Mrityunjay Choubey, Senior Scientific Officer, presented during State Media Workshop on Climate Change,held from May 10th – 12th 2018 at Darjeeling (W.B.).

1. Impact of Climate Change on Darjeeling Tea Plantation
Darjeeling Tea Research and Development Centre, Tea Board of India,
A.B. Path, Kurseong – 734203, Dist.- Darjeeling, (WB), India
Darjeeling Tea Research and Development Centre, Tea Board of India,
A.B. Path, Kurseong – 734203, Dist.- Darjeeling, (WB), India
Mrityunjay Choubey
Sr. Scientific Officer
Dept. of Botany and Agronomy

2. An experiment was conducted at DTRDC experimental farm (mid
elevation) and Sungma Tea Estate (High elevation), Darjeeling during
2012 to 2013 to study the impact of climatic variables on physiological
characteristics of Darjeeling tea clones and old china tea bush.
As nowadays climate change is threatening to impact the bottom line
of tea industry with unprecedented high temperature, excessive rainfall,
coupled with major shifts in other meteorological parameters in
comparison with long term observations have further complicated the tea
production process.. Increasing atmospheric temperature is affecting the
quality and quantity of Darjeeling tea.
Darjeeling tea plants experiences various types of climatic conditions
in Darjeeling hills such as low temperature, low soil moisture in winter
foggy climate, high humidity and low levels of solar radiation.
All physiological processes including photosynthesis need suitable
temperature and other climatic elements.

3. Tea grows best under high and evenly distributed rainfall. In the tropics, it
needs at least 1,500 mm rain per year with a dry season of less than 3 months.
Tea can be grown from the lowlands to 1500-2000 m elevation above sea level.
Many high quality teas are grown at high elevations, where rainfall less than
2000mm. In these areas the plants generally grow more slowly which results in
a better flavor.
The ideal temperature for growth is 18–30 °C. Growth is limited by
temperatures above 32–35 °C and below 12–13 °C. Strong winds, frequent
frost, hail, and excessive rainfall are also detrimental to the production of high
quality tea.
 Net photosynthetic rate (Pn) of tea leaves is influenced by the photosynthetic
photon flux density (PPFD), temperature, day length, carbon dioxide
concentration, genetic potential of given cultivar, physiological maturity,
management practices, etc.
Keeping these facts into consideration, the experiment was therefore,
conducted at DTRDC experimental farm (mid elevation) and Sungma Tea
Estate (High elevation), Darjeeling during 2012 to 2013 to study the impact of
climatic variables on Pn and other physiological characteristics of Darjeeling
tea clones and old china tea bush.

4. Objectives
To study the impact of the climatic variables on physiological
characteristics of released tea clones and old china bush planted in
Darjeeling.
To study the effect of altitude on photosynthetic activities and yield of
Darjeeling tea.
Physiological Parameters
Net photosynthetic rate (Pn), Somatal Conductance (gs), Transpiration
(E), Water use efficiency (WUE), Vapour pressure deficit (VPD) and
Leaf water potential (ψL).

5. The study was conducted at the following altitude-
Darjeeling Tea Research & Development Centre, Kurseong (Lat.
260
52’09 SN, Long.880
15’45 SE, altitude 1347 MSL).
Sungma Tea Estate, Darjeeling (Lat. 260
52’94 SN, Long.880
15’49 SE,
altitude 1510 MSL).
The topography comprised of moderate slopes (25-30%). The topsoil
is about 45 cm in depth and the sub soil is stony.
The soil is an Umbric Dystrochrept, moderately permeable and
moderately well drained.
Used Darjeeling tea clones - T78, AV2, B157 and old china tea bushes.
Experimental site and plant materialExperimental site and plant material
Materials and Methods

6. Measurement techniques
During 2012 to 2013, PN, gs, E, WUE and VPD were monitored three times in a
month at the beginning, middle and end of April, July, October and January,
using-
Portable photosynthesis system (Li- 6200, Li - Cor, Nebraska, USA) with a
well mixed 390 cm3
chamber as described (Li- Cor Inc., 1987). This portable
instrument has internal programmed to calculate physiological quantities from
measurements of air and leaf temperatures, humidity and CO2 concentrations.
Three plants randomly selected from each replicated plot were assessed on
every recording (540 reading).
All measurements were made between 10 00 and 12 00 hours when the
maximum values of PN and other physiological parameters were recorded in the
diurnal study (Ghosh Hajra and Kumar, 2002)

