Post harvest care

Tightly packed leaf, gets heated easily as respiration continues after plucking and heat cannot escape. Unless the heat generated due to the exothermic reaction caused by respiration is allowed to dissipate, temperature of the leaf mass continue to increase and the rise may even be beyond 10°C. Storage of leaf in heaps in excess of 8 kg/m2 of floor area has been found to lead to heat development that affects quality.

Ramming or compression of leaf into the basket results in ripping of leaves and generation of excess heat leading to oxidation (fermentation) even before the arrival of the leaf in the factory. The rough interior of the baskets further aggravates the situation.

Contact with foreign matter viz., sand, oil etc., also may damage the leaf.

Withering is the first processing step in the factory and is a process in which freshly plucked leaf is conditioned physically, as well as, chemically for subsequent processing stages. Indeed, withering is one of the most important tea processing steps and can be said to constitute the foundation for achieving quality in tea manufacture. Based on achieving the desired level of withering, one can make better quality teas and, on neglect, can invite serious problems in subsequent steps of manufacture. As a matter of fact, in planter's perception, "Withering makes or mars the tea".

Withering: Loss of moisture, increase in cell membrane permeability, initiation of polyphenol oxidase/ peroxidase activity, breakdown of chlorophylls, breakdown of proteins releasing amino acids, degradation of carbohydrates, increase in caffeine and inorganic phosphate contents and the development of flavour volatiles.

Rolling: Enhanced levels of polyphenols oxidase/Peroxidase activity, production of flavour compounds and degradation of chlorophylls.

Fermentation: Polyphenols are oxidized and then condensed to form theaflavins, thearubigins etc.; chlorophylls are degraded and some of flavour components are produced from lipids, amino acids, carotenoids and terpenoids.

Drying: Loss of moisture, inactivation of enzymes, loss of soluble solids, development/loss of some flavour components and phaeophytin produced from chlorophylls.

Process objectives

The process objectives to be achieved during withering are as follows:

• To breakdown complex chemical compounds in the cells to simpler compounds which along with other simpler molecules then recombine to contribute to quality attributes of tea like the 'body' and 'flavour' at a later stage. This is known as the Chemical Withering of the leaf.
• To reduce the moisture content of the fresh leaf which ranges between 74 - 83%
• To make the leaf `flaccid' or `rubbery' which is essential for the subsequent step of processing (maceration) or rather for 'twisting' or 'curling' etc.
• Both these constitute the Physical Withering of the leaf.

Red leaf formation and quality of made tea

The green leaf can turn brown/red as a result of physical damage arising from bruising of leaf and heat stress. The red colour is observed to be prominent when the leaf temperature exceeds 35?C. The increase of red leaf percentage has got detrimental effect on quality. The cause of red leaf formation is mainly due to oxidation of polyphenols. Reddening of leaf may occur more rapidly when the leaf temperature exceeds 40?C. With the increase in percentage of red leaf formation there is significant increase in undesirable TRs. It will reduce brightness and briskness of liquor along with reduction in essential volatile flavour oconstituents (VFC) of made tea.

Careless handling and transportation resulting in bruising and tearing, therefore, leads to reduction in quality. Care should be taken to allow the heat to dissipate and avoid friction to save the leaf from bruising and tearing.

It is imperative to remember that the shoots as raw material, determine the value of the end product. During manufacture the value can decrease due to faulty operation, but the inherent quality attributes cannot be enhanced. It is, therefore, essential that the quality attributes be not affected.

Effect of physical damage of leaf on made tea quality

Apart from damage of the quality attributes in green leaf due to heat generation, leaf can be damaged through rough handling, causing bruise and tear in the leaves. Cell damage is the ultimate objective in the manufacture of black tea. However, if the damage is initiated before withering and is indiscriminate, the leaf may undergo uneven oxidation process adversely affecting the desirable chemical constituents in the end product. Also, damaged leaf withers at a faster rate, as the structure of cuticular waxy layer of the leaf is disturbed. This ultimately influences the water holding capacity of the leaf and will lead to uneven wither.

Packing Density in Baskets

With the compactness of packing of the leaf in the basket/bag there is a considerable loss of quality of the made tea. There is a significant decrease in TF content, as the TFs get converted to TRs over the time. This ultimately reduces brightness and briskness of the tea. The rise in temperature disturbs the entire cell component resulting in likely occurrence of enzymic oxidation of catechins prior to maceration, which is undesirable. Thus one must take utmost care while packing the leaf in basket/bag at the field.

