Everything you need to learn about tea cultivation, harvest and growth.
Introduction to Tea:
Tea is the most important and popular non-alcoholic beverage and is consumed by almost half the population of the world. It contains caffeine and has stimulating and refreshing qualities. The beverage is prepared from the processed tender leaves and unopened buds of the plant, Camellia sinensis, by adding boiled water to them. The Chinese have been drinking tea since the fourth century. The people of upper Burma and upper Assam have also been consuming tea for a long time.
Tea plant is considered to be a native of Assam and the adjoining areas of upper Burma, Some regard southern Yunnan and Upper Indo-China to be its home.
It is not known when the cultivation of tea was undertaken on a commercial scale, but at present, it is grown in many tropical and subtropical countries. The important tea-growing countries are India, Sri Lanka, East Africa, Japan and Indonesia. Bangladesh, China, Argentina and certain other countries also grow the crop. In India, tea is grown in Assam, West Bengal, Kerala, Karnataka and Tamil Nadu.
Besides these states, cultivation of tea is done in Tripura and Himachal Pradesh also. The total area under tea in India is about 3, 58,000 hectares and the total annual production is over 468 million kg. Tea is a very good foreign exchange earner and the industry in the country employs more than one million workers.
In spite of the fact that there has been a very small rise in the area under the crop during the past twenty years or so; the yields have recorded a steady increase and this is mainly the result of scientific methods of tea culture as adopted by the progressive tea planters.
A very good progress has been made during the past few years on the selection of high-yielding clones possessing improved quality, and their release for general cultivation has been of great help to the industry. The tea planters are being encouraged by the Tea Board to improve their plantations by uprooting uneconomical clones and planting improved material.
Tea or Camelia sinensis (Linn.) O. Ktz. belongs to the family Theaceae. It is an evergreen short tree or shrub. Branches are glabrous. Leaves are simple, alternate, estipulate, elliptic, and oblong, with serrated margin, acute at both ends or cuspidate-acuminate at apex, 10-20 cm long and 3-7 cm broad. Flowers are solitary, axillary, often in a cluster of 2-4, bisexual and Sepals 5-6, unequal glabrous with membranous, ciliate margin.
Petals are white or pinkish, 5-6, broadly obovate, slightly coherent at base. Stamens are many in several whorls, 5-12 of the innermost whorl free; others united in a monadelphous ring, adnate to the base of the petals. Ovary is superior, 3-5 celled with 4-5 pendulous ovules in each cell. Styles are 3-5 united up to 2/3rd of their length. Fruit is a loculicidal capsule. Seeds are 1-2 in each cell.
Climate and Soil Required for Tea Cultivation:
Tea is cultivated on a large scale in areas with moist and warm climate. It grows from almost the sea level to an altitude of 2,460 m. A good rainfall, well-distributed throughout the year, absence of strong dry wind and freezing temperature are some of the essential requirements. The average annual rainfall of 150-370 cm is well suited for cultivation of tea. However, an annual rainfall of 750 cm does not seem to produce any harmful effect on the plant, provided the soil is well drained and there is no waterlogging.
Although tea grows on soils of all physical types, it does best on a well-drained, deep and friable loam or forest land with sufficient organic matter. Tea is grown in acidic soils (pH 4 to 6), having low calcium content and generally rich in iron and manganese.
Cultivation of Tea:
The propagation of the plant is generally done from seed, but in recent years, high – yielding clones are used for the purpose. Seeds are collected in the north-eastern parts of India in November and, in the southern parts, in May-June. The viability of tea seeds is lost soon and hence they are sown within a short time of their collection. Sowing of seeds is done in nurseries, which are properly shaded.
Considerable attention is paid to the seedlings so that healthy plants are produced. Generally, 1 to 1½ year-old seedlings are planted in the field in April-May to September-October. In the case of vegetative propagation, cuttings of selected tea plants, each with an internode and a leaf, are planted in clonal nurseries. Such clonal nurseries are now raised on a large scale by progressive planters.
The land used for planting is cleared by removing forest growth and then prepared properly, taking care to prevent soil erosion. Pits of a convenient size, generally 30-45 cm deep and 24 cm wide, are dug and filled with well – rotted cow dung or compost. Normally, a spacing of 120 × 75 cm is adopted and about 10,000 plants are accommodated in one hectare of land. Heavy mulching of the soil is practised during the first one or two years.
When tea planting is done, certain trees like the silver oak (Grevillea robusta) and Erythrina lithosperma are commonly planted to provide shade to the tea plants and this has been found by planters to be a useful practice. Species of Acacia and Albizzia are also used as shade plants, the latter being most common in northern India. In southern India, however, the silver oak is preferred.
Control of weeds is very important in tea plantations and it has hitherto been done manually. However, chemical control is now becoming popular with tea-planters.
