Diurnal and seasonal variations in gas exchange property of tea leaves.
N. Ghosh Hajra and R. Kumar

Responses of young tea clones to subtropical climate: effects on photosynthetic and biochemical characteristics
N. Ghosh Hajra and R. Kumar

Abstract
Seasonal changes in physiological and biochemical parameters of “China”- type (Camellia sinensis L.) tea clones were studied in relation to environmental factors. Net photosynthetic rate (P_N), stomatal conductance, transpiration rate, leaf water potential (L), etc monitored during different seasons showed significant clonal variations. Maximum P_N was recorded in autumn when humidity was very high. Low temperature accompanied with low soil moisture reduced P_N in winter than autumn. The correlation between P_N and air temperature was negative. In rainy season when humidity and soil moisture were highest, lowest photosynthetic photon flux density (PPFD) and low sunshine hours reduced PN at its lowest. A positive correlation between PN and PPFD existed. In general, higher P_N coincided with higher ?L values. A positive correlation also existed between P_N and VPD. Maximum total chlorophyll (Chl) content was recorded during rainy season and lowest in moisture stress period. A positive correlation between Chl content and P_N observed in the case of clones and it was negative in seasons. The correlation between Chl content and yield showed positive. Clones differed in accumulating total free amino acid (TFAA), free proline (FP), ascorbic acid (AA) and epicuticular wax. These were highest during summer and lowest in rainy season. Positive correlation existed between water use efficiency (WUE) and PN, WUE and TFAA, FP, AA in the case of seasons and clones. A high significant positive correlation also existed between WUE and FP in case of clones. The implications of these findings for clone selection are discussed.

Organic tea growing in Darjeeling hills – an overview.
N. Ghosh Hajra

Physiology of tea productivity
N. Ghosh Hajra

Abstract
Physiology in relation to tea productivity has been reviewed with respect to the distribution of crop and components of yield, harvesting and yield, photosynthesis, photosynthetic partitioning, respiration and photorespiration, and dormancy.

Advances in selection and breeding of tea - a review.
N. Ghosh Hajra

Abstract
Advances in tea (Camellia sinensis L.) breeding is reviewed. The tea plant is broadly classified as China. Assam and Cambod and grown over an area from 35°S to 42°N latitude. Tea is a cross-pollinated crop and is virtually self-incompatible. Because of the out breeding nature, seedling populations of tea are extremely heterogeneous. A large base of genetic variability was made available in vivo for plant improvement work in most research centers of the tea producing countries, the largest collections being in China, India, Japan, Kenya and Sri Lanka. The advances in the use of different plant breeding methods to evolve superior planting materials are highlighted. Future research opportunities arce identified.

Organic farming – an overview.
N. Ghosh Hajra and S.E. KABIR

Abstract
Yield of agricultural commodities, by and large, has increased due to the application of chemical fertilizers, herbicides and pesticides. But intensive use of chemical fertilisers may lead to environmental pollution, which could result in deterioration of food quality, destruction of natural soil fertility, pollute ground and surface water. Reduction in use of plant protection chemicals is a desirable objective for limiting agricultural output, lowering production costs, reducing environmental contamination and effect of non-target organisms, minim/sing pesticide residues in food delaying the development of resistant pest biotypes. Therefore, ecological equilibrium in the field by application of various techniques should be stabilised and proper fertilizers, plant protection chemicals with appropriate doses may be used. The present article gives an overview of organic agriculture including merits and demerits of the intensive use of chemical fertilizers and plant protection chemicals.

