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Sustainable agriculture is crucial for achieving SDG2 and building a resilient climate-food system. This study provides a nuanced understanding of factors that influence the adoption of precision agriculture technology by Vietnamese smallholder rice farmers as a sustainable agricultural solution. The study's objectives are: (1) to provide a nuanced understanding of factors that influence adoption of precision agriculture technology by Vietnamese smallholder rice farmers; and (2) to identify factors associated with agricultural practice in Vietnam that may impact the adoption of precision agriculture technology. The study conducted 35 semi-structured interviews with smallholder rice farmers and agriculture experts. Data were analyzed using iterative thematic analysis. The Unified Theory of Acceptance and Use of Technology (UTAUT) model was used for empirical analysis. The UTAUT constructs of Performance expectancy, Effort expectancy, Government support, and Social influence were found to be determinants of adoption. Trialability and Observability impact Effort expectancy and Performance expectancy. We also discovered that the performance of agricultural cooperatives and support of lead firms play a crucial role in facilitating agricultural technology adoption by Vietnamese smallholder rice farmers. The results confirm the applicability of UTAUT in defining smallholders' behavioural intention and predicting agricultural technology adoption. The study also provides constructive feedback on the UTAUT model by highlighting the effect of agricultural cooperatives' performance as innovation intermediaries and of the support of lead firms., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Weedy rice is morphologically similar to cultivated rice (Oryza sativa L.). It has biological characteristics that identify it as a weed. Its important weedy characteristics, that is, early and heavy seed shattering, makes it very difficult to control. Weedy rice has not been reported to be an important weed problem in transplanted, flooded rice. However, the shift to direct‐seeded rice (DSR) due to water issues and high costs of labor has increased reports of weedy rice becoming an expanding important problem in Vietnam, Malaysia, Thailand, and the Philippines. Experts believe that the growing adoption of DSR in Asian countries will result in the rise of weedy rice as one of the top troublesome weeds in rice production. Early and recent surveys in the Philippines have indicated the urgent need to increase awareness of weedy rice among farmers to allow the implementation of a number of effective location‐specific weed management strategies. These surveys and other studies conducted since weedy rice was first reported in 1991 confirmed that weedy rice and grass weed species caused major problems in DSR areas. About 35% of the 4.56 M ha harvested area in the country is planted with DSR. As cultivated and weedy rice are close relatives, it would be very difficult to implement management options very early in crop growth. However, a deeper understanding of the underlying traits of weedy rice can help develop a holistic approach toward effective and economic weed management. [ABSTRACT FROM AUTHOR]

A rice yield estimation system was developed based on the crop growth model ORYZA and SAR-derived key information such as start of season (SOS) and leaf area growth rate. Results from study sites in South and South-east Asian countries suggest that incorporating remote sensing data, specifically Synthetic aperture radar (SAR), into a process-based crop model improves the spatial distribution of yield estimates. This article highlights the detailed methodology of SAR data incorporation into crop yield simulation and comprehensive validation of yield forecast and estimates in the Philippines, Vietnam, Cambodia, Thailand, and Tamil Nadu, India. Remote sensing data assimilation into a crop model effectively captures the responses of rice crops to environmental conditions over large spatial coverage, which otherwise is practically impossible to achieve. A process-based crop simulation model is used in the system to ensure that climate information is captured, and this provides the capacity to deliver a mid-season yield forecast for national planning and policy for rice. Good agreement between SAR-based yield and crop-cut-based yield and official yield statistics and ensuring efficiency of the processing suggest that the system is a promising solution for the needed timely information on rice yield for application in food security and policies, climate disaster management, and crop insurance programs. [ABSTRACT FROM AUTHOR]

This study makes an ecological economic comparison between three different rice farming strategies in the Mekong Delta. Interviews were made with 30 farmers with two crops of rice and low dikes (2RLd), 30 farmers with three crops of rice and high dikes (3RHd) and 18 farmers with two crops of rice and one crop of fish (2RF). 2RF farmers had the highest annual net income and benefit cost ratio, because of low production costs and high yields of rice and fish. 2RLd farmers had the lowest annual net income. 3RHd had the highest annual rice yield, but also used the highest amount of rice seeds and agrochemicals, generating the lowest benefit cost ratio. Most farmers (70%) preferred two crops because of a higher production efficiency. High dikes and frequent use of pesticides and fertilizers were seen to decrease the water and rice quality, connectivity and biodiversity in farms with three crops. It is concluded that rice farming with two crops, and especially if integrated with fish and applying IPM, provides a sustainable alternative to rice farming with three crops and high dikes, because it makes use of the high connectivity within the rice-field ecosystem for an efficient production of healthy food through increased recycling of nutrients and  natural pest control mechanisms., (© 2023. The Author(s).)

Objective : The aim of this study was to examine the prevalence of heat-related illnesses (HRI) and their associated factors among rice farmers in Central Vietnam. Methods : A cross-sectional study was conducted using a sample of 379 farmers from August to September 2021 in Ha Tinh province on the north-central coast of Vietnam. A structured questionnaire was used to collect demographic information, farming activities, heat exposure, and health issues. Multivariable logistic regression was used to identify the factors associated with HRI. Results : At least one HRI symptom was experienced by 83.4% of farmers, and two or more HRI symptoms were experienced by 55.1% of farmers during the last harvesting season (the summer-autumn rice season, 2021). Factors significantly associated with HRI were age, having chronic diseases, type of farming tasks, the number of hours working in the heat, and water intake. Farmers working outdoors for more than 4 hours in the heat were 2.3 times [95%CI: 1.14-4.69] more likely to experience HRI than those working fewer than 2 hours. A higher risk of HRI was also associated with heavy farming tasks (OR = 2.35, [1.34-4.14]), having hypertension (OR = 3.75, [1.90-7.81]), cardiovascular diseases (OR = 2.53, [1.03-6.93]), and other chronic conditions (OR = 2.51, [1.51-4.25]). In contrast, a lower risk of HRI was found in the older group (OR = 0.44, [0.22-0.87]) and increased water intake (OR = 0.46, [0.27-0.77]). Conclusions : Hot weather is a significant occupational health risk for farmers in Vietnam. Changing the working schedule, working in shorter intervals, and remaining well-hydrated should be considered in HRI prevention strategies.

