Abstract The effect of green manure and crop residue (summer cover crop) on supplying nitrogen and the weed population in garlic (Allium Sativum) organic farming was the subject of this study. In a one-year experimental design, the accumulation of dry matter and nitrogen in clover (Trifolium alexandrium), Vicia (Vicica sativa) and bean (Phaseolus vulgaris) were studied as summer planting. The tuber yield of garlic cultivated following these cover crops was compared with 0, 80 and 120 Kg N ha-1 of urea. In addition, the effect of mulch from cover crops on weed biomass was evaluated. The greatest tuber yield was obtained from the 120 KgN ha-1treatment. In spite of lower nitrogen uptake in the clover treatment, the economic yield of garlic had not significantly differed. In vicia, bean and clover, the tuber yields were 7,500, 6,870, and 8,660 Kg ha-1respectively. The amount of nitrogen accumulation in clover, vicia and bean was 67.8, 40.5 and 36 Kg ha-1respectively. Due to greater residue, clover reduced weed biomass by 43%, 39% and 31% in comparison with 120, 80 and 0 Kg N ha-1 respectively. Bean and vicia, due to their lower residue production, had a smaller effect on weed growth in comparison with clover.