Bannockburn 157 – a promising clone for Kurseong.
S.E. Kabir, N. Ghosh Hajra and T.C. Choudhuri

Abstract
As the clones are most selective of environment and cultural treatment, their adaptability to the particular area varies widely. Keeping this fact in view, eight standard and quality clones were evaluated at the Darjeeling Tea Research Centre. Bannockburn 157 recorded highest yield (2 to 6 years after planting) followed by Phoobshering 312. Tukdah 78 and Tukdah 383 were remarkable. Bannockburn 157 recorded highest girth all along. The girth of Tukdah 78, 383 and Phoobshering 312 were at par. Pegged bushes of Bannockburn 157 showed excellent canopy cover in comparison with decentering and growth retardant treatments. Bannockburn 157 also recorded highest survival percentage and closely followed by Phoobshering 312 and Tukdah 78. Bannockburn 157 produced flush at the very early part of the year. The appearance of quite heavy waxy deposits in Phoobshering 312, Bannockburn 157, Tukdah 383 and Tukdah 78 may constitute considerable protection of transpiration losses and barrier to spray chemicals. Scanning electron micrographs of different varieties have shown that in Bannockburn 157 the flat irregular plates lie across and partially embedded within the underlying wax film. These plates are usually arranged in groups of clusters surrounded by zones of smooth wax. The plates are uniformly distributed over the plant surface and oriented at different angles away from the cuticle. Sometimes tube waxes occur only in the region of stomata.

Analysis of growth components of Darjeeling tea clones.
S.E. Kabir and N. Ghosh Hajra

Abstract
A study on growth parameters of six popular clones of tea (Camellia sinensis (L) O. Kuntze) was undertaken with a view to study the relationships among the growth parameters at an interval of three months starting from six months to two years. Amongst the clone, girth, plant height, dry weight of root and shoot were observed to be maximum in Bannnockhurn 157 and minimum in Ambari Vegetative 2. The net assimilation rate, crop growth rate and shoot growth rate were maximum in Phoobshering 312 and minimum in Tukdah 78. Maximum crop growth rate, net assimilation rate and shoot growth rate were recorded in Tukdah 78 and Bannnockburn 157 during 15-18 and 18-21 weeks respectively. Highest growth of leaf area in both the clones was achieved during 9-12 weeks after planting. Tukdah 135 exhibited irregular growth rates. Correlation studies amongst growth attributes indicated that crop growth rates, shoot growth rate and leaf area growth rate are significantly and positively related to net assimilation rate. Tukdah 383 and Ambari Vegetative 2 comparatively accelerate the growth at an early stage.

Comparison of methods of replanting old tea bushes.
S.E. Kabir, N. Ghosh Hajra and T.C. Chhudhuri

Abstract
The traditional method of replanting tea in Darjeeling hills by the manual uprooting of old tea bushes is expensive and promotes soil erosion. The study at Darjeeling Tea Research Centre has revealed that the traditional method can be substituted by minimum tillage replanting after killing the chopped stumps of tea with 2,4-Dichlorophenoxy-acetic acid (2,4-D) at the rate of 0.8 kg a.i. in 75 liters of water (500 ml fluid / stump) or urea at the rate of 250 g / stump The survival percentage and yield of young plants are high in 2,4-D treated plots. Chopping treatments have effectively controlled soil erosion. Primary root disease was not observed on the roots of chopped stumps nor the roots of young plants.

Strategies for improvement of tea production in Darjeeling hills.
N. Ghosh Hajra

Abstract
To increase the production of Darjeeling tea, effort will have to be made to increase the productivity per unit land area, to improve and maintain the quality, to check the soil erosion and execution of well designed interception drainage system. The quantum of increase will however depend on identification of constraints, evolving appropriate agrotechnologv, and transfer of the same to the planter. An attempt has been made here to emphasize the factors responsible for low yield and research strategies which hold promise for further improvement.

