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La N.,University of Hohenheim | La N.,Soils and Fertilizers Research Institute | Lamers M.,University of Hohenheim | Bannwarth M.,University of Hohenheim | And 2 more authors.
Paddy and Water Environment | Year: 2015

Uncertainties associated with pesticide exposure forecasts arise from many sources such as spatial and temporal variability of factors influencing pesticide behavior, inaccuracies in the measurement or estimation of input parameters and deficiencies in model structure. It is well acknowledged that, at least to some extent, simulation uncertainties should be accounted for when technical and political strategies are developed to mitigate pesticide exposure. We monitored the fate of the insecticide imidacloprid in a paddy rice field in Chieng Khoi watershed, Northern Vietnam. Pesticide fate was modeled using a new dynamic model together with the General Likelihood Uncertainty Estimation (GLUE) approach. A 95 % prediction uncertainty (PU) band was computed accounting for uncertainties in pesticide parameters, management practices, and weather conditions. As assessment criterion we used the Nash and Sutcliffe modeling efficiency (NSE). Measured paddy water concentrations of imidacloprid reached up to 53 μg L−1, paddy soil concentrations up to 9 μg kg−1. Calculated PU bands were in good agreement with field measurements. The field-scale model was extended to simulate pesticide fate in connected paddies. Imidacloprid concentrations in the afflux of the stream were estimated to be up to 83 μg L−1 under the current management practice in the research area. The loss of imidacloprid to the stream was assessed to range between 21 and 68 % of applied mass. Future studies, however, should focus on assessing loads of pesticides further widely used in connected paddies to help decision makers and farmers to adjust management strategies of protecting the environment. © 2014, The International Society of Paddy and Water Environment Engineering and Springer Japan.


La N.,University of Hohenheim | La N.,Soils and Fertilizers Research Institute | Lamers M.,University of Hohenheim | Nguyen V.V.,Hanoi University of Agriculture | Streck T.,University of Hohenheim
Pest Management Science | Year: 2014

Background: In Vietnam, paddy rice fields have been identified as a major non-point source of pesticide pollution of surface- and groundwater which is often directly used for domestic purposes. One strategy to assess the risk of pesticide pollution is to use process-based models. Here, we present a new model developed for simulating short-term pesticide dynamics in combined paddy rice field-fish pond farming systems. The model was calibrated using the Gauss-Marquardt-Levenberg algorithm and validated against measured pesticide concentrations of a paddy field-fish pond system typical for northern Vietnam. Results: In the calibration period, model efficiencies were 0.82 for dimethoate and 0.87 for fenitrothion. In the validation period, modelling efficiencies slightly decreased to 0.42 and 0.76 for dimethoate and fenitrothion, respectively. Scenario simulations revealed that a field closure period of 1day after pesticide application considerably reduces the risk of pond and surface water pollution. Conclusion: These results indicate that the proposed model is an effective tool to assess and evaluate management strategies, such as extended field closure periods, aiming to reduce the loss of pesticides from paddy fields.© 2013 Society of Chemical Industry.


Tran T.M.,Soils and Fertilizers Research Institute | Luxhoi J.,Copenhagen University | Jensen L.S.,Copenhagen University
Soil Science Society of America Journal | Year: 2013

To determine N turnover and losses during aerobic composting of animal manure, a 41-d laboratory study was performed on pig manure composting with three additive treatments (Straw: pig manure + straw only; Lime: pig manure + straw + quick lime; and SSP: pig manure + straw + single superphosphate). The NH4-N pool in the pig manure was initially labeled with 15N to determine the fate of manure NH4-N during composting. The composts were subsequently applied to soil to investigate the effects on soil mineral N and to trace the 15N during 60 d of incubation at 25°C. Of the initial manure 15NH4-N, approximately 30, 90, and 20% was lost by NH3 volatilization during composting in the Straw, Lime, and SSP treatments, respectively. Concurrently, 62, 16, and 41% of initial 15NH4-N was immobilized in the respective treatments. When the composts were applied to soil, the mineral N in soil with SSP compost was higher throughout the incubation than in soil with Straw and Lime composts. This was because of higher mineral N content in the SSP compost on application and higher net N mineralization from that compost in the soil. In soil with Straw compost, N mineralization and immobilization were slow or effectively in balance. In soil with Lime compost, net N immobilization was strong in the fi rst 10 d, but then net N mineralization dominated the remaining period of soil incubation. Overall, adding lime before composting reduced the NH4-N content in the compost and the amount available in soil, while adding superphosphate increased the NH4-N content in both. Therefore, superphosphate addition increased the potential fertilizer value of composted pig manure. © Soil Science Society of America.


