The oldest known beverage, tea is native of China in South East Asia. It was known to the Chinese as early as 2737BC, but attained the status of a popular drink in England in 1664 AD. India is the largest producer, consumer and exporter in tea industry.
Tea belongs to the genus Camellia and family Camelliaceae. The original species, which produces tea, were C.assamica (Assam jats), C.sinensis (China jats) and their natural hybrid, C.assamica subspecies lasiocalyx (Indo China or cambod type). Being a highly cross pollinated crop, the present day seedling populations are mixture of both the above two species, however, from their major share of characters Assam or China type can be distinguished by the following characters.
Morphologically, tea is an evergreen shrub or tree, leaves are simple, alternate, serrate, flowere bisexual, with superior ovary, fruit is a capsule.
Clonal selection from seedling population was taken up by UPASI, Tea Scientific Department, Cinchona and also by other Tea Research Institutes. UPASI has so far released 27 clones. Certain outstanding clones released by other Institutes are also used in South India.
Climate and soil
Tea is exacting in its climatic requirements. The temperature may vary from 16 to 320C and annual rainfall should be 125 to 150 cm, which is well distributed over 8-9 months in a year. The atmospheric humidity should be always around 80% during most of the time. Very dry atmosphere is not congenial for tea. It is grown in plains in North Eastern States but in South India, it is grown in hill ranges from 600 to 2200 m above M.S.L.
Tea is a calcifuge crop requiring comparatively low amounts of calcium but high quantities of potassium and silicon. They can be grown in lateritic, alluvial and peaty soils. Optimum pH range is 4.5 to 5.0 and soil depth should be 1.0 to 1.5m.
Tea can be propagated by seed and by cuttings. Seeds collected from the fruits of seed baries are soaked in water and only heavy seeds, which sink, are alone used for sowing in beds. Germination occurs in 20 to 30 days. At that stage they are carefully lifted and transplanted in polythene sleeves. They will be ready for planting in 9 months.
Vegetative propagation: The site for the nursery can be selected in a flat land or gentle slope, near to a perennial water source and easily accessible by road. It should have a good drainage and should be protected from wind, frost and wild animals etc. approximately, 0.15 ha nursery area is required to produce 1.25 lakhs cuttings. Nursery area is to be provided with overhead shade by erecting concrete or stone pillars at a spacing of 3x3m and spread with 6mm2 mesh double strand coirmat which provides about 67% shade.
The cuttings for rooting are collected from mother bushes, which are well maintained near the nursery area. Such mother bushes are pruned well in advance to induce juvenile shoots. These juvenile shoots are collected in the morning hours and 3cm long cutting each with a healthy mother leaf and an active axillary bud is prepared. Cuttings from top tender and bottom brown wood should be avoided. These cuttings are planted in polythene bags (30cmx10cmx150 gauge), filled with growing medium (Jungle soil: river sand 3:1) in the bottom and rooting medium (Red/subsoil:sand 1:1) in the top 8-10cm. The soil used for rooting media should have an optimum pH range of 4.8 to 5.0, if high, i.e., 5.1 to 5.5, or 5.6 to 6.0, it must be drenched with 1 or 2% aluminum sulphate solution respectively @ 1 litre per cubic foot of soil. This treatment should follow with drenching of twice the volume of plain water to wash excess aluminum sulphate. The cuttings are carefully planted at the centre of the bags in such a way that the petiole should not touch the soil and then they are watered. These bags are then covered with polythene sheets over the G.I. wire arhes and the sides are tugged well to preserve moisture content. Callusing starts in 4-6 weeks and rooting occurs in 10 to 12 weeks. When 80% of the cuttings have rooted, the tents are opened in stages and the overhead shade is gradually reduced to harden the plants.
The land is cleared of the roots of the fallen trees and drains are taken at suitable intervals depending upon the slope to conserve the soil. In the olden days, up and down system of planting at 1.2x1.2m are followed. Presently, contour planting either in a single hedge or double hedge system is followed.
The last method has many advantages over the first two viz., early and high yield, better soil conservation, less weed growth in the hedge and efficient cultural practices. Planting season normally coincides with June/July and September/October for SouthWest monsoon and North East monsoon areas. Pits of 30x30x45cm size are dug and plants of 12-15 months old are planted by removing the polythene sleeves. Immediate after planting, plants are staked to prevent wind damage.