Improvement of tea production through management practices.
S.E. Kabir, T.C. Chaudhuri, R. Saha and N. Ghosh Hajra

Abstract
This paper elucidates the experimental achievements obtained in Darjeeling Tea Research Centre concerning management practices. By introducing improved herbicidal treatment, the production of tea has gone up by 26.2%. Glyphosate has the best control on weed flora of Darjeeling tea areas. Experiment on improved and economic method of replantation has established that minimum tillage replantation - killing the old tea bushes by application of 2, 4-D, a post emergence trans-located herbicide, has not only reduced the cost of replantation but also confirmed prevention of precious top soil. Similarly, field trial on bringing up of young tea to the bearing stages conducted on major clones of Darjeeling has streamlined the effect on specific treatments, viz, pegging down, decentering and growth regulator on specific varieties of Darjeeling teas. In one of the field trials it was observed that application of nitrogen in the form of urea as basal dose (April/May) N:P:K : 90:45:60 kg/ha gives 27.6% higher production. Foliar spray of zinc sulphate @ 10 kg/ha in two splits in June and August recorded the highest yield of made tea which is 24.5% more than the average yield of 5 years taken together.

Experimental Agriculture, 35: 71-85, 1999.

Improvement in quality of Darjeeling teas through blending
during manufacture.
N. Kumar, R. Rai, N. Ghosh Hajra and T. C. Choudhuri

Abstract
In the present study some popular clones released for Darjeeling tea industry have been blended during manufacturing stage to find out their compatibility with each other and commercial jat and also evaluate its overall effects on the quality. The study revealed that blending may produce excellent flavour as compared to individual clones. Blends of quality clones when manufactured individually do not produce enhanced flavour and other desirable characters like briskness etc. Standard and yield clones when blended together or with other quality clones have been found to be most compatible exhibiting a remarkable improvement in flavour and hence quality of the product. Quality of ‘post second flush’ and also ‘autumn teas’ may also be improved through a judicious blending of compatible clones during manufacture.

Effect of dry matter content on quality of Darjeeling teas.
N. Kumar, R. Rai, N. Ghosh Hajra and T. C. Choudhuri

Abstract
Five tea clones were evaluated for their dry matter content and correlated with the quality. Dry period teas projecting high dry matter content were found superior in quality to wet period teas which contained low dry matter. Similarly quality of teas produced from different standards of plucking and pruned sections varied along with the dry matter content. But no correlation was observed between dry matter content and the quality of clones when compared with each other. Organoleptic evaluation revealed that clones possessing high dry matter content do not necessarily exhibit better quality. The chemical composition viz., total theaflavins, thearubigins and caffeine content of these teas during first and second flush period did not vary significantly. The level of caffeine content increased for 'autumn teas'. Total chlorophylls and carotenoids also varied with clones.

Seasonal and grade variation in I. S. O. specifications for black tea – a Darjeeling perspective
N. Kumar, T. C. Choudhuri and N. Ghosh Hajra

Abstract
The menace of increasing adulteration and sub-standard plucking necessitated the International Standard Organization (ISO) to evolve standard limits on the chemical requirements for black tea to be marketed. Keeping in view these standards, the Darjeeling teas at four different grades were collected fortnightly from eight different climatic and physiographic regions, and subjected to quality control tests. Standard methods of chemical analysis as specified by ISO were followed. It has been found that all the grades of Darjeeling teas investigated for six different chemical parameters were within the permissible limits of ISO. Statistical analysis of the data revealed that F values for month and parameter were highly significant. Also, there was significant correlation between the total ash and water soluble ash contents of all the teas studied.

Dry matter content of certain tea clones under the agroclimatic conditions of Darjeeling.
N. Kumar, R. Rai, N. Ghosh Hajra and T. C. Choudhuri

Abstract
Some North and South Indian tea clones which are being increasingly cultivated in Darjeeling hills were evaluated for their dry matter content considering the ratio of dry weight: fresh weight during the different seasons of a year. Seasonal variation in the dry matter content appears to vary with the climatic parameter, variety of clone and fineness of plucking. Statistical analysis of the data for clones under investigation revealed that value for month and clone was significant. The dry period teas were found to prosess higher dry matter content as compared to wet period. Similarly, quality of dry period teas was superior to the wet period teas but no correlation was observed in dry matter content and quality. Dry matter content of teas have been discussed in this paper in relation to yield and quality.

