Browsing by Author "Kularatne, J.D.J.S."

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    Assessment of Climate Variability for Coconut and Other Crops: A
    (2008) Peiris, T.S.G.; Kularatne, J.D.J.S.
    Public opinion in Sri Lanka has been seriously concerned about the possible impact of climate change on different sectors, and in particular for the agricultural sector. Annual and weekly climate data were analyzed to provide useful information to farmers, planners and scientists to assess the suitability of different types of crops. The statistical methodology of the analysis is illustrated using daily rainfall and air temperature from 1951 to 2001 for Hambantota, a major coconut growing district in Sri Lanka. The increase in maximum air temperature and decrease in the amount of rainfall per effective rainy day ( > 5mm) are the significant features of the climate variability in the Hambantota area. The warming rate for maximum air temperature was significantly higher (p<0.005) than that for minimum, mean and diurnal temperature, irrespective of time scales. The annual rate of increase of maximum temperature after 1995 is 0.026°C. The intensity of rainfall per effective rainy day (> 5mm) decreased significantly (p< 0.005). Distribution of weekly rainfall during January to September is uncertain. The probability of weekly rainfall greater than 20 mm does not exceed 50% in any week during this period. Long-term weekly rainfall was greater than 30 mm only during mid October to early December, but the probability of weekly rainfall greater than 30 mm exceeds 50% only during the first three weeks of November. The probability of occurrence of dry spells of duration greater than 60 days in a year is around 70%, but the time of occurrence of such dry spell is not consistent among years. These findings suggest that the expected future climate would not be suitable for coconut cultivation, if growers do not apply the recommended practices to face long dry spells. Also the increasing temperature could impact to dominate plant pest during dry periods.
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    Impact of Covariate on Single Palm Plot Experiments in Coconut
    (2008) Kularatne, J.D.J.S.; Peiris, T.S.G.; Samita, S.
    The most robust design in field experiments of coconut is the randomized complete block design (RCBD) with plot size of six palms. It has now become a serious problem in finding homogenous blocks for experiments in coconut and therefore a single palm plot has been recommended by the authors. This study found that single palm plot with covariate as pre yield data is the most suitable method to reduce the unknown variability of coconut palms based on analysis of data of seven concluded field experiments on cultural management and fertilization of coconut with plot size of six palms. The percentage reduction of CV in single palm plot with covariate with respect to single palm plot without covariate varied from 21% to 60% irrespectively location, period and type of the experiment. The percentage reduction of CV in single palm plot with covariate with respect to six palm plots without covariate was 40% to 71%. Thus single palm plot is recommended for field experiments in coconut except under special circumstance such as for coconut based farming system trails (CBFS).The methodology developed to select single palm from the concluded experiments with plot size more than one can easily be applied for similar studies in other tree crops.