Vol. 7 No. 1 (2024): Vietnam Journal of Agricultural Sciences

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.

Da Xanh grapefruit is a fruit tree with many nutrients and high economic value. However, nematode attack is one of the factors that limit productivity. Based on the approach of surveying gardens with symptoms of yellow leaves and root rot, collect and analyze samples. Results of surveying the composition of plant parasitic nematodes in Tien Giang province discovered 11 genera belonging to 8 families of plant parasitic nematodes present in the soil and root zone of Da Xanh grapefruit trees. Thus, 12 nematode species have been identified including: Aphelenchus avenae, C. onoensis, Helicotylenchus crenacauda, H. digonicus, P. coffeae, Rotylenchulus reniformis, Rotylenchus dalhousiensis, Tylenchorhynchus leviterminalis, Tylenchulus semipenetrans, Xiphinema insigne, X. longicaudatum. The species T. semipenetrans appeared at 80% and 76.67% in soil and root samples, which is an important species that needs to be controlled; P. coffeae and R. reniformis are dominant in roots and should be of concern as populations increase. Besides, it also shows that in garden samples with yellow leaf and root rot symptoms, the population of T. semipenetrans nematodes is very high compared to previous studies.

In Vietnam, a tea-producing country, the tea buds and top three leaves are normally used for tea production while older leaves are pruned and discarded as agricultural waste in the winter. The present study aimed to exploit catechins from pruned tea leaves and use them as natural antioxidants for applications in the food industry. Catechins were analyzed using the guideline of ISO 14502-2-2005 by HPLC-MWD. The contents of catechins in pruned tea leaves of ten popular tea varieties were relatively high, ranging from 65.57 to 136.88 mg/g dry weight. The optimized conditions for catechin extraction from Phuc Van Tien pruned tea leaves (one of the varieties with a high catechin content) were found using response surface methodology as follows: a liquid-to-solid ratio of 21.6/1 at 70oC for 31 minutes. The catechin-rich extract powder was added to sesame oil to inhibit lipid oxidation. During oil accelerated oxidation at 60oC, the catechin-rich extract powder inhibited the increase of the peroxide value compared with the negative and positive controls (no preservative and added tert-butylhydroquinone, respectively). Significant positive correlations between the decrease of catechin content and the inhibition of peroxide formation (r = 0.91, 0.94, 0.95, 0.97, and 0.96 for catechin, epigallocatechin gallate, epigallocatechin, epicatechin gallate, and epicatechin, respectively, P <0.05) proved that the inhibition of peroxide formation in the sesame oil was essentially due to the antioxidant capacity of the catechins in the pruned tea leaf extract. Catechin extracts from pruned tea leaves are potential sources of natural antioxidants for oil preservation.

Iceberg lettuce is one of the most important vegetables economically and nutritionally, but its perishable nature poses challenges for storage and long-distance transportation. This study investigated the effect of maturity stages on the quality of iceberg lettuce for export under cold storage conditions. A completely randomized design with three replications was used to evaluate four maturity stages based on days after planting (DAP): 52, 55, 58, and 61 DAP. The lettuce heads were stored at 3±2oC and a 95% relative humidity, and quality parameters were analyzed every three days until the end of storage. Sensory properties, weight loss, color change, total soluble solids, total phenolics, and decay rates were evaluated. The results showed that maturity stages significantly (P <0.05) affected the quality attributes of iceberg lettuce and that harvesting at the optimal stage is very important. Findings from this study confirmed that the quality parameters were preserved for the 58 DAP samples throughout the storage time. They indicated that at three weeks of storage time, the lowest weight loss (5.9%), color change (14.1), and decay rate (8.3%), and the highest sensory analysis (5 scores) and appearance were shown by the 58 DAP maturity stage lettuce. Therefore, harvesting iceberg lettuce at 58 DAP is recommended for long-distance exportation. 

The purpose of this study was to find the optimal conditions for extracting polyphenols from Vietnamese tropical almond leaves (Terminalia catappa L.) and to assess the anti-diabetic activities of the resulting extract. The polyphenol extraction from Vietnamese tropical almond leaves was optimized using the response surface methodology. A rotatable central composite design (RCCD) with three variables (ethanol concentration, temperature, and extraction time), consisting of 21 experimental runs with three replicates at the center, minimal, and maximal factorial points was applied to describe the experimental data. The experimental results properly confirmed the constructed model (R2 = 0.8337). The optimized conditions were as follows: ethanol concentration of 62.76%, a temperature of 62.2°C, and an extraction time of 70 minutes. Five extractions were performed in parallel at the optimized conditions to validate the model. The experimental values highly agreed with the predicted value. The extract powder has powerful effects against the α-glucosidase activity and can develop as a novel natural anti-diabetic agent.

Liquidity risk, which tends to compound other risks such as credit and market risks, has become one of the principal risks in banks. Thus, this study examined the determinants of liquidity risk measured by the loan deposit ratio (LDR). The sample included 30 commercial banks in Vietnam based on secondary data coverage from 2017-2021. Descriptive statistics were used to determine the general situation of the banks' assets, liabilities, and business performance. The random effects model (REM) was chosen to determine factors affecting liquidity risk. The results show the huge gap in the business performance of the four state-owned banks and the rest of the joint-stock commercial banks, and the state-owned banks always accounted for over 50% of the total credit, assets, and deposits of the whole banking system. The average banks’ credit and profit growth rates were around 17% and 30%, respectively, and the bad debt ratio was about 2%. Increasing a bank’s credit growth rate and profitability would push up its liquidity risk. On the other hand, holding several liquid securities that banks could sell immediately to meet solvency requirements and maintaining a high capital adequacy ratio (CAR) would reduce their liquidity risk. These findings are valuable to the banks in understanding how to minimize liquidity risk, such as controlling the credit growth rate and CAR, setting appropriate profit targets, and investing in liquid securities. Additionally, by conducting monetary policies, the State Bank should regulate market liquidity and bank liquidity for the safe operation of the financial system.

This study aimed to analyze the current situation of vocational training for farmers and farmers’ needs for vocational training in the next years in extremely isolated communities. The primary data were collected from 480 farmers in 16 communes. The selection of the study sites was based on the list issued in Decision No. 353/QD-TTg dated March 15, 2022 of the Prime Minister. The secondary data on vocational training in the period of 2016-2022 were collected from the Department of Labor, Invalids, and Social Affairs in the study sites. The research results showed that vocational training programs for farmers in the period of 2016-2022 had some achievements. The numbers of courses and trained workers increased every year (except the period of 2020 to early 2022 because of Covid-19), and the contents of the training courses were designed in accordance with the special requirements of local conditions and production and business characteristics. However, the vocational training program for farmers in extremely isolated communes in the period 2016-2022 still had limitations in terms of training contents, training methods, and training duration. It was found that in the 2023-2025 period, 73.5% of surveyed farmers desired to participate in vocational training. Based on the limitations of the vocational training program in the past, some proper solutions were proposed to improve the effectiveness of vocational training and to meet the farmers’ expectations.