| 1. |
- Duy, Duong The, et al.
(författare)
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Assessing the effects of social capital on trade credit in shrimp farming in the Mekong Delta, Vietnam
- 2024
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Ingår i: Aquaculture Economics & Management. - 1365-7305 .- 1551-8663.
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses and identify major factors of social capital that affect the use of trade credit among shrimp farmers and how these contribute to and affect the profits of households in coastal provinces of the Mekong Delta, Vietnam. Data was collected through observations, informal discussions, and interviews with 364 shrimp farmers from the Ca Mau, Bac Lieu, Ben Tre and Tra Vinh provinces. The Probit and Tobit regression models were applied to analyze and evaluate the effect of social capital on the use of trade credit and the amount of trade credit used by farmers. The results show that many social capital factors affect the use of trade credit by shrimp farmers in the investigated areas, including in descending order of importance: profit, wholesale agents, colleague-friend-family line-neighbor, and trust. Besides the factors above, other factors such as agricultural land value, households’ income, distance, experiences in shrimp production, households’ assets, savings, profits of the previous crop, and the average household income had also an effect on trade use and amount of trade credit used by shrimp farming households.
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| 2. |
- Thanh, Dang Trung, et al.
(författare)
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Effects of organic fertilizers produced from fish pond sediment on growth performances and yield of Malabar and Amaranthus vegetables
- 2023
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Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media SA. - 2571-581X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The increasing intensification of aquaculture production requires the development of strategies to reduce its environmental impacts such as the pollution caused by the discharge of nutrient-rich sediments into local water bodies. This research was undertaken to investigate and evaluate the effect of using organic fertilizers produced from the pond sludge of freshwater snakehead fish (Channa striata) composted with organic amendments of peanut shells and coir fiber on growth performance indices and yields of Malabar spinach (Basella alba L.) and Amaranthus cruentus (Amaranthus L.) vegetables in the dry and wet seasons. An organic fertilizer quality experiment showed that the richest nutrient contents of the produced organic fertilizer were achieved when using 30% sludge mixed with 70% organic amendments (50% peanut shells + 50% coir fiber). This was selected and used for a vegetable cultivation experiment. For the reference treatment, only chemical fertilizer was applied, while in the other four treatments, 25, 50, 75, and 100% of the chemical fertilizer were substituted with the organic fertilizer. A 25–50% reduction in the chemical fertilizer application resulted in better growth performance indices and final yields than the other treatments, including the reference treatment, for both crops. The highest yields of Malabar spinach and Amaranthus cruentus vegetables were found in Treatment 3 (50% chemical fertilizer combined with 50% organic fertilizer), followed by Treatment 2 (25% organic fertilizer combined with 75% inorganic fertilizer) (P < 0.05). The results show that the reuse of sludge from snakehead fish ponds mixed with agricultural by-products as organic fertilizer for vegetables not only improves vegetable productivity but also reduces the costs of chemical fertilizer and decreases environmental pollution.
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| 3. |
- Berg, Håkan, et al.
(författare)
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An ecological economic comparison between integrated rice-fish farming and rice monocultures with low and high dikes in the Mekong Delta, Vietnam
- 2023
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 52:9, s. 1462-1474
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Tidskriftsartikel (refereegranskat)abstract
- This study makes an ecological economic comparison between three different rice farming strategies in the Mekong Delta. Interviews were made with 30 farmers with two crops of rice and low dikes (2RLd), 30 farmers with three crops of rice and high dikes (3RHd) and 18 farmers with two crops of rice and one crop of fish (2RF). 2RF farmers had the highest annual net income and benefit cost ratio, because of low production costs and high yields of rice and fish. 2RLd farmers had the lowest annual net income. 3RHd had the highest annual rice yield, but also used the highest amount of rice seeds and agrochemicals, generating the lowest benefit cost ratio. Most farmers (70%) preferred two crops because of a higher production efficiency. High dikes and frequent use of pesticides and fertilizers were seen to decrease the water and rice quality, connectivity and biodiversity in farms with three crops. It is concluded that rice farming with two crops, and especially if integrated with fish and applying IPM, provides a sustainable alternative to rice farming with three crops and high dikes, because it makes use of the high connectivity within the rice-field ecosystem for an efficient production of healthy food through increased recycling of nutrients and natural pest control mechanisms.