7. Leaf water potential (ψL): ψL was measured simultaneously with PN using –
Dew point hygrometer (model C-52 sample chamber connected to an HR 33T
microvoltmeter, Wescor Inc., Logan, USA) as described by Wescor Inc. (1988).
Small circular leaf discs from the leaves on the opposite branches to those for
PN measurement were used and ψL values were expressed as megapascals (-
Mpa).
Canopy depth -
 The depth of the canopy (D) of each treatment was measured as depth from the top
most leaf to the bottom-most leaf in the canopy, using a meter ruler. Five measurements
at different places in the canopy were taken in each bush.
Productivity -
Harvesting was done by hand plucking of tender shoots from the tea bushes on every
7 days intervals during the study. In Darjeeling, yield recording started from 2nd
week
of March and ended the last week of November (Twenty-six cycles per year).
December to February no harvesting of green leaf.
On each plucking day, mass of plucked leaf from each plot was recorded and
expressed as made tea yield by multiplying the green leaf yield by factor of 0.22.

8. Result and DiscussionsResult and Discussions
Climate:Climate:
A rapid increase of temperature takes place during March and April
owing to the warmer air from the plains. In May, the southerly winds
reach the hills and causes increased precipitation which is at times are
very high. November to February are almost rainless and the light
showers which fall in December and March occur when shallow
depressions are passing eastward over the plaint.
In October, northerly winds begin, cloud is much less than the
previous months and rainfall occurs, mainly owing to cyclonic storms
that generally re-curve towards North Bengal at the end of the season.
In 2013, the highest values of photosynthetic rate were recorded
in cloudy, under shade tree, sunny, foggy and rainy weather respectively
(Table 2).

9. In Darjeeling, the extension growth stops at monthly mean maximum
and minimum temperature of 180
C and 100
C respectively in November
and it start flushing at the meddle of March when maximum and
minimum temperature exceed 200
C and 120
C respectively.
Net Photosynthetic rate (Pn) mostly depended on photosynthetic photon
flux density (PPFD). Pn significantly increased with the increase of
PPFD till it reached the light saturation at 1200 µ mol m-2
s-1
(Barman et
al 2005).
At increasing irradiance 1400-1800 µ mol m-2
s-1
, Pn decreased gradually
from lower to higher PPFD and effect between them was insignificant.

