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Table 2. The five most abundant weeds in rice at three positions on the toposequence inRajshahi District. Observations were taken in unweeded plots at 110 DAT.RankPosition on toposequenceUpper Medium Lower1 Fimbristylis miliacea F. miliacea F. miliacea2 Cyperus halpan C. halpan Paspalum distichum3 Cyperus difformis Paspalum distichum Cynodon dactylon4 Cynodon dactylon C. dactylon Leersia hexandra5 Paspalum distichum Cyperus iria C. halpanquence land. In general, fewer weeds were identified in the medium toposequence.On low toposequence fields, the perennial grass Paspalum distichum was identifiedby all focus groups as problematic. These species were included among the five mostabundant weeds observed at the yield-gap trial sites (Table 2). Fimbristylis miliaceawas the most abundant species on all land types. Low fields were infested by up tothree potentially difficult to control perennial rhizomatous grasses, Cynodon dactylon,Paspalum distichum, and Leersia hexandra.Across surveyed farms in Rajshahi District, an average of 1.1 ha of rice was plantedto T. aman, with 60% of households planting up to 1.0 ha and a further 42% plantingbetween 1.0 and 3.2 ha. The mean date of first weeding in Rajshahi District at 28 DATwas almost 2 full weeks later than in Comilla (Table 3). Farmers in both areas have asimilar perception of the weediness of their plots and of the yield loss due to weeds.The data suggest that differences in weed management are related to Land type and water depth. Table 3 shows a greater range of land types(position on the toposequence) in Rajshahi than in Comilla, where virtuallyall plots were at medium height. Water status was also more favorable inComilla, where most plots had standing water at the time of first weeding. Tillage practices, with farmers in Comilla relying almost exclusively ontractors and power tillers. This significantly reduced the number of plowingsand ladderings given before T. aman. However, mechanized tillage was lesseffective in removing weeds, and farmers in Comilla weeded more frequentlythan in Rajshahi. Labor availability, with 95% of the farmers in Comilla reporting timelyavailability of labor for first weeding compared with 67% in Rajshahi. Unliketheir counterparts in Rajshahi, farmers in Comilla have much greater accessto migrant labor for weeding.Timeliness of the first weeding was not significantly associated with tillage practices(Table 4). It appears to be positively associated with medium land type, presenceof standing water in the plot, ownership of the plot, use of family labor, and number ofImproved weed management for transplanted aman rice 95
Table 3. Weed management in Comilla and Rajshahi districts, aman 2000.Item Comilla Rajshahi Significance(P >)Farms (no.) 90 119Mean date of first weeding (DAT) a 15.14 28.06 0.000Mean date of second weeding (DAT) a 31.51 46.16 0.000Farmers’ perception of aman yield loss from late weeding (%) 33.23 40.77 0.000Adults per household (no.) 5.26 4.22 0.001Toposequence (no. of plots) a- High 9 100 0.000- Medium 105 82- Low 0 61Land preparation (no. of farms)- Animals only 0 50 0.000- Machines only 81 23- Both 9 27Mean no. of plowings per plot a 2.02 4.66 0.000Mean no. of ladderings per plot a 1.71 2.85 0.000Mean no. of weedings per plot a 2.14 1.86 0.000Weeding method (no. of plots) a- Hand 67 242 0.497- Other 1 0Water status (no. of plots) a 0 15 0.000- No water – –- Saturated water 41 125- Standing water 73 71Weeds (no. of plots) a- More than average 38 82 0.953- Average 49 100- Less than average 27 60Labor use (% of plots) a- Own 27 46 0.421- Hired 49 99- Both 38 96Labor available on time? (no. of plots) a- Yes 105 159 0.000- No, no cash 4 38- No, no labor 1 40a For subsample of plots cultivated in aman 2000 (n = 357).96 Riches et al
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Improving AgriculturalProductivity
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Bangladeshi experiences with a drum
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AcknowledgmentsIRRI is most gratefu
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The High Barind Tract: a challengin
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irrigation across the entire Barind
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Workshop synthesis
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and, with representatives from the
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Subsistence pressureLand pressure,
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HerbicidesEarlier efforts to introd
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volume). PVS is an effective way to
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Farmers may use wet-seeded DSR as a
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process and distributing HNPV to fa
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an NGO, have successfully collabora
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Workshop discussionParticipants dis
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How can we identify a short-duratio
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to fixed tenancy. The implication i
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Opportunities for improving ricepro
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that the reliability and productivi
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Table 1. Planting dates, direct-see
