Vol. 4 No. 2 (2021): Vietnam Journal of Agricultural Sciences

Mineral nutrients are essential to plant growth and development. The present study aimed to evaluate the effects of mineral fertilizer doses and N:P:K ratio on growth, yield, and raw material quality of the tea variety PH10 to improve the production of high-quality tea products. The field experiment was conducted from 2015 to 2017. A two-factor experiment was designed by split-plot design with three replications. The mainplot treatments were three fertilizer doses of N  for one metric ton of fresh shoot products (30, 40, and 50 kg N ha-1). The subplot treatments were two NPK ratios (3:1:1 and 3:1:2). Plant height, leaf canopy, plant diameter, shoot yield parameters, shoot components, biochemical compounds, and sensory quality for Oolong and Sencha tea products were evaluated. The results showed that increasing fertilizer doses from 30 up to 40 kg N per ton of fresh product improved remarkably growth, yield, and tea quality of PH10 variety. Different fertilizer ratios resulted in variations in plant growth, the content of carbohydrate, sensory quality for taste and flavor as well as total sensory quality with higher values at NPK ratio of 3:1:2. Applying mineral fertilizer with an NPK ratio of 3:1:2 and 40kg N per ton of fresh shoot products was recommended to bring about the most benefits of tea yield and quality as well as economic profit.

This study was conducted to examine the effects of baby corn density on the crop and weed performance under two different maize-soybean intercropping systems. Treatments included four baby corn densities (D1= 138,888 plants ha-1, D2 = 111,111 plants ha-1, D3 = 92,592 plants ha-1, and D4 = 79,365 plants ha-1), and three intercropping methods (P0 = a sole cropping of baby corn, P1 = 1 row of soybean + 1 row of baby corn (density of soybean, 10 plant m-2), and P2 = 2 rows of soybean + 1 row of baby corn (density of soybean, 20 plants m-2)). Physiological characteristics and yield were measured for the baby corn and soybean. The weed species, weed frequency, and the growth of the weeds were recorded at the final harvesting time of the baby corn. The results showed that the yield of soybean and the growth of the weeds were statistically different under the different maize-soybean intercropping systems. Increasing the baby corn density increased the leaf area index, dry matter accumulation, and cob yield, but did not have a clear effect on the soybean yield under both intercropping methods. In addition, the P2 intercropping method produced significantly higher soybean yield and gave better results of weed growth reduction in comparison with the P1 intercropping method. In the P2 intercropping method, baby corn should be grown at a density of 111,111 plants ha-1 to optimize the population productivity and achieve reasonable weed control for the sustainability of agriculture.

To study the effects of cover methods and nitrogen (N) levels on the growth and yield components of tomato Cv. Pear F1, field experiments with a 4x3 factorial design were conducted in the 2019 spring and winter seasons using a randomized complete block design with three replications. The cover methods included four treatments: bare soil (BS), black plastic mulch (BPM), transparent polypropylene row cover (RC), and a combination of BPM and RC (BPMRC) with the RC removed approximately 30 days after transplanting. Nitrogen (N) was applied at three levels (150, 180, and 210 kg N ha-1). Using BPM and RC generally led to an increased air temperature, air humidity, soil moisture, and soil temperature compared to the BS treatment. Higher N rates (180 and 210 kg N ha-1) did not result  in different tomato fruit sizes and fruit weights but positively increased fruit yield and quality (Brix values and fruit dry weight) as compared to the 150 kg N ha-1 addition. The cover methods positively affected the yield components and fruit yield of tomato as well as the fruit characteristics compared to the BS treatment. Using cover materials (BPM and RC) combined with a higher N application significantly increased the yield attributes and fruit yield. The highest fruit yield was achieved under the mulching treatment by black plastic (BPM treatment) combined with a 210 kg N ha-1 application, resulting in 50.90 tons ha-1 in the spring and 58.27 tons ha-1 in the winter.

Gynostemma pentaphyllum (Thunb.) Makino is a medicinal plant distributed mostly in the mountainous areas of Vietnam. G. pentaphyllum contains more than 189 types of saponin which can be used for the treatment of various diseases. Currently, due to over-exploitation, this plant species is under threaten. Our research aimed to study a suitable method for plant propagation by stem cutting techniques to promote the growth and development of G. pentaphyllum. Six experiments were conducted to (i) evaluate the established seedling rates of different G. pentaphyllum varieties, and choose the best variety to (ii) evaluate the established seedling rate influenced by different factors, viz. stem cutting position, cutting season, growing in the selected substrates, stem cutting length, number of buds per stem, and application of α-NAA. The results showed that among five varieties, G2 which was collected in Mai Chau district disclosed the highest ability to shooting, the highest number of roots per stem cutting, the shortest nursery days, the highest shooting rate, and the highestestablished seedling rate. We also determined that using middle-aged plants for stem cuttings, at 15-20cm in length, with 2 nodes and grown in Spring and Winter cropping seasons, using growing substrates with a mixture of 50% of black sand and 50% of soil, and plus α-NAA 50ppm in 3-5min produced the highest explant rate. The established seedlingsat the time of explant were 15-20cm in height, containing 4-5 leaves and at least 9-10 roots per cutting, and were 30-32 days.

