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Wednesday, September 29, 2010

Drought Management or Drought Mitigation - in tea cultivation

Drought management is not applied only in a drought but it should be integrated practices from land selection to harvesting of mature teas. Therefore, this tropic is divided into several sub-tropics and discussed separately, by each step.

Selection of land for tea cultivation

The land should be less than 70% of slope, and preferably more than 60-100 cm in depth. Gravel portion of the soil is better to be less than 10% while avoiding hard-pans containing gravel or other hard material. Also care should be paid on the type of soil, although it has no connection with the drought mitigation. Tea is well grown in Red Yellow soils with a good top soil rich with organic matter. 

Land preparation

Land preparation and minimize erosion during that will result in a healthy root system, which helps tea bush to survive in a drought. Always take care to minimize soil erosion in land preparation. Organic matter content in the soil is also a factor affecting water content in the soil. Avoiding heavy rain seasons, preparing the land from the top of the slope in small blocks, avoiding leveling land to a very fine texture, prepare lateral drains alone the couture lines, rehabilitation of the land with grass at least to 18 month time, planting alone the couture, etc. are some of the practices that matters with drought mitigation of tea.

Planting of young tea

A vigorous tea plant will always be face the drought better than a week one. Therefore, selecting a healthy nursery plant is very important. Ground propagated tea nursery plants will have damaged roots when pull out for field establishment. Select a good bag-planted tea plant for planting. Well branched tea plant with a healthy root system makes the tea plant recover and establish in the field, early. The nursery bag should be at least 6 inch in depth and 4 inch in diameter. Never cultivate plants from ground nurseries. Always go for bag planted nursery plants.

Planting is done in couture lines with spacing of 2 feet withing the row and 4 feet between two rows. Use a thatching between tea rows after planting. 

Management of tea bush

Stop harvesting in severe and prolonged droughts. When the drought is not so severe, fine harvesting method must be adopted (harvest only the bud and two leaves, leaving a leaf to the plucking table - so called as mother leaf plucking).

Always avoid pruning tea bush into drought seasons. Pruning must be done with the onset of a rainy season. Also, care must be taken to leave 2 - 3 healthy branches un-pruned in the bush to facilitate adequate photosynthesis and detoxification of toxics synthesized during root death due to branch pruning. Never harvest shoots in remained branches (lungs). Bury pruning branches in every other tea inter-row space. This will increase the organic matter content in soil increasing the water holding capacity. In the same time rain water will better absorbed into soil due to decreasing in the speed of runoff water. 

Avoid manure application. This may harmful in drought since the moisture in the soil sap is inadequate, and thus causing nutrient concentration in the soil sap more concentrated than tolerable to the tea roots.

Weeds compete with tea plant for moisture. Therefore remove weeds the tea land at the early state of the drought and preferably apply a thatching or mulch. Hand pulling and scraping weeds will loose the top soil layer causing more moisture evaporated from the soil. If the drought is prolonged and weeds are still there, slash weeds with a knife without pulling or scraping. Chemical weeding may be practiced in such a situation without affecting much to soil moisture.

When tea plant continuously producing shoots, and harvested, it adds an additional stress to the plant. Therefore, skiffing (removal of 2 – 3 inch top layer from plucking table) can be practiced, in prolonged drought conditions, so that, the production of shoots is temporarily reduced. This will reduce the annual yield but, in return, bushes will not die. 

Chemical Applications in Drought Management

Water is removed through transpiration form the tea leaves. If we can reduce the transpiration, that will help the tea bush to withstand the drought conditions. Spray kaolin or Kieserite to the foliage. Kaolin will cover the tea leaves as a thin layer on the leaves while Kieserite will close the stomata reducing transpiration. Care must me applied, when applying Kieserite to foliage, so that the solution would not too concentrated (less than 5%), sucking out the water in the leaves. 

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Agronomic Practices for High Yielding Tea Plantation

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