The paper suggests some indicators for the application of spatial methods in field experimentation. The indicators were based on the data from two field-breeding experiments with pea and field bean. Partially balanced square lattice designs were applied. The Smith’s index of soil heterogeneity b, chemical properties of the soil e.g. pH, Mg, P and K contents as well as data obtained from check plots sown with a single variety were used to evaluate spatial variation across the experiments. The Smith’s index of soil variability b showed a potential as a convenient tool to assess the purposefulness of background variation analysis by applying spatial methods. When b<0.6 one can expect a significantly increased efficiency of the experiment. Therefore the application of the nearest neighbour analysis or kriging to the data obtained from a net of check plots can produce the concomitant variable which can reduce the experimental error effectively.