Vol. 15 No. 4 (2017)

A study was conducted to identify suitable planting dates for improving yield and quality and economic eficiency of two specialtysticky rice varieties,KhauPai and Khau Luong Van in Tuyen Quang province. The experiments consisted of four sowing/planting dates(sown on May 15, May 30, June 15 and June 30; transplated at 20 DAS) together with traditional cropping season (sown on April 15, transplanted at 35 DAS)as the control. The results showed that the planting dates affectedgrowth, yield and quality of bothrice varieites. Late plantingdate decreased tillering,,especially in the control planting date. The effects of planting dateson plant height, stem sturdinessand rice quality were unclear. Two rice varieties could be sownfrom 15/5 to 15/6.The best sowing date for Khau Pai was on 15/6 (Yield: 42.82 - 42.96 quintal/ha, net profit: 32.779.400 - 33.059.400 VND/ha)and on 30/5 for Khau Luong Van (Yield: 43.15 - 44.83 quintal/ha, net profit: 33.439.400 - 36.799.400 VND/ha).

The objective of this study was to evaluate the growth and yield of rice varieties grown indifferent agro-ecological zones in different croppingseasons. Four rice varieties were MTL547, OM 517, OM 921 and OM 347. Results showed that variety OM7347 had highest plant height, grain number per panicle, filled grain percentage and yield within agro-ecological zones of acid sulphate soils (ASS) while variety OM9921 was lowest in growth and yield at three sites of Hon Dat, Hong Dan and Thap Muoi. For Phung Hiep, yield of MTL547 was lowest. Phung Hiep ASS was the most constraints due to low pH, low available phosphorus, and high exchangeable aluminium. The number of panicle per square metre, grain number per panicle and filled grain percentage indry season(DS)rice werehigher than those inwet season rice. As a result, the yieldinthe DS was higher than at least 2.5 tons per hectare compared to that inthe wet seson (WS), although the fertilizers applied per hectare (kg N - kg P2O5 - kg K2O) for dry season crop (100-60-30) was slightly different than that in WS(80-60-30).

This study was carried out at the experimental farm of Vietnam National University of Agriculture from January to December, 2016 on H’mong chickens that were raised by industrial farming practices. H’mong chickens were raised in three lots in order to observe the survival rate, growth capacity, FCR and quality of meat. The results showed that H’mong chicken adapted well with industrial farming method, which supposedly contributed to the improvement in survival rate of chickens (94,1%). H'mong chickens had low weight and considerable growth speed. Average daily gain of H’mong chickens increased gradually from one to ten weeks of age and then decreased. From one to 12 weeks, H'mong chickens consumed 24.81 grams of feed per day and FCR was 3.1 kg of feed/kg live body weight. Twelve week-old roosters and hens achieved body weight at 1206,7g and 1026,7g, respectively. H'mong chicken is a dual-purpose breed, producing an amount of thigh meat 1.3 times greater than breast meat. The proportion of iron in H'mong chicken meat is high (136,8mg - 137,7 mg/100g) and there are eight essential amino acids in the meat.

Cat fish, Ictalurus punctatusis increasingly cultured in the Northern part of Vietnam.However, the diseaseson the fish have not yet studied extensively with limited literature. The study was implemented to isolate pathogenic bacteria causing hemorrhagic disease in catfish and to find out highly effective antibiotics for disease treatment. The result showed that the external signs of the diseases are black skin with lossing mucus and haemorrhagic spots in the head part, fins, and abdomen. The internal signs showed damaged kidney and liquid accumulated abdomen. Thirteen rod shape, gram negative bacterial strains that grew in selected R-S medium were isolated from diseased fish. These strains were identified as Aeromonas hydrophila. Histopathological analysis of hemorrhagic diseased catfish revealed structural changes with slight necroses in muscle and gill filaments. There were many necrotic areas and granulomatous lesions on the liver, kidney and spleen, hydrophytic kidney and spleen tissues. After 2 day period of infection,bacterial strainsCL18, CL20, CL24 and CL26 at 108CFU/fish caused hemorrhagic septicemia in healthy catfish similarly to those in natural infection. Among 7 types of antibiotics, Doxycylin most sensitive with 13 tested isolates. Therefore, the use of Doxycylin on catfish haemorrhagic disease treatment is highly effective.

This study investigated the relationship between the salinity and development of Vibriobacteria inthefield and laboratory conditions. A totalof 90 water samples were collected from 9 ponds at timescorresponding tof 10 different salinities. Three strains of bacteria.V. parahaemolyticus, V. vulnificus14.2 and V. vulnificuswere experimentally culured in different conditions of salinity (3, 15, 25, 35 and 40 ‰). V. choleraewas cultured in sterilized shrimp pond and distilled water. The densities of bacteria in shrimp pond water samples and cultured mediawere measured. Research results showed that there was a correlation between bacterial density and salinity inpond water environment as well as in experimental culture media. The correlation coefficient betweenVibriospp. and salinity in the pond was 0.75 (P <0.05); betweenV. vulnificus17.5 and the salinity was 0.69 (P <0.05). V. cholearedensity in sterile water pond was (7,5 x 106), significantly higher than that in distilled water (1.3 x 102colonies/ml). However, the growth of V. vulnificus14.2 and V. parahaemolyticuswas not significantly correlated withsalinity ( r =0.19 and 0.17), respectively. Research showedthat salinity can have an important role in disease outbreak caused by Vibrio.

