The right stage for harvesting the crop is when the leaves are matured i.e., when the normal
1. green colour changes to yellowish green or slightly yellowish,
2. become thick, spotted and sticky to touch,
3. appearance of brown spots on the leaves, and
4. bulging of interveinal portions on the leaves. If such leaves are bent under thumb, a cracking sound is produced. There are two methods of harvesting tobacco.
(i) Priming: Harvesting is done by removing few leaves as and when they mature from bottom to top.
(ii) Stalk cut method: In this method, the entire plant is cut close to the ground with sickle and left over night in the field for wilting.
Curing is a process by which harvested tobacco leaf is made ready for the market. There are four common methods of curing.
1. Flue Curing: The harvested leaves are strung on sticks, which are then stacked in a flue curing barn. The barn is artificially heated. The curing process consists of 3 stages.
(i) Yellowing: During yellowing, leaf is kept at a low temperature (32–35°C) and high humidity for about (30–40 hrs) till it attains a bright lemon yellow colour.
(ii) Fixing colour: After yellowing, the temperature is raised gradually and humidity of barn is lowered by opening the ventilators with rapid rise in temperature when the leaf is still wet results in a bluish-black discolouration called scalding. It takes about 16–24 hrs.
(iii) Drying: The ventilators are closed and temperature is again gradually raised to 160°F to dry the veins and mid ribs of leaves. This takes about 28–42 hrs. Then, ventilators are opened to cool down the barn. The leaves are left in barn overnight for observing moisture to come to normal condition for handling and storage.
2. Air curing: The leaves are divided into groups according to their sizes and are strung on the string secured on a bamboo stick. These sticks are taken to barn with closed sides and roof. The leaves are cured under atmospheric temperature and relative humidity of 70–80% is maintained by sprinkling water inside the barn. The entire process is over in about five to six weeks.
3. Fire curing: The leaves are harvested in such way that a small portion of stem remains attached to the leaves. The leaves are wilted for a few hours in the field, then tied into bundles and hung in a smoke hut. They are smoked for about 12 hours by burning dried leaves of trees locally available. After smoke treatment, the leaf is fermented in bulks for about 3–4 weeks. The fermented leaves are given treatment with salt water or jaggery solution.
4. Suncuring: Sun curing is done in three ways.
(i) Curing whole plants on racks: After initial wilting in the field, the plants are strung on bamboo poles and cured in sun. Entire process takes about 15–20 days.
(ii) Curing leaves with pieces of stems or racks: Here, racks are not exposed to direct sun, therefore it takes longer period (6–8 weeks).
(iii) Curing whole plant on the ground: Here, leaves are allowed to dry in sun on the ground and are turned over twice a day. This process continues for about a week and then heaps are made which are opened on the next day and reheaped. This process of heaping, opening the heaps, spreading and reheaping is continued for about 10–15 days. By the end of this period, leaves becomes completely cured. For reducing the cost, stringing can be done on wire at 15–22 cm distance. By the process of turning, the plants on poles could completely be eliminated.
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