Comparative efficacy of pretilachlor and hand weeding in managing weeds and improving the productivity and net income of wet-seeded rice in Bangladesh

Field experiments were conducted for two years during 2005-2006 and 2006-2007 in farmers' fields at Sorajgonj Village in Sadar Upazila of Chuadanga District in Bangladesh. The objective was to evaluate the comparative efficacy of hand weeding and pretilachlor applied at different days after seeding (DAS) rice in effectively and economically controlling weeds and improving the productivity of rice wet-seeded using a drum seeder, during the aman and boro seasons. Three application timings of pretilachlor and five weed control treatments, including (a) pretilachlor 0.500 kg ha-1, (b) pretilachlor 0.375 kg ha-1, (c) pretilachlor 0.250 kg ha-1, (d) hand weeding thrice, and (e) unweeded (check), were tested. The reduction in grassy weeds due to different rates of pretilachlor and hand weeding thrice was inconsistent due to less efficacy of pretilachlor against Cynodon dactylon and incomplete removal of the same weed by hand weeding. The density and biomass of sedges and broad-leaved weeds at different pretilachlor rates were lower than or similar to those of hand weeding thrice during both seasons. On average, rice yield loss due to uncontrolled weeds was 43% and 51% in aman and boro seasons, respectively. Economic analysis revealed that the net income with pretilachlor application was equivalent to that obtained with hand weeding thrice in the boro season and higher than with hand weeding thrice in the aman season, in spite of getting slightly lesser rice yield with pretilachlor usage than with hand weeding thrice. Results of the study revealed that, for effectively controlling associated weeds and attaining optimal wet-seeded rice productivity and net returns, preti lachlor 0.250 kg a.i. ha-1 or 0.375 kg a.i. ha-1 application at 3 or 5 DAS in aman and at 7 or 9 DAS in boro season can be used as an alternative to hand weeding thrice, during the times of labor scarcity in Bangladesh.