Tea has been found to respond well to the application of nitrogen and potassium. The best response to nitrogen is obtained only when sufficient amount of potassium is present.
While in southern India, about 300 kg of nitrogen per hectare is found to be good for certain high-yielding varieties of tea, in northern India, a much smaller quantity, not more than 120 kg is required. Potassium is applied at the rate of 40 to 50 percent of the nitrogen applied. With regard to phosphate experiments have indicated that application of 30 to 40 kg per hectare is sufficient.
It is very necessary to apply nitrogenous manures frequently to encourage growth of leaves. Application of a large amount of compost every year and also green manuring are important. Proper manuring is necessary from the nursery stage up to maturity of the crop and all the three elements, N, P and K are included in the fertilizer mixture applied.
Deficiency of zinc affects the production adversely and, therefore, foliar application of the nutrient in the form of zinc sulphate (usually at the rate of 11 kg per hectare) should be undertaken in alternate years.
Training, Pruning and Plucking:
The central leader stem of the plant is removed within a few months of planting or at the nursery stage, in order to encourage the growth of lateral branches. The plant thus takes the shape of a small bush. The lateral branches are cut to a height of 40 to 50 cm and the growth above this is pruned periodically.
The small compact bush, which is thus formed, attains a height of 1.2 to 1.5 m in about one year after planting. It is regularly plucked or harvested. After about 4 to 5 years of planting, the bush receives a formative pruning, in which the main branches are cut at a height of 35 to 40 cm from the ground level.
New shoots, which develop on the plant are allowed to grow unchecked and are “tipped”, so as to leave a growth of 20 to 30 cm above the pruning cut. After this, the crop is harvested at regular intervals. There are various methods of pruning which may be adopted.
The pruning cycle in the plantations in southern India extends over a 4-, 5- or 6- year period. This depends on the elevation of the place and the growth of the plant. In some cases, a “skiff’ is given at a convenient height and the pruning cycle is extended by a couple of years. Periodical pruning and skiffing are done to encourage vegetative growth and to enable the bush to attain a height convenient for plucking. In northern India, annual pruning is the common practice. However, the present trend there is also to extend the pruning cycle.
The economic life of the tea bush in northern India is generally 40 to 50 years and, therefore, replanting is done in 2 to 2½ percent of the area every year, after uprooting the existing plants. In the south, however, such regular replantation are not done since plantations may continue to yield economically even when 80 years old.
Plucking of leaves is usually started when the plants are 3 or 4 years old. Either the terminal bud and two expanded leaves or the bud and three succulent leaves are plucked. This is known as fine plucking or medium plucking. In coarse plucking, extra leaves are included.
Whereas in northern India, plucking is done at intervals of 7 to 10 days from April to December, there being practically no harvesting in the dormant season during the winter, in southern India, plucking is done throughout the year, but the intervals are long during the cold and dry months of December to March.
Although plucking is done in this country almost throughout the year, there are two big flushing periods, from April to May and from September to December. About 25 percent of the annual crop is obtained from the former and 35-40 per cent from the latter. Plucking is generally done by hand by women, who collect the leaves in baskets.
Yield:
About 1 kg of green shoots is obtained annually from a mature bush. The yield can be increased considerably under suitable conditions and with good management. The yield per hectare of finished tea is 1,200 kg and it may even go up to 2,500 kg, if growing conditions are favourable.
Manufacture:
The preparation of tea is done from fresh leaves in several ways to produce black tea, green tea, brick tea and oolong tea.
The production of “black tea”, which is most important commercially, involves withering, rolling, fermenting and firing or drying. The leaves are first exposed to the sun or heated in shallow trays to eliminate 50% of their moisture content. This makes them soft and pliable. The process is known as ‘withering’. The withered leaves are then rolled by machine.
This process, known as ‘rolling’, distorts the leaves and breaks the leaf cells. The cell sap is exposed to the action of the oxygen in the air, when fermentation sets in and important chemical changes take place. After rolling, the leaves have to be fermented, the period of fermentation depending on weather, temperature and the extent of rolling undergone by the leaves.
The rolled flaccid leaves are, therefore, removed to the fermenting room, spread on a clean surface and the temperature is maintained between 24°C and 26.5°C. During this process, the oxidation, which commenced during rolling, continues. The enzymes act on tannins present in the leaves and the leaf -colour is changed from light red to brown.
After fermentation, the last operation, namely, ‘firing’ or ‘drying’, is gone through and the leaves are dried in a current of hot air very quickly. This is done by a particular type of drying machine. The temperature of the drier should be maintained at 60-65.5°C. This process requires 30 to 40 minutes. It stops fermentation and desiccates the leaves slowly without scorching them, and also preserves quality and other characters of tea.
The processed tea is passed through sieves of different meshes for sorting out different leaf grades and dust. The grades are Pekoe, Orange Pekoe, Flowery Pekoe, Broken Orange Pekoe, Fanning and Dust, which are indicative of size.
