Optimum Plot Size and Number of Replicates to Evaluate the Yield of Sweet Potato in Uncovered Soil and Mulch

This study aimed to determine the optimal experimental plot size and the number of repetitions to evaluate the yield in sweet potato, cultivated in uncovered soil, and soil covered with mulched plastic. Two uniformity trials were performed simultaneously, in uncovered soil or with black plastic and mulch coverage, both without irrigation. The planting density was 2.5 plants m-2. Two plots of 120 plants were established, and each plant was defined as a basic unit. The sweet potato variety used was ` RBS Cuia'. The plot size was determined by the method of maximum modified coverage and the segmented linear model with plateau response. The number of repetitions was estimated based on the minimum significant difference by Tukey test (p = 0.05). The average values of yield in uncovered soil and soil covered with mulch were 0.50 and 1.07 kg plant(-1), respectively. The coefficient of variation showed greater variability dispersion in uncovered soil conditions. Between the two methods used to determine the plot size, a difference of 2.0 and 1.6 basic units with mulch and in bare soil, respectively, was found. The optimal experimental plot size with mulch and in bare soil was 12.5 m(2) and 32.5 m(2), respectively. The number of repetitions to determine 50 % minimum significant difference with and in bare ground was 9 and 12 repetitions, respectively, up to 30 treatments.