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Comparative experiments with field crops
272 FIELD CROP EXPERIMENTS
Comparative Experiments with Field Crops. G.V. Dyke. Butterworth, London, 1974, 211 pp., £5.50. This book presents and explains the principles of planning and performing experiments on field sites and of analysing the observational data. It is meant for agricultural, horticultural or related activities. Its usefulness in systems ecology is obvious. Sampling procedures, testing sites for uniformity, marking out the area and the plots, doing the several operations one block at a time, counting, taking sub-samples and the addition of extra independent variates will be recognized by experimenting ecologists as the normal elements of their work. They are presented with many specific recommendations. Precautions are summed up: (a) in cases of non-homogeneity of errors, (b) for avoiding dangers of multiple regressions and (c) if few degrees of freedom are left after fitting regressions. A few appendices provide some very useful recommendations for rounding off, for calculating square roots, for using direct recording balances, for checking statistical calculations and for finding, in the form of a glossary, a number of definitions, but also for looking up more suggestions and warnings. With some imagination an experimenter could adapt a number of other recommendations to the special requirements of experiments on ecosystems. The analysis of covariance will be especially helpful in separating responses to experimental treatments imposed on systems of this kind, from responses to chance differences in other variates. Some of the special features of ecosystem research, such as the long term life of experiments, the very marked edge effects and the absence or scarcity of replications, have received no special elaboration. Moreover, the subject of representativeness of experimental sites and observations, so as to obtain results that can be generalized far enough, is not dealt with. Analysis of time series, which will usually show up in ecological research, is not among the author's objectives. Hopefully, readers will not take the subject matter of the book with the same light-heartedness as some of the author's injections suggest. The book is worthy indeed of serious reading and re-reading. G.J. VERVELDE ( Wageningen, The Netherlands)
Comparative Experiments with Field Crops. G.V. Dyke. Butterworth, London, 1974, 211 pp., £5.50. This book presents and explains the principles of planning and performing experiments on field sites and of analysing the observational data. It is meant for agricultural, horticultural or related activities. Its usefulness in systems ecology is obvious. Sampling procedures, testing sites for uniformity, marking out the area and the plots, doing the several operations one block at a time, counting, taking sub-samples and the addition of extra independent variates will be recognized by experimenting ecologists as the normal elements of their work. They are presented with many specific recommendations. Precautions are summed up: (a) in cases of non-homogeneity of errors, (b) for avoiding dangers of multiple regressions and (c) if few degrees of freedom are left after fitting regressions. A few appendices provide some very useful recommendations for rounding off, for calculating square roots, for using direct recording balances, for checking statistical calculations and for finding, in the form of a glossary, a number of definitions, but also for looking up more suggestions and warnings. With some imagination an experimenter could adapt a number of other recommendations to the special requirements of experiments on ecosystems. The analysis of covariance will be especially helpful in separating responses to experimental treatments imposed on systems of this kind, from responses to chance differences in other variates. Some of the special features of ecosystem research, such as the long term life of experiments, the very marked edge effects and the absence or scarcity of replications, have received no special elaboration. Moreover, the subject of representativeness of experimental sites and observations, so as to obtain results that can be generalized far enough, is not dealt with. Analysis of time series, which will usually show up in ecological research, is not among the author's objectives. Hopefully, readers will not take the subject matter of the book with the same light-heartedness as some of the author's injections suggest. The book is worthy indeed of serious reading and re-reading. G.J. VERVELDE ( Wageningen, The Netherlands)