Lead (Pb), cadmium (Cd), arsenic (As), chromium (Cr), and nickel (Ni) are poisonous, widely distributed, persistent, and transferable to crops, posing potential health risks. This study aims to assess the potential health risks of those elements in rice collected from North-Central Vietnam: Thanh Hoa, Nghe An, and Ha Tinh provinces. Element analysis was performed on rice harvested in November 2020 by ICP-MS. The estimated daily intake (EDI), target hazard quotient (THQ), non-carcinogenic hazard index (HI), and target carcinogenic risk (TR) were used to assess potential health risks for different population groups. The highest element levels (mg kg -1 dry weight) were observed for Cr (0.30 ± 0.11), As (0.17 ± 0.025) and for Pb (0.24 ± 0.013) in Thanh Hoa, and for Cd (0.088 ± 0.015) in Ha Tinh. Strong links were observed between geological formations, mining activities and Cr in rice (Thanh Hoa), or industrial activities and Ni accumulation in rice (Hung Nguyen and Ky Anh districts). Children had greater EDIs than adults, with As having a higher EDI than RfD. Rice THQs indicated a risk trend: Thanh Hoa > Ha Tinh > Nghe An, with As being a significant contributor to HIs. Cr and Cd were significant risk factors and HIs in female children were 1.5 times higher than in other groups. Based on TR values for Ni and Pb, a potential carcinogenic risk to rice eaters was observed, particularly Ni. The data revealed a significant human health risk (both non-carcinogenic and carcinogenic) connected with rice consumption. Therefore, crops and foods from North-Central Vietnam should be strictly regulated., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Direct seeding has been practiced in the districts of Phuoc Thoi, Thoi Lai, and Co Do in the Mekong Delta region of Vietnam, where majority of the farmers practice wet direct-seeded rice (WDSR), Oryza sativa L., for crop establishment. WDSR reduces the cost of inputs such as labour, time, and water prior to crop establishment in the field. Like other rice systems, WDSR is beset by many constraints, foremost of which is weed infestation. Surveys were conducted for two consecutive dry seasons (2012 and 2013) among farmers and/or households (FH) in these three districts to document the cultural practices used and the accompanying production constraints in WDSR. The results showed seeding rates of up to 100–300 kg ha −1 , using farmers' own seed stock. Farmers broadcast pre-germinated seeds manually because of limited (or no) access to drum seeders. The most important production constraint identified was severe weed infestation, particularly by grass species, such as Echinochloa crus - galli (L.) P. Beauv., Leptochloa chinensis (L.) Nees, O. sativa L. (as volunteers from previous seasons), and O. sativa f. spontanea or weedy rice. Most farmers were aware of the presence of weedy rice in their fields and the damage it does to the crop. They enumerated numerous strategies to improve current practices to manage weeds. Despite the constraints, yield across the sites for two years ranged from 6.27 to 8.27 t ha −1 , which may be considered higher than those obtained from other rice ecosystems across Asia. This also highlights that there is further scope to increase the rice yield in weedy rice infested fields. [ABSTRACT FROM AUTHOR]

Background The evaluation of nutrient variability plays a crucial role in accessing soil potentials and practical intervention responses in rice production systems. Synthetic fertilizer applications and cultivation practices are considered key factors affecting nutrient dynamics and availability. Here, we assessed the nutrient dynamics in surface, subsurface water and soil under local water management and conventional rice cultivation practices in the Vietnamese Mekong Delta. Methods We implemented a field experiment (200 m 2 ) in the 2018 wet season and the 2019 dry season in a triple rice-cropping field. Eight samples of surface water, subsurface water (30-45 cm), and topsoil (0-20 cm) were collected and analysed during the rice-growing seasons. Results The results showed that N-NH 4 + , P-PO 4 3- and total P peaks were achieved after fertilizing. Irrespective of seasons, the nutrient content in surface water was always greater than that of subsurface water ( P < 0.001), with the exception of N-NO 3 - , which was insignificant ( P > 0.05). When comparing the wet and dry seasons, nutrient concentrations exhibited minor differences ( P > 0.05). Under conventional rice cultivation, the effects of synthetic fertilizer topdressing on the total N, soil organic matter (SOM), and total P were negligible in the soil. Higher rates of N fertilizer application did not significantly increase soil N-NH 4 + , total N, yet larger P fertilizer amounts substantially enhanced soil total P ( P < 0.001). Conclusions Under conventional rice cultivation, N-NH 4 + , P-PO 4 3- and total P losses mainly occur through runoff rather than leaching. While N-NO 3 - loss is similar in surface water and subsurface water. Notably, nutrient content in soil was high; whilst SOM was seen to be low-to-medium between seasons. Future work should consider the nutrient balance and dynamic simulation in the lowland soil of the Vietnamese Mekong Delta's paddy fields., Competing Interests: No competing interests were disclosed., (Copyright: © 2023 Ngan NVC et al.)

Rational water and fertilizer management approaches and technologies could improve water use efficiency and fertilizer use efficiency in paddy rice cultivation. A promising water-conserving technology for paddy rice farming is the alternate wetting and drying irrigation system, established by the International Rice Research Institute. However, the strategy has still not been widely adopted, because water level measurement is challenging work and sometimes leads to a decrease in the rice yield. For the easy implementation of alternate wetting and drying among farmers, we analyzed a dataset obtained from a farmer's water management study carried out over a three-year period with three cropping seasons at six locations ( n = 82) in An Giang Province, Southern Vietnam. We observed a significant relationship between specific water level management and the rice yield and greenhouse gas emissions during different growth periods. The average water level during the crop period was an important factor in increasing the rice yield and reducing greenhouse gas emissions. The average water level at 2 days after nitrogen fertilization also showed a potential to increase the rice yield. The greenhouse gas emissions were reduced when the number of days of non-flooded soil use was increased by 1 day during the crop period. The results offer insights demonstrating that farmers' implementation of multiple drainage during whole crop period and nitrogen fertilization period has the potential to contribute to both the rice yield increase and reduction in greenhouse gas emissions from rice cultivation.

The COVID-19 pandemic has impacted the food industry and consumers, with production gaps, shipping delays, and changes in supply and demand leading to an increased risk of food fraud. Rice has a high probability for adulteration by food fraudsters, being a staple commodity for more than half the global population, making the assessment of geographical origins of rice for authenticity important in terms of protecting businesses and consumers. In this study, we describe ICP-MS elemental profiling coupled with elementomic modelling to identify the geographical indications of Indian, Chinese, and Vietnamese rice. A PLS-DA model exhibited good discrimination (R 2  = 0.8393, Q 2  = 0.7673, accuracy = 1.0). Data-driven soft independent modelling of class analogy (dd-SIMCA) and K-nearest neighbours (K-NN) models have good sensitivity (98%) and specificity (100%)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Abstract This paper examines the fieldwork undertaken by the distinguished French geographer Pierre Gourou (1900–99) in the Tonkin Delta (Red River Delta) of northern Vietnam in the 1920s and 1930s, and his wider configuration of “the tropical world” as a distinct space of knowledge and radical otherness. Gourou's fieldwork endeavours in French Indochina are interpreted in the light of recent work on “tropicality”: the idea that “the tropics” need to be understood as a western cultural construction and colonising discourse that essentialised the hot, wet regions of the world, and exalted the temperate world over its tropical counterpart. The paper focuses on Gourou's monumental 1936 study Les paysans du delta tonkinois, étude de géographie humaine. It is argued that in this study, and his later comparative work on the tropics, Gourou elaborated a distinct geographical variant of tropicality, but one that, ultimately, reinforced the essentialist logic and momentum of this discourse. Particular attention is paid to the geographical ideas, fieldwork techniques and discursive strategies that Gourou used in his 1936 study, and the French colonial context in which he worked. The article shows how Gourou appealed to western reason and science as tools of study, identified overpopulation as the key problem facing the Tonkin Delta, and suggested that colonial practices of modernisation had a limited place and ineffectual role in the rice plains of the region. [ABSTRACT FROM AUTHOR]