Le H.T.,CNRS Microbial Ecology | Le H.T.,Vietnam Academy of Science and Technology | Ho C.T.,Vietnam Academy of Science and Technology | Trinh Q.H.,Vietnam Academy of Science and Technology | And 10 more authors.
Frontiers in Microbiology | Year: 2016

Organic fertilizer application is often touted as an economical and effective method to increase soil fertility. However, this amendment may increase dissolved organic carbon (DOC) runoffinto downstream aquatic ecosystems and may consequently alter aquatic microbial community. We focused on understanding the effects of DOC runofffrom soils amended with compost, vermicompost, or biochar on the aquatic microbial community of a tropical reservoir. Runoffcollected from a series of rainfall simulations on soils amended with different organic fertilizers was incubated for 16 days in a series of 200 L mesocosms filled with water from a downstream reservoir. We applied 454 high throughput pyrosequencing for bacterial 16S rRNA genes to analyze microbial communities. After 16 days of incubation, the richness and evenness of the microbial communities present decreased in the mesocosms amended with any organic fertilizers, except for the evenness in the mesocosms amended with compost runoff. In contrast, they increased in the reservoir water control and soil-only amended mesocosms. Community structure was mainly affected by pH and DOC concentration. Compared to the autochthonous organic carbon produced during primary production, the addition of allochthonous DOC from these organic amendments seemed to exert a stronger effect on the communities over the period of incubation. While the Proteobacteria and Actinobacteria classes were positively associated with higher DOC concentration, the number of sequences representing key bacterial groups differed between mesocosms particularly between the biochar runoffaddition and the compost or vermi-compost runoffadditions. The genera of Propionibacterium spp. and Methylobacterium spp. were highly abundant in the compost runoffadditions suggesting that they may represent sentinel species of complex organic carbon inputs. Overall, this work further underlines the importance of studying the off-site impacts of organic fertilizers as their impact on downstream aquatic systems is not negligible. © 2016 Le, Ho, Trinh, Trinh, Luu, Tran, Orange, Janeau, Merroune, Rochelle-Newall and Pommier.


Vu Q.D.,Copenhagen University | Tran T.M.,Soils and Fertilizers Research Institute | Nguyen P.D.,Soils and Fertilizers Research Institute | Vu C.C.,National Institute of Animal Science | And 2 more authors.
Nutrient Cycling in Agroecosystems | Year: 2012

Increased demand for meat products has led to increased livestock production in Vietnam, which now risks environmental pollution from inappropriate animal manure management on livestock farms. Biogas technology is generally considered an efficient solution for such farms to produce renewable biofuel for use in the household and to reduce the pollution impact from animal waste. However, with biogas technology, farmers may reduce their use of manure for fertilising crops. This field survey investigated nutrient flows on small- and medium-scale livestock farms with and without biogas in Northern Vietnam, in order to identify existing problems and possibilities for sustainable livestock production. A field survey was conducted on 12 pig farms with biogas and 12 pig farms without biogas in Quoc Oai district, Hanoi city. In general, the non-biogas pig farms used on average 3. 8 ton compost and 3. 1 ton fresh solid manure ha-1crop-1 for each of three crops typically grown per year on their arable land. They discharged on average 16 % of the total manure produced into the environment in liquid form through the public sewage system. On biogas pig farms, the use of fresh solid manure for crops and discharge of liquid manure was lower, as manure was used to produce biogas. However, excessive use of washing water on several of these farms resulted in very dilute slurry (solid manure:water ratio 1:11) entering the biogas digester. This lowered the retention time in the digester (below the optimum range of 35-55 days), leading to low biogas production rates and possible accumulation of sediment. The digestate was also highly diluted and hence difficult and costly to transport and apply to crops, so it was largely (60 %) discharged to the environment. The input volume of washing water should therefore be reduced to a ratio of 1:5. For better sustainability, appropriate technologies are needed to absorb nutrients from the digestate before discharge and to recycle these nutrients to crops. © 2012 Springer Science+Business Media B.V.


