Improved weed management for transplanted aman rice

Rainfed transplanted rice grown in the monsoon aman season accounts for more than 50% of the total area planted to rice in Bangladesh. Because of rising input costs, including labor, farmers are searching for ways to maintain income, by either increasing yields or reducing costs or both. On-farm trials in the High Barind Tract indicated that one-third of the farmers would be able to gain 0.5 t ha¯¹ or more additional grain by undertaking more intensive or timelier weeding than is usual under current management practices. Higher yields were observed on-farm from a preemergence application of butachlor (1.25 kg a.i. ha¯¹) compared with hand weeding twice. In Comilla District, trials of a range of weed management practices demonstrated that the yield advantage over the farmers' practice, either one or two hand weedings, was on average 355 ± 18 kg ha¯¹ for Rifit (pretilachlor), 281 ± 39 kg ha¯¹ for Machete (butachlor), and 210 ± 34 kg ha¯¹ for Ronstar (oxadiazon), each followed by one hand weeding in aman 2003. Partial budgets calculated for inputs and returns showed that hand weeding was less profitable than herbicides in rainfed rice, incurring US$72 ha¯¹ lower return. Use of a push weeder plus one hand weeding was less profitable than herbicides, incurring $49 ha¯¹ lower return. To date, herbicides have been largely promoted for irrigated rice in Bangladesh. The trial results demonstrate that under rainfed conditions early in the aman season, water levels are adequate for herbicides to work effectively. The use of herbicides allows timely weed control when there is a shortage of labor and avoids transaction costs, such as the provision of meals and time needed to source laborers. Herbicides are likely to be adopted by growers experiencing labor shortages, particularly on large farms and for farmers seeking to reduce input costs. Sharecroppers and tenant farmers who pay rent are primarily concerned about obtaining a high aman yield, so innovations that raise aman yields (such as herbicides that will have a similar effect as a timely first weeding) are also likely to be adopted on sharecropped plots, even when costs are not shared between the landlord and tenant.