Production of indole-3-acetic acid (IAA) is well documented in various studies for the bacteria that inhabit the rhizosphere of plants, but with roots of wet rice, the outstandings have been not yet elucidated. This study began with the isolation of bacteria type strain Azospirillum sp. and developed the investigation to a screening of their ability in IAA production. This screening conducted a selection of only bacteria that was capable of the production of IAA with its content of over 25 µg. mL -1 for sequencing. Of 10 isolates only one resulted from the type strain Azospirillum brasilense (A. brasilense) with a similarity of 100%. Various factors that influence A. brasilense in biosynthesizing IAA such as temperature, pH, nitrogen presence and concentration of tryptophan in the culture medium were examined. The results indicated that the culture conditions were suitable for IAA biosynthesis at pH 6.5, 30 °C, culture media with nitrogen, and 0.1% trytophan. The next survey on the role of the immobilization of this bacteria with microalgae in alginate was highlighted to its support in microalgal growth. With the co-immobilization of bacteria and microalgae, the density of Chlorella vulgaris was significantly increased during 15-day culture, inducing 2.2 times of cell content in culture batch microalgae immobilized A. brasilense higher than that free-bacteria., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This paper presents the first attempt to capture a comprehensive spatial view of land use change in the Vietnamese Mekong Delta (VMD) for a long period, i.e., from 2000 to 2020. It is aimed at monitoring holistically the land use change and flooding situation in the region, addressing the reasons for land use change, and assessing the impacts of land use change on hydraulic aspects and farmer livelihoods during the last 21 years. MODIS products, in particular, are used to study the dynamics of land use and floods after demonstrating high validation with statistical data and radar satellites, with R 2  = 0.96 and R 2  ≥ 0.97 for land use and flood maps, respectively. The results show that rice cultivation is the most dominant land use type, accounting for 40% to 46% of the delta area, while aquaculture accounts for 10% to 22%, respectively. The total rice cultivation area increased from 3764 thousand hectares (thous. ha) in 2001 to 4343 thous. ha in 2015 based on the intensive development of triple rice cropping in the upper zone, then decreased to 3963 thous. ha in 2020. In contrast, aquaculture areas are farmed mainly in the coastal area and remained relatively steady, increasing slightly from 619 thous. ha in 2001 to 856 thous. ha in 2020. The massive construction of dikes for triple rice cropping in the upper zone appears to cause a significant impact on the annual flooding regime. Land use policies have influenced the changes in land use patterns, flooding situations, and the livelihoods of local farmers., Competing Interests: Declaration of competing interest The authors declare no conflict of interest that could influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Vietnam, one of the three leading rice producers globally, has recently seen an increased threat to its rice production emanating from climate extremes (floods and droughts). Understanding spatio-temporal variability in precipitation and soil moisture is essential for policy formulations to adapt and cope with the impacts of climate extremes on rice production in Vietnam. Adopting a higher-order statistical method of independent component analysis (ICA), this study explores the spatio-temporal variability in the Climate Hazards Group InfraRed Precipitation Station's (CHIRPS) precipitation and the Global Land Data Assimilation System's (GLDAS) soil moisture products. The results indicate an agreement between monthly CHIRPS precipitation and monthly GLDAS soil moisture with the wetter period over the southern and South Central Coast areas that is latter than that over the northern and North Central Coast areas. However, the spatial patterns of annual mean precipitation and soil moisture disagree, likely due to factors other than precipitation affecting the amount of moisture in the soil layers, e.g., temperature, irrigation, and drainage systems, which are inconsistent between areas. The CHIRPS Standardized Precipitation Index (SPI) is useful in capturing climate extremes, and the GLDAS Standardized Soil Moisture Index (SSI) is useful in identifying the influences of climate extremes on rice production in Vietnam. During the 2016-2018 period, there existed a reduction in the residual rice yield that was consistent with a decrease in soil moisture during the same time period.

It is essential to increase the production of foods to meet the increasing future food demand, but this should be done in an environmentally sustainable manner. Integrated crop-livestock systems have been suggested to balance the reduction of environmental impacts and the increase in food production. Here we assessed and compared the environmental impacts of specialized (SPC) and integrated (ITG) rice and beef production systems in the Mekong Delta, Vietnam, using a life-cycle assessment (LCA). The productions of rice and beef are separated in the SPC, whereas they are integrated in the ITG: cattle manure is treated by a biodigester for biogas production, its digestate is applied to rice paddy fields as fertilizer, and part of the rice straw is used as cattle feed. We developed an LCA model based on data collected by site investigations of rice and beef farms and the relevant literature and LCA databases. Our evaluation of the ITG and SPC rice-beef production systems using the LCA revealed that among the four environmental impact categories investigated herein, the ITG had less environmental impacts on climate change (22%), energy consumption (22%), and eutrophication (14%) compared to the SPC. With the ITG, the reduction of methane emissions from paddy fields, the avoided energy consumption by the biogas produced, and the lower ammonia, nitrate, and phosphorous emissions from cattle manure and no eutrophying pollutant emissions from grassland were the main contributors to the lower greenhouse gas emissions, energy consumption, and eutrophication potential of this system, respectively. A sensitivity analysis showed that the use of cover for digestate storage resulted in lower environmental impacts of the ITG system compared to SPC system in all of the impact categories investigated here. These results provide helpful information to develop a circular and resource-efficient rice and beef production system that balances increasing productivity with environmental sustainability in rice-producing countries, particularly in Asia., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Although rice straw open burning is one of the main sources of air pollution in Asian countries, problems remain in collecting the activity data needed to calculate emission inventories. In Vietnam, the results from traditional data collection methods, which are reported by the Vietnam General Statistics Office high levels of uncertainty. This is largely due to a lack of human and financial resources. To improve upon this, this study critically assessed the benefits of incorporating cultivation area data obtained by the Sentinel-1 Synthetic Aperture Radar (SAR) satellite in combination with crop production records during the period of 2015–2017. The results suggested that incorporating remote sensing data, especially satellite data, into a process-based crop model can improve the spatial distribution of yield estimates. Satellite data for 2018 were also applied to estimate emissions from rice straw open burning in the Red River Delta, Vietnam, for which official statistics are not otherwise yet available. The results show that a total of 3.24 Mt of burnt rice straw produced 3.82 Mt of CO 2 , 301 Gg of CO, 29.5 Gg of PM 10 , and 27 Gg of PM 2.5. The estimated emission amounts for the common air pollutants SO 2 , NO x , and NH 3 were 583 tonnes, 7.4 Gg, and 13.3 Gg, respectively. Hydrocarbon emissions were 31 Gg for CH 4 and 22.7 Gg for NMVOC. The emission of BC, which is one of the main short-lived climate forcers, totalled 1.6 Gg. Based on these results, satellite data demonstrate great potential for estimating emissions from rice croplands, having the advantages of timely availability and cost competitiveness. Image 1 • Sentinel-1 images integrated with ORYZA 2000 model improve crop-growth data. • New crop datasets reduce uncertainties by 10–12.4% compared to traditional methods. • 29.5 Gg of PM 10 , 27 Gg of PM 2.5 , 1.6 Gg of BC emitted in the Red River Delta (2018). • 3.82 Mt of CO 2 contributed the most to air emissions from rice straw open burning. [ABSTRACT FROM AUTHOR]