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| 4. |
- Berg, Håkan, et al.
(författare)
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Stakeholders assessment of status and trends of ecosystem services in the Mekong Delta for improved management of multifunctional wetlands
- 2023
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Ingår i: Journal of Environmental Management. - 0301-4797 .- 1095-8630. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- Increased agriculture and aquaculture production in the Mekong Delta during the last two decades has improved farmers' income, national export earnings and reduced poverty, but has also impacted on the environment and ecosystem services (ES) of importance to peoples' livelihoods and well-being. Through group discussions, interviews and questionnaires, this study assesses stakeholders’ perceptions of the status and trends of ES in the Mekong Delta and how these have been influenced by agriculture development. 15 of 24 ES were assessed to be impacted negatively by agriculture intensification, and especially supporting and regulating ES (SRES). Only a few provisioning ES (PrES), related to farming, were assessed to be in a good and stable supply, because of human interventions to create favorable conditions for these ES. Among the ten highest ranked ES, eight belonged to PrES and two belonged to SRES. There was a positive correlation between rank and awareness of ES. The supply of most SRES was perceived to be in a low and declining status and assessed to be in a high need for improved management. Some ES, such as pest-control had been complemented with human-made substitutes, such as pesticides, which however sometimes weakened rather than strengthened the ES. Cultural ES (CES) were often ranked lower and of less management concern than the other groups of ES. It is concluded that future agriculture strategies need a more balanced management of ES for a long-term production of healthy food and increased resilience of the Mekong Delta to cope with future challenges, such as climate change and upstream dams.
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| 5. |
- Da, Chau Thi, et al.
(författare)
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Digestibility of dietary components and amino acids in animal and plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings
- 2013
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Ingår i: Aquaculture Nutrition. - : Hindawi Limited. - 1353-5773 .- 1365-2095. ; 19, s. 741-750
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Tidskriftsartikel (refereegranskat)abstract
- The apparent digestibility (AD) of dietary components, energy and essential amino acids (EAA) of selected locally available animal and plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings was studied. The AD of the test ingredients (ADi) differed (P<0.05) and ranged from 81.1% to 90.8%, for ADi(DM), from 84.0% to 95.0% for ADi(CP), from 78.4% to 86.9% for ADi(OM) and from 79.0% to 87.8% for ADi(GE). The highest ADi(DM), ADi(CP) and ADi(OM) in the test ingredients were found for shrimp head meal, catfish by-product meal, golden apple snail and groundnut cake, while the lowest values were obtained for earthworm meal and rice bran. The highest ADi(GE) was found in rice bran, followed by golden apple snail and catfish by-product meal, while there were no differences (P<0.05) between the other test ingredients, except for earthworm meal. The AD of total and individual EAA was high in catfish by-product meal and shrimp head meal, followed by decreasing AD in golden apple snail, groundnut cake, rice bran and earthworm meal ingredients (P<0.05). The low AD of earthworm meal may limit its potential to be used as replacement for fish meal in the feed.
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| 6. |
- Da, Chau Thi, et al.
(författare)
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Digestibility of dietary components and amino acids in plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings
- 2013
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Ingår i: Aquaculture Nutrition. - : Hindawi Limited. - 1353-5773 .- 1365-2095. ; 19, s. 619-628
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Tidskriftsartikel (refereegranskat)abstract
- The apparent digestibility (AD) of dietary components, energy and essential amino acids (EAA) of selected locally available plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings was studied. The AD of the test ingredients (ADi) differed (P < 0.05) and ranged from 66.2 to 89.6% for ADiDM, from 63.6 to 91.3% for ADiCP, from 65.4 to 85.3% for ADiOM and from 69.8 to 89.3% for ADiGE. The highest ADiDM, ADiOM and ADiGE in the test ingredients was obtained for broken rice, maize meal and soybean meal, while the lowest values were obtained for duckweed meal. Soybean meal and duckweed meal had the highest ADiCP, while there were no differences (P > 0.05) between the other test ingredients. The AD of total and individual EAA was higher in soybean meal, duckweed meal and broken rice than in the other test feed ingredients (P < 0.05). The lowest AD of individual EAA was found in maize meal, followed by cassava leaf meal and sweet potato leaf meal (P < 0.05). The low AD of individual plant feed ingredients may limit their potential to be used as replacement for fish meal in the feed.
