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ThesisItem Open Access Trends in production and bienniality of coconut (cocos nucifera L.) var.wct.(Department of Agricultural Statistics, College of Agriculture, Vellayani, 2018) Fallulla, V K; Vijayaraghava KumarThe study entitled "Trends in production and bienniality of coconut (Cocos nucifera L.) var.WCT" was carried out based on data on the number of nuts harvested from 525 WCT palms planted in 1966 at Coconut Research Station, Balaramapuram with its five to six harvests per year, for a period of 25 years viz. 1993 to 2017. The objectives of the study are to identify the extent of bienniality, variations in repeatability and type of yield fluctuations over years and over different harvests. The effect of meteorological factors like rainfall, number of rainy days, maximum and minimum temperature and wind velocity of the above period also formed part of this study. Initial data analysis using box plot technique was carried out to remove the outliers present in the data. The number of nuts produced by a palm in an year was found to be 68.5 with an overall standard deviation of 37.83 nuts. A plot of the average number of nuts produced in an year against the growing periods showed a steady decrease in yield from 2012 onwards (i.e. after 50 years of planting). Preliminary statistical analysis by applying Analysis of variance (ANOVA) for the number of nuts produced by individual palms revealed high significant difference between different palms with respect to each harvest and also with respect to each year. Pearson’s correlation coefficient between yield data of different harvests in an year as well as previous years were estimated and a significant correlation were observed for the previous harvest and rest of the coefficient were non significant. Statistical tools in respect of graphical, parametric and non parametric approaches were tried as an attempt to detect and quantify the biennial bearing tendency. Graphical approach confirmed biennial bearing tendency among different years as well as among different harvests. The parametric study was carried out using orthogonal contrasts developed by Saraswathi (1983). This method used four F ratios F1, F2, F3 and F4 , the significance of which provide biennial tendency and time-trend each for four year periods. F1 ratio is used to test the biennial tendency under the assumption of absence of time trend and then confirmed by F2 ratio. F3 is used to test time trend effect under the assumption of absence of biennial effect. This assumption confirmed by F4 ratio. For the period 1997-2000, F1 was found to be significant at 5 per cent level indicating biennial tendency for this period in the absence of time trend, which was then confirmed using F2 criterion. But this method didn’t confirm bienniality for other periods The non parametric approach using biennial bearing index ‘B’ (Hoblyn et al., 1936) was made for the period of 1993-2017. The ‘B’ factor was based on 23 pairs of successive signs positive or negative indicating fall or rise in yield over continuous years for each of the palms. A test of significance of bienniality was obtained by calculating the binomial probabilities. Number of successive change in signs of 16 or above for this period indicate significant departure from the equiprobable hypothesis. Therefore a palm showing a B factor equal to or higher than 16/23 can consider as significantly biennial in bearing; and on this basis 41.1 per cent of the palms were found to be biennial in bearing. Intensity or degree of crop fluctuations was measured by the ‘I’ factor (Hoblyn et al., 1936). All palms showed an intensity of crop fluctuations less than 50 per cent; of which in 81.8 per cent, the intensity ranged from 20 to 30 per cent. A zero percent ‘I’ indicates regular bearing or no alternate bearing behavior. Regular bearing was not observed for any of the palms. 100 per cent I indicates strict alternate bearing behavior. No palms were found to be strict in alternate bearing also. Maximum number of palms were found to exhibit the biennial bearing pattern but are not strict ( 100 per cent) in bienniality. Spearman’s rank correlation coefficients were calculated for all 23 pair of alternate years and all 24 pair of adjacent years. For palms possessing biennial tendency the coefficients for alternate years should be higher than that of adjacent years and this is tested by rank sum test (Z). The Z value was found to be non significant for the period 1993-2017 indicating no strict alternate bearing behavior in the selected palms. As production is found to be in a a steady decrease from 2002 onwards ‘Z’ is separately estimated for the period 1993-2001, and found to be significant for this period indicating alternate bearing behavior for this period. Repeatability was estimated for number of nuts per tree using ANOVA estimator for different periods. While considering the whole period 1993-2017 and 2013-2016 repeatability coefficient was very low 0.13 and 0.06 respectively with variances 0.00015 and 0.00052 respectively. High estimate of repeatability, 0.397, 0.355 respectively were observed for the period 1993-1996 and1997-2000. Correlation between climatic factors in the current year, previous year, two years before and three years before with the production of nuts for the current year were estimated and were not significant except for the minimum temperature of the current year. It indicated that the parameters of annual climatic factors were not adequate to explain the temporal variation in yield. However Correlation between number of days without rain in summer (dry spell ) and yield in succeeding season of next year was found to be -0.43 which is negatively significant, showing this factor will inversely affect the yield of the next harvest. Bienniality also found to be not directly influenced by the climatic factors. A linear regression model with high R2 value, 0.98 were fitted with current year yield as dependent variables and previous year yield, Number of trees in the ‘on’ phase, Rainy days and Wind velocity as independent variables.