This work focuses on the lime pretreatment of rice straw, agricultural waste in northeast Vietnam, for microbial lipid (bio-lipid) production. A response surface methodology approach was performed to optimize parameters for the pretreatment process. These parameters are the concentration of Ca(OH) 2 , hydrolysis temperature, and maintained time; the effect is considered bio-lipid production yield. The lipid yield was estimated through consolidated bioprocessing of the pretreated rice straw as a substrate and using the fungus strain (Aspergillus oryzae 32) and the yeast strain (Lipomyces starkeyi 22). As a result, the optimal pretreatment conditions for maximum lipid yield were obtained at Ca(OH) 2 concentration of 12 g/L and hydrolysis temperature of 110 °C within 60 min. The accumulated lipid in fermentation using these oleaginous microorganisms was 8.5g/100g oven-dry weight of rice straw (10.9g/100g for pretreated rice straw). The biolipid consisted of 42.6% saturated, 21.1% monounsaturated (MUFA), and 35.1% polyunsaturated (PUFA) fatty acids., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Aquatic ecosystems are used for extensive rice-shrimp culture where the available water alternates seasonally between fresh and saline. Poor water quality has been implicated as a risk factor for shrimp survival; however, links between shrimp, water quality and their main food source, the natural aquatic biota inhabiting these ponds, are less well understood. We examined the aquatic biota and water quality of three ponds over an entire year in the Mekong Delta, Vietnam, where the growing season for the marine shrimp Penaeus monodon has been extended into the wet season, when waters freshen. The survival (30-41%) and total areal biomass (350-531 kg ha -1 ) of shrimp was constrained by poor water quality, with water temperatures, salinity and dissolved oxygen concentrations falling outside known optimal ranges for several weeks. Declines in dissolved oxygen concentration were matched by declines in both shrimp growth rates and lipid content, the latter being indicative of nutritional condition. Furthermore, as the dry season transitioned into the wet, shifts in the taxonomic composition of phytoplankton and zooplankton were accompanied by declines in the biomass of benthic algae, an important basal food source in these systems. Densities of the benthic invertebrates directly consumed by shrimp also varied substantially throughout the year. Overall, our findings suggest that the survival, condition and growth of shrimp in extensive rice-shrimp ecosystems will be constrained when poor water quality and alternating high and low salinity negatively affect the physiology, growth and composition of the natural aquatic biota. Changes in management practices, such as restricting shrimp inhabiting ponds to the dry season, may help to address these issues and improve the sustainable productivity and overall condition of these important aquatic ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in tfSupplementary materialhis paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In topsoils, the activity concentrations of natural radionuclides (hereafter NRs) increase due to the addition of NRs from fertilizers, irrigation water, and air dust pollution. On the other hand, various physical-chemical and environmental processes such as radioactive decay, volatilization, leaching, erosion, and plant uptake were responsible for the decrease of the activity concentrations of NRs in the topsoils. In this study, behaviours of 40 K, 210 Pb, 226 Ra, 238 U, and 232 Th in topsoils were modelled by the CEMC soil model and the HYDRUS-1D model. An exponential equation was proposed for estimating the accumulation rates of these radionuclides in the topsoils. Long-term accumulation of radionuclides was assessed for water spinach (Ipomoea Aquatica Forssk.) soil (hereafter VES) and rice (Oryza sativa L.) soil (hereafter RIS). We found that the current agricultural practices caused the increase of 40 K activity concentration in the water spinach soil, and 40 K, 210 Pb, 226 Ra, and 232 Th activity concentrations in the rice soil. The accumulation rates of radionuclides were in the order 238 U <  232 Th <  226 Ra < 210 Pb <  40 K. 25 years of cultivation with water spinach can increase/decrease + (165 ± 6) Bq of 40 K, - (8.2 ± 0.7) Bq of 210 Pb, - (4.3 ± 0.2) Bq of 226 Ra, - (7 0.3 ± 0.3) Bq of 238 U, and - (1.8 ± 0.1) Bq of 232 Th in 1 kg soil. For rice cultivation, these values are + (1004 ± 39), + (3.3 ± 0.2), + (3.0 ± 0.2), - (5.1 ± 0.3), (2.2 ± 0.1) Bq kg -1 for 40 K, 210 Pb, 226 Ra, 238 U, and 232 Th, respectively., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study sought to determine the factors influencing rice farmers' adaptation to a slow-onset hazard such as saltwater inundation. The research is based on a survey conducted through personal interviews using Kobotool App consisting of 326 coastal rice farmers in Northern Mindanao, the Philippines and 258 rice farmers in two provinces in the Mekong Delta in Vietnam. There were four levels of analyses for the assessment of the feasibility of the adaptation measures implemented by the farmers. First, it classified adaptation measures into specific categories: technology based, farm-based crop management, ecosystem-based adaptation, off-farm income diversification, and other measures. Second, it developed a multi-criteria assessment tool on adaptation measures based on stakeholder analysis and expert judgment based on four major feasibility criteria. Third, it determined the level of adaptation based on the combination of measures and the feasibility of the chosen measures by constructing a measure-based adaptation index (MAI). Finally, it came up with a model showing the factors influencing the MAI of the farmers. The results revealed that adaptation takes place at different levels in the two countries based on the diversity of measures, the feasibility of the various measures, and the varying conditions of saltwater inundation. The empirical evidence provides systematic support for the hypothesis that adaptation measures are influenced by a confluence of social, institutional, and economic factors.

Meloidogyne graminicola, also known as the rice root-knot nematode, is one of the most damaging plant-parasitic nematode, especially on rice. This obligate soilborne parasite induces the formation of galls that disturb the root morphology and physiology. Its impact on the root microbiome is still not well described. Here, we conducted a survey in Northern Vietnam where we collected infected (with galls) and non-infected root tips from the same plants in three naturally infested fields. Using a metabarcoding approach, we discovered that M. graminicola infection caused modifications of the root bacterial community composition and network structure. Interestingly, we observed in infected roots a higher diversity and species richness (+24% observed ESVs) as well as a denser and more complex co-occurrence network (+44% nodes and +136% links). We identified enriched taxa that include several hubs, which could serve as potential indicators or biocontrol agents of the nematode infection. Moreover, the community of infected roots is more specific suggesting changes in the functional capabilities to survive in the gall environment. We thus describe the signature of the gall microbiome (the 'gallobiome') with shifting abundances and enrichments that lead to a strong restructuration of the root microbiome., (© FEMS 2020.)

The neotropical fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is an important lepidopteran pest with a broad geographical distribution (Goergen et al. 2015, Early et al. 2018, Sharanabasappa et al. 2018). Larvae of S. frugiperda feed on more than 350 plant species, including several economically-important crops such as maize, sugarcane or rice (Montezano et al. 2018). Following its invasion of the African continent and of South Asia in 2016 and 2018 respectively, FAW has caused important crop losses and associated livelihood impacts (Baudron et al., 2019). During 2019, FAW rapidly spread across Southeast Asia and FAW-attributed feeding damage was recorded on maize in Viet Nam. In Viet Nam, maize is the second most important staple food crop after rice, is extensively used for livestock production and poultry feed, and thus plays a central role in sustaining rural livelihoods (Dang et al. 2004). Hence, the recent FAW invasion and the anticipated pest-induced yield losses will carry important repercussions for local maize value chains and are likely to degrade farmers' revenue base. In this study, we conducted a morphological and molecular identification of locally-collected FAW individuals to better characterize the species' invasion history in Viet Nam.

