The Influence of Climatic Factors on the Yield of Tea in the Assam Valley

An attempt has been made in this paper to study the effect of climatic factors on the growth of annually pruned tea and its components, the early crop, during April to June, the main crop during July to September and the late crop during October to December in northeast India. Data from two sources have been considered in this study, (i) long-term crop and weather data from the Tocklai experimental station and (ii) short-term data from tea-estates where the rainfall distribution is similar to that at Tocklai. A multiple regression of the yield of tea during a season on a number of independent climatic variables and age was fitted by the method of least squares and the independent variables were reduced step by step by the method of backward elimination until a set of critical variables associated with yield were obtained. Of all the climatic factors at Tocklai, rainfall up to 18 cm and the rise in mean temperature during the cold weather, i.e., January–March, proved most beneficial to the early crop which in turn led to an increase in the main crop. There was also some direct beneficial effect of January to March rainfall on the main crop. Increase in rainfall during January to March proved more beneficial to the crop when the mean temperature was high than when it was low. Analysis of the crop-weather data from the estates generally supported the above findings.