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Measures Used for Water Quality Management in Intensive Pangasius Catfish Production in Vietnam’s Mekong Delta: Experiences from Household Practices and Gender Roles

Nguyen Thi Hai Ninh, Ho Ngoc Cuong

Received: Apr 14, 2022 / Published: Dec 30, 2022
Intensive aquaculture on a household-scale in Vietnam’s Mekong Delta region often decreases the quality of the water. The consequences are a negative effect on the yield of Pangasius catfish, which in turn reduces the income generation potential. Water quality management has become an important consideration, not only for sustaining livelihoods from household-scale aquaculture but also for mitigating the impacts on the surrounding water bodies. The purposes of this paper are to identify strategies for improving water quality management in households practicing aquaculture and to understand the role gender plays in water management in the Mekong Delta. The effectiveness of existing household approaches to water quality management was found through analyzing data gathered through interviews. The primary data consisted of interviews with 32 operators of different household-scale aquaculture systems. It was found that in 46% of these households, water quality had declined over the last three years. Several causes were identified including the accumulation of chemicals and antibiotic residues, excessive stocking rates, and a lack of a water treatment system. Several strategies to better manage water quality in these ponds were identified including changing the clean water more frequently, removing sediment after each harvest, planting trees around the ponds, and applying lime to the base of the pond, or using potassium permanganate for disinfection before use. Although many water quality management approaches were in use by households, more than 90% of these activities were implemented by men.
Water-Saving Irrigation and Nitrogen Fertilizer Use Efficiency for Irrigated Rice in the Red River Delta, Vietnam

Ngo Thanh Son, Nguyen Thu Ha

Received: Feb 02, 2021 / Published: Oct 28, 2021
The objective of this research was to quantify the effects of water-saving regimes and fertilizer application improvement on water productivity, N-use efficiency, and rice yield. The results showed that the tested water treatments did not have significant effects on the growth and development, yield components, and final grain yield, but water productivity was significantly increased from 1.28 kg grain m-3 (W0) water to 1.74 kg grain m-3 water (W1) and 1.94 kg grain m-3 water (W2). In addition, the percentage of total irrigation water saved from W1 and W2 were 25.24-44.52% compared to continuous flooding. Fertilizer deep placement (FDP) combined with organic compost significantly increased the grain yield of the tested hybrid rice variety. Average grain yield increased quickly from 2847 kg ha-1 with 0 kg N ha-1 to 5263 kg ha-1 with 120 kg N ha-1 under the fertilizer deep placement method. The highest total nitrogen uptake, agronomic nitrogen efficiency (ANE), and nitrogen uptake efficiency (NUE) were obtained from alternate wetting and drying at a -20cm water depth and the fertilizer deep placement method (W1N2). In addition, it also gave the highest income in comparison with the other treatments. Therefore, alternate wetting and drying at a -20cm water depth and fertilizer deep placement method should be encouraged for implementation in other regions of Vietnam.
Performances of Boro Rice as Affected by Different Concentrations of Marine Water

Islam Md. Redwanul, Islam Md Mazharul, Chandra Sarker Shimul, Ullah Md. Jafar, Rahman Anisur

Received: Aug 07, 2021 / Published: Mar 30, 2022
Salinity is one of the most devastating abiotic stresses limiting crop production. Considering this issue, a pot experiment was conducted at Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during the boro season (2017-2018) using two rice(Oryza sativa L.) varieties, namely BRRI dhan28 (salt sensitive) and BRRI dhan47 (salt tolerant),to assess the effects of varied salinity levels on the growth and the performance of the rice varieties under salt stress conditions. Four salinity treatments were used in this experiment, viz. control S0 (only freshwater), quarter-strength marine water S1 (three-parts freshwater and one-part marine water; 7.5 ds m−1), half-strength marine water S2 (half freshwater and half marine water; 15 ds m−1), and full-strength marine water S3 (only marine water; 30 ds m−1).These mixtures were used for irrigation purposes throughout the life cycle of the plants. Salt stress significantly decreased the plant height, relative water content (RWC) of leaves, number of effective tillers hill−1, number of filled grains panicle−1, 1000-grain weight, grain yield, straw yield, and biological yield of the rice. In both rice types, plant growth and yield were reduced as the salinity level increased. Grain yields decreased by 50, 90, and 100% in BRRI dhan28 when irrigated with quarter strength, half strength, and full-strength seawater, respectively, but decreased by 27, 50, and 72%, respectively, in BRRI dhan47. Similarly, other yield attributes had higher reductions in BRRI dhan28 under salt stress conditions than BRRI dhan47. However, irrigation with marine water in rice might lead to some straw yield but produced little to no grain.
Using Multivariate Statistical Methods to Identify Key Surface Water Pollutants in the Dry Season in a Coastal Province, Vietnam