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| 7. |
- Da, Chau Thi, et al.
(författare)
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Evaluation of local feed resources as alternatives to fish meal in terms of growth performance, feed utilisation and biological indices of striped catfish (Pangasianodon hypophthalmus) fingerlings
- 2012
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 364-365, s. 150-156
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Tidskriftsartikel (refereegranskat)abstract
- A 16-week feeding experiment was conducted to evaluate growth performance, feed utilisation and body indices of striped catfish (Pangasianodon hypophthalmus) fed diets where fish meal protein was replaced with protein from local feed resources. The reference diet contained fish meal as the main crude protein (CP) source, whilst in the six test diets 20 to 100% of the fish meal CP was replaced with CP from local ingredients (soybean meal, cassava leaf meal, sweet potato leaf meal, groundnut cake, golden apple snail meal and shrimp head meal). Final body weight (BW) and total weight gain (WG) were lowest for the cassava leaf meal diet (P < 0.05), whilst there were no differences in BW and WG between the other diets. Final BW, WG and daily weight gain were numerically highest for the shrimp head meal diet. Fish survival rate, feed intake, feed utilisation and fish fillet proportion did not differ between the reference diet and the test diets (P > 0.05). The viscera-somatic, hepato-somatic, kidney and intra-peritoneal fat indices differed between treatments (P < 0.05). The results suggest that fish meal protein in feed for striped catfish fingerlings can be replaced with protein from locally available plant and animal ingredients without compromising growth performance, feed utilisation and carcass traits.
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| 8. |
- Da, Chau Thi
(författare)
-
Evaluation of locally available feed resources for striped catfish (Pangasianodon hypophthalmus)
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigated and compared inputs and outputs, economic factors and current feed use in small-scale farming systems producing striped catfish (Pangasianodon hypophthalmus) in the Mekong Delta. The nutrient content of locally available natural feed resources for striped catfish was determined and growth performance, feed utilisation and body indices were analysed in pond-cultured striped catfish fed diets where fish meal protein was replaced with protein from local feed resources. A survey showed that around 15 feed ingredients are used in striped catfish pond culture in the region. The combination of feed ingredients used in farm-made feeds varied among fish farms. The cost of producing 1 kg of fish using farm-made feeds was usually 8˗10% lower than that of using commercial feeds. Digestibility trials on selected potential feedstuffs showed that the apparent digestibility (AD) of DM, CP, OM and energy was highest in soybean meal, groundnut cake, broken rice, shrimp head meal, golden apple snail and catfish by-product meal and earthworm meal, whilst the digestibility was in lower cassava leaf meal and sweet potato leaf meal. The average digestibility of most essential amino acids (EAA) in selected feed ingredients was high (range 70˗92%), indicating high protein quality of these feedstuffs. In general, the AD of individual EAA was high for all diets except those with cassava leaf meal, rice bran and earthworm meal, where the AD of EAA was reduced. Two different growth experiments with the same diet (20˗100% replacement of fish meal) were performed in an indoor and an outdoor culture system. A significant finding was that daily weight gain (DWG) was much higher (3.2˗ to 6˗fold) in outdoor culture conditions compared with indoor. Feed conversion rate and feed utilisation were also 0.2˗0.7 units (kg feed DM/kg weight gain) higher in the outdoor system. The results suggest that fish meal protein in feed for striped catfish fingerlings can be replaced with protein from locally available plant and animal ingredients without compromising growth performance, feed utilisation or carcass traits.
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| 9. |
- Da, Chau Thi, et al.
