Possible effects of the recent Australian ban on prawn imports

Australia banned imports of uncooked prawns from Asia in early 2017 after an outbreak of the deadly white spot disease in southern Queensland. The ban expired after 6 months, and it remains unclear what the source of the epidemic was, or the mechanism through which it may have entered the country. The Queensland State Government offered financial assistance to selected producers, although as a group, producers benefit from the higher prices resulting from the ban. In fact, the major cost of the ban is borne by domestic consumers and foreign producers. The major impact is a transfer from Australian consumers to Australian producers. These transfers are quantified in this analysis, as are the impacts on developing country exporters.     

An application of multilevel model for the analysis of factors influencing paddy field productivity in the Northern Vietnamese Mountains

Paddy and Water Environment - In the Northern Vietnamese Mountains, paddy fields are the main source of foods and an important indicator to define wealth in ethnic communities. This paper deals...     

Changes in fineroot growth dynamics in response to phosphorus application in an Acacia mangium plantation in Vietnam

Fineroots (≤ 2 mm diameter) are dynamic components of the forest ecosystems and play important role in water and nutrient acquisition in forests. These roots are sensitive to forest fertilization and therefore, the response of fineroots to nutrient application would provide better understanding of the forest carbon and nutrient dynamics that will be helpful in sustainable forest management plans. Two fertilization treatments, including (1) F400: 400 g P₂O₅ (16.5%)/tree and (2) F600: 600 g P₂O₅ /tree, and F0: control (without fertilization), were applied in an Acacia mangium plantation with a planting density of 1100 trees/ha (3 m?×?3 m). The evaluation of fineroot growth across seasons showed that fertilization significantly increased production and subsequent mortality and decomposition. The total decomposition associated with F600 application was 7.95 tons ha^?1 year^?1, equaling 121% of F400 and 160% of the control. Mortality in F600 was 8.75 tons ha^?1 year^?1, equaling 111% of F400 and 198% of F0, while production in F600 was 10.40 tons ha^?1 year^?1, equaling 127% of F400 and 143% of F0. Fineroot production, mortality, and decomposition are seasonally dependent, with higher values measured in the rainy season than in the dry season. Stand basal area increment was significantly correlated with fineroot production (R²?=?0.75), mortality (R²?=?0.44), and decomposition (R²?=?0.48). This study showed that fertilization could facilitate fineroot production, which can then lead to a higher turnover of carbon and nutrients through the decomposition of the greater mass of the fineroots.

     

Spatial and temporal diversity of fish captured by light traps in various habitats in coastal waters in the oldest marine protected area in Vietnam and its implications for conservation

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Effect of genotype,explant size,position, and culture medium on shoot generation of Gerbera jamesonii by receptacle transverse thin cell layer culture

An unique procedure for the mass shoot propagation of Gerbera using receptacle transverse thin cell layer (tTCL) culture procedure was developed. Genotype, flower bud age, explant size, position of receptacle tTCLs and culture media were found to affect the success of culture. Ten interspecific crosses of Gerbera showed different shoot regeneration rates and callus induction via receptacle tTCL culture, all of which had shoot regeneration rates higher than 57%. Flower buds collected on the 10th day resulted in 91% shoot regeneration after 6 weeks of culture on basal MS medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassay with tobacco tissue cultures. Physiol. Plant. 15, 475–497] supplemented with 0.02 mg l⁻¹ thidiazuron (TDZ), 0.8 mg l⁻¹ adenine and 10% (v/v) coconut water (CW). This was significantly higher than those from flower buds on the 7th and 14th days (22% and 54%), respectively. Shoot regeneration rate was the highest (94–100%) in the middle layers of the receptacle. For mass shoot propagation, shoot clusters were subcultured on half-strength MS medium supplemented with 0.5 mg l⁻¹ indole-3-butyric acid (IBA), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 2.0 mg l⁻¹ kinetin after every 4 weeks. Plantlets formed when single shoots were cultured on half-strength MS medium containing 1 mg l⁻¹ IBA. All plantlets acclimatized well in the greenhouse.     