Nguyen Thanh Giao, Huynh Thi Hong Nhien

Received: Sep 20, 2021 / Accepted: Jun 27, 2022 / Published: Jun 27, 2022
This study was conducted to analyze water quality in a coastal province of Vietnam. Multivariate statistical methods, namely cluster analysis (CA) and principal component analysis (PCA) were utilized. Twelve parameters, namely pH, dissolved oxygen (DO), total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrite (N-NO2−), nitrate (N-NO3−), ammonium (N-NH4+), orthophosphate (P-PO43−), chloride (Cl−), iron (Fe), and coliforms were collected from ten locations in the 2020 dry season. The results showed that surface water was polluted by TSS, organic matters, nutrients, salinity, and coliforms compared to the national technical regulations on surface water quality (QCVN 08-MT: 2015/BTNMT). Cluster analysis results classified the original ten sampling locations into three groups due to BOD, COD, TSS, N-NH4+, N-NO2−, coliforms, and salinity. Principal component analysis (PCA) revealed that three principal components (PCs) could explain 84.5% of the variance of surface water quality parameters in the study area. Moreover, pH, TSS, DO, BOD, COD, N-NH4+, N-NO2−, N-NO3-, P-PO43−, coliforms, and Cl‑ were the key variables that influenced surface water quality in the dry season. The findings in this study can provide useful information for policymakers in developing programs of surface water quality management and protection.
Supplemental Effects of Self-extracted Organic Nutrient Solution on the Growth and Yied of Water Spinach (Ipomoea Aquatic F.) in an Aquaponic System

Nguyen Thi Ai Nghia, Nguyen Thi Ngoc Dinh, Nguyen Hong Hanh, Do Thi Huong

Received: Dec 06, 2021 / Accepted: Sep 22, 2022 / Published: Sep 30, 2022
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.
Growth and Physiological Responses of Sugarcane to Drought Stress at an Early Growth Stage

Bui The Khuynh, Vu Ngoc Thang, Vu Dinh Chinh, Pham Thi Thom

Received: May 14, 2020 / Published: May 15, 2020
A pot experiment was conducted in a net house to evaluate the effects of drought stress (a 20-day water withholding treatment from 100-120 days after planting) on the growth and physiology of five sugarcane cultivars. The results showed that water stress at an early stage significantly affected sugarcane growth and physiology. Water stress resulted in reductions in plant height, stalk diameter, and leaf number of sugarcane, in addition to reductions in the photosynthetic pigment content, Fv/Fm, and SPAD (Soil Plant Analysis Development) readings after the 20-day withholding water period (120 DAP), and in stem, root, and leaf fresh weights, and leaf area at 150 DAP. Besides, drought stress led to increases in stomata density and decreases in stomata length. Variation was also found among the cultivars in response to water stress. Significant genotypic differences in stem fresh weight and leaf area under water stress among the cultivars were observed. The highest value of stem fresh weight under stressed conditions was recorded in ROC22 (50.6 g), followed by QĐ159 (46.5g), ROC16 (46.2g), ROC10 (46.1g), and VL06 (44.4g). However, the highest DTI was recorded in ROC16, followed by VL06, ROC10, QĐ93-159, and ROC22, respectively.
Responses to Water Deficit of Mung Bean Cultivars at the Vegetative and Flowering Stages under Greenhouse Conditions

