Vol. 5 No. 3 (2022): Vietnam Journal of Agricultural Sciences

Aquaponics combines two technologies, recirculating aquaculture systems and hydroponics in a closed system. The nutrients recycled from fish tanks supply nutrients for vegetables grown in hydroponics, however in some cases, the nutrient levels may not be sufficient for the optimal growth and yield of plants. In this study, two experiments were conducted to understand the effects of supplemental organic nutrient solutions on plant growth and yield in climbing perch-water spinach aquaponics. Experiment 1 (Exp.1) was conducted to evaluate the effects of three types of leaf-based organic fertilizers on the growth and yield of water spinach, namely self-extracted organic nutrient solution (OE), and two popular commercial foliar organic fertilizers, Hydro Fulvic (OF1) and TCN HUME (OF2), with the dose of 1%. Exp.1 showed that supplementation with the self-extracted solution significantly increased the growth and yield of water spinach but did not change the quality of water spinach in terms of the Brix values and nitrate residue content compared to the control. However, the self-extracted solution showed less effectiveness than the two commercial fertilizers in this experiment. Therefore, we conducted experiment 2 (Exp.2) to determine the suitable concentration and potential use of this extract for water spinach in aquaponics. The results of Exp.2 indicated that the concentration of 2% was the most economical and effective to provide supplemental nutrients for water spinach in the climbing perch-water spinach system. The study suggests that self-extracted organic nutrient solutions can be effectively used for growing water spinach in aquaponic systems.

The study aimed to evaluate meat yield and meat quality of Hac Phong chickens. A total of 100 birds (50 males and 50 females)from 1 days of agewas raised at the experimental station of Faculty of Animal Science, Vietnam National University of Agriculture . The chickens were fed ad libitum with a complete compound feed. Twenty chickens (10 males and 10 females) were slaughtered at 20 weeks of age with an average live weight of 1303.70 kg. The results found the carcass, breast, and thigh meat percentages were 70.36%, 16.16%, and 22.42%, respectively. The pH value at 15 min and 24 h post-mortem were in the normal range. The color of the meat was dark. The L* (lightness) value was low. The drip loss and cooking loss percentages were low while the tenderness was high. Hac Phong chicken meat contained a high crude protein content (27.71%) and low cholesterol content (25.45%).

We evaluated the digestibility of plant oils and their influence on the growth of and fatty acid composition in common carp. Apparent digestibility coefficients (ADC) of lipids were determined in carp (200.2 ± 40.0g) fed with cod liver oil (CLO), linseed oil (LO), sunflower oil (SFO), or sesame oil (SO). A 96-day growth trial was then conducted using six isolipidic (from 100 to 101 g/kg diet) diets, namely CLO, LO, SFO, SO, and two blends of plant oils (SLO = SO + LO; SSFO = SO + SFO). Lipid ADC values (0.920-0.972) were similar or slightly lower in the plant oil-based diets than in the CLO-based diet. Growth and feed efficiency (FE) were not influenced by dietary lipids. The fatty acid profile in the liver and muscle reflected those of the dietary lipids. The EPA and DHA proportions were higher in the liver and muscle of the LO and SLO-fed fish than in the other plant oil groups, and lower than in CLO-fed fish (P <0.05). Higher EPA, DHA, and n3/n6 ratio levels in the muscle of fish fed on the linseed oil (LO) diet, as compared to those in fish fed on the other plant oil-based diets, were ideal for human health and suggest that it can be used as a suitable alternative to fish oil.

In this study, pot culture experiments were carried out to investigate the most suitable level of fly ash for the amelioration of soil that can enhance the management of fly ash. The fly ash recovered from the Mong Duong 2 coal-fired thermal power plant and had the main chemical composition of oxygen (43%), Si (26%), Al (15%), K (9%), and Fe (6%). The addition of fly ash to light texture soil increased some of the basic properties of the soil, such as moisture, cation exchange capacity, mechanical composition, and organic matter content. The results of the performance evaluation of an experimental crop (soybeans) showed the effects of the amended soil on the growth of the experimental plants, namely the number of fruits, number of nodules, and their dry biomass. The incorporation of manure into the sandy soil was amended with fly ash in the pot experiment as a single application of fly ash may not provide enough nutrients for plant growth despite its ameliorant effect on soil structure. The appropriate fly ash addition rate from 10-30% w/w is recommended in soil amelioration applications based on the results of this study. This research opens up an application direction for fly ash, a by-product generated from the operation of coal-fired power plants in Vietnam.

