Centering or Decentering
This is the operation in which the main stem is removed at a height of about 20 cm from the ground level. The operation is done when the plant makes one flush of growth following transplanting in the field and whilst they are banjhi.Decentering is done by leaving at least 2-3 laterals below the decentering cut. The cut should be clean and slope towards the centre. Laterals are then cut at 35 cm above the ground level. Removal of the main stem and excision of the laterals promote more laterals from lower portion of the stem, thus increasing the number of branches.
The decentering operation should be done when the reserve (starch) in the roots is sufficient for recovery and to minimize mortality after decentering.
If the plant does not have any lateral i.e. single stemmer, then lung pruning or thumb breaking is done.
Thumb Breaking or Lung Pruning
In this operation, the young plant is held between the thumb and index finger at a height of about 20 cm from the ground and the stem is broken in such a way that the tissues (bark) on one side of the stem are left intact for movement of water and nutrients. The broken portion of the stem should be bent towards the ground facing either south or west depending upon the row direction. It encourages development of laterals below the broken height. This is called thumb breaking. The broken portion of the stem should be removed when the laterals develop below and produce a flush of growth and become banjhi. Care should be taken so that the broken portion of the stem remains facing towards the ground, otherwise laterals will develop above the broken height.
If the stem is thick enough and thumb breaking cannot be done, a small pruning knife can be used to break the stem cutting one side of it. This is called lung pruning. Lung pruning or thumb breaking can be done even if starch content in roots is not at its optimum.
Pegging or Bending
It is the operation by means of which the main stem and subsequently the laterals are bent with the help of pegs to encourage lateral development. The bending is done at an angle of 60 to 70 degrees from the vertical position. Normally, this is not practised nowadays in N.E. India. It is popular in East African tea growing countries.
In this operation, buds from the leaf axils are removed from the upper portion of the plants leaving the lower 20 cm untouched. This is done with the help of a small hack-saw blade or by using finger. The top two leaves and the bud should be tipped off from the plants before debudding. This stimulates the buds below to swell and the removal of the buds becomes easy. Debudding can be done in the nursery 4-5 days before planting. Debudding at the nursery is economical and convenient. After about four weeks of planting in the field, removal of bud if any left out in the first operation should be done. When debudding is done, buds remaining below the height of 20 cm from the ground grow and form healthy laterals. The main stem should be removed by giving a clean cut at 20 cm.
The main objectives of the above operations are to suppress central dominance (apical dominance) and apical growth, distribute vigour for even radial spread so that there are uniformity in distribution and thickness of branches at the final height of the permanent frame.
Apical dominanceis a growth correlation in plants. It is complete or almost complete inhibition of growth in axillary buds with the presence of apical bud. The principle of training the tea plants is to eliminate the apical dominance by adopting different operations like debudding or pegging.
Frame forming prune
By adopting different operations described above, the plants are made to develop new branches of first tier in the frame. After about 20 -26 months from planting, a prune called the first formative prune is given at a height of 5 cm below the pre-determined height of the permanent frame. Normally, in the plain areas of N.E. India, the height of the permanent frame is maintained at 40 to 45 cm and in hilly areas at 35 to 40 cm. However, the bushes should be pruned (cut across) only when the branches are 1 cm thick at the pruning height. Thicker branches are head back on merit and any congestion at the centre is removed.
Frame forming prune
After pruning, new shoots develop from the pruned branches which form the second tier of the frame. Finally after about 2 years, the final frame formation prune is given 5 cm above the first prune. At the time of final frame formation prune, the bushes are completely cleaned out removing the crossing, diseased and weak branches and snags. After this prune, the bushes are considered to be mature ones and thereafter the tea is brought under normal pruning cycle.