Author(s): B. KARMAKAR AND M. A. R. SARKAR

Abstract: To determine optimum seedling age and characterize the effect of seedling age on the performance of the rice genotypes, the experiment was conducted during wet season of 2010 and 2011 at Bangladesh Rice Research Institute, Regional Station, Rajshahi. Strip plot design was followed with 3 replications, placing treatments (seedling age such as 14, 21, 28 and 35-d old) in vertical plots and genotypes (BRRI dhan56, BRRI dhan57, IR83377-B-B-93-3, IRRI123, IR83381-B-B-6-1 and Binadhan-7) in horizontal plots. Seedling age had strong significant effect on yield, yield components and agronomic parameters. Transplanting of 14-d old seedlings gave the highest grain yield that was at par with 21-d old seedling, however, significantly higher than 28 and 35-d old seedlings. Mean grain yield were increased by 21.9, 20.5 and 12.2% in transplanting of 14, 21 and 28-d old seedlings over 35-d old seedlings. Reversely, yield declined by 1.7, 11.2 and 21.9% in 21, 28 and 35-d old seedlings over 14-d old seedlings, across the cropping years and genotypes. Across the seedling ages, the genotype IR83377-B-B093-3 produced the highest mean grain yield (4.88 t ha-1) which was at par with IRRI 123 (4.82 t ha-1) and the lowest was in BRRI dhan57 (3.73 t ha-1). Interaction between genotypes and seedling ages showed that BRRI dhan56, BRRI dhan57 and IR83381-B-B-6-1 produced higher yield from 14 to 21-d old seedlings while Binadhan-7 gave at par yield from 14 to 28-d old seedling. In contrast, grain yield of IR83377-B-B- 93-3 and IRRI 123 was statistically similar throughout the seedling age from 14 to 35-d old. Days to flowering and maturity increased 12 to 14 days from 14 to 35-d old seedlings. Spikelet sterility also increased by 18 to 23.1% from 14 to 35-d old seedlings. In contrast, Plant height, tillers and panicles m-2, grains panicle-1, 1000-grain weight, straw yield and total above ground biomass were declined with increased seedling age.

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