Yen B.T.,Soils and Fertilizers Research Institute | Visser S.M.,Wageningen University | Hoanh C.T.,International Water Management Institute | Stroosnijder L.,Wageningen University
Mountain Research and Development | Year: 2013

The Northern Uplands of Vietnam form one of the largest ecological regions in the country, characterized by complex biophysical conditions and a high diversity in ethnic minorities, cultures, and farming systems. The Doi moi ("renovation") program has, since the early 1980s, resulted in significant changes in agriculture production and related economic trends. However, poverty, low agricultural productivity, and land degradation are still major problems. This article illustrates the factors that drive these problems by analyzing agricultural land use in Suoi Con, a small agroforestry watershed in the Northern Uplands. We first identified the current land-use systems and analyzed constraints on agricultural production. The results indicate that although low soil fertility and land degradation are considerable problems, availability of household capital, low technology levels, and land fragmentation are major constraints on agricultural development. These constraints were analyzed from different points of view to identify mismatches between the implementation of top-down government policies and specific conditions that may explain why actual land-use change in the Northern Uplands deviates from the government's development plans. Results of land-use analysis in the Suoi Con watershed suggest that participatory and bottom-up approaches are needed to better understand problems and opportunities in household agricultural production in order to develop appropriate land-use plans and policies. © International Mountain Society.


Tran T.M.,Copenhagen University | Bui H.H.,Soils and Fertilizers Research Institute | Luxhoi J.,Copenhagen University | Jensen L.S.,Copenhagen University
Soil Science and Plant Nutrition | Year: 2012

A field experiment was carried out in northern Vietnam to investigate the effects of adding different additives [rice (Oriza sativa L.) straw only, or rice straw with added lime, superphosphate (SSP), urea or a mixture of selected microorganism species] on nitrogen (N) losses and nutrient concentrations in manure composts. The composts and fresh manure were applied to a three-crop per year sequence (maize-rice-rice) on a degraded soil (Plinthic Acrisol/Plinthaquult) to investigate the effects of manure type on crop yield, N uptake and fertilizer value. Total N losses during composting with SSP were 20% of initial total N, while with other additives they were 30-35%. With SSP as a compost additive, 65-85% of the initial ammonium-N (NH4-N) in the manure remained in the compost compared with 25% for microorganisms and 30% for lime. Nitrogen uptake efficiency (NUE) of fresh manure was lower than that of composted manure when applied to maize (Zea mays L.), but higher when applied to rice (Oriza sativa L.). The NUE of compost with SSP was generally higher than that of compost with straw only and lime. The mineral fertilizer equivalent (MFE) of manure types for maize decreased in the order: manure composted with SSP > manure composted with straw only and fresh manure > manure composted with lime. For rice, the corresponding order was: fresh manure > manure composted with SSP/microorganisms/urea > manure composted with lime/with straw alone. The MFE was higher when 5 tons manure ha-1 were applied than when 10 tons manure ha-1 were applied throughout the crop sequence. The residual effect of composted manures (determined in a fourth crop, with no manure applied) was generally 50% higher than that of fresh manure after one year of manure and compost application. Thus, addition of SSP during composting improved the field fertilizer value of composted pig manure the most. © 2012 Copyright Taylor and Francis Group, LLC.


Nguyen H.V.,Soils and Fertilizers Research Institute | Nguyen H.M.,Soils and Fertilizers Research Institute | Vu D.T.,University of Queensland | Fletcher A.,University of Queensland | Bui L.P.,Institute for Agricultural Environment
Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment | Year: 2012

Industrial, agricultural and commercial activities have led to significant Arsenic (As) contamination of soils and waterways. Phytoremediation is one of several techniques employed to remediate As contaminated soils. This study aimed to enhance As phytoremediation from contaminated mined soils by combining As hyperaccumulators (fern species) and Arbuscular Mycorrhizal Fungi (AMF). Arsenic contaminated soils were inoculated with AMF strains before planting with two indigenous fern species. Plant biomass and consequently As uptake were higher in Pteris vittata than in Pittyrogramma calomelanos. Inoculation of active AMF into soils significantly increased plant growth and As uptake. In particular, plant accumulated As increased by 100 to 124% in AMF inoculated plants/pots. © 2012 Taylor & Francis Group.

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