An experiment was carried out to assess yield and nutritive value of Taiwanese Napier, an elephant grass line originated from Taiwan and imported to Vietnam from Thailand. Taiwanese Napier wasplanted and compared to 3 control grasses,elephant grass, purple elephant grass and VA06 grass in terms of productivity and nutritive value. The experiment was a completely randomized design in which each grass was grown on three plots of 10m2in the field of Vietnam National University of Agriculture. The average yield of Taiwanese Napier of 3 harvests was79.43 tons green matter/ha, 14.97 tons dry matter/ha, 1.80 tons protein/ha, and 324.68 kg dry matter/ha/day. Taiwanese Napier grass contained18.84% dry matter, in which crude protein accountedfor 12.04%. After evaluating yield and nutritivie value, an experiment with goat was conducted at the breeding area of Vietnam National University of Agriculture to determine the UE (Unite d’ encombrement) and the apparent digestibility of four grasses. Four male crossbred (Jumnapari x Saanen) 6-month old goats with weight of 16±0,5kg were randomly divided into 4 batches according to Latin square model. Each goat was fed ad libitum one of four grasses. Results showed that UE of Taiwanese Napier was at the lowest level (1.12), the digestible ratio of dry matter; crude protein and NDF of Taiwanese Napier were 59.34%, 45.33% and 55.18%, respectively.

The objective of the research was to evaluate the effect of application of P blended with DCAP on soil P availability, rice yield and P uptake. Resultsshowed that in the incubation condition, the DCAP blended with 30 kg P2O5/ha applied to acid sulfate soil increased soil P availability whileat the higher rate (60 kg P2O5/ha), the blend did not. The greenhouse condition, trialson Phung Hiep-Hau Giang acid sulfate soil showed that plant height, tiller number and percentage of filled grains of rice were low at 30 kg P2O5/ha applied. However,the blended DCAP with 30 kg P2O5/ha resulted inbetter plant height, P uptake,and,therefore,rice yield was as high as 60 kg P2O5/ha application. It is needed to perform trials using DCAP in the field condition.

Environmental efficiency of coffee - macadamia intercropping with different ages on basalt in Krong Nang district, Dak Lak province was investigated. The results showedthat macadamia trees intercropped with coffee improved soilporousityand fertility. In these models, wilting humidity increasedwith the depth of soil moisture in comparisonwith coffee - black pepper intercroppingand pure coffeestand (Control model). Macadamia intercropped with coffee improvedthe microclimate of coffee plantations through shading effect from macadamia treesresulting inhigher air humidity (by 13.67%)in comparison with pure coffee plantation. Compared with coffee monoculture,coffee -pepper intercopping also retained higherhumidity (5.48%). In addition, coffee - macadamia intercropping reduced air temperature and wind speed by 2.43 - 2.710Cand 70 %, respectivelyas compared with coffee monoculture..

This experiment was conducted during 2015 winter in neutral to slight acidic alluvial soils of the Red River delta in Gia Lam district of Hanoi. A mathematical model was appliedr determine drip irrigation regime for obtaining highest yield and water use efficiency of winter tomato. The functions determining soil moisture in mathematical model were tested and the difference with real data was less than 8%. In the case of soil moisture at 70-100% the maximum field capacity, the mathematical model predicted 11 irrigation times per season with the drip irrigated area (ahn= 52.3%) varied between 198.7 - 201.4 m3/ha/irrigation. The amount of water, taking into account the proportion of drip irrigation area (ahn= 52.3%), ranged between 198.7 - 201.4 m3/ha/irrigation. The water use efficiency was of 30.5 kg/m3, increased by 16.2 kg/m3 and water irrigation amount was saved by 42.8% compared to furrow irrigation. Drip irrigation regime was proposed for winter tomato as follows: number of irrigation for whole cropping season was 10, irrigation water amount was 198.7 m3/ha for each application (equivalent to 6.2 liters/plant/irrigation), total irrigation water amount in a cropping season was 1987 m3/ha.

