The field trial was conducted for three years on the sandy soil, the rye soil complex. The response of oat and yellow lupine to the border interaction with paths splitting the plots was determined. The characters of plants were compared between plants growing on marginal and middle rows. Oat and yellow lupine were sown as the sole crops and in mixtures with different sowing rates. Plants strongly reacted to the paths nearness; however, oats response occurred much stronger than lupine, both in pure sowing and in mixtures. As the sowing rate of oat increased in mixtures, the border effect of oat characters enhanced, while lupine characters were weakened. The sowing rate of lupine in mixtures was insignificant. The data provide evidence that characteristics of oat and lupine are wrong indexes for experimental treatment if they come from plants near paths splitting plots.

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