Experimental design and precision in trials with black oat, common vetch, and forage turnip intercropping

Abstract

The objective of this study was to determine the optimal plot size for evaluating the fresh matter of black oat (Avena strigosa Schreb), common vetch (Vicia sativa L.), and forage turnip (Raphanus sativus L.), grown in intercrop, in scenarios formed by combinations of treatments numbers, repetitions numbers, and experimental precision levels. Six uniformity trials were conducted with the consortium of black oat, common vetch, and forage turnip, with three trials evaluated at 84 days after sowing (DAS) and the other three trials at 119 DAS. Fresh matter was assessed in 216 basic experimental units (BEU) of 1 × 1 m (6 trials × 36 BEU per trial). The heterogeneity index of Smith (1938) was estimated. Plot size was determined by the method Hatheway (1961) in scenarios formed by combinations of i treatments (i = 5, 10, 15, 20, and 25), r repetitions (r = 3, 4, 5, 6, 7, 8, 9, and 10), and d precision levels (d = 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20%). To evaluate the fresh matter of black oat, common vetch, and forage turnip, in intercropping, with 5 to 25 treatments and with six repetitions, plots of 15 m² of usable area are sufficient for differences between treatments of 12% of the overall average of the experiment to show differences at the 0.05 level of significance.