Influence of Size and Shape of Plots on the Precision of Field Experiments with Potatoes

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Abstract
1. A uniformity trial with potatoes was used for investigating the effect of size and shape of plots on the precision of field experiments. Up to a certain limit the S.D. in per cent. of the mean decreases when the size of plots is increased; further increase of plot size increases the errors as a lesser part of the soil variation can be removed. 2. Two-row plots show less variation than either 1 or 3-row plots. This may be explained by row competition. 3. When the area to be used is fixed, smaller plots are more efficient than larger, owing to the greater number of replications in the former case. One exception occurs in the case where border rows are not harvested; here 4-row plots are more efficient than 3-row plots, owing to the fact that a larger part of the soil is included in the calculations when 4-row plots are used. 4. Long and narrow plots are more efficient than shorter and wider of the same size. The only exception is again explained by row competition. 5. In field experiments with potatoes fairly large plots should be used; at least 2 rows wide and preferably long and narrow strips.