Vol. 17 No. 11 (2019)

The objective of this study was to evaluate allelopathic potential of Boehmeria nivea (L.) Gaudich. against the growth barnyardgrass (Echinnochloa crus-galli) in the laboratory and nethouse conditions. In the laboratory condition, the results showed that the powder of Boehmeria nivea (L.) Gaudich. leaves and stems caused the allelopathic effects on the growth of indicator plants (rice and barnyardgrass). Barnyardgrass biomass and water absorbance were significantly inhibited by the powder ofBoehmeria nivea (L.) Gaudich. leaves and stems. In the nethouse condition, the growth of barnyardgrass was extremely reduced by the effects of powder from Boehmeria nivea (L.) Gaudich. leaves and stems. In the case of increasing the application dose of the powder from 6,2 to 50 g/L. stems, the average inhibition on barnyardgrass was increased from 36.75% to 64.56%. Similar to Boehmeria nivea (L.) Gaudich. leaves, the emergence and dry weight of barnyargrass were significantly decreased from 35,83% to 67,91%. As the result, Boehmeria nivea (L.) Gaudich. indicated a high allelopathic potential to control paddy weeds.

This study was conducted to examine the effect of partial replacement of inorganic fertilizers with microbio-organic fertilizer on the growth,yield and quality of tomato and cucumber in 4 areasas Ha Noi, Hung Yen, Hoa Binh and Ha Nam. The field experiments were carried out in a randomized complete block design with three replications. Four microbio-organic fertilizers replacing inorganic fertilizer treatments were applied: 100% inorganic fertilizer, 75% inorganic fertilizer + 25% microbio-organic fertilizer, 50% inorganic fertilizer + 50% microbio-organic fertilizer, 25% inorganic fertilizer + 75% microbio-organic fertilizer. The obtained results showed that the partial replacement of inorganic fertilizer with microbio-organic fertilizer effected on the life cycle, plant height leading to effect on shoot dry weight, and eventually effected yield and fruit quality of both tomato and cucumber in 4 areasin thespring season, 2018. The experimental studysuggeststhat the treatment of 75% inorganic fertilizer + microbio-organic fertilizer Que Lam replacing 25% inorganic fertilizer significantly increased the growth and yield of both tomato and cucumber in comparison with that at 100% inorganic fertilizer application in 4 areas.

The studywas aimed to establish atechnical protocol to extend the fruit harvest in Northern provincesfor off-season flowering of red-fleshed dragon fruit TL5 variety growingin Gia Lam, Hanoi. The study was conducted in 2 seasons of lighting, on October 20, 2016,and October 20, 2017. The lighting treatment used 60W incandescent light bulbs to supplement light from 10 pm to 3 am, in the 5 different lighting durations of 13, 16, 19, 22 and 25 nights. The experiment was arranged in RCBD, with 20 posts/treatmentforeach replication. The results showedthat in both seasons of lighting supplement, the treatments of lighting in 19, 22 and 25 nights were recorded with good flowering. The number of shoots per post-producing flower buds and number of stable flower buds per post in these lighting treatments reached 28.2-33.6 and 52.7-67.2 respectively, which were significantly different from those of the treatments with 13 and 16 nights of lighting. Actual yields in treatments of 19; 22 and 25 supplement nights reached 6.2 to 7.3 kg/post in both the 2 seasons, which were significantly different from those of treatments with fewer lighting days. Among the lighting treatments, the supplement in 22 nights was the most effective that the profits were increased to 150.8 million dong/ha in the first crop and 144.8 million dong/ha in the second crop.

This study was carried out to findthe presence of Bovine Coronavirus (BCoV) causing diarrheain calvesin Ha Tinh and Nghe An province. The detection of virus using the RT-PCR method showed that 14/180 (7.78%) stool samples were positive to BCoV. The prevalence of BCoV was the highest in the calves group under 1 month old (9.24%), followed by the calves group from 1 to 3 months old (6.25%). BCoV was not detected in the calves aged from 4 to 12 months. The S gene sequencing and analysis results revealedthat the BCoV strains isolated in the present study belonged to the C1 group, the same as Korean vaccine strain 0501.

Morphological relationshipsbetween clutch and fecundity of black apple snail (Pila polita) was studied on the 349 clutches (in Dong Thap, Hau Giang and Vinh Long provinces) with the number of: 121, 113 and 115 clutches, respectively, which were collected from May to August 2017.At the same time, four-repeated experiments on rearing of 3 height groups snails (48.0-50.0 mm; 52.0-54.0 mm and 56.0-58.0 mm) were done to determine fecundity. The rearing was carried out in foam containers (60 × 45 × 40 cm) with a density of1 pair of broodstock snail/tank. Results of the study showed that the morphological relationship between clutch weight with clutch dimensions, the length of the clutch with the size criteria is quite tight (R2= 0.6-0.8). The fecundity of black apple snail is 208 eggs/snail, relative fecundity is 6208 eggs/kg snails. Spawning activity of black apple snail is mainly at night, starting from 20 pm to 4 am and lasts up to 8-12 hours. Black apple snail female is able to re-reproduce for the first time (42.7%).However, the ratio of the second batch is very low (8.3%), the average time for re-spawning of black apple snail is 42.2 days.

Metal bending machine is a research result based on existing equipment and the use of engineering design software combined withtheexperimental works. Fabrication of this machine aimsto process many different types of parts from sheet metal billet by folding bending method. It can easily change of mold size and shapeaccording to the detailed machining requirements. The principle of deformation process is to use the punch and die to bend the blank of the sheet to create angles for the part. Bending machines are suitable for small production facilities or for practical training for students in mechanical technical training institutions. The technological parameters of the machine are calculated and selected based on the scope of the research and the purpose of processing detailed deformation.

The development of small and medium-sized agricultural production enterprises is considered as the force of agricultureand rural development. However, it iscurrently being faced with numerousshortcomings. Therefore, the paper aimed to clarify concepts, roles, and factors which affect medium-sized agricultural enterprises. Some case studies in Vietnam and abroad are also summarized. Finally, some lessons could be learnt. Relevant policies in each stage of development areneeded. Enterprises should be supported to access land and capital as well as technology transfer. Moreover, it is necessary to support them in market development, product development to increase their sales.

Hai Duong is one of the leading agricultural development provinces, especially the livestock sector. The pig herdsof the province areannually about 600 thousands ofheads. The objective of the study wasto assess the current status of livestock production, pollution andeconomic efficiency of thereductions in the greenhouse gas emissions.The study was conducted based on the secondary data and surveyeddata of 120 household farms, combined with in-depth interviews withtheofficials and technical experts in Hai Duong province. The results showedthatfarming householdsare currently using three measures to reduce greenhouse gas emissions in pig production, including biogas, enzyme probiotics and composting.In which, the composting method showedthe highest profit-cost ratio with 2.98 times,followingby 1.94times in biogas and the least is 1.21 timesby using probiotic enzymes,