Vol. 18 No. 1 (2020)

The study was conducted to assess the effect of C: N ratio (T) and frequency of turning (D) on total nitrogen loss during chicken manure composting (chicken faeces, leftovers, feathers and sawdust) to achieve good quality compost. The ratio C: N included three levels of 20: 1, 25: 1 and 30: 1 and the frequency of turning was 1, 3 and 5 days/time. The initial physical and chemical properties of chicken manure were determined. During composting process, 55% moisture in the pile was maintained, monitoring temperature, pH and total nitrogen (TN). Total dry matter, total carbon (TC), total phosphorus and total potassium were recorded at the end of the composting process. The study results have shown that the ratio of C: N and the frequency of turning to affect significantly (p ≤0.05) to the pile temperature, the change in pH, the lost amount of TN, TC, P and K while the weight of the dry matter was only affected (p ≤0.05) by the C: N ratio. All experimental treatments were reached maturation after 75 days when the pile temperature decreased close to the ambient temperature. The total amount of nitrogen loss was mainly due to evaporation of ammonia gas (NH3) in the first 20 days after composting when the pile temperature and pH reached 30oC and 7.5. The experimental treatment of turning every 3 days, the C: N 25:1 ratio (D3T25) has the lowest total nitrogen loss.

The study aimed to evaluate the effects of fruit thinning and fruit wrapping materials on fruit size, fruit quality traits and fruit loss rate due to insects and diseases infecting jujube fruit variety 05. Two independent experiments were conducted on 3-year- old jujube plants, which was designed as a randomized complete block design with four treatments and three replications per treatment. Fruit thinning treatments included removing 10%, 20%, 30% and zero % (control) of the total number of fruits per plant. Fruit wrapping material treatments included nylon bag, sponge bag, oil bag and no-wrapping (control). The results showed that fruit thinning increased fruit size, fruit weight and total soluble solids content (TSS), and decreased total acid content (TA) of the fruit. Out of fruit thinning treatments, thinning 30% of the total fruit number per plant resulted in the highest fruit weight (99.36 g) and TSS (17.2oBrix), and the lowest TA (0.180%), at the same time, the treatment reduced actual fruit yield (37.8 kg/plant) and increased the net revenue (772.000 Vietnam dong/kg). Wrapping fruits by nylon bag and sponge bag increased fruit weight of 25.3% and 17.7% compared to the control treatment, respectively. The sponge bag returned the second rank of fruit yield (44.7 kg/plant) and net revenue (1,001,000 Vietnam dong/plant) and did not affect TSS value (17.02%). The nilon bag decreased TSS (15.69%) but returned the highest fruit yield (47.8 kg/plant) and net revenue (1.258.000 Vietnam dong/plant). Therefore, the application of the wrapping materials into commercial production of jujube, nilon and sponge bags, is potentially economical.

Trialswereconducted to investigate the effects of an ephippium (resting eggs) production method and the influences of different storage conditions and durations on hatching rate of Moina micruraephippiafor live feed producing actively and hygienically.M. micrurawere cultured in 120-lit tanks and covered with black plastic to make a photoperiodofL:D=0:24 at the time of the highest density to stimulate resting eggs formation. The harvested resting eggs were introduced into trials of egg quality examination and treated with two methods: dried in room condition (28-35C) for 2 days and dried in an oven at 45C for 6h, followed by storage duration of 1 and 6 weeks in dark, 4-5C conditions. The rate of male andephippium broodreached14.5% and 69.0%, respectively,after 5 daysof the induction treatment. The rate of resting eggs with embryo was at 65.2% on average. Resting eggs started hatching at around 36h (3 days) of incubation, while the hatching rates reached 14.3-16.9% for all of the treatments. No significant difference in hatching rate and the starting time of hatchingwas foundamong the treatments of storage methods and durations.