(författare)
-
Growth performance, feed utilisation and biological indices of Tra catfish (Pangasianodon hypophthalmus) cultured in net cages in pond fed diets based on locally available feed resources
- 2016
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Ingår i: International Aquatic Research. - : Springer Science and Business Media LLC. - 2008-4935 .- 2008-6970. ; 8, s. 309–321-
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Tidskriftsartikel (refereegranskat)abstract
- The feeding experiment was conducted to evaluate the efficacy of locally available feed resources for Tra catfish (Pangasianodon hypophthalmus) cultured a series of 21 hapa net cages installed in the earthen pond during a 4-month period. The reference diet contained fish meal as the main crude protein (CP) source, whilst in the seven test diets 20-100 % of the fish meal CP was replaced with CP from local feed ingredients: groundnut cake (GNC), cassava leaf meal (CSLM), sweet potato leaf meal (SPLM), soybean meal (SBM), golden apple snail meal (GASM) and shrimp head meal. There were differences (p\0.05) among diets in final body weight, total weight gain, daily weight gain, specific growth rate, viscera-somatic weight (VSI%), hepato-somatic index (HIS%) and intra-peritoneal fat (IPF%). The respective values for the shrimp head meal diet were numerically highest, followed in descending order by the reference, GASM, GNC, SPLM, CSLM and SBM diet. Food conversion ratio, fish survival rate, total feed intake, feed utilisation, fish fillet and kidney proportions did not differ among the reference and test diets (p[0.05). However, the viscera-somatic, hepato-somatic, kidney and intra-peritoneal fat indices differed among treatments (p\0.05). These data show that fish meal protein can be replaced with protein from locally available plant and animal feed ingredient resources in feed cultured in net cages in pond for Tra catfish fingerlings in effectively compromising growth performance, feed utilisation or carcass traits of fish.
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| 10. |
- Da, Chau Thi, et al.
(författare)
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Recycled pangasius pond sediments as organic fertilizer for vegetables cultivation : strategies for sustainable food production
- 2023
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Ingår i: Clean Technologies and Environmental Policy. - : Springer Science and Business Media LLC. - 1618-954X .- 1618-9558. ; 25:2, s. 369-380
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Tidskriftsartikel (refereegranskat)abstract
- Intensive Pangasius aquaculture farming contributes to increased income and profits in Vietnam, but is also associated with many environmental problems, including pollution from nutrient-rich water and sediments that are released into the environment. This article investigates the feasibility of using Pangasius pond sediments (PPS) in combination with amendments of rice straw (RS) to fertilize cucumber (Cucumis sativus L.) and water spinach (Ipomoea aquatica Forssk) plant. The results showed that mixing a ratio of 30% PPS with 70% RS produced the highest nutrient concentrations. The study demonstrates that organic fertilizer produced from PPS in combination with chemical fertilizer can replace 2575% of the inorganic fertilizers used as a nutrient source for cucumber and water spinach, and also increase the vegetable production. The highest yields were found for treatment PPS-3 (a combination of 50% chemical fertilizer and 50% organic fertilizer used on cucumber), and for treatment PPSRS-4 (a combination of 25% chemical fertilizer and 75% organic fertilizer used on water spinach) in both the wet and dry season (P˂0.05). The lowest yields were found when growing cucumbers and water spinach either with 100% organic fertilizer (the treatment PPS-5) or with 100% chemical fertilizer (the control treatment PPS-1), respectively (P˂0.05). Overall, the results indicated that the recycling of PPS as organic fertilizer and chemical fertilizer in combination for vegetable cultivation is more environmentally friendly as compared to using only chemical fertilizers.
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| 11. |
- Da, Chau Thi, et al.
(författare)
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Use of Wastewater from Striped Catfish (Pangasianodon hypophthalmus) Pond Culture for Integrated Rice-Fish-Vegetable Farming Systems in the Mekong Delta, Vietnam
- 2015
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Ingår i: Agroecology and Sustainable Food Systems. - : Informa UK Limited. - 2168-3565 .- 2168-3573. ; 39:5, s. 580-597
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Tidskriftsartikel (refereegranskat)abstract
- This article investigates the feasibility of reusing wastewater from striped catfish (Pangasianodon hypophthalmus) pond culture as nutrient input for integrated rice-Nile tilapia-green bean farming systems, and to what extent this could contribute to decreasing the environmental impacts on water quality from the striped catfish industry in the Mekong Delta. Four treatments in triplicates were used to investigate the growth of rice and green bean varieties under different combinations of inorganic fertilizer and water from the river and a striped catfish pond culture. The Nile tilapia (Oreochromis niloticus) was cultured at low density without feeding in a canal adjacent to the rice field. Rice yields ranged from 3,514 to 4,023 kg ha(-1) with no significant differences between treatments (p > 0.05). The yield of green bean ranged from 2,671 to 3,282 kg ha(-1) (p < 0.05), with the highest yields for beans only receiving water from the striped catfish pond. The water quality concentrations decreased significantly when passing through the rice plots for almost all treatments (p < 0.05). Total phosphorus and nitrogen levels in the outflowing water were reduced by almost 50% compared to the inflowing water from the striped catfish pond. Overall, the results indicated that an integrated system generates both economic and environmental benefits as compared to monocultures.
