IMPACT OF OXADIAZON AND PYRAZOSULFURON-ETHYL ON RICE AND ASSOCIATED WEEDS IN DRY SEASON RICE CULTIVATION

An experiment was conducted at bangladesh rice research institute (brri), gazipur bangladesh in the dry season of 2009 (january-may) to study the efficacy of different postemergence herbicides and select the cost-effective treatment as an option for weed control in dry season rice. ten different weed control treatments viz. t1 = zealus 10 wp at 125 g ha-1, t2 = amaraj 10 wp at 150 g ha-1, t3 = siniron 10wp at 187 g ha-1, t4 = herbikill 10 wp at 150 g ha-1, t5 = res q 25 ec at 1.2 l ha-1, t6 = remover 10 wp at 187 g ha-1, t7 = safety 10 wp at 200g ha-1, t8 = laser 10 wp at 125 g ha-1, t9 = hand weeding at 15, 30, and 45 dat and t10 = weedy check were compared. the active ingredient of res q 25 ec is oxadiazon, whereas the active ingredient of the other products is pyrazosulfuron-ethyl. eight different weed species were present in the experimental field among which scirpus maritimusfollowed by echinochloa crus-galli were the most dominant in terms of density and importance value. among the treatments, t6 (remover 10 wp) gave the lowest weed density, dry weed biomass and weed index, and the highest weed control efficiency. the yield and yield components of rice (e.g. no. ofpanicles m-2, no. of grains per panicle, grain and straw yield) were greatly influenced by the treatments. herbicide treatment t6 (remover 10 wp) produced similar yield to hand weeding(t9), but the weeding cost of t6 was almost one-sixth of t9. maximum marginal return rate with t6 (remover 10 wp) suggests that this treatment could be used as alternative tool when labor is a limiting factor in dry season rice cultivation.