10. Table 2.
_____________________________________________________________________________
Weather Conditions
Parameters -------------------------------------------------------------------------------- se CD at 5%
Sunny Cloudy Under shade tree Foggy Rainy
_____________________________________________________________________________
PAR (μ mol m-2
s-1
) 1450.25 956.58 702.83 173.85 52.94 14.62 45.06
Pn (μ mol m-2
s-1
) 11.17 12.54 11.48 6.65 3.60 0.33 1.01
E (m mol m-2
s-1
) 4.23 4.96 3.40 3.37 6.05 0.11 0.34
gs (mol m-2
s-1
) 0.15 0.30 0.39 0.27 0.61 0.02 0.06
WUE (μ mol/ mmol-1
) 2.58 2.53 3.38 1.98 0.59 0.08 0.23
VPD (kPa) 2.82 1.68 1.61 1.45 0.67 0.04 0.12
Lt. (0
C) 28.91 25.49 23.01 21.60 21.07 0.21 0.65
ψL (Mpa) -3.05 -2.54 -1.96 -1.54 -1.12 0.05 0.17
_____________________________________________________________________________
Note: Photosynthetically active radiation (PAR), Net photosynthetic rate (Pn),
Transpiration rate (E), Stomatal conductance (gs), Water use efficiency (WUE),
Vapour pressure deficit (VPD), Leaf temperature (Lt) and Leaf water potential
Table 2.
_____________________________________________________________________________
Weather Conditions
Parameters -------------------------------------------------------------------------------- se CD at 5%
Sunny Cloudy Under shade tree Foggy Rainy
_____________________________________________________________________________
PAR (μ mol m-2
s-1
) 1450.25 956.58 702.83 173.85 52.94 14.62 45.06
Pn (μ mol m-2
s-1
) 11.17 12.54 11.48 6.65 3.60 0.33 1.01
E (m mol m-2
s-1
) 4.23 4.96 3.40 3.37 6.05 0.11 0.34
gs (mol m-2
s-1
) 0.15 0.30 0.39 0.27 0.61 0.02 0.06
WUE (μ mol/ mmol-1
) 2.58 2.53 3.38 1.98 0.59 0.08 0.23
VPD (kPa) 2.82 1.68 1.61 1.45 0.67 0.04 0.12
Lt. (0
C) 28.91 25.49 23.01 21.60 21.07 0.21 0.65
ψL (Mpa) -3.05 -2.54 -1.96 -1.54 -1.12 0.05 0.17
_____________________________________________________________________________
Note: Photosynthetically active radiation (PAR), Net photosynthetic rate (Pn),
Transpiration rate (E), Stomatal conductance (gs), Water use efficiency (WUE),
Vapour pressure deficit (VPD), Leaf temperature (Lt) and Leaf water potential
Effect of different weather conditions on
physiological parameters in Darjeeling tea.
Effect of different weather conditions on
physiological parameters in Darjeeling tea.
The maximum net photosynthetic rate (Pn) (12.54 µ mol m-2
s-1
) was recorded in cloudy
when humidity was high, air temperature; soil moisture and photosynthetically active
radiation (PAR) were moderate. In rainy day, higher temperature prevailed but Pn was
minimum (3.60 µ mol m-2
s-1
).
During sunny, Pn recorded at lowest rate than cloudy and under shade tree. When PAR
in sunny weather increasing from lower intensities to (1450 µ mol m-2
s-1
) than the
lower rate of Pn recorded
in sunny when atmosphere
was dry and plants were
suffering from moisture
stress.
There is abundant
evidence in the literature
that Pn is inhibited by
water stress (Balasimha et
al., 1991; Sobrado, 1996).

11. Light Intensity
The maximum seasonal
average of photosynthetic
active radiation (PAR)
were recorded during
summer followed by
autumn, winter.
 Lowest PAR in rainy
season which affected the
Pn

12. Soil Moisture (%)
The volumetric water content of
both top and sub-soils decreased
gradually from autumn and
declined rapidly during winter.
In the last 3-5 years gradual
reduction in moisture content in
all the seasons was observed
compared to last 15 years.
The decrease in gs and E were
more pronounced in summer
when both soil and atmospheric
moisture was low and demand for
water was high.

13. Higher average value of LWC noted in T253 & T135 and lowest in ND& P312
Clones Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Averag
e
T253 62 61 62 66 67 65 66 66 68 67 64 64 65.17
T383 62 61 61 66 64 62 65 64 66 67 61 64 62.58
T135 62 62 61 64 65 68 67 65 67 66 65 66 65.00
B777 63 62 59 66 64 66 66 65 66 66 62 65 64.25
B157 63 62 58 61 64 65 63 63 65 64 62 64 63.08
AV2 61 60 62 64 64 62 68 67 66 66 64 65 63.67
T78 62 61 59 69 66 62 64 63 64 66 61 64 63.42
RR/17/144 62 61 61 62 61 63 66 65 66 67 64 65 63.58
MB-6 62 62 60 62 65 62 66 67 68 68 63 65 64.17
TtV1 62 61 61 63 62 62 66 65 66 67 62 63 63.42
HV-39 62 61 59 63 62 63 64 65 66 68 65 64 63.50
ND 63 62 60 61 64 60 63 64 66 63 64 63 62.75
Pandian 62 61 61 63 65 67 66 67 68 68 63 65 64.67
Springfield 60 61 58 60 62 61 65 65 67 67 63 64 62.92
P312 60 60 59 62 61 64 64 65 64 65 63 63 62.50

