In this article we will discuss about the cultivation and improvement of tea.
Tea:
Tea, Camellia sinensis, is one of the most popular caffeine containing beverage, obtained from tender leaves of the tea plants after processing. Tea contains 13-18% tannin, 2-5% theine and a volatile oil. There are two main varieties, e.g., bohea (Chinese tea) and assamica (Indian, i.e., Assam tea).
Cultivation Area:
In India, tea is cultivated largely in Assam, West Bengal (Darjeeling & Jalpaiguri districts), Kerala and Tamil Nadu.
Climate:
Following climatic condition, are suitable for tea plant:
Soil:
Loamy or forest land rich in organic matter with acidic pH is suitable for tea cultivation. Hill slopes favour the growth of tea or any other place where water doesn’t become stagnant.
Preparation of Land:
Firstly the area under cultivation should be cleaned of forest growth.
The land should be prepared carefully considering the three important aspects:
(i) Protection of land from soil erosion;
(ii) Cultivation primarily for weed suppression and better root development;
(iii) Use of shade plants to protect soil and young plants.
Planting Methods:
There are two methods of planting, viz., ‘Square’ and ‘Rectangular’ systems. In both cases, pits measuring 30.4-45.2 cm in depth, 22.8 cm in diameter and 1.2-1.5 m apart in either direction are dug and filled with organic matter containing surface soil.
Preparation of Seedling and its Transfer:
Tea is normally propagated by seeds but propagation by means of cuttings, budding, etc., is also successful. Seeds are first sown in germination bed; neatly young seedlings are transferred to ‘jungle’ or ‘basket’ nurseries. Then, either 6-18 months old ‘basket’ seedlings or 1-2 years old ‘jungle’ seedlings are planted in April-May or September-October respectively in pits already dug in the ‘square’ or ‘rectangular’ system.
Plantation of Shade Trees:
Plants like Albizzia spp., Dalbergia anamica, Derris robusta, Leucaena glauca, etc., are planted to provide shade to tea bushes.
Manuring:
Frequent nitrogenous manuring is essential for better growth of leaves. Application of compost, green manure and fertilizer mixtures supplying 27 kg N, 13.5 kg P2O5 and 13.5 kg K2O per acre are essential.
Disease and Control:
Common diseases of tea and their control are as follows:
Pest and control:
Common Tea Pests and their Control are as follows:
Pruning:
Tea Bushes are Pruned Regularly and the Best Pruning Practice is:
(i) 1st year after planting: The plant is decentered by cutting the centre of growing stem at 20-30.4 cm from the ground.
(ii) 2nd year after planting: Plants are left un-pruned.
(iii) 3rd year after planting: Plants are pruned across at 45.5 cm removing strong growing centre shoot leaving lateral branches.
(iv) 4th and following years: Pruned to leave 1.2 cm of new wood.
Plucking:
Tea leaves are plucked by hand or with scissors. The first plucking is usually made when the plants are five years old and is restricted to the terminal bud, tender leaves and three expanded leaves.
Yield:
The average yield/acre of tea from seed borne plants is 326 to 372 kg. and vegetatively propagated plants of about 1006 kg.
Grades:
Generally there are eight grades of tea:
(i) Broken Orange Pekoe,
(ii) Orange Pekoe,
(iii) Orange Fannings: made from the bud, first leaf and the softer stalk;
(iv) Broken Pekoe,
(v) Pekoe,
(vi) Broken Pekoe Souchong,
(vii) Pekoe Fannings: made from the larger first, second, third leaves and the intervening stalks;
(viii) Dust : Consisting merely of grains of tea.
Processing of Tea:
Processing of tea leaves varies for different commercial varieties, e.g., Black Tea, Green Tea, Brick Tea and Oolong Tea.
(a) Black Tea:
Black tea, common in India, is manufactured through following operations:
(i) Withering:
The plucked leaves are taken to withering house where these are spread out either on slopping wire netting racks or on horizontal hessian cloth ‘chung’ for 18-24 hours to eliminate water content of leaves.
(ii) Rolling:
Withered leaves are taken to rolling rooms where they are subjected to three rolls, each of 30 mins. duration by machine. This process curls the leaves and burises the cells of the leaves, so that their sap is exposed to action of oxygen in air. Room temperature is maintained at 24°-26°C.
(iii) Fermenting:
Rolled leaves are spread on a cement floor of fermenting bed for 2.5 to 4.5 hours at about 24°-26.5°C. During this operation, tannins of leaves acted on by enzymes causing the change of leaf colour from light red to brown.
(iv) Firing:
Fermented leaves are dried in a current of hot air by ‘pressure’ type drier machine at about 60°-65°C for 30-40 minutes in order to arrest fermentation and for slow desiccation of leaves.
(v) Sorting and Grading:
The dried leaves are passed through sieves of different meshes and sorted out which are then graded into different grades and packed in separate plywood tea chests lined with aluminium foil.
(b) Brick Tea:
Brick tea, mainly consumed in Tibet and USSR, is manufactured through following operations:
(i) Panning:
Leaves are subjected to heat treatment at a temperature of 71 94°C in a large iron vessel built into a brick stove for 10 minutes. This operation makes the leaves a little soft and turn olive green.
(ii) Rolling:
Leaves are then taken to rolling machine to roll for 30 minutes by which the fibre of the leaves well lacerated and broken.
(iii) Fermenting:
Leaves are placed in a heap upon a cement floor, covered with tarpaulin for 5 days. This operation helps in fermentation process by fungus to cause typical flavour.
(iv) Drying:
Fermented leaves are dried either in sun or on brick furnace fired by charcoal.
(v) Moulding:
Bulk of dried leaves is rammed as tight as possible into the moulds (23.0 cm x 11.3 cm x 1.2 m) which hold materials for four bricks of 1.8 kg each. After three days, the bricks have settled to allow of the moulds opening. The bricks are then packed in paper and put in the sun.
(c) Green Tea:
Green tea, mainly produced in China and Japan, is manufactured in the following ways:
(i) Panning:
Same as brick tea.
(ii) Steaming and Rolling:
After panning, leaves are heat treated at 120°C by steaming to make the leaves soft so that these are rolled by hand on a bamboo mat.
(iii) Drying:
Rolled leaves are subjected to brick furnace to dry upon trays over charcoal fires until they are perfectly crisp.
(d) Oolong Tea:
Oolong tea with colour of black tea and flavour of green tea is mainly produced in Formosa.
(e) C.T.C. Tea:
Now-a-days tea processing method has been reduced, e.g.:
(i) Crushing,
(ii) Tearing and
(iii) Curling, which is called C.T.C. method.
Crop Improvement through Plant Breeding:
Chinese type tea was introduced in India, Assamese type tea is grown all over world. As tea is cross-pollinated crop, seed setting is poor, mainly clonal propagation by stem cutting is done. Clonal selection, varietal crosses, mutation, etc., are the ways of crop improvement.
Introduced and selected varieties: TV-1, and TV-2.
Hybridized and selected varieties: TV 17 (TV-1 x St. 202)
TV 24 (Chinese x Assamese type)
Variety developed by polyclonal cross: Gaurisankar (St. 203)
Variety developed by bi-clonal F, hybrid: Nandadevi (St. 378), F, hybrid-St. 397.
Application of Tissue Culture:
As the crop is mainly clonally propagated, so the micro-propagation technique is very much helpful to maintain the stock of raised hybrid variety. And as the crop is cross-pollinated, so the hybrid seed production is also difficult to maintain the line. Tissue culture procedure helps to get the selected clones in multiple amount.
Research Station:
Tocklai Experimental Station, Jorhat runs in association with Tea Research Association.