Vu Thi Thuy Hang, Le Thi Tuyet Cham, Phan Thi Thu Hien, Pham Thi Ly

Received: Aug 22, 2023 / Published: Dec 29, 2023
Mung bean (Vigna radiata L. Wilczek) is grown mainly under rainfed conditions, facing water deficits in different growth stages. This study was conducted to evaluate the responses of a local cultivar, Dau tam Thanh Hoa, and three introduced mung bean cultivars (DX14, Mongo Labo, and TV06425) to water stress at the different growth stages. The experiment was carried out in a greenhouse following a completely randomized arrangement with two replications. Drought was induced by withholding water at either the vegetative or flowering growth stages for 20 consecutive days. The control consisted of well-watered plants. After 8, 12, 15, and 20 days of drought, plant available water, growth characteristics, and the weights of fresh stems and roots were measured. After 20 days of drought, plants were watered to assess their recovery after 7 days and the growth characteristics, weights of fresh stems and roots, and yield components at the harvest stage were evaluated. The results showed that drought affected the growth, resilience, and yield-related factors more severely at the vegetative stage than at the flowering stage. The longer drought was imposed, the greater decline in plant growth was observed. Despite the recovery, fresh root mass and root length were still 40-50% and 10-30% worse than the control, respectively. Based on the growth responses and individual yields, Dau tam Thanh Hoa and DX14 were more tolerant to water deficit and can be used as materials for improving the drought tolerance of mung bean.
A Novel Multi-Criteria Decision Making Method for Evaluating Water Reuse Applications under Uncertainty

Le Thi Nhung, Nguyen Xuan Thao

Received: Feb 13, 2019 / Published: Feb 13, 2019
There are currently many places in the world where water is scarce. Therefore, water reuse has been mentioned by many researchers. Evaluation of water reuse applications is the selection of the best water reuse application of the existing options; it is also one of the applications of multi-criteria decision making (MCDM). In this paper, we introduce a new dissimilarity measure of picture fuzzy sets. This new measure overcomes the restriction of other existing dissimilarity measures of picture fuzzy sets. Then, we apply it to the multi-criteria decision making. Finally, we refer to a new method for selecting the best water reuse application of the available options by using the picture fuzzy MCDM.
Sustainability Assessment of the Rural Clean Water Supply System in Hai Phong City

Nguyen Thi Thu Quynh, Nguyen Quoc Hung

Received: Feb 22, 2021 / Published: Oct 29, 2021
Since the end of 2019, 92.1% of rural households in Hai Phong city had been able to access and use clean drinking water, which meets national standards as a result of developing a clean water supply system consisting of 205 plants with various management models. The authors applied the desk-study method to collect and review literature research, select a group of six criteria, and then applied the criteria to assess the system's sustainability based on Likert's 3-point scale. The results show that criteria scores ranged from 1.9 points to 2.5 points, while the total score of the whole system is 12.9 points - reaching an average sustainability level. The authors propose that in order to improve the sustainability of the clean water supply system in the rural areas of Hai Phong city in the future, management agencies and investors need to apply a solution of propagating rural people to increase their usage volume of clean water, which will help to increase the actual operating capacities of the plants, thereby increasing the revenue and profits of plant investors.
Water Quality Assessment and Eutrophic Classification of Hanoi Lakes Using Different Indices

Nguyen Thi Thu Ha, Dinh Tien Dzung, Ho Thi Thuy Hang, Trinh Quang Huy, Nguyen Ngoc Tu

Received: Nov 05, 2020 / Published: Dec 31, 2021
The trophic levels in urban lakes are typically based on the forms of nutrition and phytoplankton communities in the lakes. In this study, comparisons between eutrophication indices and the water quality index (VN-WQI) were used to classify the water quality of 20 lakes in Hanoi, Vietnam. The results showed that the water quality ranged from very bad to poor. High levels of the eutrophication phenomenon in terms of total N and P were observed in all sampling sites. Cyanobacteria was the dominate algae phylum making up 65.78% of the total population, whereas Chlorophyta (including 19 genera) was the most diverse phylum. The density of the algae was 5,000-14,000 cells mL-1 and the chlorophyll-a level was 10-40 µg L-1. Based on this information, the water quality levels in the lakes were classified from eutrophic to polytrophic. The Trophic Status Index (TSI) and Trophic Level Index (TLI) values were 66.9-86.0 and 54.4-76.0 points, respectively, corresponding from eutrophic to extreme-trophic. Classifications based on algae community structure indices were from oligotrophic to eutrophic, similar and consistent with the TLI classifications. According to the results in this study, the TLI was found to be more accurate and precise than the other indices. It is recommended that the TLI is an applicable tool to classify eutrophication in urban lakes.
Effects of Nitrogen Forms on Root System Development, Physiological Traits, and Dry Matter Production of Rice

