The variability interference was verified on the estimates of the values used to determine the plot size with simulations of different numbers of plants per plot and groupings of harvests. Three experiments were performed with the tomato crop in the winter/spring of 2007, accomplished in Santa Maria, Rio Grande do Sul State, Brazil. In two of the experiments we used a plastic tunnel, with drip irrigation, black mulching of PEDB, three lines with 24 plants per row, spacing between plants of 0.8 m and between rows of 1.2 m and a plastic greenhouse in the third experiment, 24 m long and 10 m wide in eight cultivation rows. Cultural practices were carried out as recommended for the culture, being applied concurrently in all experiments. The sequence of two, three and four plants in the crop line formed the plots of two, three and four UB of size. Analyses were accomplished considering only individual and combined harvests. For each one of the three experiments, the estimates of the variance, the variation coefficient and the index relative information had been obtained. The Bartlett test was applied among the variances of the individual and combined harvests in each size of simulated plot to verify the homogeneity among the variances. The variances, among the grouped harvests were homogeneous, considering the grouping of six harvests. There were some increases in the estimates of the average and in the variance of the fitomass of fruits when the size of the plot and/or the number of grouped harvests was increased. The arrangement of four plants in the cultivation rows, combined with grouping of six in six crops reduce the variability.
Lycopersicum esculentum L.; experimental precision; horticulture; protected environment; plot size
