Estimation of Optimum Field Plot Size and Shape in Paddy Yield Trial

The present study was designed to estimate the optimum plot size with the shape for field research experiments on paddy yield trial considering the effect of plot size on variability in yield of crop as well as studying the coefficients of variation of different plot sizes and shapes of plots. The Smith’s index of soil heterogeneity was computed to estimate optimum plot size and shape using yield data of the 12m×24m recorded separately from each basic unit of 1m×1m (288 basic units). Soil productivity contour map described graphically the productivity level of the experimental site. The index of soil heterogeneity (b = 0.491) indicated a degree of low similarity among the experimental plots. Variance per unit area and coefficient of variation decreased rapidly with an increase in the plot size. Based on the coefficient of variation the optimum plot size for paddy yield trial was estimated to be 6m×12m with rectangle shape for Rice Research Institute, Kala Shah Kaku, Lahore. This estimated plot size is larger than the plot size of 3m×5m generally used for paddy yield in the study area.