Thiem Thi Tran, Akira Yamauchi

Received: Aug 20, 2018 / Accepted: Aug 20, 2018 / Published: Aug 20, 2018
The objectives of this study were to evaluate the effects of nitrogen forms on root system development (expressed as total root length, nodal root number, nodal root length, and lateral root length), water use, photosynthetic rate, and dry matter production under water deficit (WD) at 20% w/w and continuously waterlogged (CWL) conditions. Rice plants cv. Nipponbare were grown in plastic pots in a vinyl house. Six N forms were applied at the same rate of 360 mg N per pot, and were prepared as follows: N-NH4+ alone (A); N-NH4+ with nitrification inhibitor (A+DCD); N-NO3- alone (N); N-NO3- with nitrification inhibitor (N+DCD); combined N-NH4+ and N-NO3- (AN); and combined N-NH4+ and N-NO3- with nitrification inhibitor (AN+DCD). The nitrification inhibitor, dicyandiamide (DCD) (C2H4N4), was applied at the rate of 100 mg pot-1. The results of the experiment showed that under both WD and CWL conditions, significant increases were seen in the root system development as expressed through total root length, nodal root number, nodal root length, and lateral root length in the N-NO3- treatments with and without DCD compared to the application of N-NH4+ treatments with and without DCD. This led to an increase in water use, and eventually a significant increase in dry matter production. Similarly, the A treatments with and without DCD also significantly increased root system development as compared with the AN and AN+DCD treatments. Furthermore, under both CWL and WD conditions, the positive and notably significant correlations between the total root length and water use, as well as between the total root length and shoot dry weight, were found only in the A and A+DCD treatments. These results indicate that rice prefers sole ammonium over the mixed ammonium-nitrate treatment, and sole nitrate applications under both WD and CWL conditions.
Effects of Osmotic Stress Induced by Peg and NaCl on the Germination and Early Growth of Mung Bean

Thang Ngoc Vu, Khuynh The Bui, Gioi Huy Dong, Tuan Anh Tran, Tuyet Cham Thi Le, Chinh Dinh Vu

Received: Oct 15, 2018 / Accepted: Oct 19, 2018 / Published: Oct 22, 2018
This study was performed to evaluate the effects of osmotic stress (measured by different water potentials) induced by Polyethylene Glycol 6000 (PEG) and NaCl solutions at the germination stage of five mung bean varieties (DX11, DX208, DX14, DX17, and DX22). Five water potentials: 0 (control), -0.15, -0.49, -1.03, and -1.76 Mpa were used as treatments in this study. The germination rates, root and shoot lengths, root and shoot fresh weights, and dry weights of the plants were measured. The results showed that the germination rate of the mung bean varieties decreased with increased NaCl or PEG concentrations. The germination rates of the mung bean varieties in the PEG treatments were higher than those in the NaCl treatments. In addition, low water potentials induced by NaCl (-1.76 Mpa and -1.03 Mpa) inhibited germination and seeding growth of all the mung bean varieties. The growth parameters of the mung bean seedlings, such as root and shoot lengths, fresh weights of roots and shoots, and plant dry weights, were reduced under low water potentials treated with either PEG or NaCl. However, more severe damage in seedling growth was observed in the NaCl induced treatments. Amongst five mung bean varieties used in this study, DX17 was more drought and salt tolerant than the other mung bean varieties.
Evaluation of the Physicochemical Properties and Sensory Attributes of Yoghurt Made from Mixtures of Goat’s and Cow’s Milks

Nguyen Duc Doan

Received: Mar 06, 2019 / Published: Dec 24, 2019
The objective of the study was to evaluate the effect of cow’s milk added to goat’s milk on physicochemical properties and sensory attributes of yoghurt. Yoghurts prepared from five different proportions of cow’s milk and goat’s milk were stored at 4-6ºC for 1, 7, and 14 days and then evaluated for their physicochemical (total solids, protein, pH, and acidity) and physical properties (viscosity and water holding capacity), and sensory characteristics (acceptability). The total solids of the evaluated yoghurts significantly increased, but the protein content decreased when the amount of cow’s milk increased in the mixtures of milk. The results showed that the pH value of the yoghurt made from only goat’s milk was higher, while the titratable acidity was lower than those of the yoghurts made from the mixtures of goat’s and cow’s milks. The yoghurt obtained from the mixture of milks containing 80% goat’s milk and 20% cow’s milk exhibited the highest viscosity and water holding capacity among the evaluated yoghurts. All the yoghurts received similar scores for color, odor, and texture after all periods of storage, while the highest score in terms of flavor was received for the yoghurt made from the mixture of milks containing 60% goat’s milk and 40% cow’s milk. Addition of cow’s milk to goat’s milk was shown to significantly contribute to the viscosity, water holding capacity, and flavor of the resulting yoghurts.
Effect of Waterlogging Duration on Germination, Physiological Characteristics, and Yield of Mungbean (Vigna radiata L.)

