Pakistan Journal of Meteorology Vol 2: Issue 4: (Nov, 2005) 3 STUDIES ON THE EFFECT OF SATURATION DEFICIT ON THE YIELD OF TEA Md. Jasim Uddin 1 , Md. Rafiqul Hoque 2 , Mainuddin Ahmed 3 , J. K. Saha 4 Abstract: The study was done to see the effect of saturation deficit on the yield of tea during the production period (April-October) in 2003. The meteorological data were averaged on 7 day interval to correlate the yield and saturation deficit which was also collected in 7 day interval. From the study it was found that saturation deficit (SD) has negative effect on yield of tea. The correlation coefficient between them is r =-0.77 which was statistically significant at 95% level of significance. Moreover effect of saturation deficit (SD) on evaporation was also studied. The study showed the positive correlation between SD values and evaporation also this was statistically significant at 95% level of significant. There was no significant relationship among saturation deficit, rainfall and evaporation. Introduction: Saturation deficit is the difference between the actual vapour pressure of the moist air sample at a given temperature and the saturation vapour pressure corresponding to that temperature. It may be called dryness of the air. It is one of the important climatic variables which determined the potential growth of plant (Stepens, Othieno & Carr 1992). It is the difference between the pressure exerted by the water vapour actually present in the atmosphere at a given time and given temperature and the pressure that would be exerted if the atmosphere were saturated with water vapour at the same temperature (Weaver and Clements, 1973). Temperature is the major environmental factor affecting shoot growth and photosynthesis, hence closely linked to the influence of temperature is the influence of large saturation deficit. Squire (1979) in Malawi showed the adverse effect of high saturation deficit on shoot growth of tea. Dry air can result in minimum shoot water potential at midway even when soil moisture is close to field capacity. Carr (1992) identified a critical mid day value, 2.0 kPa beyond which 1 Assistant Professor, Department of Tea Technology, Shah Jalal University of Science and Technology, Sylhet-3114, Bangladesh. 2 Professor, Department of Irrigation & Water Management, Bangladesh Agricultural University, Mymensingh, Bangladesh 3 Principal Scientific Officer, Bangladesh Tea Research Institute, Sreemangal, Moulvibazar, Bangladesh. 4 Principal Scientific Officer, Bangladesh Tea Research Institute, Sreemangal, Moulvibazar, Bangladesh.