Outbreaks of the Southern rice black-streaked dwarf virus (SRBSDV) have caused significant losses in many rice-growing areas in Vietnam, especially in both North and Central Vietnam in recent years. To detect the virus, traditional reverse transcription polymerase chain reaction (RT-PCR) methodology and immunoassays are currently employed. RT-PCR is accurate but requires expensive chemicals and instruments, as well as complex procedures that limit its applicability for field tests. To develop a cheaper, simpler, and reliable SRBSDV diagnosis assay based on the dot-enzyme-linked immunosorbent assay (dot-ELISA) method, anti-SRBSDV polyclonal antibodies were produced by using the antigens derived from the P10 coat protein of SRBSDV, which was achieved from a previous study. The IgG antibody purified from the antiserum of recombinant P10-immunized mice by protein A-agarose affinity chromatography could specifically detect both the target protein and SRBSDV at a dilution of 1:100000. In the trial test of SRBSDV diagnosis, the dot-ELISA assay using the obtained anti-SRBSDV antibody showed an accuracy rate of 90.9% in comparison with the standard RT-PCR assay. These results are important premises for the large-scale application of dot-ELISA assay for SRBSDV diagnosis in order to protect rice crops against viral disease damage.

Freshwater aquaculture has played key roles in the livelihood development of farm households in the Red River Delta through freshwater fish ponds, rice-and-fish, and marine cage culture. A market-driven approach is being addressed more and more in promoting new production. This study aimed to analyze the marketing channels of freshwater aquaculture fish in Hai Duong province. The study was conducted with 151 farm households belonging to three fish production system: Fish system engaging fish production only (FS); animal fish system combining animal and fish production (AF) ; and new garden-pond-animal house system (VAC) in the province. The attained results reveal that fish farmers diversified their marketing strategies to obtain a marketing margin of about 87% of the retail price of the finfish along with their value distribution while the remaining portion of the marketing margins belonged to the intermediary market actors. The cost of the purchased fish commodities accounts for the majority of the total cost for all actors. The cost of dead fish presented the highest proportion of the total marketing cost. A large portion of the marketing costs represented wages, fuel, and the rent of a business place. The marketing margin for the intermediary stakeholders in both the studied channels was 12.7%, in which marketing costs accounted for approximately 5.0%. The results will be used for designing better promotion strategies for freshwater fish production and providing good lessons for small-scale fresh aquaculture development towards livelihood diversification and development in rural areas.

This study aimed to identify the factors affecting  farmers’ adoption of sustainable land management (SLM) practices to combat land degradation in Vietnam. Based on the survey data from 826 farmers in three representative regions, the study showed that the SLM model and SLM adoption rate were quite varied due to differences of natural and socio-economic conditions. The results of logistic regression showed that household income and access to loans had positive impacts on SLM adoption with statistical significance in all the regions surveyed. More extension visits in the upland and coastal regions, and more agricultural laborers in farm households in the coastal and Mekong delta regions were found to increase the probability of SLM adoption. Meanwhile, the number of plots and number of members in households were found to have negative impacts on adoption. Providing training courses for farmers, building SLM demonstrations, and providing financial support for farmers through credit programs should be enhanced for better SLM adoption in farm households.

The basket of meat consumption has changed during the last decade in Vietnam, including increased consumption of beef. This paper analyzes the beef consumption behaviors of households in Dien Bien province, located in Northwest Vietnam. Data were collected from a survey of 108 consumers and three focus group discussions. It was evident that the preferences of beef consumers were varied between different ethnic groups. The important criteria used in selecting meat were color, freshness, and tenderness. Consumers mentioned, but had little concern, for meat packaging, nutritional information, or quality certification, while they showed almost no concern for animal welfare in purchasing beef. As the consumers’ choice of purchasing beef was very much influenced by meat appearance, improving the conditions of butcher counters is suggested as an immediate measure. There exists an opportunity to introduce ‘cold’ beef widely as a longer-term measure.