Vu Tien Binh, S. K. Tai Sorgan

Received: Feb 27, 2020 / Published: Jun 18, 2021
The study was conducted to evaluate the germination, physiological responses, yield-related traits, and seed yield of three mungbean varieties, viz. DXVN7, DXVN5, and DX11, under waterlogging coditions in the 2019 Summer. In experiment 1, the seeds of the three mungbean varieties were immersed in distilled water in Petri dishes for 12, 24, 36, 48, and 72h. Afterwards, water was removed and the percentage of germinated seeds was calculated at 84h after sowing. In experiment 2, plants were waterlogged at the seedling stage (25 days after germination) for 3, 6, and 9 days. Waterlogging depth was maintained at 3cm above the soil surface. Physiological traits were determined at the recovery period after termination of waterlogging (45 days after germination). The results showed that waterlogging significantly decreased germination percentages, plant height, root dry weight, leaf relative water content (RWC), SPAD value, Fv/Fm index, leaf photosynthesis, total dry weight, and seed yield of all varieties. Germination percentages at 12 and 24h of waterlogging were not significantly affected, whereas germination was significantly reduced at up to 36h of waterlogging. Seventy-two hours of waterlogging caused failure in germination. Nine days of waterlogging at the seedling stage adversely affected the physiological traits and seed yield of the mungbean varieties with 31% of yield reduction. Meanwhile, plants grew better at 3 days of waterlogging. Among the three varieties, DXVN7 showed the best adaptability under waterlogging conditions, attaining the highest seed germination and yield.
Effects of Nitrogen Applications on Transpiration, Physiological, and Growth Characteristics of Sugarcane (Saccharum spp.)

Dinh Thai Hoang

Received: May 21, 2023 / Published: Jun 30, 2023
Improving fertilizer and water use efficiencies is an important strategy in agricultural production. This study aimed to evaluate the effect of nitrogen fertilization on the daily whole-plant transpiration, growth, and physiological activities of sugarcane. The pot experiment was conducted under glass-house conditions. Five treatments of various nitrogen application rates (0, 4, 8, 12, and 16mM) were assigned in a randomized complete block design with three replications. The result showed that higher nitrogen applications led to higher growth, physiological, and biomass parameters. Nevertheless, biomass nitrogen use efficiency and photosynthetic water use efficiency declined because of applying nitrogen at higher rates. During the first weeks of plant growth, no significant differences in plant height, leaf number, SPAD, and whole-plant transpiration among nitrogen treatments indicated that higher nitrogen added was not necessary during this time. Nitrogen and water use efficiencies could be improved if the remaining soil nitrogen and crop growth stage nitrogen requirements are estimated in cultivation practice.
Effects of Mulching Materials on the Growth and Yield of Peanuts Cultivated in Coastal Areas of Thanh Hoa Province

Vu Thi Thuy Hang, Nguyen Duy Bach, Le Thi Tuyet Cham

Received: Sep 04, 2023 / Accepted: Mar 29, 2024 / Published: Mar 29, 2024
Mulches have been widely applied in crop production in order to minimize water requirements, preserve soil moisture, and curb weed growth for higher yield and water use efficiency. This research aimed to assess the impact of organic mulches on peanut productivity in the coastal areas of Thanh Hoa province. The experiment was carried out during the 2019 spring growing season. A split pot design was used with two peanut cultivars (L14 & L23) as the main plots and five types of mulching materials (clear plastic, rice straw, sugarcane bagasse, water hyacinth, and bare soil) as the subplots. It was revealed that rice straw exhibited a positive influence on the growth attributes and yield of peanuts, comparable to clear plastic and other organic mulch materials. Notably, rice straw contributed to enhanced plant growth, dry matter production, pod filling, and yield. Additionally, the net return of rice straw application was also the highest. The results suggested that organic mulching materials (rice straw and plant residues) can be effectively used for peanuts because of their availability and biodegradability as an eco-friendly agricultural practice.
Effects of Land Preparation and Iron-coated Rice Seeds on Yield, Growth Parameters, and Soil Properties in the Mekong Delta, Vietnam

