Effects of soil moisture conditions on the emergence of weeds and rice plants from rainfed paddy soils in north‐east Thailand

Morita, H.; Kabaki, Nobuyuki

doi:10.1046/j.1445-6664.2002.00070.x

Cited by 7 publications

(5 citation statements)

References 1 publication

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Section: Discussionmentioning

confidence: 99%

“…As the soil moisture content decreases from an optimum level in a drought, the comparative advantage for weed growth over rice increases in key processes, such as germination (i.e. a higher percentage of weed seed emergence compared to rice; Morita & Kabaki (2002)), seedling growth, and resource acquisition (Inamura et al 2003;Ikeda et al 2008;Hayashi et al 2009); hence, the produced and scattered weed seeds on soil surfaces for the next season will increase if appropriate weed control measures are not taken. In contrast, the weed growth in the fields in both 2005 and 2006 was not related to the size of the weed seed bank before planting, unlike the observation of several studies in paddy fields (Mineta & Oki 1997), upland cropping fields (Roberts & Neilson 1981), and forestry (Hamada & Kuramoto 1994).…”

Section: Weed Seed Bank and Water Availabilitymentioning

confidence: 99%

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Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Kamoshita¹,

Ikeda

Yamagishi

et al. 2010

Weed Biology and Management

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Weed infestations are a major cause of yield reduction in rice (Oryza sativa) cultivation, particularly with direct-seeding methods, but the relationship between weed dynamics and water availability in Cambodian paddy fields has not been documented previously.We surveyed the weed abundance and weed seed banks in the soil of paddy fields with inferred differences in their water regime in 22 farm fields in three provinces of Cambodia in the 2005 and 2006 rainy seasons.We studied rain-fed lowland fields in upslope and downslope topographic positions and fields at different distances from the irrigation water source inside an irrigation rehabilitation area.The weed seed banks were estimated by seedling emergence in small containers and weed abundance and vigor were estimated by a simple scoring system.The estimated weed seed bank in the top 5 cm of soil ranged from 52.1 to 167 ¥ 10 3 seeds m -2 (overall mean of 8.5 ¥ 10 3 seeds m -2 ) and contained a high proportion (86%) of sedge species, such as Fimbristylis miliacea L. and Cyperus difformis. Several fields had particularly large seed banks, including one near the reservoir. No clear difference was found in the weed seed banks between the irrigated fields that were located close to (upstream) and distant from (downstream) the water source or between the irrigated and rain-fed lowland fields, but the weed scores were larger in the rain-fed fields and the downstream fields within the irrigated area. A water shortage during the late growing season in 2005 led to a proliferation of weeds in some fields and an associated increase in weed seedbank size in 2006. However, the weed scores in 2006 were more strongly associated with that year's water conditions than with the weed seedbank size.

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Section: Discussionmentioning

confidence: 99%

Section: Weed Seed Bank and Water Availabilitymentioning

confidence: 99%

Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Kamoshita¹,

Ikeda

Yamagishi

et al. 2010

Weed Biology and Management

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“…For rain-fed rice, drought tolerance will be important not only to reduce losses due to moisture stress but also to maintain or improve the crop's competitiveness against weeds (Asch et al 2005). Elsewhere, systems to conserve irrigation water, such as aerobic rice and alternate wetting and drying, may be adopted but will have consequences for weed abundance, and concomitant rice yield losses, due to the extended periods when the soil will not be flooded (Morita & Kabaki 2002; de Vries et al 2010; Krupnik et al , in press). Effective weed control technologies for such production systems will be required.…”