Saline water intrusion has become a severe threat in the coastal areas of Mekong delta of Vietnam, though offering farmers the option to diversify their land use, and switching, for instance, from permanent rice to alternating rice-shrimp systems or even to permanent shrimp systems. The objective of this study was to evaluate the respective impacts on soil salinity, nutrient status and their binding forms. Hence, we sampled the topsoils (cultivation layer, 0-15 cm) from 10 permanent rice systems and the rice platforms of 10 alternating riceshrimp systems. Furthermore, the sludges and the soils 10 cm underneath of the sludges from the ditches of the alternating rice-shrimp as well as from ponds of the permanent shrimp systems were sampled in Bến Tre and Sóc Trăng provinces, Vietnam, respectively. The samples were analyzed regarding their electric conductivity, total and plant-available nutrient contents. To reveal possible changes in nutrient binding forms, sequential P and S extraction, 31P-nuclear magnetic resonance spectroscopy, and S and P X-ray absorption near edge structure spectroscopy were applied. The results showed that permanent and alternating shrimp cultivation lead to elevated salt concentrations but also improved the overall nutrient status relative to the permanent rice management and especially in the sludges relative to the soils underneath. The continued deposition of shrimp and feed debris promoted the accrual of stable, Ca- and Mg-associated P forms as well as of P-monoesters, whereas the S forms were depleted in thiophene S groups but enriched in sulfides relative to permanent rice fields. As effects by alternating rice-shrimp management were intermediate, this management has more potential to serve as a no-regret strategy for farmers to remain flexible in their response to climate changes and concurrent salinity intrusion relative to permanent shrimp production, which requires strict maintenance of adequate salinity levels also during the rainy season., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A total of 239 isolates of blast ( Pyricularia oryzae Cavara) collected from northern and central Vietnam showed a wide variation in pathogenicity based on the reaction patterns to 25 differential varieties (DVs) harboring 23 resistance genes and susceptible cultivar Lijiangxintuanheigu (LTH). The frequencies of isolates virulent toward DVs for Pish , Pik-m , Pi1 , Pik-h , Pik , Pik-p , Pi7 (t), Pi9 (t), Piz-5 , Pita-2 , and Pita were low, but they were high for DVs for Pib , Pit , Pia , Pii , Pi3 , Pi5 (t), Pik-s , Piz , Piz-t , Pi12 (t), Pi19 (t), and Pi20 (t). Isolates were classified into three cluster groups Ia, Ib, and II based on reaction patterns to DVs and LTH. The frequencies of isolates virulent toward 11 DVs for Pik-m , Pi1 , Pik-h , Pik , Pik-p , Pi7 (t), Pi9 (t), Piz , Piz-5 , Pita-2 , and Pita in cluster II and DV for Piz-t were higher and lower than those of Ia and Ib, respectively. The frequencies to DVs for Pii , Pi3 , Pi5 (t), and Piz-t were different between clusters Ia and Ib. Clusters Ia and Ib were distributed with similar frequencies in the northeast, north central, and south central coast regions, but the frequencies among three cluster groups in the Red River Delta and northwest regions were different. This means that the blast races in these two regions were different from the others. Overall, the blast isolates were categorized into 153 races. Among them, 26 were selected as a set of standard differential blast isolates for characterizing 23 resistance genes and developing a differential system in Vietnam.

In this paper, we try to understand pesticide input decisions among Vietnamese rice producers by examining the production risk effects of pesticide use, applying both a lottery game and a more traditional production function approach. Production function estimates show that excessive pesticide use makes production riskier. This result is supported by the lottery approach, which signals that more risk averse farmers use less pesticide, implying that pesticide is a risk-increasing input. We also show, that higher uncertainty regarding drought relative to pest is likely driving the increasing risk effect of pesticides. Therefore, we claim that the relative importance of multiple uncertainties on pest and water is relevant to determine the risk property of pesticide., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The Mekong Delta paddies are known as hotspots of methane emission, but these emissions are not well studied. We analyzed methane emission patterns based on monitoring data from typical triple rice cropping paddies collected over 5 years. We found that the total emissions in a crop season doubled in the second crop, tripled in the third crop, and reset after the annual natural flood of the Mekong River. The emission peaks occurred around 0 to 3 weeks after starting irrigation, then gradually decreased. This suggests that methane was generated by the soil organic matter, because the small rice plants provide little carbon for methanogenesis. In general, the main source of emitted methane is rice-derived carbon by current-season photosynthates and the emission peaks at the rice heading stage. However, the contribution of the rice-derived carbon is negligible in the hotspot paddies while total emission is high. The increase in emission levels from the first to the third crop can be explained by the accumulation of rice residue from the preceding crops, especially rice straw incorporated into the soil. The reset of emission levels after annual flood means that the rice straw is decomposed without methanogenesis in water with dissolved oxygen. Thus, the annual emission pattern shows that decomposing rice straw in paddy surface-water is an effective method to reduce methane emissions., Competing Interests: No competing interests were disclosed., (Copyright: © 2020 Oda M and Nguyen HC.)

This research investigated the distribution and contribution of polycyclic aromatic hydrocarbons (PAHs) and nitro-polycyclic aromatic hydrocarbons (NPAHs) bound to particulate matter (PM) emitted from open burning of rice straw (RS) into the atmosphere in the north of Vietnam. The experiments were conducted to collect PM 2.5 and total suspended particulates (TSP) prior to and during burning in the period of 2016-2018 in suburban areas of Hanoi. Nine PAHs and 18 NPAHs were determined using the HPLC-FL system. The results showed that the proportion of RS burning seasonally affects the variation of PAHs emission in atmospheric environment. The levels of nine PAHs from RS burning were 254.4 ± 87.8 µg g -1 for PM 2.5 and 209.7 ± 89.5 µg g -1 for TSP. We observed the fact that, although fluoranthene (Flu) was the most abundant PAH among detected PAHs both in PM 2.5 and TSP, the enrichment of Flu in TSP from burning smoke was higher than that in PM 2.5 while the contribution of benzo[ a ]pyrene (B a P) and indeno[ 1,2,3- cd ]pyrene (IDP) in PM 2.5 from burning smoke were much higher than those in TSP. This research found that 1-nitropyrene (1-NP) and 6-nitrochrysene (6-NC) emit from RS burning with the same range with those from wood burning. The 2-nitrofluorene (2-NF) and 2-nitropyrene (2-NP) released from RS burning as the secondary NPAHs. This research provides a comprehensive contribution characterization of PAHs and NPAHs in PM with different size emitted from traditional local rice straw burning in the north of Vietnam. The results help to clarify the environmental behavior of toxic organic compounds from RS burning in Southeast Asia.

Agricultural farmers in developing countries are at high risk of pesticide exposure and adverse effects because of unsafe practices and inappropriate legislation. Biological monitoring is considered a useful tool for pesticide exposure assessment; however, its use is limited in developing countries due to a lack of techniques and resources such as laboratory analysis, trained staff and budgets. This study examines whether the World Health Organization predicted exposure assessment model (WHO-PEAM) is a suitable alternative tool for assessing insecticide exposure among agricultural farmers. WHO-PEAM was used to predict daily doses (PDD) of chlorpyrifos for a group of Vietnamese rice farmers using a set of exposure parameters obtained from a questionnaire survey of participant famers during a field study. These results were compared to absorbed daily doses (ADD) of chlorpyrifos for the farmers measured using a biological monitoring program, in which 24-h urine samples were collected and analysed for the chlorpyrifos metabolite, 3,5,6-trichloro-2-pyridinol (TCP) using LC/MS. Validation of the model results was tested using the Wilcoxon signed-rank test (WSR) and two-way mixed-model intraclass correlation coefficient (ICC). The mean of total ADD was 20 μg/kg/day while that of total PDD was 22 μg/kg/day. The WSR test revealed no statistically significant difference in the average values of ADD T and PDD T . ICC indicated substantial agreement for both single and average measures between ADD T and PDD T (ICC, 0.62 and 0.77, respectively). The results demonstrate that a refined WHO-PEAM model can be readily used as a field method, without biological monitoring, to evaluate chlorpyrifos exposure among agricultural farmers in Vietnam and similar developing countries.

