The combination effect of sowing and transplanting time on harvest time, yield, and external bulb quality was investigated to achieve earlier shipment of onions in northeastern Hokkaido, Japan. A total of five cultivars with different levels of photoperiodic responses for bulb formation were used in both the 1996/97 and 1997/98 trials. The seeds were sown on a monthly basis in a soil bed in an unheated plastic greenhouse from December to March, and the seedlings were transplanted outdoors from late April to mid-May. The daily minimum soil temperature was kept at almost 0°C, even when the air temperature in the plastic tunnel inside the greenhouse fell to −14.4°C in mid-winter. Seedling emergence took approximately 20 and 35 days in the 1996/97 and 1997/98 trials, respectively, when the seeds were sown in December and January. However, these seedlings grew slowly, and the leaf length, fresh leaf number, and leaf sheath diameter of the seedlings at transplanting time were all greater when the onion seeds were sown earlier. In addition, the bulb ripening time advanced with earlier transplanting. The cultivars, ‘Kitawase No. 3’ and ‘Kitahayate’, with an intermediate photoperiodic response, were harvested in early August if they were sown in December and January and transplanted from late April to early May. Moreover, with this combination of sowing and transplanting time, these cultivars produced an acceptable yield and bulb appearance in terms of marketable quality. The cultivar, ‘Sonic’, a typical short-day cultivar, had the earliest harvest time. However, the yield was very low due to the short period of leaf growth. On the other hand, for the cultivars ‘Okhotsk No. 1’ and ‘Kitamomiji 86’, which belong to a long-day photoperiodic response group, although the yields tended to increase under early sowing or early transplanting, they were not harvested by early August. On the basis of these observations, a new cropping type for early sowing and early transplanting will be adopted in northeastern Hokkaido by using the ‘Kitawase No. 3’ and ‘Kitahayate’ cultivars for early shipment in the domestic fresh onion market.

研究了播种和移栽时间对收获时间，产量和外部鳞茎质量的综合影响，以实现日本北海道东北部洋葱的早期运输。在1996/97和1997/98试验中，总共使用了五个对球茎形成具有不同水平的光周期反应的品种。从12月至3月，每月将种子播种在未加热的塑料温室的土壤床中，从4月下旬至5月中旬将幼苗移植到室外。即使温室中的塑料隧道中的空气温度在冬季中旬降至-14.4°C，每日最低土壤温度仍保持在几乎0°C。1996/97年和1997/98年的试验分别在12月和1月播种时，出苗时间分别约为20天和35天。然而，这些幼苗生长缓慢，并且在移植时，早播洋葱种子时，叶片长度，新鲜叶数和叶片鞘直径都较大。此外，球茎成熟时间随早期移植而延长。如果在12月和1月播种，则具有中等光周期反应的'Kitawase No.3'和'Kitahayate'品种将于8月初收获，并于4月下旬至5月初移植。此外，结合播种和移栽时间，就可销售的质量而言，这些品种产生了令人满意的产量和鳞茎外观。品种“ Sonic”是典型的短日栽培品种，具有最早的收获时间。但是，由于叶片生长时间短，单产非常低。另一方面，对于品种'鄂霍次克号 1'和'Kitamomiji 86'属于一个长期的光周期反应组，尽管在播种早期或早期移植时产量倾向于增加，但到8月初仍未收获。基于这些观察结果，北海道东北部将采用“ Kitawase No.3”和“ Kitahayate”品种，在北海道东北部采用一种新的早播和早移植作物，以便在国内新鲜洋葱市场上早日发货。