Laura Paganucci)

Adversity and pests

In seedbed: they are serious because they cause the loss of seedlings or their lack of vitality.
The greatest damages are caused by the rot of the seedlings (Pythium spp., Rhizoctonia solani, Colletotrichum spp.) And by the root rot (Thielaviopsis basicola). The best prevention system is the use of insensitive varieties and uninfected substrate either because it is inert (e.g. pozzolan) or because it is sterilized with steam or fumigants. The blue mold (Peronospora tabacina) is extremely fearful. Fearsome insects are the Collemboli. With the float system method all adversities in seedbeds are kept under control.
Field adversity:
Plant pests
- Radical rot. It is caused by the mushroom Thielaviopsis basicola attacks the newly transplanted seedlings and in seedbeds, with a wet and cold seasonal pattern and soil with defective drainage. The use of resistant varieties and respect for crop rotation are the most recommendable measures.
- Blue mold. The causative agent is the mushroom Peronospora tabacina,
- Virosis. Several viruses affect tobacco, often causing serious damage. Among the most common are the mosaic, caused by TMV (Tobacco Mosaic Virus) and nerve necrosis by PVY (Potato Virus Y). There are no direct means of virosis control, but only preventive means: sterile seedbed substrate, hygiene rules for transplant personnel, eliminating potentially infected spontaneous herbs.
- Parasitic phanerogams. The tobacco on the field is subject to being parasitized by the orobanche (Orobanche ramosa, mainly), a superior plant that has lost its photosynthetic capacity becoming a parasite of other plants, on whose roots it imposes its austori with which it sucks the lymph of the host-victim. Attached tobacco plants slow down or stop growth with underdeveloped leaves that are not marketable when treated. Orobanche produces a huge quantity of seeds that remain viable in the soil for many years: it is therefore a serious problem that has not yet found certainly effective means of control.
Serious but fortunately rare diseases are angular spotting and wild fire, which was recently seen to be caused by the bacterium Pseudomonas syringae itself.
Bacterial blight is caused by Pseudomonas solanacearum.
Insects:
- Agrotidae (or noctue). The most common species in Italy is Scotia ipsilon, a moth whose terrestrial larvae come out at night gnawing at the collar the stem of recently transplanted tobacco plants.
- Elateridae. The terrestrial larvae of the beetles of the genus Agriotes attack tobacco penetrating the underground portion of the transplanted plants.
For both cases, geo-disinfestation along the row at the same time as transplanting is recommended.
Nematodes:
In the case of crop systems in which tobacco occurs for several years, the intensification of attacks by galligerr nematodes occurs; (Meloidogyne spp.). Attacks are particularly severe in sandy soils if tobacco returns to the same soil at short intervals.

Climate adversity

Hail: The leaves, which represent the useful product of tobacco, are torn or punctured with total loss of the product or with serious damage to quality. If the hail came early, it is possible to recover a part of the product by cutting the plants at the collar and raising one of the shoots that develop after cutting. The lacerations of the leaves seriously affect the quality of the band tobacco. The insurance for hail damage is very common.


Video: Saving Nicotiana Seeds in the Garden (December 2021).