Abstract
In order to produce green asparagus (Asparagus officinalis L.) spears in November by forcing culture in the Ohotsuku region of Hokkaido, the effect of the timing of digging up one-year-old rootstock on the spear yield was examined in 2010 and 2011. In this study, one-year-old rootstocks of ‘UC157’ grown in the field were dug up in early, middle, and late October in both years. There were no significant differences between the three digging times in the fresh weight of rootstock or soluble solid content (Brix%) in storage roots, although the fresh weight varied between the two years. On the other hand, significant differences in spear yield from one-year-old rootstock in the forcing culture bed were seen between the three digging times. Both the marketable and total spear yields were much higher with late October digging than with the other digging times throughout this experiment. Especially, the marketable yield from late October in 2010 was more than three times as high as that from early and middle October. These results suggest that the differences in spear yield between the three digging times might be attributed to the bud dormancy in one-year-old rootstock, and the high spear yield in late October digging implies that the release of bud dormancy might occur before late October. The cumulative hours of chilling exposure to an air temperature below 5°C for one-year-rootstocks of ‘UC157’ up to late October was 110 hours in 2010 and 130 hours in 2011. Since the harvest with late October digging started in middle November in both years, forcing culture in the Ohotsuku region of Hokkaido may make the domestic production of green asparagus in November possible in a short time.
