We aimed to obtain large-sized Japanese bunching onion (Allium fistulosum L.) for August harvesting in cold regions, which were cultivated using seedlings grown in chain paper pots maintained in an unheated plastic house. For this, we investigated the effects of nitrogen application and the number of seedlings per cell in the chain paper pots on the growth, nitrogen uptake, and yield of Japanese bunching onion. Seedlings of Japanese bunching onion grown in chain paper pots were transplanted in

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... field, and subjected to three nitrogen application treatments: control (2.9 kg・a -1 ; the standard application rate of nitrogen fertilizer in Akita Prefecture), heavy (3.5 kg・a -1 ; 20% greater than the control), and light (2.3 kg・a -1 ; 20% less than the control). The plant growth (number of emergent leaves, shoot weight, and leaf sheath diameter) under the heavy treatment was temporarily and slightly superior to both the control and light treatments during the middle-growth stage. However, the differences in plant growth among the treatments were not apparent by the harvest time. Hence, because there was no significant difference in yield among the treatments, we considered that the amount of nitrogen supplied under the light treatment was sufficient for plant growth. Different numbers of seedlings per cell (1, 2, and alternating 1 and 2 [1.5] seedlings) in chain paper pots resulted in differ ences in growth after planting and yield. With an increase in the number of seedlings per cell (1, 1.5, and 2 seedlings), we noted the increased inhibition of growth after planting, a decrease in the amount of nitrogen uptake per plant, and decrease in the fresh weight of shoots per plant. In contrast, the yield per area increased, because of an increase in the number of plants. The shoot weight was negatively correlated with the planting rate (plants・m -2 ), and positively correlated with the ground area covered by plants (cm 2 /plant). Thus, we observed a quadratic relation between the shoot weight and planting rate, and a linear relation between the shoot weight and ground area covered by plants.