Effect of green leaf temperature on made tea quality

The principal precursors for liquor characteristics are primary polyphenols, which through enzymatic processes are converted to large polyphenols like TF and TR. Leaf temperature and storage time have got a significant effect upon the variation of TF and TR profile. The effect is more prominent when the leaf temperature rises beyond 35?C.

Rise of temperature increases the enzymic oxidation of primary polyphenols and the products, which are formed by the oxidation process, overtakes the enzymic hydrolytic reaction desirable for quality.

Green Leaf Plucking

Plucking

Shoots comprising of 1+ bud and 2+bud are detached either by hand, shears or by machine, put normally in a basket, weighed and taken to the factory either manually or in a multi-tired trolley by a tractor.

Chemical changes after plucking

Once the leaf is plucked the anabolic reactions practically cease and catabolic reactions leading to the breakdown of large organic compounds to simpler molecules start. Burning of sugar molecules produced earlier through photosynthesis provides the energy required to run these biochemical reactions in the shoots.

There is rise in temperature in the mass of the plucked leaf during storage and transportation due to respiration as well as the aforesaid reactions. In the process of respiration organic substances in the cells (usually sugar) get oxidised into carbon dioxide and water with release of fairly considerable amount of water as may be seen from the following equation :

C₆H₁₂O₆ (Glucose) + 6O2 (Oxygen) 6CO2 (Carbon dioxide) + 6H2O (Water) + 674 calories (Heat)

After the leaf is plucked, biochemical reactions are initiated towards biological degradation of the shoots. In this direction, large molecules like cellulose and lignin, which are responsible for the rigidness of the shoots degrade to make the shoots more flaccid. Lipids carbohydrates etc., which are also large molecules, degrade. Carbohydrates degrade to produce sugars, which burn in presence of oxygen and produce energy to run various biochemical reactions, which are enzymatic and temperature dependent. If in the plucked shoots sufficient oxygen is not available, anaerobic reactions take place. Those reactions produce much less energy than aerobic reaction mentioned above. Secondly, the results of anaerobic reactions are different and are not desirable for making quality teas. Adequate oxygen availability is, therefore, a must. The lipids degrade to produce smaller molecules, which are quality attributes. Therefore, if before the lipids are degraded, cell rupture and manufacture are initiated, quality attributes will be missing. It is, therefore, essential to make the lipids degrade by providing proper conditions, i.e. temperature and time.

Leaf Quality Assessment

Ballometric Count

Green leaf shoots equivalent to 100 numbers of balls of equal size are picked up at random from each withering trough and thereafter these are separated into fine leaves and coarse leaves. The fine comprise of two leaves and a bud, smaller shoots and also soft banjis. The separation of fine leaf from coarse leaf is done, where necessary, by breaking back the two and a bud/soft banji from the plucked shoot. In the case of three and a bud shoot, the two and a bud comprises the fine leaf and the rest of the broken stem is coarse leaf. Thereafter, the fine leaf is weighed against the equivalent number of balls/coins and this gives the Ballometric/Paisometric Count. It may be noted that the loading of the trough should be done prune-wise, plucking challan-wise and also section-wise, if possible, for each of the three weighments.

Leaf/Bud Count

Total hundred shoots are collected at random from each plucking challan for each of the three weighments and thereafter these shoots are separated into one and a bud, two and a bud, three and a bud, single banji, double banji and single/coarse leaf. This count enables tracking of the percentage of different sizes of shoots being plucked.

Damaged Leaf Count

Total hundred shoots are collected at random and are separated into damaged shoots on one side and undamaged shoots on the other side. The damaged shoots are counted and this gives the Damaged Leaf Count for each of the three weighments.

GAP increases tea yield

Good Agronomic Practices (AGP) always increases tea yield. Even maintaining a even plucking table increases tea yield in approx. 10-15%. From planting to final harvesting there are numerous recomended agronomic practices to be applied for a sustainable tea cultivation. Although now-a-days, tea growers are forcussing only on instant income, tea cultivation is a long running system, which without GAP will be a failure in several years.

Careful with applying chemical

When you apply chemical to the tea fields, carefull to follow the recommendations issued by the producer and/or relevant authoriety. Residues will be there if you don't allow the Post Harvest Interval (PHI) before next plucking. Never spray herbicides to tea canopy.