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| 12. |
- Duy, Duong The, et al.
(författare)
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Assessment of technical, economic, and allocative efficiencies of shrimp farming in the Mekong Delta, Vietnam
- 2023
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Ingår i: Journal of the World Aquaculture Society. - : Wiley. - 0893-8849 .- 1749-7345. ; 54:4, s. 915-930
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Tidskriftsartikel (refereegranskat)abstract
- This study applied a stochastic frontier production model to analyze the technical (TE), allocative (AE), and economic (EE) efficiencies of intensive shrimp farming households, and to identify socioeconomic and shrimp farm-specific factors (farm size, labor, feed, seed, chemicals/medicine) that influence the TE, AE, and EE of shrimp production in the Ca Mau, Ben Tre, Bac Lieu, and Tra Vinh provinces of the Mekong Delta, Vietnam. The AE was calculated based on TE and EE. The stochastic frontier production and cost function model were used to evaluate the EE and TE at the shrimp farming household level. The results showed that the mean TE, AE, and EE of shrimp farming systems were 75%, 68.5%, and 61.4%, respectively. Age, gender, education, experience, cooperatives, and technical training significantly impacted the efficiency of shrimp production. The results suggest that shrimp farmers can improve shrimp productivity and EE by decreasing feed cost (FEE) and medicine/chemical cost (MED) of farm inputs. The study showed that shrimp farmers who participated in training activities, cooperatives, or management boards of aquaculture associations were more technically efficient than other farmers. The findings of this study provide essential information about the TE, AE, and EE of shrimp production, which can help local policy makers and shrimp farmers in the region to make better decisions on how to improve the EE and sustainability of shrimp production in the future. There is a need for recommendations on how to improve policies, technical guidance, and training courses on feed management and feeding practices, water quality, and disease management, to help shrimp farmers in the coastal provinces of the Mekong Delta to improve their shrimp production efficiencies in the future.
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| 13. |
- Duy, Duong The, et al.
(författare)
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Assessment of the impacts of social capital on the profit of shrimp farming production in the Mekong Delta, Vietnam
- 2022
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Ingår i: Aquaculture Economics & Management. - : Informa UK Limited. - 1365-7305 .- 1551-8663. ; 26:2, s. 152-170
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses capital assets and factors influencing on farmers’ decision to participate in social networks, and how these contribute to and affect household’s profits of small-scale shrimp farmers in four coastal provinces in the Mekong Delta, Vietnam. Data was collected through observations, and informal discussions and interviews with 350 small-scale shrimp farmer households. The results show that farmer’s age, education of household head, dependency ratio, village residence time, village population density are important factors influencing positively on shrimp farmers´ participation in social networks. The study also shows that contacts with fisheries association, traders, wholesale agencies, trust, household savings, labors’ education, household’s agricultural land size, post larvae quality and equipment significantly influenced on the profit variable with 1–10%. The results also indicate that a 10% increase in social capital would bring an increase in household income of 3.9%.
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| 14. |
- Kiessling, Anders, et al.
(författare)
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Alternative protein sources for fish, not competing with the human food demand evaluated by traditional and novel approaches
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- At present, most alternative feed sources in fish is since long known in terrestrial animals. However, in a longer time frame this is questionable from a food security perspective, as these sources often are of human food quality. This is an argument rapidly growing in importance. Microbes, insects and products from other forms of extractive aquaculture are of major interest considering their growth potential, nutritional profile, probiotic qualities and ability to use simple resources as substrates. However, with a transition towards a circular economy, substrates that produce such feed ingredients will to a higher degree be based on waste and by-products. This development will demand novel approach in nutrition research in order to understand non-intuitive positive and negative effects in the fish gut biota, immune response, metabolism, welfare and product quality/safety. We will present our ongoing work, concerning physiological implications of alternative protein sources using in situ experimental technologies, such as cannulation and repeated tissue sampling. This work also combines advanced analytic methods of metabolomics and gut microbiota using amplicon next generation sequencing that targets 16S rDNA for bacterial identification. Data on post-prandial plasma AA profile, hematological parameters and erythrocyte indices will be presented together with data concerning the interaction between diet and stress in fish where fishmeal has been replaced by yeast up to 60%. Also, data concerning changes of the microbiota of fish given fungal mycelium-, yeast-, insect- (if ready) and mussel meal will be presented, including comparison between nutrient efficiency of feed given in clear or “green” water environments. Finally, experiments concerning yeast as biological barrier to prions, i.e. food safety, will be discussed. In all, an overall picture of one possible future development in fish nutrition will be painted with a focus on the use of novel feed stuffs in circular food production systems.
