2015 Volume 84 Issue 1 Pages 22-33
Seeds of high-yielding rice cultivars for forage were scattered over a paddy field in Daisen, Akita in autumn to elucidate the effects of post-harvest lime nitrogen (LN) application to control volunteer rice. The pseudo-dropping seeds were treated with LN. For seeds overwintering on the field surface, LN application (50 g m-2) in autumn, winter, and spring suppressed volunteer rice emergence more than in control plots, to which LN was not applied. Furthermore, LN application in autumn was more effective in suppressing volunteer rice emergence, because the temperature was higher than in other seasons, which intensifies the breaking of seed dormancy and germination preventing effects of cyanamide. In addition, the effective period was longer in the autumn treatment than in treatments during other seasons. Furthermore, the results suggest that maintaining a nontillage state for a definite period after LN application was important to suppress volunteer rice effectively. Actually, LN has dormancy-breaking effects, with subsequent damage on germination. In the cultivar whose germination was damaged rapidly by LN, suppression of volunteer rice generation by LN was conspicuous. The results suggest that post-harvest application of LN to high-yielding cultivars for forage at 500 kg ha-1 in autumn suppresses volunteer rice generation the following year to 1/6 or less than that without LN application in the Japan Sea coastal area of the Tohoku region.