The Red River Delta is a major agricultural production area of Vietnam with year-round use of pesticides for paddy rice cultivation and other production systems. The delta is protected from flooding, storm surges and saline water intrusion by a sophisticated river and sea-dyke system. Little is known about the effects of such a dyke system on pesticide pollution in the enclosed landscape. Our aim was to address this gap by i) determining pesticide prevalence in soils and sediments within a dyked agricultural area, and by ii) assessing whether and to which degree this dyke system might affect the spatial distribution of pesticides. After sampling paddy rice fields (topsoil) and irrigation ditches (sediment) perpendicular to the dyke in Giao Thuy district, we analysed 12 of the most commonly used pesticides in this area. In soils, we detected most frequently isoprothiolane (100% detection frequency), chlorpyrifos (85%) and propiconazole (41%) while in sediments isoprothiolane (71%) and propiconazole (71%) were most frequently found. Maximum concentrations reached 42.6 μg isoprotiolane kg -1 in soil, and 35.1 μg azoxystrobin kg -1 in sediment. Our results supported the assumption that the dyke system influenced residue distribution of selected pesticides. More polar substances increasingly accumulated in fields closer to the sea-dyke (R 2  = 0.92 for chlorpyrifos and 0.51 for isoprothiolane). We can thus support initiatives from local authorities to use the distance to dykes as a mean for deliniating zones of different environmental pollution; yet, the degree at which dykes influence pesticide accumulation appear to be compound specific., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study evaluates the risks of pesticides applied in rice-fish and rice farming, with and without integrated pest management (IPM) strategies, to non-target aquatic organisms in two provinces of the Mekong Delta, Vietnam. Pesticide inventories and application patterns were collected from 120 Vietnamese farmers through interviews. Risks were assessed using (1) Pesticide RIsks in the Tropics to Man, Environment, and Trade (PRIMET), a first-tier model, which calculates predicted environmental concentrations (PECs) of pesticides in the rice field, based on the compound's physico-chemical properties and the application pattern, and then compares the PECs to safe concentrations based on literature data, and (2) species sensitivity distribution (SSD), a second-tier assessment model using species sensitivity distributions to calculate potentially affected fraction (PAF) of species based on the PECs from PRIMET. Our results show that several of the used insecticides pose a high risk to fish and arthropods and that the risks are higher among rice farmers than among rice-fish farmers. This study indicates that the PRIMET model in combination with SSDs offer suitable approaches to help farmers and plant protection staff to identify pesticides that may cause high risk to the environment and therefore should be substituted with safer alternatives.

Organophosphates (e.g. chlorpyrifos ethyl) and carbamates (e.g. fenobucarb) are commonly used to control a wide range of pests in rice fields of the Mekong Delta in Vietnam. This study assesses the combined effect of chlorpyrifos ethyl (CPF) and fenobucarb (F), applied at concentrations used by rice farmers, on the brain acetylcholinesterase (AChE) activity in climbing perch fingerlings from rice fields in the Mekong Delta. It also investigates if Pyridine-2-aldoxime methiodide (2-PAM) can be used to reactivate cholinesterase that has been blocked by CPF. Three days after spraying, the water concentrations of both insecticides decreased quickly below the detection levels. However, the brain AChE activity in fish was inhibited for more than 7 days. The results indicate a quicker but less prolonged inhibition of the brain AChE activity by the mixture than by only CPF. The inhibition levels were above 70 % only during the first 48 h, which could explain why all fish survived. 2-PAM resulted in a significant reactivation of the cholinesterase blocked by a combination of CPF and F, and it is proposed that the reactivation by 2-PAM could provide a way to assess the AChE inhibition levels in organisms, when no unexposed individuals are available as controls. The results indicate that the current use of CPF and F in rice farming in the Mekong Delta is likely to cause negative effects on non-target organisms. Many of these effects may be sub-lethal, and there is a need to develop biomarkers that are relevant, inexpensive and easy to apply. The results show that brain AChE in climbing perch fingerling is a relevant biomarker for monitoring of exposure to, and sub-lethal impacts from organophosphates and carbamates under tropical conditions in developing countries.

This study assesses the effects of sequential applications of the insecticides Bassa 50EC (fenobucarb-F) and Vitashield 40EC (chlorpyrifos ethyl-CPF), sprayed at concentrations used by rice farmers in the Mekong Delta, on the brain acetylcholinesterase (AChE) in climbing perch fingerlings. After spraying the pesticides on the rice fields, the water concentrations of both insecticides decreased below the detection levels within 3 days. The sequential applications caused significant inhibition on the brain AChE activity in the exposed fish. The inhibition by F was quicker, but less prolonged, than for CPF. The inhibition levels caused by the sequential applications were lower than those caused by only CPF and by a mixture of CPF and F. The results indicate that sequential applications of pesticides could have a negative impact on aquatic organisms and fish yields, with implication for the aquatic biodiversity, local people's livelihood and the aquaculture industry in the Mekong Delta.

There is a rapid transformation afoot in the rice value chain in Asia. The upstream is changing quickly-farmers are undertaking capital-led intensification and participating in burgeoning markets for land rental, fertilizer and pesticides, irrigation water, and seed, and shifting from subsistence to small commercialized farms; in some areas landholdings are concentrating. Midstream, in wholesale and milling, there is a quiet revolution underway, with thousands of entrepreneurs investing in equipment, increasing scale, diversifying into higher quality, and the segments are undergoing consolidation and vertical coordination and integration. Mills, especially in China, are packaging and branding, and building agent networks in wholesale markets, and large mills are building direct relationships with supermarkets. The downstream retail segment is undergoing a "supermarket revolution," again with the lead in change in China. In most cases the government is not playing a direct role in the market, but enabling this transformation through infrastructural investment. The transformation appears to be improving food security for cities by reducing margins, offering lower consumer rice prices, and increasing quality and diversity of rice. This paper discusses findings derived from unique stacked surveys of all value chain segments in seven zones, more and less developed, around Bangladesh, China, India, and Vietnam., (© 2014 New York Academy of Sciences.)

We have reported that newly diagnosed type 2 diabetes mellitus (DM) patients in Vietnam have a low body mass index (BMI) of around 23 and that the major factor for this is high white rice (WR) intake. Brown rice (BR) is known to be beneficial in the control of blood glucose levels; however, it has the property of unpleasant palatability. Pre-germinated brown rice (PGBR) is slightly germinated by soaking BR in water as this reduces the hardness of BR and makes it easier to eat. This study was designed to evaluate the effect of a 4-mo PGBR administration on various parameters in Vietnamese women aged 45-65 y with impaired glucose tolerance (IGT). Sixty subjects were divided into a WR or PGBR group. For the first 2 wk, WR was replaced by 50% PGBR, then for 2 wk by 75% PGBR and from the second month 100%. Before the beginning of the study and at the end of the study, 1) anthropometric measurements, 2) a nutrition survey for 3 nonconsecutive days by the 24 h recall method and 3) blood biochemical examinations were conducted. Fasting plasma concentrations of glucose and lipids and the obesity-related measurements and blood pressure were favorably improved only in the PGBR diet group. The present results suggest that replacing WR with PGBR for 4 mo may be useful in controlling body weight as well as blood glucose and lipid levels in Vietnamese women with IGT.

