マラヤ水稲の生育相と施肥の効果に関する研究 : II. 地上部・地下部の生育とチッソ・ケイ酸の効果

抄録

The author carried out an experiment on rice cultivation from 1962 to 1964 at Bukit Merah Padi Experiment Station in double cropping areas of Malaya. The results of main experiment are summarized as follows. 1. Changes of the growth phase of top and root (Fig. 1 and 2) Radin China 4, a medium-term variety in main season, and Pe Bi Fun and B. M. 5, both short-term varieties in off season, were cultivated under non-fertilized, fertilized and furnace-slag-applied conditions. It was seen that the stage of fertile-tiller-formation came about 30 to 35 days after the rice transplantation and the stage of maximum number of tillers was 40 to 42 days after transplantation in all plots tested. The soil in B. Merah was under a heavily reduced condition, showing Eh values of between-100 and 50 mV during the paddy season. The rate of dry weight increase of the root became gradually greater after transplantation and reached to its max. around the spikelet differentiation stage. The maximum index of rooting ability was seen concurrently just after or 10 days after transplantation. Following this, there was a gradual decrease throughout the stage. The index of rooting ability was extremely low after the spikelet differentiation stage. 2. The influence of pruning of spikelets on percentage of ripened grains (Fig. 3) The percentage of ripened grains in control hills was 81 to 91 in the non-fertilized plot and 76 to 88 in both the fertilized and furnace slag plots for four seasons. It was noticed that there was not much a difference in the percentage of ripened grains when the primary rachis were cut off at 1/3 or 1/2 to decrease the spikelet. The percentage of ripened grains in the pruned hills was 89 to 96 %. The non-pruned hills, except for the non-fertilized plot, produced imperfect grains amounting to 12 to 24 %. The reason for this can be attributed to rather excessive number of spikelets in each panicle. 3. Morphological observation of lodged hills and changes of index of lodging (Fig. 4 and 5) It was seen that N₃ or N₄ internode was longer and much thinner in the lodged hills. This was the main cause for breaking. Measurement of the moment (plant height × fresh weight of plant) and breaking strength of N₄ and N₃ was measured after heading. According to Dr. SEKO in Japan, if the index of lodging (moment / breaking strength × 100) is bigger than 200, lodging is very likely to occur. The index of lodging showed its maximum value at the maturing stage in all plots. It was seen that the fertilized plot was greater in the moment and less in the breaking strength compared with non-fertilized plot. The reading of the index of lodging was 240 to 300 in the fertilized plot. Thus the fertilized hills showed to be weak to lodging. From the above investigation, it can be said that the varieties in Malaya have a greater tendency for lodging. 4. Experiment on fertilizer response of 7 varieties (Fig. 6) It was found that heavy fertilizing in most cases brought about an increase in the yield, especially when the maturation period was longer in a fertile field. But in a poor field, like B. Lima, Mayang Ebos 80 and Subang Intan 16 gave a better yield than the varieties having a relatively longer maturation period. It can be stated that Sigadis, M. Ebos 80 and S. Intan 117 have a high fertilizer response. 5. Experiment on the amount of nitrogen and its application time (Fig. 7 and 8) It was generally presumed that suitable amount of nitrogen to increase the yield would be 0.34 to 0.68 kg per are in the main season and 0.34 kg in the off season respectively. This might be attributed to the difference in the maturation period of the varieties used. It was also found that top-dressing at the stage of spikelet differentiation or reduction division was most effective in the main season while in the off season the effective time of the application could not be determined. [the rest omitted]