Comment—Enhanced heritabilities and best linear unbiased predictors through appropriate blocking of progeny trials 1 E.R. Williams and Y.-B. Fu In a recent article in the Canadian Journal of Forest Research (Ericsson 1997) discussed the use of postblocking in the analysis of progeny trials. We would like to comment on three aspects of this paper: (1) Postblocking The idea of postblocking a trial is well known and has been used to advantage by Patterson and Hunter (1983) as a means of studying the nature of spatial variation at trial sites. A more detailed assessment of postblocking was carried out by Ainsley et al. (1987) who supported earlier views that “the technique is not without problems. ” For example, Pearce (1983, p. 294) has warned that estimates of error may be biased with postblocking. We strongly recommend that designed experiments be used in the first instance. This is particularly the case since suitable incomplete block and row–column designs are available for a wide variety of field conditions. The power and availability of modern computers have encouraged the development of effective software packages for the generation of suitable designs for most practical situations. For example, the software package CycDesig
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