The distributions of tuber sizes in droughted and irrigated crops of potato. II. Relation between size and weight of tubers and the variability of tuber-size distributions

Summary

Tubers from six cultivars of potato grown in irrigated and droughted conditions were examined to show whether observed differences in grade distributions were simple consequences of differences in yield or were the results of changes in tuber shape or in the relative variability (Rv=σ/μ) of the distributions.

Differences in tuber shape, indicated by the relations between tuber size (mm) and weight, were statistically significant but were insufficient to cause measurable changes in the grade distributions.

There was a range of values of Rv but drought had no statistically significant effect on Rv and may only affect it by influencing the numbers of tubers set.

The main effect of drought on the distribution of tuber sizes was through its effect on total yield and hence on mean tuber size. Yield and number of tubers define a unique tuber-size distribution regardless of the soil moisture stress experienced by the crop.