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S. Samita
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Control of spatial effects due to neighboring palms in coconut (Cocos nucifera) experiments T. S. G. Peiris; P. Waidayaratne; S. Samita; O. Thattil
International Coconut Community Journal Vol 23 No 2 (2007): CORD
Publisher : International Coconut Community

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37833/cord.v23i2.166

Abstract

The RCBD is the most robust design for field experimentations in coconut. In this study the effect of neighboring palms to control local variation in field experiments of coconut was evaluated using two long-term coconut trials. Four types of spatial models are suggested to consider the spatial effect due to neighboring palms and the use of such models is illustrated using two long-term field experiments. When data were analyzed separately by years or using repeated measures analysis, significant percentage reduction of CV was observed in all four spatial models relative to the RCBD model without covariates as well as pre-treat data as covariate irrespective of the experiment. Inclusion of the mean of two neighbouring palms in N-S or E-W direction as a covariate was clearly superior to the RCBD without covariate as well as pre-data as covariate when data were analyzed separately by years. Inclusion of the mean of four neighbouring palms in N-S and E-W direction as a covariate was superior to repeated measures analysis in reducing local variation, irrespective of experiments. It is recommended to include effect due to neighbouring palms when analyzing field experiments in coconut. The methodology can be applied to other tree crop experiments as well.
Impact of Covariate on Single Palm Plot Experiments in Coconut J. D. J. S. Kularatne; T. S. G. Peiris; S. Samita
International Coconut Community Journal Vol 24 No 2 (2008): CORD
Publisher : International Coconut Community

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37833/cord.v24i2.549

Abstract

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.
Co-Authors J. D. J. S. Kularatne O. Thattil P. Waidayaratne T. S. G. Peiris