“Green tea” is mostly produced in China and Japan. A small quantity is also made in north-east India. In this case, artificial withering and fermentation are not required. Natural withering or wilting is, however, allowed to take place and the leaves retain the green colour. “Oolong tea” is an intermediate type between black and green tea and is almost exclusively produced in Formosa.
This is only partially fermented and its colour is like that of black tea and flavour like that of green tea. “Brick tea” is used in Tibet and, to some extent, in USSR. In its manufacture five different processes are gone through, namely, panning, rolling, fermentation, drying and moulding. In panning, coarse leaves with twigs are given heat treatment at a temperature of 71-94°C for about 10 minutes to make them soft.
The leaves become olive green in colour. Withering is not necessary for them. The next process is rolling, which is done by a machine. As the leaves are too coarse, no curling takes place. The fibres of the leaves are, however, lacerated. In the third process, the leaves are heaped (about 15 cm deep), covered with a tarpaulin and left for five days or so. A fungus begins to grow in the heap and does an important job in connection with fermentation.
After completion of fermentation, leaves are dried either in the sun or on a brick furnace, in which charcoal is used. The last process is moulding. After drying, the leaves are rammed tightly in moulds. In Tibet and China, the moulds hold four bricks, each weighing 1.8 kg. After about three days, the bricks are packed in paper and put in the sun.
The tea planter recognizes three varieties, namely, China, Assam and Indo- China. Assam varieties have 5 types, light leaved Assam, and dark leaved Assam, Manipuri, Burma and Lushai.
Diseases of Tea:
The diseases that commonly attack tea are:
(i) Red rust (algal red spot) caused by Cephaleuros mycoidea, which can be controlled by improved cultivation and manuring and by spraying with Bordeaux mixture.
(ii) Blister blight caused by Exobasidium vexans, which can be controlled by spraying with Peronox, Cuprokyt or Blitox or by dusting with Cuprosan (4.5 kg per hectare) every week or ten days.
(iii) Black rot caused by Corticium invisum, which can be controlled by burning the pruning of the affected bushes or by spraying Bordeaux mixture.
(iv) Brown blight caused by Colletotrichum camelliae, which can be controlled by pruning all dead and discoloured wood and also by spraying Bordeaux mixture.
(v) Bird’s eye spot caused by Cercosporella theae, which can be controlled by spraying with 1/2 percent Bordeaux mixture.
(vi) Copper blight caused by Guignardia camelliae and Laestadia theae, which can be controlled by burning affected leaves and spraying with Bordeaux mixture.
(viii) Branch canker caused by various fungi, which can be controlled by pruning cankered branches, scraping out dead wood, applying Bordeaux paste, treating the pruned cuts with coal-tar and giving an extra dose of potash in manure.
(viii) Pink disease caused by Pellicularia salmonicolor, which can be controlled by burning affected branches and by spraying with Bordeaux mixture.
(ix) Die-back caused by Nectria cinnabarina, which can be controlled by pruning the diseased bushes and spraying Bordeaux mixture.
(x) Stump rot caused by Index destruens, which can be controlled by applying coal- tar to the pruned cuts.
(xi) Black root rot caused by Rosellinia spp., which can be controlled by collecting and burning all infected material, isolating diseased plants by digging a trench and by applying Perenox solution in holes before replanting.
(xii) Charcoal rot caused by Ustulina zonata, which can be controlled by cutting down the trees and uprooting the stumps of shade trees, by digging a trench around the over-grown trees and cutting out all side-roots.
(xiii) Root rot caused by Botryodiploidea theobromae, which can be controlled by treating the soil with lime @ about 1 kg per bush during early stage of the disease and by burning all infected material.
Insect Pests of Tea:
The common insect pests of tea are:
(i) Tea mosquitoes (Helopeltis antonii and H.febriculosa), which can be controlled by collecting and destroying bugs during the initial stages and spraying 0.1% Malathion or 0.05% Lindane.
(ii) Tea looper (Buzura supperssaria), which can be controlled by the same method as in No. (i) above.
(iii) Termites (Microtermes spp.), which can be controlled by mixing 5-10% Aldrin dust with soil.
(iv) Tea thrips (Taeniothrips setiventris and Dendrothrips bispinosus), which can be controlled by spraying 0.1% Malathion.
(v) Bag worm (Clania cramer), which can be controlled by the same method as in No. (i) above.
(vi) Tea slugs (Eterusia spp., Conytheyla rotunda, Thosea cervina), which can be controlled by the same method as in No. (i) above.
(viii) Mites (Acaphylla spp., Aceria gossypii, Brevipalpus obovatus, Oligonychus coffeae, Tetranychus bioculatus), which can be controlled by dusting sulphur or spraying 0.05% wettable sulphur.