In a pot experiment, carried out in an additive design on light and heavy soils, the effect of interaction between spring barely and pea was evaluated on nitrogen accumulation in different forms of the above-ground matter (stems, leaves, spikes, pods) and roots of both plant species. The experiment included three series, carried out in years 2003-2004 in five periods determined by the developmental stages of spring barley (the BBCH scale): emergence (10-13), tillering (23), stem elongation (32), earing (55), and ripening (87-89). It was demonstrated that the species grown in a mixture accumulated less nitrogen in the above-ground parts and roots than in pure sowing from barley tillering stage to the end of growth. Competition for nitrogen started at the tillering stage, and its intensity increased gradually until the end of the growth period. During tillering, it limited to the greatest extent nitrogen accumulation in the roots of both species, at the straw shooting stage in their above-ground parts, and at the stages of earing and ripening in the roots. With the exception of barley earing stage, pea proved to be a better competitor for nitrogen. Competition was the most intensive on heavy soil.

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