14. __Table-1 ___________________________________________________________________________
DTRDC experimental Farm, Kurseong Sungma Tea Estate, Darjeeling
(1347 MSL, Lat. 260
52’09 SN, Long. 880
15’45 SE) (1510 MSL, Lat. 260
52’94 SN, Long. 880
15’19 SE)
Months ---------------------------------------------------- ---------------------------------------------------
Air Temp. Rainfall R. H. Air Temp. Rainfall R. H.
Max (0
C) Min (0
C) (mm) (%) Max (0
C) Min (0
C) (mm) (%)
__________________________________________________________________________________
April 26.70 (22) 12.81 (16) 85.50 86 (75) 24.30 (21) 12.10 (16) 67.50 87 (75)
May 27.20 (24) 13.10 (18) 60.00 87 (76) 24.70 (21) 12.21 (15) 81.50 86 (75)
Jun 26.80 (23) 18.20 (20) 489.00 88 (85) 25.00 (22) 20.8 1(20) 281.50 88 (86)
July 24.00 (23) 18.90 (16) 1555.00 88 (86) 24.00 (22) 18.00 (21) 483.75 90 (88)
Aug 27.70 (25) 19.20 (20) 478.50 88 (85) 26.00 (22) 18.00 (20) 127.50 88 (86)
Sep 27.60 (23) 18.20 (19) 157.50 88 (86) 25.10 (22) 17.81 (18) 399.00 88 (86)
Oct 23.60 (22) 13.10 (16) 26.50 88 (79) 22.00 (21) 14.50 (15) 17.00 88 (86)
Nov 21.70 (19) 9.90 (12) 0.00 82 (73) 21.50 (18) 8.80 (13) 0.00 84 (76)
Dec 16.80 (15) 7.20 (9) 0.00 86 (72) 15.00 (14) 8.00 (9) 0.00 86 (73)
Jan 16.90 (15) 4.60 (8) 13.50 80 (66) 16.20 (16) 4.00 (9) 7.50 82 (70)
Feb 22.30 (18) 7.80 (16) 10.50 86 (62) 21.00 (22) 6.50 (12) 39.00 86 (68)
Mar 23.70 (21) 10.90 (14) 9.00 85 (65) 23.00 (20) 10.00 (15) 22.00 86 (68)
___________________________________________________________________________________
Meteorological parameters recorded at DTRDC ,
Kureseong and Sungma Tea Estate E, Darjeeling
during the year 2012 to 2013.
Mean maximum air temperature ranges from around 16 0
C in January to 27 0
C in August; a
mean minimum temperature of 4.5 0
C was recorded in January and total rainfall are 2884.5 mm
in mid altitude at Kurseong and 1526.50 mm in High altitude at Sungma T. E. Darjeeling.

15.  Highest value of Pn, E, gs were recorded in canopy
depth 0 -10cm and lowest in ›30cm. Among the
clones, T78 showed the highest value of Pn, gs, in all
canopy depth (figure 1).
 The daily maximum net photosynthetic rate (Pn-
12.01 µ molm-2
s-1
) was recorded in clones T78 and
minimum in old china bush in canopy depth (from
the top of bush) 0-10 cm during autumn (September)
when humidity was (88%), air temperature (24o
C)
and PAR (1270 µ molm-2
s-1
) were moderate. A
positive correlation between Pn and PPFD was
observed.
 Therefore, distribution of radiation incident within
the canopy through light penetration along with Pn as
determined by the internal and external factors
discussed above which determine the magnitude of
Pn.
 Using 13 CO2, Okano et al. (1995) showed that 85%
of canopy photosynthesis (Pc) of tea growing in
autumn in Japan was carried out by the top 5 cm leaf
layer of the canopy and that the maximum canopy
Net photosynthetic rate (1270 µ molm-2
s-1
)Net photosynthetic rate (1270 µ molm-2
s-1
)
(A)
(B)

16.  The maximum value of transpiration rate (E- 5.908 m
mol m-2
s-1
) in old china bushes and minimum in clone
T78 in canopy depth (from the top of bush) 0-10 cm in
both elevations.
 Transpiration rate was lowest in summer season and
higher in rain, though the PAR reached minimum but the
temperature, Sm (Soil moisture), wind velocity and RH
were reasonably high. Barbora, (1994) also reported a
sharp decline of E with reduced soil moisture in Assam
tea plantation.
 Water use of tea and its controlling factors have been
studied extensively (Stephens and Carr, 1991; Kigalu,
2007; Anandacoomaraswamy et at., 2000). However,
water use (evapo-transpiration) include both transpiration
form the foliage canopy and soil evaporation.
Transpiration ( E- m mol m-2
s-1
)Transpiration ( E- m mol m-2
s-1
)
(A)
(B)
 A well-maintained tea canopy (including nutrients)
covers the ground almost completely allowing very little
solar radiation to penetrate down to the soil surface

