Optimizing Plot Size for Field Studies of Phymatotrichum Root Rot of Cotton

Publisher Website
Google Scholar
Abstract
A study was conducted to determine the effect of plot size on the variance and mean percent disease incidence in field studies of Phymatotrichum root rot [Phymatotrichum omnivorum] of cotton. The variance among samples areas (.sigma.2) and within plots (.sigma.2), the coefficient of variation (CV), and the mean of percent disease were systematically evaluated. Measurements were made in 1983 at 3 locations in the Blackland Prairie that differed in respect to disease incidence. Plot sizes ranged from 5.5-88.0 m2. The .sigma.2 and the respective CV were reduced by increasing the sizes of the smapling area. Minimum plot sizes of 33 m2 (i.e., 3 rows .times. 16 m or 2 rows .times. 24 m) were necessary to estimate the true mean. However, when plot size was held constant, the .sigma.2 and associated CV was lower when plots had a greater number of adjacent rows compared to increased row length. This occurred irrespective of location or level of disease incidence. Because the .sigma.2 was not reduced further when plot size exceeded 33 m2, that minimum plot areas of 33 m2 (i.e., 3 rows .times. 16 m) are required to give the best estimate of the true mean and to provide the lowest variance in field experiments of Phymatotrichum root rot on cotton.

This publication has 1 reference indexed in Scilit: