Analytical and empirical relationships are established among parameters of spatial interactions among plants (Mead's coefficient of inter‐plant interaction (competition), Smith's empirical law of soil heterogeneity, intra‐plot correlations, and spatial autocorrelation). The significance of spatial inter‐plant interactions on the statistical efficiency of field design, sample sizes, and field estimates is discussed. Besides providing insight into the complexities of inter‐plant interactions, the exposition also provides procedures for removing the bias generated by these interactions, and algorithms for obtaining spatial parameters from ANOVA results.