Traditional complementary foods (CF) with a low nutrient density have been implicated in growth faltering, stunting, and other adverse outcomes in children. The efficacy of 2 types of locally produced, micronutrient-fortified CF to prevent stunting of infants living in rural Vietnam was evaluated. In a village-randomized controlled study, 426 infants, 5 mo of age, received for 6 mo a fortified CF, either as an instant flour (FF) or a food complement (FC) in village canteens, or traditional CF at home (C). After 6 mo of intervention, weight, length, length-for-age Z-score (LAZ) and weight-for-age Z-score were greater in the 2 intervention groups compared with the C group, with an estimated effect of +0.22 LAZ for the FF group and +0.21 LAZ for the FC group. At the last follow-up, 18 mo after the intervention, there was no significant difference in height-for-age Z-score (HAZ) between the groups, even though the HAZ in the FF group was 0.17 greater than that in the C group (P = 0.18). In contrast, the weight-for-height Z-score and BMI Z-score, indices of ponderal growth, were greater in the FF group (-0.49 and -0.26, respectively) than in the FC group (-0.73 and -0.49, respectively), with Z-scores in the C group intermediate and not significantly different from the others. This study shows that regular provision of locally produced CF fortified with micronutrients partly stopped growth faltering in Vietnamese infants, with differential effects on long-term length and ponderal growth. Providing only micronutrients instead of a complete array of nutrients might result in only short-term length growth benefits.

Chlorpyrifos is the most common organophosphate compound registered for agricultural use in Vietnam. The aim of this study was to evaluate chlorpyrifos exposure to rice farmers in Vietnam, using a probabilistic approach. Urine samples on a 24-h basis were collected from farmers before and post application of pesticide. Samples were analysed for 3,5,6-trichloro-2-pyridinol (TCP), the major urinary metabolite of chlorpyrifos, using an enzymatic pre-treatment for extraction and HPLC-MS/MS. Absorbed daily doses (ADD) of chlorpyrifos for farmers were subsequently estimated from the urinary TCP levels. The baseline and post-application exposure levels were evaluated at the 5th, 50th, and 95th percentile representing low, medium and high-exposure groups in the population. Regression analysis was applied to examine the association between exposure level and factors. The baseline exposure level, which ranged from 0.03 to 1.98 μg/kg/day was below the chronic guidelines recommended by international and national bodies. However, the post-application exposure level, which ranged from 0.35 to 94 μg/kg/day exceeded most of the acute guidelines at the 95th percentile level. Multivariate analysis provided strong evidence for a relationship between post-application exposure level and amount of chlorpyrifos used, as well as body coverage of personal protective equipment.

Chlorpyrifos is the most common organophosphate insecticide registered for use in Vietnam and is widely used in agriculture, particularly rice farming. However, chlorpyrifos exposure to and adverse effects on farmers has not been evaluated. In this study, biological monitoring of chlorpyrifos exposure in a group of rice farmers was conducted after a typical application event using back-pack spraying. Urine samples (24 h) were collected from the rice farmers before and post insecticide application. Samples were analysed for 3,5,6-trichloropyridinol (TCP), the major urinary metabolite of chlorpyrifos, using an enzymatic pre-treatment before extraction followed by HPLC-MS/MS. Absorbed Daily Dose (ADD) of chlorpyrifos for farmers were then estimated from urinary TCP levels, expressed as μg g(-1)creatinine. The analytical method for urinary TCP had a low detection limit (0.6 μg L(-1)), acceptable recovery values (80-114%), and low relative percentage differences in duplicate and repeated samples. Post-application chlorpyrifos ADD of farmers varied from 0.4 to 94.2 μg kg(-1) (body weight) d(-1) with a mean of 19.4 μg kg(-1) d(-1) which was approximately 80-fold higher than the mean baseline exposure level (0.24 μg kg(-1) d(-1)). Hazard Quotients (ratio of the mean ADD for rice farmers to acute oral reference dose) calculated using acute oral reference doses recommended by United States and Australian agencies varied from 2.1 (Australian NRA), 4.2 (US EPA) to 6.9 (ATSDR). Biological monitoring using HPLC-MS/MS analysis of urinary TCP (24 h) was found to be an effective method for measuring chlorpyrifos exposure among farmers. This case study found that Vietnamese rice farmers had relatively high exposures to chlorpyrifos after application, which were likely to have adverse health effects., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus, known vectors of Japanese encephalitis (JE), are distributed in rice agroecosystems in Asian countries. Very few integrated studies on the breeding habitats of rice-field mosquitoes, including JE vectors, have been conducted in Vietnam. We investigated the mosquito fauna and potential predators in 8 rice growing areas in the Mekong Delta region of southern Vietnam, during the wet and dry seasons of 2009. Mosquitoes and their predators were collected from a variety of aquatic habitats (rice fields, ponds, wetlands, shrimp ponds, ditches, canals, and rivers). We collected 936 Culex spp. (354 Cx. tritaeniorhynchus, 240 Cx. vishnui s.l., 189 Cx. fuscocephala, and 42 Cx. gelidus), 33 Uranotaenia, 25 Anopheles, and 9 Mimomyia (4 Mi. chamberlaini) in the dry season. During the rainy season, we collected 1,232 Culex spp. (132 Cx. vishnui s.l., 66 Cx. tritaeniorhynchus, 9 Cx. gelidus, 4 Cx. fuscocephala, and 2 Cx. bitaeniorhynchus), 236 Anopheles spp. (40 An. vagus and 1 An. sinensis), and 7 Uranotaenia (3 Ur. lateralis). Heteroptera such as Micronecta, Veliidae, and Pleidae were abundant and widely distributed in both seasons. Based on a stepwise generalized linear model, the abundance of mosquitoes and their predators in rice fields was high when the rice plant length was short and water depth was shallow. Therefore, the use of insecticides during the earlier stages of rice growth should be avoided in order to preserve the predator populations.

In this review, we summarize the current knowledge on exposure, metabolism, and health effects of arsenic (As) in residents from As-contaminated groundwater areas of Vietnam and Cambodia based on our findings from 2000 and other studies. The health effects of As in humans include severe gastrointestinal disorders, hepatic and renal failure, cardiovascular disturbances, skin pigmentation, hyperkeratosis, and cancers in the lung, bladder, liver, kidney, and skin. Arsenic contamination in groundwater is widely present at Vietnam and Cambodia and the highest As levels are frequently found in groundwater from Cambodia. Sand filter system can reduce As concentration in raw groundwater. The results of hair and urine analyses indicate that residents from these As-contaminated areas are exposed to As. In general, sex, age, body mass index, and As exposure level are significantly associated with As metabolism. Genetic polymorphisms in arsenic (+III) methyltransferase and glutathione-S-transferase isoforms may be influenced As metabolism and accumulation in a Vietnamese population. It is suggested oxidative DNA damage is caused by exposure to As in groundwater from residents in Cambodia. An epidemiologic study on an association of As exposure with human health effects is required in these areas.

Extrusion cooking and amylase addition are two processing methods used for the preparation of high energy dense (ED) gruels of suitable consistency. A quantitative study of energy and nutrient intakes of 67 infants aged 6 to 10 months in rural areas in Vietnam was carried out to compare the effects of these processes used alone or in combination. Twice a day, for a period of four days each, infants successively ate four gruels prepared from different flours based on a blend of rice, sesame and soybean: an instant flour obtained by extrusion cooking (gruel A), a ready-to-cook flour obtained by extrusion cooking plus alpha-amylase addition (gruel B), a flour produced by milling crude rice, sesame and roasted soybean plus alpha-amylase addition (gruel C) and without amylase (control gruel D). Gruels A, B and C had a high ED of respectively 94, 122 and 124 kcal/100 g while the control gruel D had a low ED (59 kcal/100 g). The intakes of the four gruels were inversely linked to their ED. However, despite the fact that gruels B and C had similar ED, larger intakes were obtained with gruel B, which was attributed to better acceptability. The average energy intakes of high ED gruels A, B and C, respectively 112, 134 and 117 kcal/meal, were significantly higher than that of gruel D (81 kcal/meal). Of the three processing methods, the one combining extrusion cooking and amylase addition gave the best results in terms of gruel acceptability and energy intake.