Maximum Residue Levels (MRL) will be exceeded when mal-practiced, ultimately your tea will be rejected in the world market.

Mechanical means of Tea Harvesting

Plucking is the most labour intensive operation in a tea plantation when it is done manually. Bud with with immature one or two leaves is the best time of plucking or picking of tea leaves. Mechanical was of harvesting now popularizing in asian countries now-a-days with the lacking of labour for field operations. In countries near to the equator, as sunshine and rainfall is high all over the year, this makes bushes debilitated and deduction in yield by around 20-30%. Therefore, mechanical harvesting is recommended only in rush crop seasons.

Manage weeds by Agronomic Practices

In a tea land, weeds become a problem only if the land is not fully covered by tea bushes. Therefore, the best way to control weeds in a mature tea field is keeping the land free of vacancies.

If this is a new clearing, thatching is a good practice, not olny to control erosion and/or as a organic matter source, to control weeds. Controlling weeds in a young tea land also helps tea plants withstand drought conditions.

Manual weeding is recommended in tea plantations, where, scraping is highly demortivated since this increases the soil erosion.

Not all the naturally grown plants are considered as problamatic weeds. Soft weeds such as Centella spp., etc. can be remained in the tea field since they do not compete with the tea bushes for water, nutrient, etc.

Soil pH and nutrient testing in soil

Site specific fertilizer application is the newest method of manuaring. This method need to have checked the soil pH and nutrient levels in a lab. Chemical testing for nutrient is essencial if site specific fertilizer applications are to be done.

It is necessary to maintain soil pH in 4.5 to 5.5 range to make soil nutrients available or soluble for tea plant

Fertilizer for Seedling Tea Nursery

Fertilizer applicatoin for tea nursery is an important matter for a vigorous and healthy young tea plant for planting. The nursery mixture of fertilizer is suitable to having N%, P% & K% 10%, 11% & 4% respectively, since it has been found that a tea plant in that stage requires nutrients in such composition.

Approximately 25-35 g of the mixture desolved in 5L of water is adequate for approximately 100 nursery plants as a folier application. The rate could be made double with the age and growth of young plants. ZnSo4 can also be applied to foliage for inducing bud break, at the rate of 5g in 5L of water for 5000 plants.

Planting & Management of Seedling tea Nursery

Seedling plantign is now not widely done since Vegetatively Propergated (VP) plants give higher yields and uniform growth. (This article is written on a request by a reader)

Harvesting of seeds

Mature tea fruits are dark greed to light brown in color depending on cultivar. When the ourter coating of the fruit is removed, seed(s) must be dark brown seed coat. Light brown and yellowish ones are not mature enough to propergate. Picking fruits before they are fallen is a must as viability of seeds become low when they fall on the ground. If you collect seeds after falling them on ground, it should done daily to avoid collecting old fallen seeds, also ground must be free of weeds.

Tea seeds don't have any dormant period, once picking from the tree they can be put in a nursery. Never take seeds picked more than 7 days before, as viability decreases rapidly.

Nursery management

Presoaking seeds 2-3 days in water, could be done prior to put in the nursery to decrease the time taken for crackin the seed coat. This is not necessary practice. However, put seeds in water for float-sinker assessment. Seeds that are sinking can be taken for germination.

Coarse river sand removed only with larger particles is suitable as a nursery media. Depth of the nursery is 4"-6" with any convenient width and length. 1" sand layer is removed from the nursery and seeds are sown after which they are covered with the sand layer removed before. Seeds must be sown at 0.5"-1" depth. Placing piece of coir matting will protect seeds from bird's damages. Water twise a day.

Transfer plants from nursery to bags.

Germination commences about 2 weeks after sowing and reaches maximum at the 3rd-4th week. Once the tip of the root emergs from the seed coat, they should transfer to nursery bags filled with soil medium. Care should be taken not to damage the root end emerging (tap root).

Fertilizer application

After 2 weeks of planting fertilizer application can be done. Pls refet to my blog archive on Fertilizer for Tea Nursery for the details. (Fertilizer for seedling & VP has no much difference in nursery management) Shading is not necessary as this is a natural process.

Planting in the field

After 8-10 months in nursery bags, depending on growth, plants are ready to plant in field. Care should be taken not to allow the tap root to reach or penetrage in to nursery soil coming out from the bag. This will sure damage the tap root when transplanting.