Effect of nitrogen, phosphorus and potash fertilizers on yield of made tea (Camellia sinensis)
Mukherjee, S. K., Chandran, P., Ghosh Hajra, N., Choudhuri, T. C. and Saha. R.

Abstract
In a 5 year field trial on the effect of various doses of NPK fertilizers on the yield of made tea in Darjeeling it has been observed that a single basal dose in April/May of N:P:K @ 90:45:60 kg/ha (in the form of urea, rock phosphate and muriate of potash) gave the highest made tea yield. This was followed by a 3 split application in April/May, July and September of ammonium sulphate :Rock Phos : MOP: @ 30:15:20 kg/ha.

Phosphate and potash fertilizers in the optimization of yield and quality of Darjeeling black tea
Saha, R and Bisen, J. S.

Abstract
An experiment was conducted to ascertain the optimum dose of phosphatic fertilizers (rock phosphate) along with the various combinations of potashic fertilizers (MOP) keeping the dose of nitrogenous fertilizers constant and also the uptake of NPK nutrients. The highest yield was obtained by following the treatment combination viz. 120:45:00 kg/ha of N:P:K. The N content varies from 2.40 to 5.42% and 2.10 to 4.01% in the flush and third leaf components respectively. The percent of phosphorous content of the flush and third leaf component was observed to be high where the dose of phosphate was also maximum (45 kg/ha of phosphate). But in the case of percent of potassium, the third leaves of all the treatment combinations contain more of this nutrient than their flush component counterparts. It was also observed on the basis of organoleptic evaluation reports that varying dose of phosphatic and potashic fertilizers have little or no bearing at all on quality of teas.

Tea Soils of Darjeeling
Saha, R., Mondal, D., Bisen, J. S.

Abstract
X-ray diffraction analysis of more than 122 soil-clay samples revealed that the dominant mineral in Monteviet and Chamong series is chlorite (2:1:1) mineral. A considerable amount of 2:1 vermiculite mineral has also been found in these soils although the abundance of illite group precedes the-former. Rutile and anatase are also found in this series in lesser amounts. But in case of Tessta Valley series the dominant mineral is kaolinite (1:1) and illite (2:1). Smectite (2:1) has also been detected in Teesta Valley series with no traces of rutile and anatase. Another interesting feature that has been observed is the relationship between the presence of chlorite and rutile plus anatase minerals in the quality sections of most of the tea garden soils belonging to Monteviot, Chamong and Thurbo series. The non-quality sections of most of these tea garden soil-clays showed the preponderance of illite mineral with traces or no amounts of rutile and anatase mineral. These chlorite, rutile and anatase minerals has to be studied in details to ascertain the pivotal role played by these minerals, if any at all, in contributing to the production of quality Darjeeling teas vis-à-vis the proportionate role of soil as a whole in governing the quality of Darjeeling tea. It is also evident from the study on amorphous ferri-aluminosilicate mineral (AFAS mineral) that all the four soil series contains a remarkable quantity of these minerals. The K-fixation capacity due to these minerals has been studied and found to be quite noticeable. These AFAS-minerals have high phosphate fixation properties also. So, any recommendation on the rock phosphate fertilisation should be ascertained vis-à-vis the presence of AFAS-minerals in these soils. A study on rock phosphate fertilization in the Monteviot series soil revealed that 45 kg of phosphate/hectare in the form of Rock phosphate (Mussourie Phos) gives highest return in terms of made tea as compared to 20kg and 30kg phosphate/hectare.

Effect of foliar application of zinc in tea (Camellia sinensis) under the agroclimatic condition of Darjeeling
Mukherjee, S. K., Chandran, P., Ghosh Hajra, N., Choudhuri, T. C. and Saha. R.

