Plot size and experimental precision in wheat trials in no-tillage system

Abstract

The aim of this paper was to estimate the optimal plot size using different methods and to verify the possible precision in experiments with wheat in no-tillage system for spike number, spike weight, and kernel weight. Two uniformity trials were carried out in 2003 and 2004, with the purpose of evaluating basic units formed by two .0 m long lines organized in twenty four 2 m long rows by twelve l.0 m long columns for planning different plot sizes. The ideal plot size was estimated by the methods of the modified maximum curvature (LESSMAN & ATKINS, 963 and MEIER & LESSMAN, 974), maximum curvature as a function of the variance and of the variation coefficient (THOMAS, 974). The number of replications and the significant minimum difference between treatment means for different combinations between treatment number and plot size (HATHEWAY, 96). The experimental plot size for wheat in a no-tillage system should be between 0.74 m² and 4.06m² for number of spikes, 0.69 m² and 2.64 m² for weight of spikes and 0.89 m² and 6.48 m² for grain yield so to obtain the minimum percentage difference among means to observe significances of up to 4.2, 4.6, and 7.5% for the respective variables. Additional keywords: Triticum aestivum, soil heterogeneity index, replication number, experimental plans