Immediately after planting, the soil surface around the plants should be mulched, usually cutgrasses of gautemala are employed for this purpose. About 25 tonnes of grass is required to mulch one hectare. Care must be taken to keep the mulch materials away from the collar region last they may cause collar diseases. If there is a dry weather, mud tubes or etah tubes may be buried 15cm deep near the plant in a slanting position and one litre of water per plant may be poured or injected at weekly intervals. This subsoil irrigation helps to minimise the causality besides encourages developing deeper roots.
Tea requires filtered shade and if it is exposed to direct sun, its growth is affected. Shade is hence essential and beneficial to tea as
The desirable characters of a good shade tree like
Weeds will be a problem in young and pruned fields. Manual weeding is never recommended in tea lest more soil erosion and damage to surface roots and collar regions. Therefore, the following chemical weed control is alone recommended in tea.
Training and Pruning
In the young tea, when it has established well, centering i.e. removing the growing point leaving 8 to 10 mature leaves from the bottom, is done to induce secondaries. When the secondaries reach more than 60 cm, they are tipped at 50-55 cm height by removing 3 to 4 leaves and bud to induce tertiaries. Therefore, plucking at mother leaf stage is continued for better frame development. It takes nearly 18 to 20 months from planting to reach regular plucking field stage.
Pruning is done in tea
Pruning is normally done 4 to 6 years interval depending upon the altitude of the garden, nature of the materials etc. the bushes marked for pruning should have adequate starch reserves in roots otherwise the sprouting following pruning should have adequate starch reserves in roots otherwise the sprouting following pruning will be less. This can be normally tested by the common Iodine test and if the starch reserve is less, bushes are allowed to rest for 2 to 3 months. The different types of pruning are as follows: -
Immediately after the rejuvenation or hard pruning, the cut ends are smeared with a paste made of copper oxychloride and linseed oil (1:1). The prunings, consisting of only small twings and leaves are buried in trenches of 30cm width and 45cm depth taken across the slope in alternate rows. The pruned bushes are given washing with 10% lime solution using No. IV nozzle of power sprayers in order to kill the epiphytic growth of moss and lichen so as to induce early and even bud break. Lime washing also minimises sunscorch to the bush frame.
The buds from the pruned shoots grow in a steady succession without any cessation of growth. These are known as a periodic shoots or primary shoots. These primary shoots should be induced to produce flush shoots, otherwise known as periodic shoots by regular tipping operation. Tipping is the removal of terminal portion of the shoot and it varies with jats and pruning height as given below. Tipping height refers to the number of leaves that must be left above the pruned cut while tipping in material refers to that portion of the terminal shoot, which must be tipped off.
Manures and fertilisers
Tea responds to manuring and it has been estimated that to produce 100kg of made tea, tea plant utilises on an average 10.2, 3.2 and 5.4kg of Nitrogen, Phosphorus and Potash per ha. Manuring in tea starts from nursery stage itself. Once they strike roots (after 4 months) 30g of soluble mixtures (Ammonium phosphate (20:20) 35 parts, potassium sulphate and Magnesium sulphate each 15 parts and zinc sulphate and Magnesium sulphate each 15 parts and zinc sulphate 3 parts) is dissolved in 10 litres of water and is applied with rosecan for about 900 plants. This must be repeated at 15 days intervals.
Nitrogen: The recommendation for mature tea is based mostly on soil organic matter status and anticipated yield. For a field with medium organic matter status the following rates of application is suggested for every 100kg of made tea anticipated:
Twenty per cent of the total nitrogen is given in the form of Ammonium sulphate during March/April. Urea is recommended in May/June and receding monsoon months avoiding very wet and very dry periods and it will come to 65% of total nitrogen. Fifteen percent of the total nitrogen is applied in the form of Calcium Ammonium Nitrate during pre-winter (November-December).
Potassium: Nitrogen and potassium are always applied together. NK ratio of 1:1 is used for plucking fields while for a pruned field 2:3 NK ratio is recommended. For rejuvenation pruned field 1:2 NK ratio is suggested. The enhanced rates of potassium application in the pruned year is to encourage formation of healthy farmers. Muriate of potash is the sources of potassium used in tea fields. The NK fertilizers are applied by broadcast for mature tea and is broadcast and dibbled in along the drip circle for young tea. The interval between two successive applications should be atleast 3-4 weeks.
