抄録
From experiments until now it has been known that when the sugar beet plant is cultivated in the warmer districts of Japan, summer-sown type is most ideal from both points of root yield and its chemical quality if in a suitable environment. However, the climate during August is apt to bring severe damages to seed germination and to seedling growth by too high temperature and by too little or much rainfall. Accordingly, it is now thinking that it is rather better to sow after August for avoiding these damages. Here, we traced the growing behavior of sugar beet plant sown in September, and discussed comparing it to the plant sown in August. The varieties used were two, Do-nyu No 2 and KW-AA, and both were sown on September 9 and 27. The summarized results are as follows: Both the top growth and root development up to December are very poor and winter-kill of leaves is very little, in comparison of summer sown plants. However, the plant regrowth from early March gets very rapid (fig. 1.2). On the other hand, the root development in fall-sown plants till late December is extraordinarily poor, accordingly, the main part of stored root must be expected in development during spring (fig. 2, tab. 4). R·T ratio is in a trend of decreasing and after then increasing, having a bottom in late March, and is always higher than in summer-sown plants throughout the life cycle (fig. 3). This shows us that the producing efficiency of aerial part to storing root is fairly lower in fall- sown plants. Numbers of brix and pol in root keep until late February and after then decrease rapidly as in summer-sown plants, however, decreasing rate is relatively more than in summer-sown plants. Accordingly, when a time of harvest would be decided by a certain sugar per cent, it in fall-sown plants, though having young age, is not always prolonged later than in summer-sown plants. It is around late April or early May (table 5). Conclusively speaking from the results above, the fall-sown sugar beet cultivation would be much useful in regions with higher air temperature in winter and with conditions, in which the decrease of sugar content in root during spring is relatively less.