Section: Climate Change Effectsmentioning

confidence: 99%

Challenges for weed management in African rice systems in a changing climate

Rodenburg¹,

Meinke²,

Johnson

2011

J. Agric. Sci.

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SUM M ARYGlobal changes including increases in temperature, atmospheric greenhouse gases, soil degradation and competition for land and water resources, will have multiple impacts on rice production systems in Africa. These changes will affect weed communities, and management approaches must be adapted to take this into account. Higher temperatures and limited water availability will generally advantage C 4 over C 3 plants (e.g. rice). Conversely, elevated carbon dioxide (CO 2 ) levels will improve the competitiveness of rice relative to C 4 weeds, which comprise many of the problem weeds of rice. Increased atmospheric CO 2 levels may also improve tolerance of rice against parasitic weeds, while prevalence of parasitic species may be amplified by soil degradation and more frequent droughts or floods. Elevated CO 2 levels tend to promote growth below-ground relative to above-ground, particularly in perennial (C 3 ) species. This may render mechanical control of weeds within a cropping season less effective or even counterproductive. Increased CO 2 levels, rainfall and temperature may also reduce the effectiveness of chemical control, while the implementation of adaptation technologies, such as water-saving irrigation regimes, will have negative consequences for rice-weed competition. Rain-fed production systems are prevalent throughout Africa and these are likely to be most vulnerable to direct effects of climate change (e.g. higher temperatures and changes in rainfall patterns). Effective weed management strategies in these environments could encompass off-season tillage, the use of well-adapted cultivars (i.e. those with drought and heat tolerance, high weed competitiveness and parasitic weed resistance or tolerance) and rotations, intercropping or short, off-season fallows with weed-suppressive legumes including those that suppress parasitic weeds. In irrigated, non-flooded rice systems, weeds are expected to become more serious. Specifically, perennial rhizomatous C 3 weeds and species adapted to hydromorphic conditions are expected to increase in prevalence. By implementing an integrated weed management strategy primarily targeted at weed prevention, dependency on flood water, herbicides and mechanical control can be lessened. Off-season deep tillage, stale seed bed techniques, use of clean seeds and irrigation water, competitive cultivars, timely transplanting at optimum spacing and judicious fertilizer timings are suitable candidate components for such a strategy. Integrated, novel approaches must be developed to assist farmers in coping with the challenges of weed control in the future.

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“…Furthermore, the direct effects of SRI-prescribed management strategies on these weed communities have not been rigorously examined. In other production systems similar to SRI where flooding of rice fields is either delayed (e.g., direct seeded systems) or eliminated altogether (e.g., aerobic rice, upland systems), such management changes have resulted in increased weed emergence, greater percent coverage by weeds relative to rice, and increased species diversity (Morita et al, 2002;Tomita et al, 2003). In a prescriptive study conducted in Bangladesh, Sarker et al (2002) observed that by increasing the intensity of weeding regime, the density and dry weight of weeds can be reduced in direct seeded rice.…”

Section: Introductionmentioning

confidence: 98%

Weed Community Dynamics in the System of Rice Intensification (SRI) and the Efficacy of Mechanical Cultivation and Competitive Rice Cultivars for Weed Control in Indonesia

Haden

Duxbury²,

DiTommaso³

et al. 2007

Journal of Sustainable Agriculture

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ABSRACT. The system of rice intensification (SRI) prescribes the use of young seedlings, planted at reduced densities and managed using reduced irrigation and frequent mechanical weeding, as a means of optimizing rice yields and reducing input costs. Such changes in management practice have been known to result in prominent shifts in weed flora, which if anticipated could help refine future weed control strategies. This study, conducted at four locations in West Java, Indonesia, examines the effects of two complimentary control tactics, mechanical cultivation and competitive rice cultivars, on individual weed species, broader weed classes and entire weed communities. Relative dry weights of individual weed species ranged widely from site-to-site. Differences in dry weight among weed classes were observed, with sedges accumulating greater biomass than either broadleaved weeds or grasses in nonweeded plots across all sites and cultivars. Mechanical cultivation was effective in reducing the dry weight, density, and species number of all weed classes. Effective weed control by mechanical cultivation also resulted in weed communities with lower species richness, greater dominance by fewer species, and hence lower overall diversity. The weed competitive cultivar (Sarinah) more effectively suppressed the dry weight of sedges and grasses than did the control variety (IR64), but had no influence on the dry weight of broadleaved weeds. Despite reducing total weed dry weight by 32%, use of a competitive cultivar had no effect on the density and species number of weed classes or any of the communityscale measures of diversity. Although competitive cultivars may have little effect on the relative abundance of resident weed species from an ecological standpoint, this should not diminish the practical potential such cultivars may have in reducing the number and intensity of weeding operations.

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Effects of soil moisture conditions on the emergence of weeds and rice plants from rainfed paddy soils in north‐east Thailand

Cited by 7 publications

References 1 publication

Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Challenges for weed management in African rice systems in a changing climate

Weed Community Dynamics in the System of Rice Intensification (SRI) and the Efficacy of Mechanical Cultivation and Competitive Rice Cultivars for Weed Control in Indonesia

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