Tran Van Dung, Nguyen Van Qui, Tran Huynh Khanh, Do Ba Tan, Vu Van Long, Nguyen Canh Cong, Masaaki Miyauchi, Sashi Kazumichi

Received: Jul 18, 2022 / Published: Jun 30, 2023
The objective of this study was to evaluate the effects of land preparation methods and iron-coated (Fe-coated) rice seeds on the growth, yield, and Fe uptake of rice in alluvial soils in the Mekong Delta region. The experiment was conducted in the 2020 summer-autumn cropping season under the triple rice cultivation system in Chau Thanh district, An Giang province. The field experiment was designed as a randomized complete block design (RCBD) with six treatments and four replications. The treatments were: (T1) puddled + water seeding + Fe-coated seeds; (T2) non-puddled + dry seeding + Fe-coated seeds; (T3) zero-tillage + non-puddled + dry seeding + Fe-coated seeds; (T4) puddled + water seeding + sprouted + non-Fe-coated seeds; (T5) puddled + wet seeding + sprouted + non-Fe-coated seeds; and (T6) puddled + transplanting + sprouted + non-Fe-coated seeds. The results showed that changes in the land preparation, planting method, and Fe-coated seeds did not significantly affect the number of tillers, plant height, yield components, soil chemical properties, grain yield, or Fe uptake of the rice plants and grains. However, the T3 and T6 treatments tended to have higher grains yields (5.86-5.90 tons ha-1), and higher total Fe content in grains (93.0-94.3 mg kg-1) and rice plants (83.1-84.0 mg kg-1). The findings from this study confirmed that the new planting method using zero-tillage + non-puddled + dry seeding + Fe-coated seeds can maintain the germination rate, growth, and grain yield of rice.
The Dispersion of Total Suspended Solids in Seawater Following Submersion of Dredged Material in the Vung Ang Port

Nguyen Thi Hong Ngoc, Tran Anh Quan

Received: Feb 27, 2023 / Published: Dec 29, 2023
Dredging plays a crucial role in port management, but disposing dredged material in the ocean raises environmental concerns. In recent years, this practice has become more prevalent in Vietnam. This study examined the dispersion of total suspended solids (TSS) in seawater from the submersion of dredged material in Vung Ang Port, northern Vietnam, to evaluate the environmental impact. The study utilized MIKE modeling to simulate the dispersion of TSS during the 16 weeks following the submersion of dredged material into the sea. The model was validated with observed data and adjusted to accurately reproduce wave, water flow, and water level fields. The simulation showed that the propagation of TSS had a significant impact within a radius of 16-17km from the submersion location, with the most severe impact occurring within a radius of 2-3km. The TSS concentration is expected to exceed allowable limits, peaking after 4-5 weeks. Seawater occupation will reach maximums of 49.05ha and 140.66ha for depth increases above 0.5m and 0.1m. The submersion will negatively impact the environment. It is essential to regularly monitor TSS in affected areas during and after dredging to evaluate long-term effects and mitigation effectiveness. The significance of conducting additional research on the matter and the crucial insights offered by this study to pertinent management agencies for their decision-making processes are emphasized in the article. The study offers crucial insights for pertinent management agencies.
Inhibitory Effects of Ludwigia Octovalvis (Jacq.) Raven Extracts on the Growth of Microcystis Aeruginosa

Nguyen Xuan Hoa, Tran Thi Thuy, Vu Thi Huyen, Phung Thi Vinh, Pham Trung Duc, Doan Thi Thuy Ai

Received: Jun 12, 2023 / Published: Dec 30, 2023
This study examined the phytochemical composition and algicidal effectiveness of Ludwigia octovalvis. The powder samples were extracted by ultrasound-assisted extraction with polar solvents (water-diluted ethanol, acetone, methanol, and water). The preliminary phytochemical analyses used standard procedures following Sofowora and Harborne. Total phenolic contents in extracts were determined by the Folin-Ciocalteu method using a calibration curve of gallic acid. The results showed that this plant contains polyphenols, flavonoids, anthraquinones, glycosides, and saponins. The best conditions for the extraction of polyphenol compounds with a total polyphenol content of 149.22 ± 0.96 mg GAE g-1 were acetone/water 70:30 (v/v) and a solvent-to-material ratio of 20 mL g-1. The inhibitory effect of the extracts against M. aeruginosa growth increased from 40.71 to 81.56% on day 7 when exposed to concentrations of the extract from 50-200 μg mL-1 according to the cell counting method. The L. octovalvis extract was identified as an effective inhibitor of the growth of M. aeruginosa.
Application of the Internet of Things technology (IoT) in Designing an Automatic Water Quality Monitoring System for Aquaculture Ponds

