The experiment described in the paper was carried out in 2002-2005. The successive effect of green manure in the form of forecrop plants (oat, field pea, spring vetch, and mixtures of these plants) on yield of leek cv. ‘Arkansas’ was studied. Two forms of forecrop utilization were used – the whole biomass and post-harvest residues. The fertilizing effect of green manures was compared with farmyard manure at the dose of 25 t·ha-1 and with cultivation without organic fertilization. Leek was grown in the second year after organic fertilization. Green manures of vetch and the mixture of oat and field pea caused a significant increase in the total yield, however, vetch, field pea and the mixtures of oat and field pea, vetch and oat, as well as vetch with oat and field pea gave the marketable yield on a level comparable with cultivation without organic fertilization. The successive affect of forecrop on the yielding of leek was similar to that of farmyard manure. The most favourable influence on the level of marketable yield, mass and length of blanched part had plough-down green manures of vetch. Greater successive fertilizing effect were obtained by ploughing-down of the whole biomass forecrop than through post-harvest residues. The leek cultivated after plough-down of the whole biomass of vetch and the mixture of vetch and oat formed significantly greater mass of blanched parts, and after plough-down of the whole biomass of vetch as well as the mixture: oat and field pea, vetch at oat and vetch at field pea significantly longer blanched part in comparison with cultivation after farmyard manure. The leek cultivated in the second year after plough-down of the post-harvest residues of vetch was characterised by significantly greater mass of blanched part in comparison with the cultivation after farmyard manure. The succession effect of forecrop was dependent on the weather conditions in the successive years of study.