17. Stomatal conductance (gs mol m-2
s-1
)
Stomatal conductance (gs- 0.499 mol m-2
s-1
) were
recorded in old china bush and minimum in clones in
canopy depth 0-10cm to 10-20cm in DTRDC plantation
but in old china bush was lowest in high altitude.
The highest value of gs was recorded in rainy season
and lowest in summer season. The gs at different
seasons followed the patterns of changes in transpiration
rate (E).
Decreased gs in response to increasing irradiance, leaf
temperature (TL) and air vapour pressure deficit (VPD)
played a key role in inducing photoinhibition of tea. In
a field study on mature tea, Mohotti and Lawlor (2002)
observed that increasing irradiance, TL and VPD with
the progress of the day towards midday do decrease gs
and sub-stomatal CO2 concentration (Ci), thus leading
to reduced Pn.
The stomatal conductance was highest with the canopy
depth from 10-20 cm than 0-10 cm. These results may
indicate that the number of stomata per unit area is not a
factor that can be changed due to environmental
conditions

18. Water use efficiency (WUE) of clone T78 was
maximum value (2.618 µmol mmol-1
) as
compared to clone, B157, AV2 and old china
cultivation at high elevation (Sungma T. E.) than
mid elevation from the top of canopy (0-10 cm).
The WUE was highest with the canopy depth
from 10-20 cm than 0-10 cm in at mid elevation
(DTRDC, Kurseong).
WUE is the amount of yield produced per unit of
water used through evapotranspiration. It could
be affected by factors influencing shoot growth
and water use. At lower Temperature (cool dry
season), WUE respond more to nitrogen fertilizer
than to rainy.
Stephens and Carr (1991) observed that WUE of
tea is influenced by water availability, nitrogen
application and season.
Water use efficiency (WUE - (μ mol/ mmol-1
)Water use efficiency (WUE - (μ mol/ mmol-1
)
(A)
(B)

19. Vapour pressure deficit (VPD- kPa)
(A)
(B)
 Stomata normally close in response to increasing VPD.
Higher value of VPD was recorded in summer (2.82
kPa) and minimum in rainy season (0.67 kPa) (table 2).
 Maximum VPD was recorded in canopy depth from 0-
10 cm (2.34 kPa) and minimum in depth from >30 cm
(1.72 kPa) (figure 5) in at both elevations.
 A positive correlation between WUE and Pn.
 In general, a reduction in gs with higher VPD values
was
observed in the present study which is in conformity
with the findings of Squir and Callender (1981).
 Squire and Callander (1981) also cite the frequent
observation of higher Pn even during periods of low
shoot growth rates due to higher VPD or cooler air
temperature (Ta). (Squire, 1979) or higher soil water
deficits (Stephens and Carr, 1991) as evidence for the

20. Leaf water potential (ψL-Mpa)
(A)
(B)
 Leaf water potential (ψL) of clone T78, B157, AV2
and
Old china cultivation was -2.05, -2.21, -2.45 and -2.54
(-Mpa) at mid elevation (DTRDC, experimental farm)
and clone T78, B157, AV2 and Old china cultivation
was -1.94, -2.01, -2.33 and -2.44 (-Mpa) respectively
at high elevation from the top of canopy (0- 10 cm) .
 Among the clones, AV2 and Old china bush showed
lower rate of ψL than clone, T78 and B157 at both
elevation of Darjeeling hill (figure 6).
 Leaf water potential was recorded lowest in summer
season and higher in rainy season. The plant
effectively conserves water by stomatal closure. It was
supported by lower levels of gs in the dry season.
 In the present study, no correlation between Pn ψL and
was observed and ψL was closely depend on
environmental conditions, mainly ambient temperature

21. Yield of Processed Tea and Plucking round
The mean annual yield of made tea was recorded 714
Kg ha-1
and varied with clones.
The yield from clone AV2 was lower (699.85 kg ha-1
at DTRDC and 675 kg ha-1
at Sungma Tea
Estate, Darjeeling) than those from T78 and B157
(729 and 715 kg ha-1
at DTRDC; & 710 Kg ha-1
and
706 kg ha-1
at Sungma Tea Estate, Darjeeling
respectively) (figure 8).
Maximum plucking round was recorded at mid
elevation than high elevation due slow growth (figure
8). The productivity of tea is quantified in terms of
the weight of ‘made tea’ per unit land area per year.
‘Made tea’ refers to the form of tea obtained after the
harvested (or ‘plucked’) shoot has gone through the
manufacturing process (i.e. withering, fermenting and
drying). Weight of made tea is directly related to the
fresh weight of plucked shoot (2-3 leaves and a bud)
by a factor of 0.2.

