Effects of seedling age, spacing and season on phyllochron, yield and yield components of rice using the principles of the system of rice intensification

To evaluate the effects of seedling age, spacing and season on phyllochron, yield and yield components of two rice varieties, two field experiments were conducted at the Central Experiment Station, University of the Philippines, Los Banos [College, Laguna, Philippines] in the dry and wet seasons of 2003. In the first experiment, 8, 15, 20, and 25-day old seedlings of Elon-elon and PSBRc-82 while in the second experiment, 20 x 20, 30 x 30 and 45 x 45 cm plant spacings were evaluated in terms of phyllochron, number of leaves per culm, yield and yield components of the same varieties in two cropping seasons. Experiment 1 showed that phyllochron was shorter in younger seedlings than in older seedlings. In both cropping seasons, panicle length and weight of one thousand seeds were not significantly affected by seedling age. In both seasons, number of leaves per culm after transplanting, productive tillers per hill, plant height, number of filled spikelets per panicle, grain weight per panicle, and final grain yield were significantly higher in 8 and 15-day old seedlings than in 25-day old seedlings. In both cropping seasons, 99% of the differences in yield were explained by these agronomic traits. Among these agronomic traits, the number of productive tillers per hill, filled spikelets and grain weight per panicle significantly contributed to the yield differences in both cropping seasons. In the wet season, but not in the dry season, the number of leaves per culm contributed significantly to the final yield. Experiment 2 showed that phyllochron was shorter with wider spacing in both cropping seasons. In both seasons, the number of productive tillers per hill, filled spikelets per panicle, grain weight per panicle and final grain yield increased with wider spacing compared to closer spacing. In the dry season, 97% and the wet season 98% of the yield differences were explained by the number of productive tillers per hill, plant height, number of filled spikelets per panicle and grain weight per panicle. Except for plant height, all these agronomic traits significantly contributed to the yield. Shorter phyllochron, higher number of productive tillers per hill and final grain yield were observed in the wet season plants than in the dry season for both experiments. Transplanting the 8 and 15-day old seedlings carefully at wider spacing under the full set of SRI [System Rice Intensification] agronomic management practices shortened phyllochron and increased the tillering and final grain yield of the two varieties