Field establishment of young tea

Tea is well grown in Reddish Brown soils in 4.5-5.5 pH range. Depth of the soil layer 1m is optimum where less than 60 cm is considered unsuitable for tea cultivation. Tea is cultivated alone the contour lines where the slope of the land is not exceeding 70% (45 degrees = 100%). The spacing between two rows is 1.2 m & within row is 0.6 m.

Planting holes are digged to a depth of 18" and diameter is 12". Fill the planting holes 3/4 way with top soil, removed with gravel & leave about 1 week to settle before planting the young plant. This prevents the collor region of the stem covered with soil, when it settles, and possible fungal infections.

Remove the polythene bag from the young plant and plant it in the partially filled planting hole. Fill the rest of the gap with soil. Supply some backing with 2 sticks to prevent movement with wind, and a mulch to prevent siol erotion. (keep mulch 4"-6" away from stem to avoid fungal infections and scratches to the bark)

(this article is made very brief, if someone is interested pls leave a comment/question in the archive to get further help)

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. 

Manure or fertilizer for Vegetative Propagated (VP) tea Nursery in Sri Lankan weather and climatic conditions

Fertilizer for tea nursery is not meant for fast and high growth in green foliage. It should be focused on the development of the frame of the young tea plant, since; a sustainable crop could not get from a bush with a poorly developed frame of the plant. The formulation of the tea nursery fertilizer mixtures have been done with that scope in mind. 

Basically there are two tea nursery mixtures used in Sri Lanka, namely T65 (MAP) (P-source is mono-ammonium phosphate) and T65 (DAP) (P-source is di-ammonium phosphate).  Apart from the market availability, it doesn’t matter to use MAP or DAP for the mixture. But, T65 (MAP) dissolves fast, so that, it is easier to handle. 

Composition of T65 (MAP) Mixture

Parts by weight	Chemical name of the ingredient	Nutrient content
15	Sulphate of Ammonia	20.6% of N
20	Mono-Ammonium Phosphate (MAP)	20% of N and 35% of P2O5
15	Sulphate of Potash	48% of K2O
15	Epsom Salt	16% of MgO
65 (Total Parts)

T65 (MAP) mixture contains 10.9% N, 10.8% P₂O₅, 11.1% K₂O and 3.7% MgO

Composition of T65 (DAP) Mixture

Parts by weight	Chemical name of the ingredient	Nutrient content
20	Sulphate of Ammonia	20.6% of N
15	Di-Ammonium Phosphate (DAP)	18% of N and 46% of P2O5
15	Sulphate of Potash	48% of K2O
15	Epsom Salt	16% of MgO
65 (Total Parts)

T65 (DAP) mixture contains 10.5% N, 10.6% P₂O₅, 11.1% K₂O and 3.7% MgO

There is no need to use exactly the same mixtures mentioned above, to a tea nursery, but be sure the nutrient content and composition is approximately the same, as indicated.

How to apply the nursery fertilizer mixture to a VP tea nursery (in polythene bags) 

Tea nursery fertilizer mixture is a foliage application with watering cans. If you use T65 (DAP), it should be ground well and make a paste, before dissolving it in water, since DAP is poorly dissolve in water.

It is not advisable to apply fertilizer to the young plant, or planted shoot cuttings, before the roots are emerged. Therefore, the time of the first application of fertilizer is, after 2-3 months of planting.  

Dissolve 35 g of above mixture in 5L of water and apply it onto, approximately 1 m² of the tea nursery, in fortnightly intervals. Generally, with 4 inch diameter polythene bags, 1 m² contains 120 nursery plants.

In about 5-6 months after planting of shoot cuttings in nursery bags, increase the weight of fertilizer up to 70 g/5L water/m^-2 of nursery area. 

Note that, it is compulsory to wash off the fertilizer mixture from foliage with clean water within 15-30 min time, to avoid scorching the leaves due to high concentration of fertilizer. 

Application of Zinc Sulphate (ZnSO₄) to induce bud break in tea nurseries

Branching is important in tea bush because, the higher the number of branches, higher would be the number of shoots harvested. Also, branching must be induced from the lower parts of the main stem of the bush, so that, they would not be cut off in seasonal pruning of branches. Therefore, induce of branching from the base of the main stem is commenced from the nursery stage. 

Foliar application of ZnSO₄ is done to induce bud break at the nursery stage. One week after each application of T65, 14 g of ZnSO₄ is dissolved in 4.5L of water and spray this with a Knapsack (hand) sprayer to approximately 4500 (38 m²) nursery plants. Repeat the application at 4-6 week intervals up to 4 applications per year.