Phosphorus: Phosphorus is applied once in alternate years @ 90kg P2O5/ha for fields yielding less than 3000kg/ha for fields yielding between 3000 and 4500kg/ha, 60 to 80kg P2O5/ha is suggested every year. The soils being acidic, rock phosphate could be advantageously used. The fertilizer should be placed at 15-22cm depth.
Micronutrients: Among the micronutrients, zinc deficiency is often manifested in young shoots characterised by reduced leaf size, rosetting, chlorosis and formation of more banji shoots. Application of zinc sulphate @ 6 to 8kg/ha for high yielding fields every year is the general recommendation. The above quantity can be given in 4 to 5 split applications during has been found beneficial to combine other micronutirents viz., Manganese sulphate @ 15.5g/10 litres and boric acid @ 5.5g/10 litres of spray volume along with zinc sulphate spray.
Liming: In the hill soils, due to the leaching of bases by rain and also due to the incessant application of acid forming fertilizers, the soil pH is often reduced which affects the physical and chemical properties of soil. Therefore, periodical application of lime is essential properties of soil. Therefore, periodical application of lime is essential to amend the soil and maintain optimum pH. Agricultural lime (Calcium carbonate) and dolomitic lime (Calcium Magnesium carbonate) are generally recommended for tea soils. The rate of application is based on soil pH, rainfall, fertilizer usage and length of the pruning cycle. Roughly lime @ 1.5mt/ha for a pH between 4.5 to 4.9, 3.0mt/ha for a pH between 4.0 to 4.4 and 4.0mt/ha for a pH of less than 4.0 is suggested.
The lime is applied by evenly broadcasting prior to pruning once in a pruning cycle. First manuring following liming can be had after 6 weeks and a minimum of 15cm rainfall should have been received during this period.
Harvesting or Plucking
Plucking consists of harvesting 2 to 3 leaves and a bud. It is the most labour intensive operation in a tea industry and also decides the yield and quality of made tea. Normally, a pluckable shoot takes 60 to 90 days for harvesting since its sprouting from the axillary buds. When the shoot is plucked upto mother leaf, it is known as light plucking and if it is plucked below mother leaf, it is called hard plucking. The plucking interval and plucking standard in relation to cropping is given below:
It is essential to add one tier of active maintenance foliage to the bush every year. This is done by mother leaf plucking during January to March. During the rest of the period level plucking can be carried out.
Consequent to plucking, bush height increases every year in the order of 10cm over tipping height in the first year, 7.5cm, 7.5cm, 5cm and 5cm over the previous year height in the second, third, fourth and fifth year respectively.
Yield of made tea per hectare depends upon many factors such as elevation, clonal or seedling jats, management practices, severity of pruning, processing techniques etc., Generally, in tea industry, a field which yields upto 2000kg of made tea/ha is considered as low yielding and 2000 to 3000kg as medium yielding and anything above 3000kg as high yielding fields.
Manufacturing of tea
Basically, there are two types of processing viz.,
Irrespective of the method, manufacturing of tea involves the following steps:
Withering: The objective of withering is to reduce the moisture content of leaves by spreading them in troughs which receive artificial air from fan fitted on one end. At the end of withering, the leaves attain a flaccid condition for which it may take 12 to 18 hours depending upon the weather condition.
Rolling: This operation is carried on by a series of machines or in a single roller, during which the cells in the leaves are broken to liberate the sap containing the polyphenol oxidase, an enzyme, which in the presence of oxygen, oxidises the polyphenols to produce theaflavins and thearubigens. These are responsible for colouring of the tea and is a 30-40 minutes. Afterwards, the fine sifted rolled ones are sent for fermentation while the coarse ones are again sent for rolling.
Fermentation: Rolled tea materials are either spread in concrete floors or kept in aluminum trays. In the presence of high humidity and proper step decides the quality i.e. strength, colour and briskness of tea. Fermentation requires 1 hour or 2 hours depending upon the environmental conditions.
Drying: This step aims at stopping the fermentation process and slowly removing the moisture content without a burnt smell but preserving the inherent quality. This is achieved by passing the fermented tea in thin layers through conveyors into a drier in which the inlet temperature is maintained around 250 2800F and outlet temperature is a round 150-2000F. Proper drying takes 30-40 minutes.
Grading: Before grading, the dried tea is removed of the stalky fibres, which affect the quality, by passing through fibre separate machines. The bulk tea is passed through different sized meshes which aid in separation into different grades.
Many pests and diseases are known to infect tea bushes and cause economic losses. The important pests and diseases, their typical symptoms and control measures are