Abstract
In order to compare the forms of rice culture at the present time in Japan, and to research some of the conditions having influence upon their local characteristics, we have investigated 1, 001 towns and villages, which have been drawn from all of the country by random systematic sampling of one-tenth. Relation between day length, temperature and rice growing season was studied in this first report. According to the result of this investigation, rice growing seasons can be grouped into two cases, later or earlier seeding and transplanting toward each limits. And we ascertained rice culture has been performed with right varieties and by suitable methods, coresponding to day length and temperature in each stage of growing. In the first case, seeding can be hastened by taking the proper nursery bed forms against the low temperature injury in the early stage of growing, and the earlist limits are observed to be at the time when the temperature rises more than 5°C∼10°C in spring. In the second case, transplanting is performed at 90∼110 days, at least 70 days, before the time when temperature fall downs below 15°C in autumn, because rice plant needs at least 45 days interval between heading date and that day in autumn.