 Well grown Tea (VP) Nursery Plants

Land Selection and Preparation for Tea Cultivation

Land is the most important property in agriculture. If we consider it more further, soil is the priceless property in our agricultural lands. These posts will describe and explain how a land should be selected and prepared for tea cultivation without leaving the land to be eroded and precious soil is washed off with runoff water. Kindly click on the "Land Preparation" button above or follow the links below to read them in detail.

Land Selection for Tea

Tea is economically cultivated in a wide range of soils. In tropical, sub-tropical and temperate climatic conditions, tea grows in soils derived from Gneiss or Granites, Flat Alluvial lands, Peat Soils, Volcanic Ashes and Residual Formations.

Albizia moluccanais the best indicator plant that shows the suitability of a soil for the cultivation of tea, especially  in South-East Asian region, i.e. countries like India and Sri Lanka, etc. Tea is a plant that love to grow in acidic soils. It is considered that it can grow in a range of pH 4 - 6.5, where the optimum range is pH 4.5 - 5.5. If the pH of the soil is out of that optimum level, it should be corrected with Aluminum Sulphate or elemental Sulphate, before the planting. Lands naturally grown with Bracken fern (Gleichenia linearis), generally known as in this optimum pH range. Red-Yellow Podzolic Soils (RYP) is the best tea growing soil. These are the dominant soils in the low country and upcountry wet zone in Sri Lanka.

Albizia moluccana Leaves & Flowers

Gleichenia linearis Plant

If you are planning to replant old tea cultivation, it is always better to select lower “B” category and upper “C” category fields for that. Generally, tea estates have categorized their tea fields as A, B & C based on the yield (kg/ha/yr) over a period of not less than 2-3 years. Highest yielding lands come under category “A” while lowest in “C”.

The lands selecting must be undulating terrains, well drained and with a good soil depth and un-eroded. It is always advisable to avoid eroded lands with slab rock, concentrated boulders, surface rocks and gravel. In Sri Lankan conditions well drained lands less than 70% (31.5^o) of slope (Mid elevations 55% of slope or 24.75^o), more than 60 cm of soil depth, less than 20% of surface rockiness and less than 50% of gravel in top 90 cm layer of soil are considered as generally accepted parameters in land selection for ea cultivation. Flat lands adjoining paddy fields, water bodies or boggy areas are advisable to avoid due to poor drainage and soil aeration.

Land slope can be easily measured (either in percentage or degrees) with Clinometers. Otherwise, it could be simply measured with a rope. One end of the rope is wedge to the slope while a person below to that point raise the other end so that the rope would remain in the horizontal pane. Vertical height to the hand of the man at the point which the rope is held (A) divided by the horizontal length of the rope from the wedge to man’s hand (B), multiplied with 100 will give you the slope in percentage.

Simple way of finding Land Slope in percentage

Simple Home-made Clinometer, its Mechanism, Pocket Clinometer and Hand-held Clinometer in use

Soil depth is measured after preparing soil pits. Number of soil pits dig will be depended on the variation of the land. But generally, there should be at least 12 – 15 soil pits made to cover a one hectare land. The soil pit is 1 m X 1 m X 1 m in dimension and one wall should directly face the sunlight. Soil depth is measured with the meter tape from the upper brim of the pit to the parent rock. Apart from the soil depth, we can inspect for any hard layers underneath the soil surface, type & structure of the soil, depth of the gravel layer, depth of the top soil layer, soil color, etc. in the same location. At least 60 cm of soil depth is considered compulsory for commercial tea cultivation while 60 cm – 90 cm is moderately suitable and more than 90 cm will be the optimal.   

Duly Prepared Soil Pit for Inspection

In determining gravel percentage, take samples from the top 90 cm layer of the soil pit. Air-dry the sample and carefully break any soil aggregations with hand and weigh (Initial weight) it. Then sieve it through 10 mm mesh & collect what is remained in the sieve and weigh (Weight of Gravel). The following equation gives the percentage gravel content.

Set of Siever for partical size analysis

Surface rockiness is measured visually. Visually inspect the land from a distance and determine how much surface area covered with rocks and approximate percentage of that.

