Performance of Randomized Block Designs in Field Experiments
1993
Lin, C.S. | Binns, M.R. | Voldeng, H.D. | Guillemette, R.
Successful application of randomized block design in field experimentation depends on whether the blocking is done properly with respect to the direction of soil variation, and on whether plot variability within blocks is homogeneous. To investigate to what extent the first problem (orientation) causes inefficiency in the design, 60 sets uniformity trial data of soybean [Glycine max (L.) Merr] yield were used to investigate soil variation in one and two directions. The results show that the total sum of squares of soil variation attributable to one direction (taking the direction of the larger variation of row or column) was 39.3%, and to two directions was 52.7%. The difference of 1.3.4% reflects the fact that the blocking was not perpendicular to the direction of the soil variation. To study the second problem (heterogeneity within blocks) two sets of soybean data were used to compare various statistical techniques, namely:. (i) lattice design and analysis, (ii) fitting constants by position effects of rows and columns, (iii) covariate analysis by plot number, and (iv) neighbor analysis. The general conclusion is that when variability within blocks is homogeneous, a randomized block is satisfactory. However, if the plots are heterogenous then ceanalyzing the data by (ii) does reduce the error, but the average variance of difference is not as good as the standard (lattice) design, (i). In contrast, the analyses by (Hi) and (iv) can result good precision as by lattice design. Contribution no. R-089 from the Research Program Service.
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