Vol. 17 No. 7 (2019)

This study was conducted to evaluate the effects of planting density and fertilizer level on the growth and yield of the potato variety KT4 grown in Thanh Tri, Hanoi. The field experiment was a split-plot designwith three replications. Plant density was main factor with3 levels: 4 tubers/m2(M1), 5 tubers/m2(M2) and 6 tubers/m2(M3); the sub-factor consisted of three fertilizer levels(kg/ha): 120N: 120P2O5: 120K2O (P1); 150N: 150P2O5: 150K2O (P2); 180N: 180P2O5: 180K2O (P3). Theresults showed that there weresignificant differences(P≤0.05)in plant height, leaf area index, dry matter, yield components and tuber yield when plant density increased from M1 to M2 and fertilizer application level increased from P1 to P2. However,there was no significant differencesin the above parameters between M1 and M2 as well as between P2 and P3. In addition, the effect of interaction between plant density and fertilizer level was significant for tuber yield. The highest tuber yield (26.21-27.44 tons per ha-1)was found at M2 and M3 density combining with P2 and P3 fertilizer leves.

This study was conducted to reveal the clinical and non-clinical characteristics as well as gross lesions of chickens infected by chicken infectiousaAnemia virus (CIAV) under an experimental condition. Via intra-abdominal inoculation of the virus at a dose of 104TCID50/mL, one-week oldchickens were sucessfully infected by the field strain of CIAV with the viremia appeared at 3 weeks postinfection (20.0%) and reached 100% at the sixth week postinfection. Under the current condition, viremic CIAV chickens exhibited minimum clinical signs. From the fifth week after infection, CIAV infected group exhibited a reduction inthe growth rate and had significantly lower body weight than that of the control group. Additionally, at eighth week postinfection, the packed cell volume of CIAV positive group was less than 27% and was significantly lower than the control group. The chickens of the experimental group had compatible gross lesions of anemia, such as pale of bone marrow (77.8%) and atrophy of primary lymphoid organs (bursa of Fabricius and thymus, 33.3% and 55.6%, respectively). The results of this study appeared helpful for differential diagnosis of chicken infectious anemia in the field.

An evaluation on the exploitation status of Yellowcheek (Elopichthys bambusaRicharson, 1844)was conducted from January to June 2019 in the Northern and Northern Central provinces of Vietnam including Nghe An, Hai Duong, Hoa Binh, Son La, Yen Bai and Tuyen Quang provinces. The data on fishing gear, season and catch area, size of Yellowcheek, Yellowcheekproduction andthe ratio of Yellowcheek production per totalcatchesproductionare collected through, through direct interviews of 120 fishermen catching fish in rivers and reservoirs. The results showed that there were 5 fishing gears mainly used to exploit natural fish in the Northern and Northern central provinces, of which the three-layer gill net and lighting lift net were ofhighest rate of exploitation Yellowcheek. The peakfishing season of Yellowcheekwas from May to September in the surveyed provinces with the size of Yellowcheekvaried in the range of 100-5,000 g/fish depending on the type of fishing gear used and the location of exploitation. Yellowcheekwere exploited mainly in rivers and reservoirs, with an average fish production ranged from 8-20 kg/household/year. The natural resources of Yellowcheekaregradualy reducing due to the construction of hydropower dams and the use of nets with the small mesh size to exploit fish. Currently, catching Yellowcheekhas not been profitable for fishermen in the investigated areas.

This study aimed to assess the knowledge, attitudes and levels of application of safety measures in the use of pesticides by tea farmers. Primary data were collected by interviewing 60 tea farmers using a structured-questionnaire in Binh Thuan commune, Dai Tu district, Thai Nguyen province. The survey results showed that the tea farmers still hadlimited knowledge of toxicity groups of pesticides based on information on pesticide containers and how to treat pesticide containers after use. The tea farmers hada high level of interest in the harmful effects of pesticides on human health, but only on an average level of environmental damage, especially for natural enemiesbeneficial for crops. The research results also showed that people hadapplied relatively good safety measures in pesticide use, except still regularly poured the waterfrom washingpesticide sprayer into canals or ponds and occasionally discarded pesticide containers after use right on the tea farms where the pesticideswereprepared for spraying. The gender of the household heads, participation in training, area of ​​agricultural landand household income from agriculturewere the factors affecting the knowledge, attitudes and levels of application of safety measures in pesticide use on tea farms.These results provide necessary information to local authorities and relevant organizations in deciding suitable pesticide management measures to protect the human health and the environment.

Cardamom (Amomum aromaticumRoxb.) is one of the precious medicinal herbs. It also has been used as a spice in food processing. The aim of this study was to establish a protocol for in vitropropagation of Amomum aromaticumRoxb. fromrhizome buds, producing materials for mass-scale production as well as conservation.The most suitable time to collect rhizome buds of Amomum aromaticumRoxb. samples for in vitropropagation was from April to June. The rhizome budswere best sterilized with 0.1% HgCl2in 8 minutes. The highest shoot multiplication rate (4.13 shoot/explant; length of shoots 5.4 cm) was obtained on MS medium supplemented with 1.0 mg/L BAP after 6 weeks of culture. 100% of the shoots produced roots within 8 weeks on MS medium containing 0.5mg/L IBA.

Lai Chau ginseng (Panax vietnamensis var. fuscidiscus K. Komatsu, S. Zhu & S. Q. Cai), is a precious medicinal plant in Vietnam rich in saponin and of high economic value. The objective of this study was to examine the cultivation techniques of Lai Chauginseng to effectively conserve and develop this valuable species.The results showed that September and October were most suitable for planting and the productivity of the six-year-old plants was about 24.98 to 25.31 quintals/ha. At 2.000 m altitude above the sea level, Lai Chauginseng grew rapidly, and reached higher quality than plants in planting areas at 1.000 and 1.500 m above sea level. At 90% of shade, the seedlings grew well and pest infestation was reduced. Plant spacing of 30×30 cm and 35×30 cm was suitable for cultivation of Lai Chauginseng.

Binh Phuoc is known as the capital of cashew production and processing in Vietnam, which contributes significantly to the economic development of the province as well as to the farmers. However, theuncertainty about prices, pests andthe competition withother crops such as black pepper and rubberaffectthe cashew production development of Binh Phuoc province. The objective of the study was to assess the current status of cashew production development in Binh Phuocprovince, analyze the influencing factors and propose some policy orientations. Thestudy was based on secondary data and survey data of 420 households, combined with in-depth interviews with technical staff and experts in Binh Phuoc province. Research results showesthat cashew production households with an average scale of 7.2 ha attainedan average income of nearly 50 million VND/ha. However, the linkage in productionwasnot yet available, the conditions of infrastructure were not synchronized, pests and diseases significantly affected thecashew production. The study proposes a number of solutions to promote the development of production in a sustainable way, exploiting the potential advantages in Binh Phuoc province.