Avoid steep rocky clayey or gravelly patches even in a good land you have selected. Such bad patches of land can be easily identified by the growth of rehabilitation grass (Guatemala & Mana). If rehabilitation grass noticed retarding or wilting like symptoms, such land pockets may be having some kind or limitation for tea as well. Therefore, use such areas continue with grass as thatch banks, or diversify them into fuel or timber crops, rather than cultivating tea.

Apart from above discussed land and soil parameters, climatic factors such as rainfall & its distribution, prolonged drought conditions, desiccating wind areas should be avoided from tea cultivation. In Sri Lanka, only wet and intermediate zones could be cultivated with tea. The Agro Ecological Regions (AER,) suitable for tea cultivation, are as follows. (W – Wet zone, I – Intermediate zone, U – Up Country, M – Mid Country, L – Low Country)

• Wet zone -                    WU1, WU2a, WU2b, WU3

WM1a, WM1b, WM2a, WM2b, WM3a, WM3b

WL1a, WL2a

• Intermediate Zone -       IU1, IU2, IU3a, IU3b, IU3c, IU3d, IU3e, IM1a, IM2a, IM2b, IM3c

Land Preparation for tea Cultivation

Tea may be replanted in old lands after the reoval of old cultivation or in new lands. In either operation, there are many factors that should be considered to minimize the soil and nutrient losses and to protect the soil structure. Regardless which one you are going to do, almost all the operations are the same. Therefore, we consider it as replanting tea after uprooting the old cultivation.

Uprooting of Old Tea Cultivation

When your tea cultivation gives poor yield and with debilitated bushes, and cannot be corrected with agronomic practices such as fertilizer, pruning, etc. tea has to be uprooted and re-planted. In some estates, up-rooting is a manual practice but, it is always better to use a winch (lifter/puller) since it will remove the whole root system. All the roots must be pulled out to remove all Poria and Nematode infested roots, so that they would not infest into new clearing.

At the time of old tea up-rooting, it is advisable to remove all the shade trees. It is a well known fact that, when we cut down shade trees at once, the reserved carbohydrates in the root system would not be depleted. In such situation, remaining carbohydrates will facilitate root disease like Charcoal root, etc. Ring balking (removal of Phloem) stops the translocation of synthesized carbohydrates in leaves into roots without damaging the vascular bundles in the Xylem. This makes water & nutrient supply to the upper parts of the plant continue, and hence, plant dies gradually depleting all carbohydrates in the root system. Therefore, it is always advisable to ring balk the high-shade trees (Albizia) 2 – 2.5 years prior to up-rooting of old tea, to a width of approximately 45 – 60 cm from the base.

If root diseases or Nematode infestations could be seen in up-rooting old tea, treat the soil immediately to prevent their spread. Fork the field and remove all roots in pencil thickness, or even smaller, to prevent re-infestations. All infected roots must be burned in an incinerator and destroyed.

When land preparation is done in a large and hilly area, start it from the upper most sections, in a block-wise manner. This will prevent cleared blocks from re-infestation with pests/diseases and damage to new clearing by rolling rocks, etc.

Always thoroughly keep in your mind that, soil is the utmost priceless component in your land, specially the top 30 cm layer. If you are too haste and didn’t apply measures to minimize erosion during land preparation, it is not only the soil created during millions of years you miss, but also a huge amount of money that you would earn from your tea yield in future. The following paragraphs will briefly explain you on the practices to be done and how to do them with minimum erosion of soil.

Land preparation should always be done avoiding heavy rains. Always try to minimize the time gap between up-rooting and establishment of rehabilitation grass. Finish the job in blocks and complete it up to planting of rehabilitation grass immediately as possible preventing exposed and loosen soil from rain. Never level the land into a very fine texture. It will make falling rain water runoff fast without leaving much time to soak it into the soil and ultimately soil particles will be washed off severely making land eroded. Therefore, it is always better to maintain somewhat rugged soil surface, decreasing the speed of runoff water. It will decrease erosive power of runoff water, and allow spread and percolate into soil pores.

Drains and terrains are then built to maintain the flow of water and save soil from erosion. Drains, terraces and planting of rehabilitation grass and planting of tea are done along the contour lines.  Therefore, marking of contour lines is very important in the field.

Next step is to build up of drains. Sometime, people are used to build drains after several months from the establishment of rehabilitation grass, since it is easier and no collapses of the banks. But that practice is not advisable since it will allow the soil to be washed off with rain water and priceless top soil layer would be lost. Drains are very important to manage the flow of water and minimize erosion. There are two main types of drains, viz. Lateral drains and Main (Leader) drains.

