Climatic variability and small cardamom (Elettaria cardamomum Maton) production across the Westren Ghats

Abstract

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.