The study was conducted to evaluate the time - of - use of Artemiabiomassfor feed affecting to tilapia fillet on survival and growth performance of mud-crab (Scylla paramamosain) in crablet stage. The experiment was performed with 5 treatments, forty crablets were individuallyreared in 250mL jar. Jars were drilled with many small holesto exchange waterand immersed in 150L tanks at 25 ‰ seawater. Artemiabiomass and tilapia fillet wereused as feed for crablets. Artemiabiomass was provided to crab in 20 days, 15 days, 10 days, and 5 days of culture and then they were provided with tilapia fillet to compare with crab in the culture where crablets wereprovided with solely fish fillet. After 20-day of culture, the results showed that the highest survival and growth performance (carapace widthand weight) was obtained in solelyArtemia-fed crabs, the growth performance was gradually decreased when the increased time to provide crabs byfish fillet, the lowest survival and growth performance was obtained in the culture where fish fillet was solely provided to crablets.

The multivariate linear regression model was applied to analyze the factors affecting residential land prices as a basis for determining specific land prices and land price tables prescribed in Chi Linh city.There are larger differences between positions, between segments in a route of residential land prices and market prices of Chi Linh city, Hai Duong province, besides residential land are influenced by many factors. The five-level Likert scale of 1 to 5 was used to design the questionnaire form on measuring the influence of the factors affecting the residential land price. Collected data were processed in the statistical software SPSS, the consistency coefficient measured with Cronbach's Alpha for scaling test and Exploring Factor Analysis (EFA) was used. The results of running a linear regression model had identified the linear regression equation as: Y = - 0,345 + 0,153X1+ 0,218X2+ 0,121X3+ 0,122X4+ 0,220X5+ 0,259X6. Thus, the group of infrastructure elements has the greatest impact on the price of residential land in Chi Linh town with the rate of 24.11%; followed by distinct factors, economic factors, position and group of legal factors with the contribution rate of 21.18%, 19.43%, 13.34% and 11.18%, respectively. Finally, the group of economic factors had a contribution rate of 10.76%.

Our research was conducted to develop a multiple-choice test systemon Computers, because this system is necessary to increase the effectiveness of evaluatingstudents' achievement. We studied new technologies such as NoteJS, MongoDB, AngularJS, and performed the stepsof the software development life cyclesuch as analysis, design, installation, testand deployment of the multiple-choice test system. After the testing process, our system has achieved very good results in theevaluating students’achievement. The results of our experiments haveconfirmed that our system can be effectively applied in practice.

This study aims to assess the implementation of one commune - one product (OCOP) programme in Binh Lieu district, Quang Ninh province. The main analytical methods used in this study include the descriptive statistics and comparative analysis. The study results show that up to the end of 2019, there are 11 units that have participated the programme with 26 products of good brands, professional styles and compliance with national standards. However, the implementation of the programme still face with several limits of its organizational system, establishing the raw material supply area in the district, business management capacity of units participating OCOP programme, and OCOP product market development. The major measures implicated for enhancing the implementation of OCOP program me in Binh Lieu District include the improvement of the organizational system for OCOP programme, enhancement of proganda and dissemination for raising people’s awareness on OCOP program, capacity building for units participating OCOP programme, and promoting the OCOP product market development in the coming time.

The study of beef value chain in Tuan Giao district aimed to show value chain mapping, described the activities of the actors and analyzed the difficulties in the chain to propose “bottleneck” point and leader of value chain basing for the future research. Mapping value chain and descriptive statistics methods were used in the study, interviewed 45 farmers raising cattle, in-depth interview with 1 collector, 3 collectors and slaughterhouses, 2 retailers, 2 wholesalers and 1 veterinarian who has been responsible for examination slaughter and purchasing cattle, and 1 FGDs with consumers. The results of the study showed that the value chain of beef cattle includes actors from producers, collectors, slaughterers, wholesalers, retailers and consumers. There are five channels to sell beef and selling at Tuan Giao district. Base on the value chain and actor analysis indicated that slaughterhouses play decisive role in the beef value chain in Tuan Giao. The actors in the chain mainly operate independently and do not have a link to increase the value of the chain and meet the needs of customers.