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Thị Trấn Thanh Lưu, Vietnam

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. Source

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. Source

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. Source

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. Source

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. Source

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