Uniformity Trials: Variation and Correlation in the Yield of Wheat

Abstract

There has been much interest in examining the effects of possibly correlated errors among plots in agricultural field trials. Many uniformity trials have been conducted to investigate this aspect. In these trials, every plot receives the same treatment. Two well-known experiments of this kind are those of Mercer and Hall (1911) and Wiebe (1935). Their data have been used extensively in other investigations; see, for example Barbacki and Fisher (1936), Besag (1974) and Wilkinson, Eckert, Hancock and Mayo (1983). Further, Fairfield Smith (1938) discussed these and other uniformity trials and determined an empirical relationship between variance of yield as a function of plot size of field experiments and plot to plot correlation. Papadakis (1937), Bartlett (1938, 1978, 1981) and Wilkinson et al. (1983) discuss methods for adjusting the analysis of field experiments by using the yields of neighbouring plots.