
Determination of optimum plot size and shape has been regarded as an important and useful area to measure soil heterogeneity in field experiments. The smith’s heterogeneity index method assumes the condition of independence of observations but often this condition of independence of observations does not satisfied. In this paper, we propose a method of determination of heterogeneity index using semivariances instead of variances used in smith’s method. The main advantage of semivariogram technique is it considers magnitude and direction of heterogeneity in field experiments. The heterogeneity index calculated using semivariogram technique and Smith’s technique is 0.17 sand 0.24 respectively and corresponding optimum plot size (〖 x〗_opt) is 4.5 m2 and 7.1m2.