22. Canopy photosynthesis: Overall canopy photosynthesis (Pc) is the sum of the product
between Pn and surface area of all individual leaves of the canopy. A strong
relationship exists between Pn and light intensity incident on a given leaf located at a
given canopy depth. It was observed that the top two layers (i.e. 0-10 cm and 10-20
cm canopy depths) contributed 70- 80% of gross photosynthetic rate (Pg)
Okano et al., (1995) showed that 85% of (Pc) of tea growing in autumn in Japan was
carried out by the top 5 cm leaf layer of the canopy and that the maximum canopy
depth effective for photosynthesis was only 10 cm.
Smith et al., (1993) computed (Pc) dividing the canopy in to five types of leaves
(depending on their maturity) and summing the product between Pn and fraction of
radiation interception of each layer. The rate of Pn was highest in the fully-expanded
dark green, mature leaves on the plucking table, with both the younger leaves above
them and the older leaves below them showing lower Pn.
However, there was an appreciable variation between the three cultivars in their
distribution of Pg among the different canopy layers despite there being no
significant difference in the corresponding distribution of LAI.
Summery

23. There have been some conflicting opinions on how important the photosynthetic rate
is in determining the productivity of tea.
 Based on evidence compiled from several studies, Squire and Callander (1981)
concluded that the current rate of Pn is not directly linked to leaf yield of tea. The
basis of their argument was that leaf yield of tea is controlled more by the rates of
shoot initiation and extension rather than by the supply of assimilates from current
Pn.
Rates of shoot initiation and extension are primarily controlled by air temperature
and
VPD and shoot turgor whereas Pn is primarily controlled by light intensity.
Therefore, yield components of tea are the number of plucked shoots per unit land
area (Number of shoot) and the mean weight per shoot (shoot weight). Out of these
two yield components, it is the variation of number of shoot that has the stronger
correlation with yield variation.
Therefore, both Tanton (1979) and Squire and Callander (1981) argued that
assimilate
supply cannot be a limiting factor in yield determination, when harvested yield is
There have been some conflicting opinions on how important the photosynthetic rate
is in determining the productivity of tea.
 Based on evidence compiled from several studies, Squire and Callander (1981)
concluded that the current rate of Pn is not directly linked to leaf yield of tea. The
basis of their argument was that leaf yield of tea is controlled more by the rates of
shoot initiation and extension rather than by the supply of assimilates from current
Pn.
Rates of shoot initiation and extension are primarily controlled by air temperature
and
VPD and shoot turgor whereas Pn is primarily controlled by light intensity.
Therefore, yield components of tea are the number of plucked shoots per unit land
area (Number of shoot) and the mean weight per shoot (shoot weight). Out of these
two yield components, it is the variation of number of shoot that has the stronger
correlation with yield variation.
Therefore, both Tanton (1979) and Squire and Callander (1981) argued that
assimilate
supply cannot be a limiting factor in yield determination, when harvested yield is

24. ConclusionConclusion
The results indicate that the highest photosynthetic activities were recorded in the
mid elevation at DTRDC, Kurseong.
The rising ambient temperature (Ta) triggers a variety of changes in the atmosphere
leading to modified rainfall patterns, evapo-transpiration rates and VPD. Because of
the close relationships between tea yield and these atmospheric variables, long-
term climate change is likely to cause significant impacts on the key physiological
and developmental processes that determine the yield and yield components of tea.
 Responses to different aspects of climate change can be both positive and negative.
The yield increases due to increasing atmospheric CO2 concentration (Ca) were
augmented by increasing Ta at high altitudes. However, at low altitudes, yield gains
of higher Ca were pulled back because the rising Ta pushed the already high Ta in to
the DTRDC, Kurseong for most of the key physiological processes that determine
yield.
The climate change scenarios specified by different Global Circulation Models also
showed increased yields at higher altitudes, but reduced yields at lower altitudes in
future.