Nguyen Quang Huy, Vu Thi Thu Giang, Le Vu Quan, Ho Vo The Cuong

Received: Apr 12, 2020 / Published: Nov 27, 2020
The current aims to apply the Internet of Things technology (IoT) in designing an automatic system for measuring and monitoring important parameters of aquaculture ponds such as temperature, pH, and dissolved oxygen (DO). The system includes the Arduino Nano main microcontroller (the device that transmits and pushes data to the Raspberry Pi 3 Web server), the DS18B20 temperature sensor module, the pH sensor module V1.1, and the DO Sensor SKU SEN0237. The system is capable of continuously measuring the above parameters of aquaculture ponds. The measurement results are stored and transmitted wirelessly to smart devices such as computers and mobile phones. Farmers can continuously monitor water quality parameters of aquaculture ponds (pH, DO, temperature) through these smart devices. In addition, a warning message will be sent to the farmer's phone when the DO index of the aquaculture pond falls below the prescribed level. The results of the test evaluation also show the high accuracy of the system when compared with the sample measuring device. All relative errors are satisfied less than the limit value of 5%.
Effects of Fertilization Ratios on the Growth of Pinto Peanut (Arachis Pintoi) under Drought Stress Conditions

Vu Duy Hoang, Nguyen Thi Loan, Bui Thi Tam, Tran Thi Thiem

Received: Jan 23, 2019 / Published: Feb 16, 2019
The objectives of this study were to evaluate the effects of different fertilization ratios on the growth of pinto peanut (Arachis pintoi) propagated vegetatively under varying water regimes. The experiment was carried out in a net-house in a completely randomized design with three replicates. The N:P2O5:K2O ratios were applied at six levels: F1 (1:1:1), F2 (1:3:1), F3 (1:1:3), F4 (3:1:1), F5 (3:3:1), and F6 (3:3:3) while soil moisture included three different levels: 30% (W1), 60% (W2), and 100% (W3) field capacity. Water stress conditions were treated from 30-65 days after planting, and then the pots were irrigated to 100% field capacity. The results indicate that drought conditions significantly reduced (P<0.05) the growth of stolons, leaf appearance, number of secondary stolons, and dry matter, while the root/shoot ratio was higher compared to plants under well-watered conditions. There was no significant effect of the fertilization ratios on the number of secondary stolons. Higher-NP and NPK application ratios showed significant influences on the growth of A. pintoi under drought conditions by stimulating stolon lengths and the number of leaves, while the root/shoot ratio was decreased. Higher ratios of single fertilizers (N, P, or K) did not show a consistent effect on the growth of A. pintoi under drought conditions. The results suggest that a higher-NP fertilization ratio stimulates the growth of A. pintoi under both drought and well-irrigated conditions.
Effects of Furrow Height and Amount of Manure Compost on the Growth, Yield, and Quality of Organically Grown Green Asparagus

Nguyen Hong Hanh, Nguyen Thi Ai Nghia, Nguyen Thi Ngoc Dinh, Do Thi Huong

Received: Nov 12, 2020 / Published: Aug 10, 2021
A two-season field trial was carried out in the Upland Crop Experiment Field of the Faculty of Agronomy, Vietnam National University of Agriculture (VNUA) to assess the effects of three furrow heights (20, 35, and 50cm) and three manure compost levels (15, 25, and 35 tons ha-1) on the growth, yield, and quality of green asparagus (Asparagus officinalis L.) grown organically. The experiments were arranged in a randomized completely block design (RCBD) with three replications. The results showed that the harvested yield was highest (11.3 and 25.1 quintals ha-1 in the 2019 autumn and 2020 spring season, respectively) in the treatment with a furrow height of 35cm and compost level of 35 tons ha-1 in both seasons, and explained by the increased spear diameters and number of spears per plant in this treatment when the furrow height and compost level were increased. Additionally, the chlorophyll content, water loss, and dry matter weight of the spears also increased when the furrow height and compost level increased. The obtained quality of the spears under organic management at the furrow height of 35 cm and compost level of 35 tons ha-1 was higher than the other treatments with higher reducing sugars, vitamin C, and Brix values, while the residue nitrate contents of all the treatments were lower than the allowed safety threshold.
Variations in Growth Performance and Nitrogen Uptake of Sugarcane Cultivars Under Rain-Fed Conditions