Vật liệu xúc tác nano MnO2được tổng hợp từ mangan sunfat và kali pemanganat bằng phương pháp đồng kết tủa ở nhiệt độ thường. Các đặc trưng cấu trúc sản phẩm được phân tích bằng các phương pháp hóa lý: Diện tích bề mặt riêng (BET), nhiễu xạ tia X (XRD), phổ tán xạ năng lượng điện tử (EDX), kính hiển vi điện tử quét (SEM), kính hiển vi điện tử truyền qua (TEM). Kết quả cho thấy sản phẩm thu được có kính thước hạt nhỏ mịn 0,5µm, diện tích bề mặt riêng lớn 113.0601m2/g. Nước thải được lấy sau hệ thống biogas tại trang trại chăn nuôi lợn. Bước đầu nghiên cứu sử dụng hệ xúc tác cho phản ứng ôzôn hóa xử lý chất hữu cơ trong nước thải chăn nuôi sau biogas trong phòng thí nghiệm. Kết quả cho thấy các phản ứng có xúc tác nano MnO2thời gian phản ứng xảy ra nhanh hơn, hiệu quả tốt hơn so với phản ứng ôzôn hóa thông thường. Kết quả xử lý của xúc tác với nồng độ 0,02g/l mẫu nước chăn nuôi sau biogas cho kết quả hàm lượng COD giảm từ 1138,64 mg/l xuống 43,27 mg/l, đạt hiệu quả xử lý 96,20%. Phản ứng ôzôn hóa chất hữu cơ với hệ xúc tác nano MnO2là một phương pháp có hiệu quả, có thể áp dụng để xử lý chất hữu cơ trong nước chăn nuôi sau biogas.

In this study, four raw material types (bud with two young leaves, B type, C type ,and old tea leaves) of the Shan tea were examined for polyphenols, caffeine, gallic acid and antioxidative activity. The results indicated that the content of these compounds varied tremendously with raw material types. The younger the material was, the higher the levels of these components were, and vice versa. In the material types examined, the total content of polyphenol, catechins, caffeine and gallic acid ranged from 13.3% dry weight (DW) to 26.1% DW, 9.63% DW to 21.54% DW, 1.3% DW to 4.1% DW, 0.07% DW to 0.89% DW, respectively. With regard to catechins, the content of these compouds was in the decreasing oder: EGCG > EGC > ECG > EC > C. In addtition, the antioxidant activity was closely correlated with the total polyphenol content (r2= 0.9852) and the total catechin content (r2= 0.8986). Moreover, the antioxidant activity was also strongly dependent on the age of materials (bud with two young leaves > B type > C type > old tea leaves).

This experiment was performed to explore the effects of harvest maturity and low temperature storage on qualityof tomato cv. Savior. Tomato wascultivated in winter season and fruits were harvested at 3 ripening stages,breakersstage, turning stage and pink stageandpacked in PE bags 0.03 mm thickness, then stored at 12oC and 18oC. Fruit quality was examined every week after removing from cold room and keptat ambient temperature for 1 hr. The results demonstrated that i) at 12oC, tomato fruitsharvested at breakersstage had the lowest respiration rate, therefore,they had a low rate of weight loss and little change infruit firmness. Fruit color slightly changed during low temperature storageand no decay was observed after 28 days of storage. ii) At 18oC, tomato fruitsharvested at pink striped color stage had the best quality after 14 days of storage. Skin color and carotenoid content of these fruitswere similar to those of natural ripe fruitsin the plant. From the results found in this study the recommendations could be madeforgrowers to choose ripening stage suitable for their storage conditions to meet the diversemarket demands.

This study aimed to analyze the situation of linkage in maize consumption in Son La province and the factors affecting ability to engage linkage in maize consumption for farmer households. 536 maize production households and 26 local stafts in Son La province were interviewed by using direct investigation tools such as stuctureedquestionairescombined with participatory rural appraisal (PRA). Descriptive statistics was used to analyze the situation of linkage in maize consumption in Son La while econometric model (probit model) was employed to evaluate factors affecting ability to engage linkage for households. The research results showed that therewas asignificant difference in income from maize production among households engaging linkage with households who were not involved. However, the linkage of maize consumption in Son La was employed at the simple levelof oral negotiation. The involvement inthe commitment to linkageimplementationwas not strong enough about the legality, leadingto a lack of sustainability. Another results illustrated that the factors belongingto the characteristics of individual householdsand the headsof household,such as education level, ethnic group, social position,andscale maize production hadsignificant positive impact on maize household’s ability to engage in the linkage in maize consumption, whereas some other factors hadsignificant negative effects, including number of household members and houshold’s processing activities.

This studyattemptedto estimate the technical efficiency and its determinants ofdragon fruit farming, based on the data collected from 118 dragon fruit farming householdss in Chau Thanh district, Long An province. A Cobb-Douglas stochastic frontier model incorporating inefficiency effects was employed to analyze the data using the Frontier 4.1. The results revealed that the technical efficiency rangedbetween 49.5%-97.4 %(76.0%on average).Significant factors that were found to positively affect dragon fruit yield were cultivated area, potash fertilizer, and labor while seed (planted density) was negatively related to the fragon fruit yield. In addition, significant determinants that positively related to technical efficiency were farmers’ education attainment, membership of local associations, technical training and credit access. The improvement of these factors would lead to an increase in technical efficiency.