Lateral Drains

Width and depth of the lateral drains are 45 X 45 cm (18 inch) and the slope is maintained 1:120 towards the main drain.  That means if we consider two points each 120 units (m, cm, ft, inch, etc.) apart from other, the difference of vertical elevation between two points is one unit.

Now you might be having a problem, if the depth is 45 cm without changing, and slope is 1:120 how these two conditions come together. Although it is technically said that lateral drains are made along the contour, practically it is not. They are made crossing the contours so that the slope is maintained at 1:120 ratio. We can use the road tracer or clinometers in this purpose.

There are two modifications for lateral drains to control the displacement of silt (soil) from the field, viz.;

• Lock and Spill drains and
• Drains with Silt pits

Surface View of a Lock & Spill Drain

Surface View of a Drain with Silt Pits

Lateral drains should not cut open to the main/leader drain directly opposing each other, but in slightly different elevations to minimize collapse of drain banks and erosion.

The spacing between two lateral drains is dependent on the slope and amount of approximate rainfall received. It ranges from 6 m to 12 m. When the slop reduces, and lower rainfall is received, spacing can be made wider (12 m) and vice versa.

Brim or the banks of the drain should be cultivated along sides of the drain with Vetiver Grass (Vetiveria zizanoides) or African Love Grass (Eragrostis curvula) to minimize erosion and collapse of the brim.

Drains should de-silted and clean regularly. Silt removed from drains should always be put upper side of the drain, but not the lower side.

Leader Drains

Leader (Main) drains (Neththi) are cited in the naturally occurring drain lines to carry away the water from lateral drains in non-erosive velocities. Width and depth of the main drain or leader drain is dependent on the amount of water that has to be carried away.

Leader drains are made in step-wise structure with reverse slope and sides and bottom paved with stones to prevent gullies by eroding. Check dams are made in frequent intervals to collect silt carried away with runoff water and sides or banks are planted with Vetiver grass. Leader drains must always be cleaned and de-silted in frequent intervals as done in the lateral drains.

Reverse Slope in Step-wise Leader Drain

Well Maintained Leader (Main) Drain

Stone paved terraces area built along the contour lines to minimize soil erosion and reduce the slope. The upper brim of the terrace must be above the ground/soil level and slope towards the hill side.

Planting of Rehabilitation Grass

Rehabilitation of new clearings prior to the establishment of tea is a compulsory practice. This helps in soil conservation, enhancing soil fertility and structure, minimize erosion and ultimately very important to get a sustainable high yield from tea.

There are only two rehabilitation grasses to re-gain the soil conditions after uprooting the old tea bushes. They are;

• Guatemala (Tripsacum laxum) and

• Mana (Cymbopogon confertiflorus)

Just after drains are being constructed rehabilitation grass must be planted, Guatemala in 20 x 60 cm spacing. Planting material for Guatemala is 4 – 6 node stem. Plant stem 3 – 4 nodes below ground using a crowbar. Mana is planted in 10 x 60 cm spacing. Planting material is little tillers separated from large bushes. Rehabilitation grass must be maintained at least 1.5 years to improve soil conditions after uprooting old tea. Grass is frequently (3-4 month interval) cut and put between the rows to increase organic material. Roots of the grass penetrate into the soil and bind soil particles minimizing erosion. On the other hand, such organic matter content incorporated into soil will help in enhancing cation exchange capacity (ability of soil to hold fertilizer in it), water holding capacity, soil aeration, soil micro & macro organisms, etc.

If the land is reported to be infested with Nematodes (Radopholus similis) it is better not to use Guatemala, but Mana for rehabilitation, since roots Guatemala grass found to be hosting that nematode species.

It is always advisable to apply Dolomite to the land prior to establishment of rehabilitation grass. The amount of dolomite to be applied is given below, according to the pH level of soil. This also helps to prevent Magnesium deficiency in young tea. Therefore, you need to know the pH level of your land as well.

Below 3.9 pH                      2500 kg/ha

3.9 – 4.2                               2000 kg/ha

4.2 – 4.5                               1500 kg/ha

4.5 – 5.5                               1000 kg/ha

Lop the grass regularly in 3 – 4 month interval. Fertilizer (U 625) application is done when the plants having sufficient foliage beginning from 160 kg/ha, next the dosage is increased to 210 kg/ha after lopping. After 2 – 3 lopping it is further increased to 310 kg/ha.