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| 15. |
- Livsey, John, et al.
(författare)
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Do alternative irrigation strategies for rice cultivation decrease water footprints at the cost of long-term soil health?
- 2019
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 14:7
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Tidskriftsartikel (refereegranskat)abstract
- The availability of water is a growing concern for flooded rice production. As such, several water-saving irrigation practices have been developed to reduce water requirements. Alternate wetting and drying and mid-season drainage have been shown to potentially reduce water requirements while maintaining rice yields when compared to continuous flooding. With the removal of permanently anaerobic conditions during the growing season, water-saving irrigation can also reduce CO2 equivalent (CO2eq) emissions, helping reduce the impact of greenhouse gas (GHG) emissions. However, the long-term impact of water-saving irrigation on soil organic carbon (SOC)-used here as an indicator of soil health and fertility-has not been explored. We therefore conducted a meta-analysis to assess the effects of common water-saving irrigation practices (alternate wetting and drying and mid-season drainage) on (i) SOC, and (ii) GHG emissions. Despite an extensive literature search, only 12 studies were found containing data to constrain the soil C balance in both continuous flooding and water-saving irrigation plots, highlighting the still limited understanding of long-term impacts of water-saving irrigation on soil health and GHG emissions. Water-saving irrigation was found to reduce emissions of CH4 by 52.3% and increased those of CO2 by 44.8%. CO2eq emissions were thereby reduced by 18.6% but the soil-to-atmosphere carbon (C) flux increased by 25% when compared to continuous flooding. Water-saving irrigation was also found to have a negative effect on both SOC-reducing concentrations by 5.2%-and soil organic nitrogen-potentially depleting stocks by more than 100 kgN/ha per year. While negative effects of water-saving irrigation on rice yield may not be visible in short-term experiments, care should be taken when assessing the long-term sustainability of these irrigation practices because they can decrease soil fertility. Strategies need to be developed for assessing the more long-term effects of these irrigation practices by considering trade-offs between water savings and other ecosystem services.
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| 16. |
- Livsey, John, 1983-, et al.
(författare)
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Floods, soil and food – Interactions between water management and rice production within An Giang province, Vietnam
- 2021
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 320
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Tidskriftsartikel (refereegranskat)abstract
- Rapid intensification of Vietnamese rice production has had a positive effect on the nation's food production and economy. However, the sustainability of intensive rice production is increasingly being questioned within Vietnam, particularly in major agricultural provinces such as An Giang. The construction of high dykes within this province, which allow for complete regulation of water onto rice fields, has enabled farmers to grow up to three rice crops per year. However, the profitability of producing three crops is rapidly decreasing as farmers increase their use of chemical fertilizer inputs and pesticides. Increased fertilizer inputs are partly used to replace natural flood-borne, nutrient-rich sediment inputs that have been inhibited by the dykes, but farmers believe that despite this, soil health within the dyke system is degrading. However, the effects of the dykes on soil properties have not been tested. Therefore, a sampling campaign was conducted to assess differences in soil properties caused by the construction of dykes. The results show that, under present fertilization practices, although dykes may inhibit flood-borne sediments, this does not lead to a systematic reduction in nutrients that typically limit rice growth within areas producing three crops per year. Concentrations of total nitrogen, available phosphorous, and both total and available potassium, and pH were higher in the surface layer of soils of three crop areas when compared to two crop areas. This suggests that yield declines may be caused by other factors related to the construction of dykes and the use of chemical inputs, and that care should be taken when attempting to maintain crop yields. Attempting to compensate for yield declines by increasing fertilizer inputs may ultimately have negative effects on yields.
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| 17. |
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| 18. |
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| 19. |
- Scaini, Anna, et al.
(författare)
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Pathways from research to sustainable development: Insights from ten research projects in sustainability and resilience
- 2024
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Ingår i: AMBIO. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 53
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Tidskriftsartikel (refereegranskat)abstract
- Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.
