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 Irrigated Rice Research Consortium
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Focusing on the farmer
Determining intervention points for improved weed management—socio-economic dimensions
Researchers conducted rapid rural appraisals in Comilla and Rajshahi districts to learn about the following: So, why did yield gaps occur? Yield loss was linked to time of first weeding. Researchers found that farmers' weed-management practices varied greatly between districts, within districts and between individual farmers. Farmers' decision-making depended on many factors, including tillage operations, type of tillage, frequency of weeding, and timing of first weeding (see decision tree). For example, the average date of first weeding differed by 8 days between farmers in Comilla District, 13 days between Comilla and Rajshahi districts, and in some cases by as many as 19 days. This suggests that there is considerable scope for raising average aman yields by improving farmers' weed management, especially by making it more timely. Variation could arise from both demand (weed abundance) and supply (availability of labor). Regression analysis (studying the dependence of one variable on one or more other variables) showed that variation in the timing of the first weeding was determined primarily by the labor supply, land tenure and some other differences between districts. Once other factors were accounted for, weed abundance did not significantly affect the timing of first weeding. One difference between districts is probably farmer knowledge, as farmers in Comilla have enjoyed longer exposure to technology associated with modern rice cultivars, including the optimum time for first weeding. Labor-supply constraints reflected the difficulty of hiring labor at the required time and the large area of aman crop to be weeded using labor-intensive methods like hand-weeding or rotary weeders. First weeding occurred later on rented plots, as farmers gave priority to their own fields. Focusing on the farmer Herbicide adoption would be problematic. It would reduce fodder supplies for livestock, particularly in Comilla District, where many farmers feed their cattle (primarily milk cows) weeds from their own and others' fields. This would increase their reliance on other, possibly more expensive, types of fodder and would represent one of the hidden costs of herbicide adoption. Maintaining fodder supplies would require the introduction of quick-growing plants or trees in homesteads or on field boundaries. Sharecropping was associated with fewer tillage operations, less frequent weeding, and later first weeding. Other things being equal, these factors would have reduced rice yields on sharecropped plots. However, fertilizer use was universal both on sharecropped and farmer-owned plots, and sharecropped plots were more likely to grow the local aman variety Swarna, which has higher average yields than modern varieties. Thus, sharecropped plots in Rajshahi District, where farmers grew Swarna, were possibly more productive than farmer-owned plots that grew modern varieties. The preference for Swarna over modern varieties suggests that tenants were primarily concerned with retaining as much paddy rice as possible after dividing the crop with the landlord. If so, they should favor innovations like herbicides to raise aman yields. They may be less willing to adopt innovations like direct-seeding or shorter-duration modern varieties, which would increase the scope for growing valuable rabi crops but may reduce aman yields or worsen the risk of rice crop failure[PF2]. Landlords interested in total productivity may take the alternative view[PF3], as rabi crops may be 3 times more profitable than rice. In summary, the main explanations for yield gaps are lack of knowledge of the optimum time for first weeding and lack of labor. Training in weed management can improve farmers' knowledge. The problem of labor shortage is more complex. In theory, it can be overcome by either increasing labor supply or reducing labor demand. As the supply of labor is already constrained, the only realistic option to improve farmers' weed management is to reduce labor demand through the introduction of labor-saving technologies such as herbicides or rotary weeders. Herbicides coupled with direct seeding may also improve total farm productivity, because rabi crops are more profitable than rice. However, farmers in Rajshahi have chosen to cultivate a local aman variety, Swarna, which has a higher yield than currently available modern varieties but whose long field duration limits the scope for subsequent dryland rabi crops. Changing this preference will require the introduction of a commercially attractive rabi crop that would give farmers an economic incentive to switch from Swarna. Chickpea may fill the bill, but farmers must first be convinced of its market potential before they will sacrifice aman yields (see figure). Closing the yield gaps in rice production in these districts will require research that focuses on the interface between water, weed and fertilizer management. Integrated crop management is essential if farmers are to close the yield gap in irrigated rice, which is the foundation of food security in Bangladesh, as well as the area in which research can have the most impact. Research on weed management in irrigated and rainfed rice is broadening its scope to address wider issues of crop management. Funded by the Natural Resources Institute (NRI) and the Department for International Development (DFID, http://www.dfid.gov.uk/), this work was a partnership of the Weed Ecology Workgroup, M.A. Mazid and J. Uddin Ahmed of the Bangladesh Rice Research Institute, C.R. Riches and A.W. Orr of the NRI in the U.K., and M. Mortimer and L. Wade of IRRI. |
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About Weeds |
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In the Comilla and Rajshahi districts of Bangladesh, farmers' know their weeds - their local names, how and where they grow, and how difficult they are to control. Farmers are well aware of the conditions that favor weed growth and the need for early weed management. So, why do weed-induced yield gaps still occur?
