Variation in the yields of fruit trees in relation to the planning of future experiments

does not appear. First page follows. The yields resulting from field trials have, in many cases, indicated the varying responses of plants to soil conditions which appear to be independent of the considerations of the trial. These normal fluctuations in yield constitute a source of experimental error to which all field trials are subject. They are of such importance that they must be taken into account in the planning of such experiments, as well as in the interpretation of the results. In orchard trials such errors may be especially large. The great variation observed is due, in part, to the relatively large area of land involved in a single experiment, with the attendant possibilities of important changes in soil and topography. It is also due in some degree to the individuality of the trees. These two classes of factors ordinarily increase the observed variations greatly above those found in experiments with agronomic crops, for in the latter the use of a large number of plants in a single plot results in practical elimination of the effects of individual plant variation. In addition, the relatively small size of the plots permits them to be located on a small area of land.