水杉苗期对氮素营养需求的研究

为研究水杉苗对氮素营养的需求 ,按 0 0 ,1 0 ,2 0 ,3 0 ,4 0和 5 0g氮 /盆 6个水平进行试验研究。结果表明 :水杉苗高、地径、分枝数、分枝总长等随着施氮量的增加而提高 ,但当施氮量超过 3 0 g/1 5kg土后 ,这些项目又随施氮量的继续增加而下降。水杉苗叶绿素的含量对氮素的反应亦与此类似 ;根、茎、叶的含氮量随施氮量的增加而增加。     

Social networks and information access: Implications for agricultural extension in a rice farming community in northern Vietnam

Village communities are not homogeneous entities but a combination of complex networks of social relationships. Many factors such as ethnicity, gender, socio-economic status, and power relations determine one’s access to information and resources. Development workers’ inadequate understanding of local social networks, norms, and power relations may further the interests of better-off farmers and marginalize the poor. This paper explores how social networks function as assets for individuals and households in the rural areas of developing countries and influence access to information and benefits from research and development. A case study of such networks in Phieng Lieng village, in the northern mountains of Vietnam, provides evidence for the need for the efficient delivery of extension services and research and development interventions at the micro level. Lan Anh Hoang is a social scientist with a special interest in social networks and gender and power relations in rural areas. She is currently working on her PhD at the School of Development Studies, University of East Anglia (UK) on “Gender relations, household power hierarchies, and social norms in migration decision-making in rural Vietnam.” She was involved in the Mountain Agrarian Systems Program in Bac Kan Province from 1999 to 2002. Jean -Christophe Castella is a production systems agronomist from the Institut de Recherche pour le Développement (IRD, France). Between 1998 and 2003, he coordinated a joint research program on “comprehensive study of land use changes in northern Vietnam uplands” in partnership with the Vietnam Agricultural Science Institute (VASI, Hanoi, Vietnam) and the International Rice Research Institute (IRRI, Philippines). Paul Novosad was involved with the Mountain Agrarian Systems program from January to July 2002. He helped to synthesize the results of field research and also was involved in analyzing data related to social networks. Since fall 2002 he studies Public Administration and International Development at the Kennedy School of Government in the United States (Cambridge, Massachusetts).     

玉米愈伤抗病性的快速鉴定技术

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Use of GIS and machine learning to predict disease in shrimp farmed on the east coast of the Mekong Delta,Vietnam

Diseases in shrimp farms in the Mekong Delta of Vietnam cause significant crop losses and are therefore of great concern to producers. Once a pond becomes infected, it is difficult to prevent spread of the disease to nearby shrimp farming areas. Thus, predicting the occurrence of disease is an essential part of reducing the risk for shrimp farmers. In this study, we applied an integrated geographic information system and machine learning system to predict three serious diseases of shrimp, namely, acute hepatopancreatic necrosis, white spot syndrome disease, and Enterocytozoon hepatopenaei infection, based on data collected from shrimp farms in the Tra Vinh, Bac Lieu, Soc Trang, and Ca Mau provinces of Vietnam. We first constructed a map showing the distribution of these diseases using the locations of affected farms, and then we conducted spatial analysis to acquire the geographical features of the affected locations. This latter information was combined with environmental factors and clinical signs to form the set of independent variables affecting the outbreak of diseases. The neural network model outperformed the logistic regression, random forest, and gradient boosting methods in terms of predicting infection to estimate the probability of disease occurrence in farmed areas. Acute hepatopancreatic necrosis disease infected farms downstream of the Co Chien and Hau Rivers of Tra Vinh and west of Ca Mau. Enterocytozoon hepatopenaei infection is distributed in Soc Trang Province, while white spot syndrome virus has spread to the coastal districts of Soc Trang and Bac Lieu Provinces, where it is highly associated to water from a complex canal system.