Tea (Camellia spp.) is an important beverage and the world drinks more of it than any other beverage. It is made from the tender or young leaves and unopened buds of the evergreen tea-plant, popular as a ‘healthful herb’. The tea plant is in the polymorphic species Camellia sinensis Kuntz, but recent findings show that this plant of commerce is derived from more than one species. Two distinct varieties of tea-plant are generally recognised, the small-leaved China (sinensis) and the large-leaved Assam (assamica) which have been raised to a specific rank by a well-known tea botanist. Careful field observations, however, reveal that more than one or two species are involved in the evolution of the present-day tea-plant of commerce. Considerable interspecific hybridization has taken place in nature. Thus, the taxonomy of the tea-complex is confounded.
The tea-plant, in the natural state,grows into a small or medium-sized tree, but in commmercial plantations it is pruned and trained to form a many-branched low bush and is encouraged to produce vigorous vegetative growth by adopting an appropriate schedule of fertilizer applications.
The important tree growing countries are India, Sri Lanka and East Africa; Japan and Indonesia also produce sizeable quanties of tea. It is also grown in Bangladesh, China, Georgia, Argentina and some other countries. In India, the crop is grown in Assam, West Bengal, Kerala, Karnataka and Tamil Nadu, and to some extent in Tripura and Himachal Pradesh. The total area under tea in our country is about 3,58,000 hectares and over 468 million kilograms of product is obtained anually. Over one million workers are employed by the tea industries.
Yeilds have steadily increased during two decades. Tremendous progress has been made on the selection of clones and those with high yeilds and improved quality have been released to the industry. The tea planters are encouraged to uproot poor section of their plantation and replant them with improved planting material.
CLIMATE. Tea is grown on plantation scale in many areas of the world in warm and moist climate. These range from Georgia (USSR) to Corrientes (Argentina). It is grown from sea level to about 2460 m. A well-distributed rainfall is essential for its cultivation. The rainfall varies from 125 cm to 750 cm in the tea-growing regions in this country.
SOIL. Tea is planted on soils of widely different geological origin and of almost all physical types. a well drained, deep and friable loam or forest land rich in organic matter is ideal. Tea soils are acidic (pH 4 to 6), low in calcium and generally rich in iron and manganese.
CULTIVATION. Tea is propogated from seed, but high yielding clonal material has also become popular. The plants are initially raised in nurseries to produce healthy plants. 1 to 1 and 1/2 year old nursery seedlings are used for planting in the field. The vegetative propagation of selected tea-plant cuttings, each with a leaf and internodes has been standardized and progressive planters now raise colonial nurseries on a large scale.
The area intended for planting is first cleared of forest growth and adequate steps are taken to prevent soil erosion. Planting lines are traced (as at present on contour on hill slopes) and pits of a convenient size(generally 30-45 cm deep and 24 cm wide) are dug. The normal accepted spacing is 120 X 75 cm, accommodating about 10,000 plants in a hectare. The soil is heavily mulched during the initial one or two years.
In most of the tea areas in our country, a system of shading the tea plants is practiced. In southern India, the silver oak (Grevilla robusta) is a shade tree of choice (planted 600 by 600cm, later thinned to 600cm by 1200cm or 1260 cm by 1200 cm as required). Other trees used for shading are Erythrina lithosperma (dadap), Acacia and Albizia. Albizia species are used in tea gardens in northern India.
Weeds compete with the tea plant for nutrients, and weed control is important in tea plantations. In recent years, the control of weeds with chemicals has gained popularity. Grasses and broad-leaf dicot weeds are kept under check. Pests and diseases are effectively controlled with chemicals.
A manuring scheme is followed from the nursery stage up to maturity. A special 1:1:1 NPK soluble fertilizer mixture is used in the nursery; a 4:3:3 NPK mixture in the first 3 years in the clearing and thereafter the dosage of the fertilizer applied is varied, depending on the type of tea, its performance, soil fertility and the yield potential of the crop. On an average 10 kg of nitrogen is applied for every 100 kg of the crop.
