MSc

A study was undertaken at the Department of Agricultural Meteorology,
College of Horticulture, Kerala Agricultural University, Vellanikkara to analyse the
variability of rainfall and surface air temperature over a period of time and its
influence on the cardamom production and productivity across the Western Ghats for
which the monthly data on rainfall, temperature (maximum and minimum) and
nutritional status of soils were collected from six selected locations across the
cardamom tract along with the data on area and production of small cardamom.
The annual rainfall and rainfall during southwest monsoon (J une-Sep)
increases from south to north across the cardamom tract and western parts (Kerala
and Karnataka) of the Western Ghats receive better rainfall when compared to that of
eastern parts (Tamil Nadu). The reverse trend was noticed during post monsoon (Oct-
Nov) and winter (Dec-Feb) and eastern parts receive more rainfall than western parts.
In summer (Mar-May), Kerala and Tamil Nadu receive relatively more rainfall than
Karnataka. Trend analysis in rainfall revealed that a declining trend was noticed in
annual rainfall at all the locations except Pampadumpara and Madikeri. Similar was
the case during southwest monsoon except at Madikeri. In other seasons, no such
uniform increasing or decreasing trend was noticed across the cardamom tract except
at Thandikudi, where rainfall was declining in all seasons.
The surface air temperature and its range were high (5.3 -15.9° C) over
Karnataka, followed by Kerala (5.2 -11.7° C) and Tamil Nadu (6.9 -10.7 ° C). In
majority of the locations, an increasing trend in annual maximum temperature was
noticed. It was true in the case of southwest monsoon and post monsoon periods
while a declining during winter and summer. Interestingly, an increasing trend was
noticed in majority of the locations in the case of minimum temperature. It reflected
on the temperature range also at fifty per cent of the locations (Pampadumpara,

Madikeri and Thandikudi) during southwest and post monsoon seasons. It was
reverse during winter and summer at all the locations except Saklespur and Mudigere.
The study on the trends in moisture index (Im) showed that it declined at all
the locations during southwest monsoon and annually except at Madikeri. During
post monsoon and winter, an increasing trend in moisture index was noticed at all the
locations except Thandikudi in post monsoon period. All the locations except at
Pampadumpara, showed a declining trend in moisture index during summer. It was
also noticed that the intensity of aridity was high towards north of cardamom tract.
Studies on agroclimatic zonation of small cardamom revealed that the
production potential of Zone I was relatively better (>200 kg / ha) when compared to
that of Zone II and III across the Western Ghats, where the length of crop growing
season was more than 300 days with annual Ima of more than 90 per cent. In
addition, the annual temperature range was very low and optimum across the Zone 1.
The production potential of small cardamom was low (100-150 kg / ha) over Zone III
(Karnataka), where the length of crop growing season was less than 250 days with
annual Ima of 70-75 per cent. The annual temperature range was also high, which
may be detrimental to cardamom production in the Zone Ill. The Zone II fall under
intermediary category (150-200 kg / ha), where the length of crop growing season
was more than 250 days with annual Ima varied between 80 and 85 per cent.
From the crop weather relationship studies, it was understood that the
rainfall from December to May, annual temperature range and temperature range
during southwest monsoon could explain up to 78 per cent variability in cardamom
production. It was also noticed that cardamom production was high whenever the
annual water deficit was low and vice-versa.