Summary
Methods of estimating Smith's b and, thereby, optimum plot size are compared from a theoretical viewpoint. For estimating b, generalized least squares is recommended over Smith's (1938) original method and other methods because the points used to fit the required regression are correlated and have unequal variances.
Optimum plot size for once-over-harvest trials measuring yield (as number of fruits per plot) of pickling and frest-market cucumbers (Cucumis sativus L.) was estimated to be 0.7 to 3.8 m2 (0.5 to 2.5 m of row for rows 1.5 m apart) for conventional harvesting, and 1.0 to 5.6 m2 (0.7 to 3.7 m of row) for simulated harvesting using paraquat to defoliate plots before evaluation. Estimates of optimum plot size were calculated from a number of uniformity trials differing in year (1982 or 1983), planting date (early or late), and field. The estimates were sufficiently stable to suggest that they have useful generality.
For multiple-harvest yield trials, optimum plot sizes for determining yield of pickling (expressed in $/ha or q/ha) or fresh-market cucumbers (i.e. USDA Fancy and No. 1 grade fruit combined or USDA Fancy, No. 1, and No. 2 grade fruit combined, in q/ha) were estimated from experimental data to be 6.4 to 10.3 m2 (4.3 to 6.8 m of row).
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Swallow, W.H., Wehner, T.C. Optimum plot size determination and its application to cucumber yield trials. Euphytica 35, 421–432 (1986). https://doi.org/10.1007/BF00021850
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DOI: https://doi.org/10.1007/BF00021850