ANALYSIS OF THE TILLERING BEHAVIOR OF THE RICE PLANT IN THE PADDY FIELD .1. THE TILLERING PATTERN UNDER 2 NITROGEN LEVELS OF BASAL DRESSING

Under the two types of nitrogen dressing which prevail in Miyagi prefecture, rice cv. Sasanishiki was cultivated in the paddy field, and the tillering pattern was analyzed. One type of nitrogen dressing is 3.0 g N m-2 for basal dressing and 1.0 g N m-2 at the early panicle formation stage (N 3.0 plot); the other is 4.5 g Nm-2 for basal dressing only (N4.5 plot). Primary tillers emerged from the second (T2) to the seventh (T7) node of main stem, and secondary tillers mainly from T3 and T4. Number of tillers increased more rapidly in N4.5 plot than in N3.0 plot, and plant age expressed by the leaf number of the main stem advanced more rapidly in N4.5 plot. At vigorous tillering stage, the tiller increasing curve of N4.5 plot plotted against the plant age overlapped with that of N3.0 plot. On the contrary, the number of tillers in N4.5 plot showed slightly higher than that of N3.0 plot, supposing all tillers emerged according to the Katayama's synchronous theory. The authors inferred that this inconsistency was due to differences in growth speed (leaf expansion rate) between the main stem and each primary tiller.