25. Conclusion
 Overall result clearly showed the shade tree favours leaf
photosynthesis rate compared to sunny weather.
 From the result it is clear that under field conditions, light intensity
plays the vital role for leaf photosynthesis and controls the other
factors for the growth of Darjeeling tea cultivation.
 Maintaining tea cultivation regulated under shade tree is beneficial
in terms of reducing temperatures of the tea plant, reducing
excessive transpiration, reducing moisture losses and minimizing
the effects of photoinhibition and thereby maximizing bush health
of tea plants during the long dry period in Darjeeling hill.

26.  Study indicates that water deficit has negative effect on
physiological process, which is clearly expressed through an overall
decline in gas exchange parameters (Pn, E, gs, ψL).
 Due to slow growth of shoots under soil water stress condition,
there is a great decline in green tea yield. Slow growth under
environmental stress is a result of low shoot ψL that affects cellular
turgor pressure which in-turn affect cell growth and division.
 Water stress delays or stops bud break leading to accumulation of
dormant buds in the tea bush. These buds start growing
simultaneously (synchronized bud break) with rain, thus forming a
peak in the crop (rush crop) known as main cropping peak period.
 Low Photosynthetic photon flux density (PPFD) was in rainy and
winter season at high elevation which affect the photosynthetic rate.
 To combat the impact of climate change following strategies can be
adopted : judicious selection of suitable lands for new planting or
replanting, use of drought tolerant cultivars, soil and soil moisture
conservation, soil improvement, organic tea cultivation, crop
diversification, establishment and management of shade trees.

27. Another study was also conducted at Darjeeling Tea Research and
Development Centre (DTR &DC), Kurseong to see the effect of climate
change on production of tea.
As the reason of reduction in yield may not be solely due to climatic change but
there are so many reasons viz. switching over inorganic to organic cultivation
practices, age of tea bushes, density of the plants per unit area, rainfall pattern,
steep slope, removal of upper layer of fertile soil due to the erosion, depth of the
soil etc. may be the major causes behind the gradual declining in production. of
Darjeeling Tea in general and DTRDC in particular.
To accomplish the objective of this study, data on total plantation area
(ha), rainfall, temperature, sunshine hour, relative humidity and green leaf
yield (kg ha-1) of tea for last 20 years were collected from Farm division of
Darjeeling Tea Research and Development Centre, Kurseong.
Results demonstrate that productivity of green leaf in 2012 has reduced
by 41.97 % and 30.90 % as compared with 1993 and 2002, respectively.
Highest productivity of 1974.44 kg green leaf ha-1 was obtained during
1994, thereafter productivity was declined continuously.

28.  Coefficient of determinants indicated that highest variation of
(81.9 %) green leaf yield was due to relative humidity, followed
by total annual rainfall (61.4%) and minimum temperature (13.6
%).
Stronger positive and significant correlations were found
between green leaf yield and relative humidity (r= 0.905) and
total rainfall (r=0.78), whereas average maximum temperature
showed negative correlation (r=-0.287) with green leaf yield.
As the farm of Darjeeling Tea Research and Development Centre
follow the inorganic method of cultivation so there is no question of
yield reduction due to shifting of inorganic to organic cultivation
practices. The probable reason may be due to temperature rise, lack of
total as well as distribution of rainfall and less humidity, through the
influence of these factors on carbohydrate assimilation, respiration,
evapo-transpiration, pest and disease infestation, drought and heavy
rainfall incidence and soil degradation.
It is observed that maximum temperature was rise by 0.510
C over
the last 20 years while 152.50 cm of total annual rainfall and 16.07 %
relative humidity has decreased, leading to overall production
declines.

29. Year Temperature (0C) Relative
Humidity
Sunshine
Hour
Total
rainfall
(cm)
Productivi
ty
Green leaf
(kg/ha)
Minimum Maximum
1993 13.33 19.99 92.71 3.03 439.25 1828.47
1994 13.87 19.69 92.42 3.62 467.87 1974.44
1995 14.88 18.89 91.77 3.61 494.04 1666.42
1996 14.26 18.88 91.17 3.72 425.77 1664.61
1997 14.64 19.24 91.00 3.47 411.81 1658.52
1998 14.53 19.05 90.79 2.96 558.03 1633.57
1999 14.47 19.67 89.92 3.11 400.72 1605.23
2000 12.58 19.31 89.60 2.70 399.71 1598.77
2001 11.02 18.77 89.38 2.95 398.30 1549.83
2002 11.18 18.47 89.21 2.66 387.15 1535.70