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Table 2. (A) Mean effect of fertili
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Table 5. On-farm trials of a drum s
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Upper toposequenceYield (t ha -1 )7
Page 53 and 54: and perennial grasses (e.g., Ischae
Page 56 and 57: Direct-seeded rice in the HighBarin
Page 58: Table 1. Sample selection for costs
Page 61 and 62: Table 4. Variations in weed managem
Page 63 and 64: Table 7. Labor requirements (days h
Page 65 and 66: Table 10. Farmer perceptions of dis
Page 67 and 68: Farmers (no.)1412108DSRWet-seededDr
Page 69 and 70: able commercially. Other OFT farmer
Page 71: Box 1. Farmers’ comments on DSRPo
Page 74: NotesAuthors’ addresses: M.A. Jab
Page 78 and 79: This paper explores the role of som
Page 80 and 81: (Olsen method, atomic absorption),
Page 82 and 83: Mean biomass (g m −2 )1,000.000Fi
Page 84 and 85: Fig. 3. Log rank abundance of weed
Page 86 and 87: attested by Fig. 2). Diversity in t
Page 88 and 89: Bangladeshi experiences with a drum
Page 90 and 91: Table 1. Grain yield and crop durat
Page 92 and 93: Table 5. Grain yield and growth dur
Page 94 and 95: ACEy = 0.0001x + 0.7089Yield (t ha
Page 96 and 97: Table 11. Partial budget analysis f
Page 98: ConclusionsDirect wet-seeded rice u
Page 101 and 102: A 178% increase in rice production
Page 103: Table 1. Components of yield gaps d
Page 107 and 108: Table 5. Weed management practices
Page 109 and 110: Table 7. Significance (P H o ) of t
Page 111 and 112: Since 2000, there has been an incre
Page 114 and 115: Identifying varieties for the High
Page 116 and 117: Table 1. Rice varieties bred by cli
Page 118 and 119: Table 2. Grain yield advantage of J
Page 120 and 121: Table 3. Plant height and crop dura
Page 122 and 123: Table 6. Summary of adoption and sp
Page 124 and 125: Freeman GH, Perkins J.M. 1971. Envi
Page 126: Opportunities for improving rabi cr
Page 129 and 130: Grain yield (t ha -1 )2.0npp1.5LSD
Page 131 and 132: In each of the plots, numbers of He
Page 133 and 134: Table 2. Effect of IPM components o
Page 135 and 136: Unit plot size was 10 10 m and the
Page 137 and 138: Yield (t ha -1 )5Straw4321GrainP (g
Page 139 and 140: Nodulation score3AControl Soil Mo P
Page 141 and 142: even at low levels of production. B
Page 144 and 145: Integration of chickpea and other r
Page 146 and 147: Grain yield (t ha -1 )3.02.51989-99
Page 148 and 149: Improved Improved Rainfed rainfed C
Page 150 and 151: Table 1. Preharvest and postharvest
Page 152 and 153: Greater resistance to Helicoverpa p
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wheat varieties). There is also sco
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Developing seed systems fordissemin
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This paper describes attempts to em
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seed needed to attain the recommend
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introduced to permit sale beyond th
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pesticides, inoculation with benefi
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for the rabi crop in 2001. Hence, b
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where farmers decided not to relay-
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Table 2. Mean dates of T. aman harv
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Table 4. Subsistence pressure and r
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Table 7. Subsistence pressure and r
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cite the absence of rent as a facto
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abi cropping in the HBT through ear
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Formulation and dissemination ofimp
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in India, for which shorter-duratio
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Applied researchOFTsAdaptive resear
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Table 1. Recommended package of pra
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Table 2. Grain yields (kg ha -1 ) o
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Table 4. Grain yields (t ha -1 ) of
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Table 6. Mean grain yields (t ha -1
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constraints present. This in itself
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Extending rabi cropping in rice fal
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Table 1. Estimates of rice area dur
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Yield (kg ha -1 )1,2001,00080060040
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Future disseminationThrough dialogu
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Direct seeding of rice andopportuni
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Table 1. Time of establishment and
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Table 3. Weed density and biomass a
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than in Central Java and many farme
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Proportion abundance (log scale)Ran
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CAN FIELD BE DRAINED?YesCAN FIELD B
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Johnson DE, Mortimer AM. 2005. Issu
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Zhao DL, Atlin GN, Bastiaans L, Spi
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