Effect of seedling age and plant density on growth and yield of rice varieties
1989
Aragones, D.V. | Wada, G. (International Rice Research Inst., Los Banos, Laguna (Philippines))
A short duration variety (IR66) and a medium duration advanced line (IR36892-163-1-2-2-1) were grown in the field under three spacings (5x5, 20x10, and 20x30 cm) and three seedling ages at planting time (0,3 and 6 leaf stage or 6, 14 and 25 day-old seedlings, respectively) to obtain fundamental information on direct-seeded rice cultivation. Young seedling age and close spacing increased the number of tillers, promoted the early occurrence of the maximum tiller number stage, but decreased the percentage of bearing tillers to total tiller number. The occurrence of panicle initiation stage was slightly varied by seedling age and spacing. The vegetative lag phase was longer in young seedling and close spacing than in old seedling and wide spacing. Close spacing increased the yield by promoting early growth and by increasing the number of panicles and sink size which was more apparent in IR66. Under close spacing, however, younger seedling decreased yield more apparently in medium duration variety than short duration variety. This can be attributed to the decrease in sink size as reflected in the increased number of degenerated spikelets and nonbearing tillers caused by a longer vegetative lag phase. In relating potential sink size to sink degeneration, 4-14 days of vegetative lag phase is favorable for increasing sink size and yield. Therefore, it can be said that short duration varieties are more suited for direct seeding than medium duration varieties.
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