This study was conducted to evaluate the salt tolerance ability of two soybean cultivars under salinity conditions using a selection of growth and physiological parameters. Three weeks after germination, plants began being treated with either a 100 mM concentration of NaCl in Hoagland solution or a non-salinity (0 mM NaCl) solution. The results showed that the plant height, number of leaves, leaf area index, and shoot and root biomasses were significantly reduced under salt conditions. A similar tendency was observed in several physiological parameters (SPAD, Fv/Fm). Since all the salt-treated plants of the D8 cultivar were dead after 40 days under the 100 mM NaCl treatment, the yield of D8 could not be obtained, while the treated plants of the D140 cultivar experienced a marked decrease in yield compared to the control plants. In this study, we identified that the D140 soybean cultivar had a better salt tolerance than the D8 soybean cultivar at a 100 mM NaCl concentration.

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.

Stingless bees are distributed in tropical and subtropical regions. There are over 16,000 species of stingless bees around the world, among which, 42 species are from Asia (Kerr & Maule, 1964). Sixteen species of stingless bees have been identified in Vietnam (Sakagami, 1975; Sakagami, 1978; Engel, 2000; Chinh et al., 2005; Rasmussen, 2008). In this study, the biological characteristics of Tetrigonilla collina, as a representative for Southeast Asian stingless bees, were observed and recorded. The worker cell dimensions were 5.30 ± 0.34mm in length by 4.28 ± 0.37mm in width with a volume of 45.02 ± 5.74mL (food volume: 19.05 ± 3.5mL; ratio: 42.27%). The new cells were mostly built in the morning (from 2:00 to 10:00 am) and the queen laid eggs (2.52 ± 0.81 sec per egg) and capped the cells in the afternoon (from 12:00 to 17:00 pm). The average worker-cell building period was 12.03 ± 3.78 hours. Mainly, six of first ten bees that inserted made food discharges in a cell. The food discharge occurred in a very short time, which was 1.58 ± 0.6 minutes. The new cell numbers of the colony were reduced at the end of the experimental period.

Erwinia is a genus of Enterobacteriacea containing mostly pathogens, which cause soft rot disease in many ornamental plants and crops, including Asparagus officinalis. Chemical treatments to control Erwinia have lost their attractiveness because of the development of resistant strains and the negative impacts on the environment and human health. Therefore, the study of biological controls of soft rot disease has gained great importance. There are several types of microorganisms that show activity against Erwinia spp. such as Pseudomonas fluorescence, Bacillus subtilis, and Streptomyces spp. Among them, Streptomyces spp. are found to be the most effective control agents. In this study, 64 isolates of Streptomyces were screened for their antibacterial activity against Erwinia spp. The results indicated that 18 isolates showed an antagonistic reaction against Erwinia spp. Among them, isolate D5.1 showed the highest inhibition activity. In addition, the morphological and antibacterial activities of isolate D5.1 grown in different conditions were also characterized. 

This paper aims to review the current situation of the Vietnamese geographical indication (GI) system from both the legal and practical perspectives. It examines how the top-down approach influences the effectiveness and sustainability of the whole system. Further, the paper refers to the European Union (EU)’s experiences, particularly those of France - a representative of the bottom-up approach - to examine whether a shift to the producer-driven approach in GIs is workable in Vietnam. The paper argues that more active roles should be vested on producers represented by their associations during the course of establishment and management of GIs. Taking into account the capacity of producers and their associations in this current stage, the paper suggests a transition period before the producers assume the leading role in the whole system. During that period, it is recommended to endorse the producers’ role through legal recognition of the producers’ representative organizations, capacity building, and awareness-raising for producers and their associations to achieve desirable outcomes for GI development.

Climate change is one of the greatest threats to human beings, and agriculture is one of the fields that is most negatively affected by climate change. Farmers around the world and global food supply chains are impacted by the more extreme weather phenomena and increased damage of diseases and pests caused by climate change. Today, almost all agricultural enterprises and farms consider climate change a serious long-term risk for their production. Agricultural land systems can produce significant greenhouse gases (GHGs) by the conversion of forests to crop- and animal lands, and also through the weak management of crops and livestock. Around the world, cultivation and cattle production accounts for 25% of global GHG emissions (Javeline, ‎2014). However, under suitable conditions, agriculture can create environmental conditions that can help minimize pollution and the negative effects of climate change including carbon absorption by green plants in forests, and fields for watershed protection and biodiversity conservation. Sustainable agriculture helps farmers to adapt, maintain, and improve productivity without applying harmful techniques. In turn, this allows farms to manage and mitigate climate-related risks in their supply chains. The Sustainable Agriculture Network (SAN) has found new ways to incorporate smart climate cultivation methods into all farming practices to help farms and enterprises carry out agriculture sustainably.