Abstract
Productivity of early, ordinarily and late sown rice plants cultivated under upland condition was compared with that of early and ordinarily sown ones grown under water-logged condition. 1. Possibility of productivity increase was shown only by the early grown rice plant under upland condition and in this case a vigorous growth in the early stage leading to the enlargement of the leaf area is considered to be a major factor of the yield increase. 2. Increase of the seeding density and amount of nitrogen fertilizer resulted in a little increase in productivity in the case of direct sowing under upland condition while in a slight decrease in the case of direct sowing under water-logged condition. 3. For the late cultivation, it is the most important to prevent the cool weather damage by making heading occur within a certain time limit and also the increase of the number of panicles per area depending upon the main stem is helpful for yield increase. 4. In the case of the late sowing (on August 1, 1963) of Eiko, an extremely early variety, at the rate of 600 grains per m2, a yield of 34.6 kg/a of brown rice was obtained.