30. Year Temperature (0C) Relative
Humidity
Sunshine
Hour
Total
rainfall
(cm)
Productivi
ty
Green leaf
(kg/ha)
Minimum Maximum
2003 10.73 18.10 87.96 2.92 382.93 1496.39
2004 11.48 18.27 86.29 2.83 382.31 1387.85
2005 10.73 19.16 85.98 3.17 367.55 1458.41
2006 10.05 19.92 82.72 3.19 367.36 1365.30
2007 8.38 19.20 82.07 1.59 362.16 1357.41
2008 7.91 19.65 82.00 2.06 334.78 1354.67
2009 8.30 19.63 81.18 2.31 326.88 1353.35
2010 11.16 20.05 78.20 2.78 226.64 1326.44
2011 13.93 20.23 83.36 5.12 242.76 1207.68
2012 14.93 20.50 76.64 5.71 286.75 1061.12
Mean 12.12 19.33 86.72 3.18 383.14 1504.21

31. Tea being a rain fed crop requires certain soil and air
temperature as well as moisture condition for its growth.
It is apprehended that increased temperature and decreased
rainfall pattern observed in Darjeeling region are undoubtedly
going to affect the above conditions posing a threat to the
sustainability of tea crop.
 The probability of pest infestation increases with the increase
in temperature.
Increased temperatures and decreasing rainfall patterns will
influence both the quantity and quality of tea production.
Both excess and shortage of water affect growth of tea
bushes.Tea bush need adequate and well distributed rainfall, but
heavy and erratic rainfall is responsible for damage to tea
plantation in terms of soil erosion, lack of growth due to less
sunshine hours and different types of diseases, besides flooding.

32.  It is an urgent need to critically identify and evaluate options for
adaptation to climate change in future scenarios.
 The following strategies can be adopted to combat the impact of
climate change: (i) Use of Drought tolerant clones: Such as
P312,B157,T78,AV2,RR4/5,TS378,TS379,TS557, TS569. It is believed
that seed plants are more climate resilient than the clonal varieties.
 (ii) Improving farm management practices: Reduction of chemical load
by integrated nutrient management: Integrated nutrient management is
a practice where all sources of nutrients namely organic, inorganic and
bio-fertilizer are combined and applied to the soils. It gives optimum
crop nutrition, optimum functioning of the soil health and minimum
nutrient losses or other adverse effect on the environment.
 Organic farming is highly adaptable to climate change when compared
with the conventional agriculture. Organic agriculture preserves inherent
soil fertility and maintains organic matter in soils which can sustain
productivity in the event of drought, irregular rainfall with floods, and
rising temperatures. Soils under organic management retain
significantly more rainwater due to the 'sponge properties' of organic
matter.

33.  In tea, mulching should be done at the time of new plantations, in
young tea and in mature tea.
 Mulching conserves soil moisture by reducing evaporation losses,
reduces the impact of falling raindrops, surface run-off and soil
erosion, as a result more water can infiltrate into the soil.
 Mulching lowers the soil temperature in summers.
 The most preferred mulching material is Guatemala, Napier grass
or any cut jungle vegetation such as Eupatorium, Ageratum and
Water hyacinth.
 Irrigation: Irrigation in tea can be attempted with one of two
objectives, or with both, it can be used to keep the tea bushes
alive, or to produce early growth when this is prevented by
drought
 Integrated Pest Management: It is a sustainable approach for
managing pests by combining biological, cultural, physical and
chemical tools in a way that minimizes economic, health and
environmental risks.

34.  Crop Diversification: The basic aim remains that if one
crop fails, still some returns can come from the other
crop or as additional returns
 Shade Tree: Shade trees afford some measure of
protection to the tea bushes from hail and wind, besides
reducing temperature. The popular shade tree species
are : Albizzia odoratissima, Albbizzia chinensis, Albizzia
procera, Accacia lenticularis, Derris robusta, Albizzia
lucida, Delberzia sericea, Albizzia lebek, Adenanthera
pavonina, Albizzia moluccana

35. !
Chai piyo mast jiyo !
Thank you