Abstract
Wet seeding of rice will facilitate timely planting of crops in aman and boro seasons, thereby increasing total productivity and profitability of rice-based systems in Bangladesh. Wet seeded rice (WSR) requires suitable crop management options for optimizing rice productivity in different rice ecosystems. Nine field experiments were conducted in the farmers' field of Chuadanga, from June 2005 to May 2007 to identify a suitable crop management package WSR and to compare the methods of wet seeded rice and conventional transplanted rice with better crop management practices for optimizing the productivity of rice-rice and rice-wheat ecosystems. Wet seeded rice seeded on 27 June and 04 July produced significantly higher grain yield during aman (wet) season and matured earlier by 16 to 19 days compared to conventional transplanted rice under farmers' condition. Seeding under wet condition on 25 November in boro (dry) season produced significantly higher grain yield than all other succeeding dates of seeding. For weed management practices in WSR revealed that the pre-emergence herbicide pretilachlor applied at 3 and 5 DAS in aman season and at 7 and 9 DAS in boro season performed better in terms of higher grain yield and less or similar weed density and weed dry matter than the treatment of herbicide applied at 7 and 5 DAS in aman and boro seasons, respectively. The pretilachlor rates, 375 and 250 g ha⁻¹ were found more effective in partly controlling weeds compared to 500 g ha⁻¹ in aman and boro seasons, respectively. The water regime, saturation throughout the crop growing period produced the highest grain yield followed by saturation up to 40 DAS in WSR. Water use efficiency (WUE) was similar in all the water regimes. Irrespective of water regime, seeding with drum seeder using single thick row at rate of 40 kg ha⁻¹ produced significantly higher grain yield and showed higher WUE than that of 25 kg ha⁻¹ using single thin row in boro season. Variety exerted significant influence on grain yield in WSR. BRRI dhan44 performed better than BR11 and Swarna as WSR. Irrespective of variety, drum seeding with the seed rates of 40 and 25 kg ha⁻¹ gave similar grain yields. Grain yields obtained from WSR and normally transplanted rice, transplanted 30 and 35 DAS of WSR (TP₂) in aman and boro seasons, respectively, were statistically similar. Longer field duration of WSR resulted in significantly lower per day grain production. The WSR matured earlier by 8 and 11 days and received 14 and 6 % less irrigation water than TP₂ in aman and boro seasons, respectively. Overall 23 and 24 % labour input were saved in WSR and resulted in 6 and 4 % higher gross margins by incurring 20 and 12 % higher input costs than TP₂ in aman and boro seasons, respectively. The total grain yields of Boro-Aman cropping pattern under wet seeding and transplanting combinations were similar. The WS aman-TP boro, TP aman-WS boro and WS aman-WS boro required about 9, 13 and 22 % less labour input than the existing TP aman-TP boro cropping pattern. The TP aman-WS boro and WS aman – WS boro achieved 3.9 and 5.3 % higher gross margins, respectively, compared to TP aman-TP boro. Thus, wet seeding of rice could be an alternative to transplanting, especially when farmers face the labour shortage during planting. If practiced well, WSR could enhance total productivity, resource use efficiency and profitability in rice-rice and rice-wheat systems.