The aim of this study was to test the ability of two new products, an instant infant flour and a food supplement containing amylases, to increase energy and micronutrient intakes of infants older than 6 months. Three groups of 48 infants were randomly constituted. Infants in groups 1 and 2 consumed at least twice a day gruel made either from the instant flour or from the food supplement. Infants from the control group received complementary foods prepared in the usual way. Each infant was surveyed during a whole day in order to measure feeding frequencies and characteristics as well as amounts of the different types of complementary foods consumed. Foods consumed by infants in the two experimental groups differed considerably in energy, micronutrient density and in consistency from the home-made complementary foods. Due to the incorporation of amylases, gruels made from the food supplement had a higher energy density, a more appropriate consistency and resulted in higher intakes per meal than gruels made from instant flour. In comparison with home-made complementary foods, both experimental products resulted in significantly higher energy and nutrient intakes. The two experimental products appeared to increase sufficiently both energy and nutrient intakes of infants to complement their breastmilk intake.

Objective: To assess the risk of skin disease among farmers occupationally exposed to wastewater., Methods: One-year follow-up study with monthly assessments of wastewater exposure and skin disease in Nam Dinh, northern Vietnam, in two adjacent communes with contrasting levels of wastewater use. In each commune, 200 households were randomly selected., Results: Of the 1103 individuals aged > or =15 years, 381 reported a skin problem at baseline or at any of the monthly visits, primarily dermatitis (eczema) and superficial fungal infections. Among the 874 subjects who were free from skin disease at baseline and who could be followed up > or =11 months, 183 developed a new skin disease (cumulative incidence 21%). Exposure to wastewater was a major risk factor for skin disease with a relative risk (RR) of 1.89 [95% confidence interval (CI) 1.39-2.57] in multivariable analysis. Other risk factors for skin disease were involvement in agriculture in general (RR = 2.59, 95% CI 1.11-6.02), flower cultivation (RR = 1.36, 95% CI 1.01-1.83), vegetable farming (RR = 1.47, 95% CI 1.04-2.08), and a history of eczema (RR = 1.47, 95% CI 1.05-2.05)., Conclusion: Exposure to wastewater is a major risk factor for skin disease. In future studies, an attempt should be made to link specific chemical or biological agents in the wastewater to specific skin diseases.

This case-control study assessed the effects of pesticide use on semen characteristics among rice farmers of Kienxuong District, Thaibinh Province, Vietnam. Semen samples of 1,036 rice farmers were obtained by manual masturbation and screened at Commune Health Stations. Of these, 156 abnormal semen samples were identified; 314 rice farmers with normal semen were recruited as controls. The semen characteristics (volume, sperm concentration, total sperm count, motility, vitality and morphology) of the cases were considerably poorer than the controls. Factors associated with abnormal semen after adjusting for age, smoking and alcohol drinking by logistic regression were: distance of less than 300 meters from household to rice fields and duration of work over 10 years as a farmer (adjusted OR = 3.16, 95% Cl: 1.97-5.05 and adjusted OR = 3.98, 95% Cl: 2.20-7.21, respectively). Rice farmers without personal protective equipment (PPE) when spraying pesticides and without pesticide training (adjusted OR = 3.05, Cl: 1.92-4.85 and adjusted OR = 1.90, Cl: 1.14-3.16, respectively) were also at risk for abnormal semen compared to controls. These findings showed the strength of association between pesticide use and abnormal semen characteristics among rice farmers in Kienxuong District, Thaibinh Province, Vietnam.

Rodents cause significant damage to lowland irrigated rice crops in the Red River Delta of Vietnam. A four-year study was conducted in 1999-2002 to examine the effectiveness of applying rodent control practices using the principles of ecologically based pest management. Four 100-150 ha study sites adjacent to villages were selected and farmers on two treated sites were asked to follow a set of rodent management practices, while farmers on the untreated sites were asked not to change their typical practices. Farmers on the treated sites were encouraged to use trap-barrier systems (TBS's; 0.065-ha early planted crop surrounded by a plastic fence with multiple capture traps; one TBS for every 10-15 ha), to work together over large areas by destroying burrows in refuge habitats soon after planting (before the rats reestablish in the fields and before the onset of breeding), synchronizing planting and harvesting of the their rice crops, cleaning up weeds and piles of straw, and keeping bund (embankment) size small (<30 cm) to prevent burrowing. A 75% reduction in the use of rodenticides and plastic barrier fences (without traps or an early crop) was achieved on treated sites. The abundance of rodents was low after implementation of the management practices across all sites. There was no evidence for an effect of treatment on the abundance of rodents captured each month using live-capture traps, and no difference in damage between treatments or in yields obtained from the rice crops. Therefore, ecologically based rodent management was equally effective as typical practices for rodent management. Farmers on the treated sites spent considerably less money applying rodent control practices, which was reflected in the comparative increase in the partial benefit:cost of applying ecologically based rodent management from 3:1 on treated sites and untreated sites prior to the implementation of treatments to 17:1 on treated sites in the final year of the project.

In a 4 x 4 Latin square design study, four rumen-cannulated local yellow cattle, average weight 330 kg, were fed urea-treated fresh rice straw (UFRS) ad libitum and given 1 kg cassava root meal daily as basal diet in each 30-day trial period. Four treatment levels of crude protein of fresh cassava tops (FCT) were supplied: 0 (FCT0), 50 (FCT50), 100 (FCT100) and 150 g (FCT150) crude protein per 100 kg body weight. The results showed a continuous decrease in dry matter intake (DMI) of UFRS with increasing level of FCT supplementation (p<0.001). Total DMI for treatments FCT150, FCT100, FCT50 and FCT0 were 2.66, 2.42, 2.23 and 2.05 kg dry matter per 100 kg live weight per day, respectively. Increasing levels of FCT supplementation increased the concentration of total volatile fatty acids (p<0.05) and ammonia (p<0.001) and resulted in a decrease in pH (p<0.05). Rumen protozoa population varied widely but was significantly lower with increasing FCT supplementation (p<0.001), while rumen bacteria population was higher (p<0.05). Overall, average plasma triiodothyronine and thyroxine concentrations in the four groups were respectively 1.36, 0.94, 0.91, 0.80 ng/ml (p<0.01) and 60.9, 48.7, 45.2, 42.5 ng/ml (p<0.001). There were non-significant differences in alanine aminotransferase and aspartate aminotransferase concentrations among the treatments.

After conducting a preliminary survey, a feeding trial was carried out to determine the effect of urea-molasses-multinutrient block (UMMB) and urea-treated rice straw (UTRS) as a feed supplement on the productivity of dairy cows. Sixty Holstein-Friesian crossbred cows on 11 smallholder farms were divided equally into control, UMMB and UTRS supplementation groups. Milk yield and feed intake were recorded daily. Milk fat content, body weight and body condition score (BSC) of each cow were determined at two week intervals. Milk samples for progesterone analysis were collected once a week commencing one month after parturition. Data were recorded for date of onset of ovarian activity, estrus, insemination, and conception rate. Milk production increased by 10.3-11.9% and milk fat content increased by 3-5%, therefore, profit for farmers increased by US $0.55-0.73 per cow per day (exchange rate US $1 = VN $11,000). The intervals from calving to onset of ovarian activity (91-94 days), to estrus (110-114 days), to conception (121-122 days) and the calving interval (13.4-13.6 months) in the trial groups were significantly shorter than those in the control group (112, 135, 152 days and 14.4 months, respectively.