Tea readily responds to the application of nitrogen and potassium. Potassium is applied at the rate of 40 to 50 percent of the amount of nitrogen applied, depending on the soil type and weather conditions. In southern India tea responds to nitrogen up to 300 kg per hectare applied to some high-yielding varieties of tea, whereas in northern India, the application of nitrogen is limited to about 120 kg whereas 30 to 40 kg of phosphate per hectare is adequate.
Zinc deficiency is a limiting factor in crop production in most areas and a schedule of foliar application of zinc sulphate usually 11 kg per hectare in alternate years is recommended.
TRAINING, PRUNING AND PLUCKING. The tea-plant is initially trained into a small bush by centring low within a few months of planting, by removing the central leader stem in order to encourage development of lateral branches. The lateral branches are cut to a convenient height of 40 to 50 cm and the growth above this is periodically cut. Thus a small, compact bush is formed. New shoots are allowed to grow unhampered and these shoots are tipped, leaving a growth of 20 to 30 cm above the pruning cut, depending on that kind of plant. The crop is then harvested at regular intervals.
In southern India, the pruning cycle extends over a period of 4,5 or 6 years depending on the elevation and growth. In some caes, a ‘skiff’ is given at a cinvenient height and the pruning cycle extended for 2 or 3 years. Pruning and skiffing are done periodically to keep the height of the bush at a cinvenient level for the pluckers to operate and to encourage vegetative growth. Annual pruning is a practice in northern India (Assam), but even there the present trend is toward an extended pruning cycle. After a series of pruning cycle, hard pruning, removing all cankered and diseased portions of the stem, rejuvenates the bushes.
In northern India, the economic life of the tea bush is generally 40 to 50 years and therefore 2 to 2 and a 1/2 percent of the area is uprooted and replanted every year. In southern, such regular uprooting and replanting is not practiced, because economic yields are obtained from sections, which are 80 years or more old. Usually plucking is restricted to the terminal bud and two expanded leaves, or to the bud and three succulent leaves, known as fine or medium plucking. Coarse plucking includes extra leaves. In northern India the tea bush is plucked at weekly intervals from April to December and there is a dormant season during winter. In southern India the crop is harvested during the cold and dry months (December to March).
TEA MANUFACTURE. The shoots may be prepared in several ways to make black or green tea. To make the former, the leaf is usually withered and rolled or distorted by rolling in the conventional tea rollers, or is passed through tea machines, the ‘rotorvane’ and CTC rollers which exert drastic action on the withered leaves. The juice of the leaf cells is exposed in the air to oxidize (fermentation) when important changes take place. When the optimum fermentation is reached, the action of enzyme is arrested by drying the fermented leaf in a current of hot air in suitable tea-dryers. In the production of green tea, the shoots are steamed as soon as possible after plucking and the leaf oxidized is soon destroyed so that fermentation does not take place on rolling.
The processed tea is passed through a series of meshes, sorting out leaf grades and dust. The tea leaves are sorted into different grades, for example, pekoe, Orange pekoe, Flowery pekoe, Broken Orange pekoe and Fanning.
Tea intended for export is packed in plywood chests and shipped directly to various centers or sold through auctions at centers like Calcutta and Cochin.
Instant tea, soluble in water, tea bag and ready mix tea are new developments.
GENERAL. The information in this section touches only the salient points of tea culture and manufacture.
Tea research is carried out in the country at two centers: Tocklai Experimental Station of the tea research association, Jorhat (Assam) and the Tea Research Station of the United Planters Association of Southern India (UPASI) Cinchona P.o., Coimbatore district, Tamil Nadu.
Certain adhoc schemes on tea research are carried out at centers such as the Central Food Technological Research Institute at Mysore and the Department of Applied Chemistry, Calcutta University.
The Tocklai Experimental Station publishes its findings in its annual reports, bulletin the Tea Encyclopedia and in the journal Two and a Bud. The UPASI tea Research Station publishes the results of research in its annual reports, bulletins Handbook of tea Culture and in the Planter’s Chronicle.