In order to establish fertilizing technique for the increase of grain yield and its stability, the total absorbed amount of nutrients and nutritional status of rice plants at different growth stages were studied with respect to the nutrient contents and its relation to grain yield and yield components. This experiment was carried at three different level of nitrogen fertilization; two different seeding and transplanting times, and eight cultivars including both Japonica-and Tongil-type.
The results of a part of these experiments are summarized as follows:
1. The calm length tended to increase with increasing fertilizer amount, but no significant difference between ordinary and heavy fertilization was observed in Tongil-type cultivars.
2. The panicle length was some what longer in ordinary and heavy fertilization than non-fertilization.
3. As the N-fertilizer level increases the number of panicles per plant increased with higher response in Japonica-type cultivars than in Tongil-type cultivars.
4. The number of grains per panicle increased significantly in ordinary and heavy fertilization, compared to non-fertilization, but the difference in grain number per panicle among fertilizer treatment was smaller in Japonica-type cultivars than Tongil-type.
5. The 1,000 grains weight showed no significant difference among fertilization levels in ordinary transplanting, but indicated gradual decreasing tendency as the transplanting delayed.
6. In percentage of ripeness, there was no significant difference in ordinary transplanting, but highly significant in late transplanting among N-fertilization levels and cultivars.
7. In yield, highly significant difference was shown among N-fertilizer levels and cultivars. In Tongil-type variety, higher yield was obtained in ordinary fertilization than heavy fertilization.
8. The straw weight showed the tendency to increase in higher nitrogen level, but no significant difference between ordinary and heavy fertilization was observed in Tongil-type cultivars.
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