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| 20. |
- Sen, Sorphea, et al.
(författare)
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Effect of dietary replacement of fishmeal with spent brewer’s yeast on growth performance of Asian seabass (Lates calcarifer) in Cambodian coastal aquaculture.
- 2019
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Ingår i: Livestock Research For Rural Development. - 0121-3784. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- Coastal Asian seabass farming is an emerging industry in Cambodia, but most farmers depend upon trash fish to feed seabass due to the high cost of formulated diets, with inherent biosecurity and sustainability problems. Use of locally sourced, low-cost ingredients would overcome the major cost obstacle to integration of dry, formulated diets into Cambodian seabass aquaculture. We conducted two feed trials, one in tanks and one in hapas, to evaluate replacement of fishmeal in dry formulated diets with spent yeast sourced from a local brewery. Replacement of fishmeal with dry brewer’s yeast at 0%, 20%, 37% and 47% did not significantly affect performance in terms of growth and feed conversion in either culture system. Brewer’s yeast can thus be an affordable, locally sourced replacement for fishmeal in formulated diets for farmed seabass in Cambodia.
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| 21. |
- Thanh, Bui Xuan, et al.
(författare)
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Effects of Hydraulic Retention Time on Organic and Nitrogen Removal in a Sponge-Membrane Bioreactor
- 2013
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Ingår i: Environmental Engineering Science. - : Mary Ann Liebert Inc. - 1092-8758 .- 1557-9018. ; 30:4, s. 194-199
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Tidskriftsartikel (refereegranskat)abstract
- This is the first study on application of a sponge-membrane bioreactor (sponge MBR) for recirculation of aquaculture wastewater in the Mekong delta, Vietnam. Performance of a sponge MBR with a moving-cube sponge medium (20% v/v) was evaluated at different hydraulic retention times (HRTs) for the specific example of catfish pond wastewater. The sponge MBR was operated at HRT values of 8, 4, and 2 h, which correspond to membrane fluxes of 5, 10, and 20 L/m(2) per hour, respectively. The average chemical oxygen demand (COD) removal efficiencies were maintained at 93%, 94%, and 87% at an HRT of 8, 4, and 2 h, respectively, while the average total nitrogen (TN) removal efficiencies were 84%, 70%, and 57%. The COD and TN removal efficiencies decreased with a decrease in HRT (increase in membrane flux). Permeate concentrations of COD and TN were as low as 6.3 and 2.7 mg/L at the operated HRTs, respectively. Compared to the conventional MBR, the sponge MBR had twice the TN removal capacity at the same HRT due to simultaneous nitrification-denitrification. In addition, results implicated that the fouling rate (dTMP/dt) increased in an inverse proportion with HRT (h) according to the power equation (fouling rate = 4.2474 HRT-2.225). Free movement of sponges in the reactor improved fouling due to sweeping of the cake layer on the membrane surface. Results reveal that the sponge MBR was effective in terms of simultaneous organic and nitrogen removal, fouling control, and water recirculation.
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| 22. |
- Thi, Chau Da, et al.
(författare)
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Improving Productivity in Integrated Fish-Vegetable Farming Systems with Recycled Fish Pond Sediments
- 2020
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Ingår i: Agronomy. - : MDPI AG. - 2073-4395. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- The increasing intensification of aquaculture systems requires the development of strategies to reduce their environmental impacts such as pollution caused by the discharge of nutrient rich sediments into local water bodies. Recycling of fish pond sediments (FPS) as fertilizer has been proposed as a possible solution that may also reduce the reliance on synthetic fertilizers. With a case study in the Mekong Delta, Vietnam, we determined suitable mixtures of striped catfish (Pangasianodon hypophthalmus) pond sediment (PPS) and locally sourced organic amendments of rice straw (RS), or common water hyacinth (WH) to fertilize cucumber plants (Cucumis sativus L.) in an integrated cucumber–giant gourami fish (Osphronemus goramy) farming system. Highest nutrient concentrations were found when mixing 30% PPS with 70% RS or WH. When used in combination with chemical fertilizer, it was found that a 25% to 75% reduction in chemical fertilizer application could be achieved, while also increasing cucumber yields, with the highest yields found when RS was used in organic amendments. In combination with the additional income from fish production, integrated farming systems such as that demonstrated in this study, may increase both farm income and production diversity.
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