This study aimed to quantify relationships between female weight and some reproductive parameters, yolk sac volume, and larval length of striped catfish (Pangasianodon hypophthalmus). Mature fish were selected from the broodstock conditioning tank in a recirculating system. Females (n = 36) weighing 1.7 to 7.0 kg were artificially propagated with the same male group. The results showed that realized fecundity (331,667 - 1,404,791 eggs/female) was positively correlated (P < 0.01), while relative fecundity (73,849 - 255,214 eggs/kg female) had a negative relationship with females’ weight (P < 0.01). Eighteen females were divided into 3 groups of weights (6 - 7 kg, n = 5; 5 - 5.5 kg, n = 8; and 3 - 4.8 kg, n = 5) to examine other reproductive parameters. Egg diameter (1,014 - 1,024 µm), fertilization rate (65.78 - 79.00%), and hatching rate (42.73 - 57.27%) were not significantly different among female groups. Larvae produced by medium and large-sized females appeared to grow (in length) faster than those by small-sized females, and these differences were significant at hatching, 24, and 72 h post-hatch (P < 0.05). Yolk sac volume was not different among the three groups (P > 0.05), ranging from 0.37 to 0.41 mm3 at hatching, and decreasing 62.2 - 68.3% after 36 h and 83.8 - 85.4% after 48 h post-hatch. In sum, females weighing 5 to 7 kg had higher realized fecundity and better growth of larvae during the first five days compared to small females. 

In environmental management, continuous water quality monitoring is essential to provide information on the status, distribution, and trends of water quality. However, monitoring work may not be conducted continuously for various reasons, resulting in a lack of data or discontinuity in data sets. The lack of data and the discontinuity of the monitoring data set can result in the heterogeneity or weak representativeness of the analysis/assessment results regarding the level quality or self-cleaning capacity of water. High-order polynomial empirical curve equation (HoCEq) and multivariable regression correlative equation (MREq) are commonly used interpolation/simulation methods because they are integrated in the office analysis tools like Excel or SPSS and give suitable results. In the study, the assessment of water quality and self-cleaning capacity of Nhieu Loc Thi Nghe canal in Ho Chi Minh City, the HoCEq and MREq were applied to “fill up” monitoring data sets for the period 2012 - 2021. This approach helps to increase efficiency in the analysis/assessment and increases the representativeness of research results with an appropriate square correlation coefficient (R2 larger than 0.5) and corresponding degree of close correlation.

This study was conducted to evaluate the effects of waterlogging time on growth, physiology and yield of L14 peanut cultivar in the grasshouse of Faculty of Agronomy (Vietnam National University of Agriculture, Ha Noi) in Spring 2020. The experiment was designed as a randomized block design with 2 factors. Factor 1 was irigation regime including CT1: normal irrigation and CT2: waterlogging for 10 weeks and then drainage (soil moisture: 70 - 80%); Factor 2 was the time of waterlogging, including waterlogging at the seedling (3 leaves stage), flowering (25 days after begining of flowering), and full pod stages (65 days after begining of flowering). The results showed that waterlogging reduced both growth and physiological parameters, such as plant height, primary branch length, number of leaves/plant, fresh weight and dry matter, and nodule formation, soil plant analysis development index, and chlorophyll fluorescence efficiency. Only the increased ion leakage indicated the level of waterlogging stress. However, waterlogging at the seedling stage had a great impact on the number of pod per plant, and the pod set rate resulted in a 60.3% reduction in the individual yield of the cultivar L14 compared to the control. Meanwhile, waterlogging at the flowering and full pod stages caused a similar decrease in yield of peanut cultivar L14 ( 31%). Thus, waterlogging at the seedling stage for 10 weeks had the greatest effect on the yield of peanut variety L14.

Selection of waxy corn varieties with high yield, good quality and appropriate planting density for disseminating to production is a job that is interested by seed centers and companies. The experiment aimed to evaluate effects of planting density on growth and yield of 3 waxy corn varieties and was carried out from April 2021 to June 2021 in Cu Chi district, Ho Chi Minh City. The two-factor experiments were arranged in a split-plot design with 9 treatments and 3 replications. The main plot included 3 varieties of V068, V247 and V659. The subplot included 3 different planting densities of 74,100 plants/ha (70 x 20 cm), 57,100 plants/ha (70 x 25 cm, control) and 47,600 plants/ha (70 x 30 cm). The results showed that the planting density of 57,100 plants/ha was the most appropriate one for the growth and development of the corn varieties. At this plant density, the V068 variety produced 18.2 tons/ha with 66.0% of grade 1 corn and the profit margin was 1.15. The V247 variety produced 18.4 tons/ha with 70.2% of grade 1 corn and the profit margin was 1.23. The V659 variety produced 18.4 tons/ha with 71.8% of grade 1 corn and the profit margin was 1.28.

The physiological and biochemical metabolism of Nhan Hau persimmon variety collected in Thanh Hoa province from formation to maturity was studied in order to determine the physiological ripening time of the fruit, which is crucial for collection and preservation. Fruits were collected at 4, 8, 12, 15, 17, 19, 20, 21 & 23 weeks and surveyed for size, pigment content, reducing sugar, starch, total acidity, vitamin C, pectin and tannin. Results showed that persimmons fruit reached the maximum size at week 21 (6.39 cm in length, 6.17 cm in diameter). The content of chlorophyll a and b increased gradually from fruit formation to week 15 (0.43 mg/100 g and 0.61 mg/100 g, respectively), then decreased rapidly until the fruit was fully ripe. The concentration of carotenoids increased gradually until the fruit ripened (reaching 0.81 mg/100 g at week 23). Starch content and total acidity content increased gradually and peaked at week 17 (starch reached 7.61%, total acidity reached 74.70 mg/100 g), then gradually decreased. Reducing sugars and vitamin C content increased during the early stages and peaked at week 21 (reducing sugar reached 14.11%, vitamin C reached 46.54 mg/100 g), then decreased gradually. Pectin and tannin content increased and reached their maximum at week 15 (pectin reached 4.04%, tannin reached 2.02%), then decreased. These results show that the Nhan Hau persimmon fruit should be harvested at physiological maturity (21 weeks old) to ensure the high nutritional value and quality of the fruit during storage. 

Fertilizer trials were carried out at Ea Sar commune, Ea Kar district, Dak Lak province and Kong Yang commune, Kong Chro district, Gia Lai province in order to find out the type, amount and number of applications of fertilizer that would be suitable for sugarcane on sloping land. The trials were arranged in a randomized complete block design (RCBD) with five treatments, three replications and 50 m2 per lot. All parameters of the trials were evaluated through 2 crops of the plant cane and the first ratoon cane, from January 2020 to January 2022. The trial results showed that in sloping soil conditions, applying controlled release NPK fertilizer (18-8-22) with NPK content equal to 70% of the control gave the cane yield of 80.6 - 92.7 tons/ha. The sugar content was 11.84 - 11.95 CCS (commercial cane sugar) and the cane yield equivalent to 10 CCS was 96.0 - 110.8 tons/ha with about 16.30 - 30.86% higher than that of the control. The profit increased from 3,416 to 12,351 thousand VND/ha compared to the control.