Abstract
In a 5 year field trial the effect of foliar spray of zinc in Darjeeling teas has been studied. 10kg and 5kg of zinc per hectare has been sprayed in a single spray, 2 splits and 4 splits during April, June, August and October. Out of those 3 doses 10kg/ha of zinc applied, in 2 splits @ 5kg/ha during June and August increased the yield of made tea by about 24.5% above the control. This was followed by the application of 5kg/ha of zinc in 4 splits @ 1.25kg/ha during April, June, August and October.

Potassium ion potential and the quantity-intensity relationship as affected by organic matter and exchangeable aluminium ions in acidic tea soils of Darjeeling, West Bengal.
Saha, R., Mondal, D., Bisen, J. S.

Abstract
Q/1 and Q/P relationships of potassium ion of three Darjeeling tea growing acidic soils with or without organic matter has been investigated. It revealed that the mineralogical make up of these soils has got profound influence on Q/l and Q/P isotherms. The role of organic matter has also been found to cover the exchange sites and transformed the Q/l isotherms by increasing the value of Q. The Q/l parameters particularly, the equilibrium activity ratios, buffering capacities, total pool of available K(Ki), the difficultly available K(Kx) and easily available K(K0) has been derived from the Q/I curves which are also the functions of the factors which determine the Q/l isotherms. The Q/P and Q/I isotherms also provided a good index of the mineralogy of these acidic soil-clays.

Sulphur in Darjeeling Tea Soils - its deficiencies and Remedies
Saha, R and Bisen, J. S.

Abstract
In a 3 year field trial the critical level of available sulphur, its deficiencies and remedies has been studied in Darjeeling tea soils. It has been observed that estimation of available soil sulphur varied with the extractants used. The optimum ratio of leaf sulphur to leaf nitrogen was 1:9/10 and was found to be a better index for ascertaining deficiencies. The critical level of soil availble sulphur was found to range between 20-30 ppm for Darjeeling soils. Among the easily available fertilisers the best source to rectify the sulphur deficiency was to apply 20kg/ha of Ammonium sulphate in a single basal dose during April/May.

Botanical pest control – an alternative to minimize residue toxicity in
Darjeeling tea.
N. Ghosh Hajra, S. E. Kabir and J. S. Bisen

Abstract
The Darjeeling tea often referred to as the champagne of tea, holds the place of pride in the world. It is the image bearer of the tea exports of India. Maintaining quality commensurate with increased production is of vital importance to the Darjeeling tea industry. Pest and disease cause on an average 10-25% loss in crop, varying from garden to garden and even from section to section. The seasonal appearance of pests and diseases needs timely management mostly by use of pesticides. But considering the stringent measures on pesticide residue being enforced by the developed countries and the growing awareness among the consumers for residue free tea, there is an urgent need to take adequate measures to keep the pesticide residue level within the permissible limit. Further, growing public alarm over the harmful side effects of conventional pesticides and the prospect of many insect pests becoming resistant to the synthetic insecticides has prompted in searching effective alternative to reduce reliance on chemical pesticides. The present article deals with the effect of certain chemicals on yield, quality and magnitude of their residues on black tea. Further an attempt has also been made to search for plants exhibiting insecticidal activity which could be effectively utilized for the control of specific type of pest.

Persistence and degradation of some insecticides in Darjeeling tea.
J. S. Bisen and N. Ghosh Hajra

Abstract
A field trial was conducted during dry and wet seasons to understand the occurrence of residues, persistence, dissipation rate and half life values of six widely used insecticides at recommended doses/dilutions viz. Monocrotophos 36% SL, Malathion 50% EC, Fenvalerate 20% EC, Dimethoate 30% EC, Quinalphos 20% AF and Dicofol 18.5% EC in processed tea. The insecticides were applied as aqueous solutions at the dilution of 1:400 for all insecticides except Fenvalerate which was applied @ 1:4000 during dry and wet seasons. The initial deposits (4 hrs) of different insecticides except Fenvalerate were found to be higher in dry season than wet season. No residue of Monocrotophos after 4 hrs of its application was detected. The residues of malathion, fenvalerate, dimethoate on 5th day after application were found below the prescribed maximum residue limit. But in case of quinalphos it was observed on 7th day after application. The residue of dicofol on 7th day during wet season (0.03 ppm) was found below the tolerance limit. Dissipation followed a first order reaction in all cases and the half life values varied from 0.24 to 2.73 days. This study also indicated that one round of plucking may be discarded in dry season when Quinalphos and Dicofol are applied on the tea bushes of Darjeeling.

