Abstract
In order to obtain the data on the periodical changes of the viability of barnyardgrass (Echinochloa Crus-galli BEAUV. var. caudata KITAGAWA) seed, a germination test was carried out by using the air-dried seeds stored under the three different conditions of temperature and also by using the seeds kept in soil. The results obtained were as follows: 1. The seeds matured in autumn were dormant. The dormant seeds awakened after a certain period, and after that, the secondary dormancy was not observed on these seeds in any case. 2. In the case of air-dried seeds, the period for dormancy awakening was varied according to the storage conditions: three to seven months in the indoor storage (10〜20℃, in winter), six to eleven months in the outside condition (-2.1〜30.7℃ of every ten days average, in a year), and one to two years in the low temperature storage (5℃). It is considered that higher temperature accelerates breaking dormancy. 3. About 50 percent of the seeds kept in soil started to awaken within one month after dropping, and began to have the germination capacity under the alternating temperature condition (30℃/20℃). These seeds perfectly awakened from their dormancy by next February to April. 4. The air-dried seeds stored either indoor or outside lost their viability rapidly under high temperature in the second or third summer from harvesting. On the other hand, the life-duration of seeds was longer than four years when they were kept under low temperature condition. 5. Eighty-five to ninety percent of the seeds located in 0〜0.5cm of upper soil emerged naturally from late April to September of next year, and by the second year, about 50 percent of the seeds located 0.5〜3cm in soil depth also emerged in the same season within two years. The rest of the seeds located in above-mentioned soil layers and the seeds located in the soil deeper than 3cm almost died within three years. The life-duration of the seeds under humid and submerged soil condition was longer than that under upland condition. Also, seeds in deeper soil layer could keep their viability longer than those in upper soil layer.
