The relation of size, shape, and number of replications of plats to probable error in field experimentation

Altho large numbers of experiments that attempt to measure small variations of characteristics in variety tests or slight differences resulting from unlike soil treatments or tillage operations are conducted each year, comparatively little attention has been given to the establishment of uniform methods that will reduce the error in such experiments. When we consider that the differences which the tests are expected to disclose are only too often smaller than the probable error of the methods used, the need for attention along this line becomes strikingly evident. It has been demonstrated repeatedly that even soils which possess apparent uniformity really vary a great deal. This variation is often so great as to cast doubt on a large portion of published field experiments when yield is primarily involved. The experimental error arising from soil variation is influenced by the size and shape of plats and by the number of replications. To determine the effect of these factors on experimental error is the purpose of this investigation.