Efficacy of some organic fungicides against blister blight disease of tea in Darjeeling hills.

J. S. Bisen and N. Ghosh Hajra

Abstract
A field trial was conducted at Darjeeling Tea Research & Development Centre, Kurseong during 1996 to 1998 to study the efficacy of certain fungicides against blister blight (Exobasidium vexans Massee) disease of Tea. The results revealed that Bitertanol (Baycor) @ 0.15% concentration, as prophylactic application, recorded lowest incidence of blister blight which was followed by dithianon (Delan) @ 0.2% and 0.15% concentrations. As curative, dithianon (Delan) @ 0.2% concentration closely followed by bitertanol (Baycor) @ 0.15% proved best for disease control. Since these fungicides are quite expensive and considering the economics of spraying and intensity of the disease infestation, three rounds of bitertanol @ 0.05% at fortnightly intervals as prophylactic spray starting from the middle of June till the end of July would be cost effective.

Abstract
Petroleum ether (6O-80⁰C) extract of four plants viz Artimisia vulgaris (Titepati), Urtica dioica (Shishnu), Polygonum runcinctum (Ratnaulo) and Eupatorium glandulosum (Banmara) were evaluated in the laboratory for their antifeedant action against IInd instar larvae of bunch caterpillar on tea. All the plant extracts showed varying degree of antifeedant effects. One percent concentration of each of Artimisia, Urtica, Polygonum and Eupalonum extracts offered 77.52 to 87.19% protection to tea leaves over control against feeding by bunch caterpillar. The maximum antifeedant action was exhibited by the extract of Artimisia vulgaris followed by Polygonum runcintum, Urtica dioica and Eupatorium glandulousm at 1.0% concentrations each. The remaining two concentrations 0.5% and 0.25% of each of the four plant extracts has also been found effective as antifeedant but to a lesser degree as compared to 1.0% concentrations.

Bioefficacy of neem products in controlling certain pests of tea (Camellia sinensis).
J.S.Bisen and N. Ghosh Hajra

Botanical pest control – an alternative to minimize residue
toxicity in Darjeeling tea.
N. Ghosh Hajra, S. E. Kabir and J. S. Bisen

Abstract
Pest and disease cause on an average 10-25% loss in crop, varying from garden to garden and even from section to section. The seasonal appearance of pests and diseases need timely management mostly by use of pesticides. But considering the stringent measures on pesticide residues being enforced by the developed countries and the growing awareness among the consumers for residue - free tea, there is an urgent need to take adequate measures to keep the pesticide residue level within the permissible limit. Further, growing public alarm over the harmful side - effects of conventional pesticides and the prospect of many insect pest becoming resistant to the synthetic insecticides has prompted in searching effective alternative to reduce reliance on chemical pesticides. The present article deals with the effect of certain chemicals on yield, quality and magnitude of their residues on black tea. Further, an attempt has also been made to search for plants exhibiting insecticidal activity which could be effectively utilised for the control of specific type of pest.

Environmental impact of pesticides and alternatives of pest
control in tea (Camellia sinensis).
N. Ghosh Hajra, G. Sarker and A. Ghosh Hajra

Abstract
Non-judicious use of pesticides has, however, created some major environmental as well as health problems in recent years such as reduction in the abundance and diversity of wild life, human health hazards associated with acute or chronic exposure to dangerous products at the work place, and contaminated air, food and water. The monograph provided a glimpse into the impact of pesticides on the environment and ecosystem, the pesticide residue scenario in tea, its consequence, alternatives to chemical pesticide and integrated pest management in tea.