Weed is the major constraint to rice production and the integrated weed management reduces the dependency on herbicidal and mechanical weed control. Weed suppression in transplanted rice can be augmented by adoption of weed competitive varieties and adjusting the planting spacing. The present study was conducted to find out the effect of variety and planting spacing on weed suppression and yield performance of transplanted rainy season (Aman) rice. A field experiment was conducted with four newly developed mutant rice varieties viz., Binadhan-7, Binadhan-12, Binadhan-17 and Binadhan-16 and five plant spacing viz. 25cm × 20cm, 25cm × 15cm, 20cm × 20cm, 20cm × 15cm and 15cm × 15cm in a Split-Plot Design (SPD) with three replications. The lowest weed density was found with Binadhan-7 at 15 cm × 15 cm spacing while the lowest weed biomass was found with Binadhan-16 at 15 cm x 15 cm spacing. On the contrary, the highest crop biomass was found with Binadhan-7 at 25 cm x 20 cm spacing. Variety Binadhan7 and Binadhan17 gave higher grain yield than other two varieties. The highest grain yield (5.38 t ha-1) was found with the variety Binadhan-7 at 20cm × 15cm plant spacing, whereas the lowest grain yield (2.60 t ha-1) was achieved with the variety Binadhan-12 at 15cm × 15cm plant spacing. Among the four varieties Binadhan-7 gave best yield performance. Binadhan-12 showed the worst performance in respect to the yield ability while the highest weed suppression was found with Binadhan-17. The study concludes that Binadhan-7 transplanted at 25 cm x 15 cm or 20cm × 15cm plant spacing provided substantial weed control and gave the best yield in Aman season.
Key words: planting spacing adjustment, weed biomass, weed density, crop yield loss, crop biomass, grain yield.
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