Abstract

Weed has become one of the most serious problems in dry seeded rice (DSR). To increase the competitiveness with weeds and achieve the optimum growth of rice, weed management in DSR needs an integration of herbicides and optimum nitrogen (N) fertilizer rates. In this study, the bioassay species were treated with a series of pre-emergence (pretilachlor and pendimethalin) and early post-emergence (propanil+thiobencarb) herbicide concentrations and N fertilizer. It was found that pretilachlor at an application rate of 0.25 and 0.50 kg ai ha-1 almost completely inhibit the emergence and shoot growth of E. indica by 100% inhibition, at 50, 100 and 150 kg ha-1 N, respectively, but it showed severe injury symptom to the root of rice seedlings. Meanwhile, pendimethalin and N fertilizer at moderate application rate gave a strong reduction of weed emergence (>50% inhibition) and shoot fresh weight (>85% inhibition), with negligible effect on the rice seedlings growth. Significant inhibitory effects on weed emergence (60% inhibition) and shoot growth (90% inhibition) also were noticed at the highest application rate of propanil + thiobencarb (3.6 kg ai ha-1) and N fertilizer (150 kg ha-1 N), with stimulation effects on the growth of rice seedlings. This promising effect showed combination of propanil + thiobencarb and N fertilizer (3.60 kg ai ha-1 propanil + thiobencarb + 150 kg ha-1 N) was the most efficient treatment for E. indica control in dry seeded rice.

Key words: Eleusine indica, herbicides, N fertilizer, dry seeded rice.