Tamanho ótimo de parcela para avaliação do rendimento de grãos do girassol

The aim of this study was to determine the appropriate size of plot for evaluation of grain yield of sunflower. An experiment in randomized complete block design with 14 cultivars of sunflower and 10 replications was conducted in the period of May to July 2011. The plots consisted of four rows of 6 m in length, spaced 0.7 m and 0.3 m between plants. The useful area of the plot, consisting of the two central rows was divided into 12 basic units (UBs), each consisting of three plants in the row, the yield of sunflower per basic unit was determined. Grain yield of adjacent UBs were grouped to form 7 types of plots of five different pre-established sizes. The optimum plot size was estimated by the methods of modified maximum curvature (3.74 m2) and the segmented linear model with plateau (2.48 m2), with the size of 3.74 m2 of floor area considered suitable for assessment of grain yield of sunflower and less than the size generally used in research with sunflower.