Effect of Rainfall Abnormalities on Rice Yield in Hambanthota District, Sri Lanka
Keywords:Rain fall distribution, Rice yield, Crop seasons, Climate change
AbstractThe sown area is continuously being increased in Hambanthota district; the rice production has not fulfilled its expected optimum yield. As the agriculture is mainly based on the rainfalls received to this region, the sentiment of the farmers on this matter is the shift of the crop season due to the climatic consequences. However, no proper scientific investigation has been done to see whether the rainfall pattern and intensity has changed. Neither future projection is available. Therefore, there is an urgent need to study the shifting the rainy seasons to re-determine the crop season in order to enhance the rice production in the district. It was collected available monthly rainfalls data for three stations called Hambanthota, Tissamaharama and Mamadala from 1869 to 2010. The recent data related to the rice production and cultivated area was obtained for last six years. Changes of the rainfall data were analyzed with the help of SPSS 16.0 and trends, percentage attainment of rainfalls during the Yala, and Maha seasons were calculated. It is clear that the expected yield has not been attained, though it receives 61.7%, 68.4% and 61.2% of the annual rainfall in Hambanthota, Tissamaharama and Mamadala respectively during the Maha season. The trend of mean annual rainfall moves along a steady line for next two decades. There is not a significant spatial variation (p>0.05) of the rainfalls among three different stations as well as monthly rainfall data over the last century in Hambanthota district. Since there is not a significant shift of rainy season, the reduction of expected rice yield cannot be introduced as a cause of an abnormality in rainfalls in the district.
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