Dinh Thai Hoang, Takaragawa Hiroo, Trong Lu Le, Taira Eizo, Kawamitsu Yoshinobu

Received: Apr 03, 2020 / Published: Nov 27, 2020
The experiment was conducted to evaluate growth and nitrogen uptake of the twelve sugarcane varieties, viz. NiF3, NiF8, Ni9, Ni12, Ni15, Ni17, Ni21, Ni22, Ni25, Ni27, Ni28, and Ni29, under rain-fed conditions during the period from 70 to 160 days after transplanting (DAT) at the experimental field, Faculty of Agriculture, University of the Ryukyus, Okinawa, Japan. The results showed that water shortage from a rain-fed condition caused reductions, but not significant in plant height and SPAD of sugarcane varieties. The genetic variation in leaf area, yield components, partial and total biomass, and cane yield was found among the investigated varieties. The positive associations between total nitrogen uptake with total biomass production and cane yield suggested that higher nitrogen uptake supports better growth performance of sugarcane under rain-fed conditions. From this study, NiF3 and Ni27 could be introduced as the promising sugarcane varieties for better growth performance and high nitrogen uptake under rain-fed conditions.
Reproductive Parameters and Larval Growth of Bighead Catfish (Clarias microcephalus Günther, 1864) from Wild and Cultured Broodstock Strains

Tran Quoc Cuong, Duong Thuy Yen

Received: Jul 17, 2020 / Published: Dec 31, 2021
Bighead catfish, Clarias macrocephalus, is an important species for aquaculture. Nevertheless, information on population variation in their reproductive characteristics and larval growth is limited. This research aimed to evaluate the reproductive performance and larval growth of three bighead catfish broodstock strains collected in Ca Mau (CM) and Hau Giang (HG) provinces (wild strains), and Can Tho (CT, domesticated strain) in the Mekong Delta, Vietnam. The three groups of fish were cultured under optimal maturation conditions in a recirculating system for three months. Then, 16-18 pairs from each broodstock source were artificially propagated. Relative fecundity differed among the sources, from 48,600 (CM) to 69,300 (CT) eggs/kg female (P< 0.05). The three broodstock sources also differed in fertilization and hatching rates. In addition, wild breeders (CM and HG) had slightly larger eggs, and their offspring had larger sizes at hatching and larger yolk sac volumes than those of cultured (CT) breeders (P< 0.05 for all tests, except for egg sizes). In the larval rearing experiment, 2 day-old larvae were stocked in 40 L-rectangle tanks (1,000 individuals/tank) in a recirculating water system. Larvae were fed with Moina combined with commercial feed. After 40 days, survival rates of the three fish groups ranged from 46.7% (CT) to 54.7% (HG). The final weights varied from 177 mg (CM) to 201 mg (HG) and 202 mg (CT). However, the effects of broodstock sources on the growth and survival rates of the offspring were not statistically significant (P> 0.05).
Effects of Heat Treatment Process on Mechanical Properties of Medium Carbon Steel

Pham Thi Hang

Received: Oct 27, 2020 / Published: Dec 31, 2021
In order to select an appropriate heat treatment process for an industrial application of S45C medium carbon steel, it is necessary to investigate the influence of technological parameters during the heat treatment process such as heating temperature, holding time and cooling medium on the microstructure and mechanical properties. In this study, the experiments were conducted in various heating temperatures, holding times and cooling mediums for specimens made of S45C steel. Then, the relationship between the microstructure and the hardness of the steel was examined. The obtained results show that the heating temperature and cooling medium strongly affect the microstructure of this steel, leading to considerable changes in the hardness. The hardness of S45C steel was markedly improved when heated above 800oC and cooled in water. Moreover, the holding time needs to be carefully calculated to obtain finer grain structure to prevent an increase in the brittleness.

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