The aim of this study was to estimate the optimum block size with the shape for field research experiments. A uniform crop of Indian mustard (Brassica juncea L.) variety RH-749 was raised during 2013-14 rabi season over an area of 48m × 48m (2304 basic units) at Research Farm of Oilseed section, Department of Genetics and Plant Breeding, CCSHAU, Hisar, Haryana, India. The harvesting of crop was done in small units each of size lm × lm (1m2). The blocks of sizes 4, 6, 8, 12 and 24 plots with various shapes, for different plot sizes were considered. The coefficient of variation (CV) decreased from 10.66 to 3.89 with the increase in block size from 4 to 24 , indicating that as the block size increased, homogeneity within the block also increases and the blocks elongated in E-W direction were more effective in reducing error variation than those elongated in N-S direction. It was also observed that C.V. without blocking (20.04) was much higher in comparison with the C.V. with blocking (3.89), thus indicating that blocking was beneficial in reducing error variation. The 24 plot blocks were found to be most efficient with 12m × 2m block shape. Rectangular blocks are also advisable either when the experimenter does not have any idea about the fertility pattern of the experimental area or when border effects are large.
Blocking, Efficiency, Optimum block size, Optimum block shape, Uniformity trial
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