1967 Volume 36 Issue 1 Pages 55-62
The study was carried out to clarify the relationship between climatic condition, especially temperature, and the growth of Italian ryegrass sown in mixtures with common vetch. The relationship between temperature and the growth rate of Italian ryegrass calculated from the data of 1961, 1963 and 1964, can be seen in Fig. 1, showing that growth of Italian ryegrass begins about at temperature of 5°C and. becomes optimum about at temperature of 16°C. The same relation was gained from the data of the experiments carried out all over Japan, as seen in Table 1 and Fig. 2. From these facts it can be said that effective temperature for the growth of Italian ryegrass is more than 5°C. It is presumed, therefore, that the sum of daily mean temperatures for the growing periods except days of degrees below 5°C is the total effective temperature for the growth. The relationship between total effective temperature and yield of the first cutting of Italian ryegrass is very close as seen in Fig. 3, except that enclosed by dotted line. As seen in Fig. 4, Italian ryegrass sown in mixtures with common vetch 200 seeds per m2 under light manuring condition reaches to the yield having no significant differences from Italian ryegrass sown alone under heavy manuring, if the cutting is practiced within the range of less 1030°C of the total effective temperature, and under more than 1030°C, mixture shows inferiority, If the amount of seeds of common vetch in mixtures is less than 100 seeds per m2 as shown in Fig. 5, the mixture can not reach to the yield level without significant differences from Italian ryegrass sown alone under heavy manuring at any total effective temperature. From these results, it can be said that by seeding in mixtures with common vetch (at the rate of 200 seeds per m2) with light manuring and by cutting before the total effective temperature reaches 1030°C, we can gain the yield at the first cutting with no significant differences from Italian ryegrass sown alone under heavy manuring. As seen in Report II, the difference in the yield between mixture under light→heavy manuring and Italian ryegrass sown alone under heavy manuring mainly depends on the first cutting, so it can be said that whether or not the mixture under light→heavy manuring can gain the yield almost equal to the yield of Italian ryegrass sown alone under heavy manuring depends on the total effective temperature at the first cutting.
