Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2003
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Stephen Woodward Jan Stenlid Marco Michelozzi Halvor Solheim B. Karlsson Panaghiotis TsopelasAbstract
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Svein Ole BorgenAbstract
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Pierre Ackerman Bruce TalbotAbstract
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Erik Jautris Joner C. LeyvalAbstract
Phytoremediation of organic pollutants depends on plant-microbe interactions in the rhizosphere, but the extent and intensity of such rhizosphere effects are likely to decrease with increasing distance from the root surface.We conducted a time-course pot experiment to measure dissipation of polycyclic aromatic hydrocarbons (PAHs) in the rhizosphere of clover and ryegrass grown together on two industrially polluted soils (containing 0.4 and 2 g kg(-1) of 12 PAHs). The impact of the fungal root symbiosis arbuscular mycorrhiza (AM) on PAH degradation was also assessed, as these fungi have previously improved plant establishment on PAH-polluted soils and enhanced PAH degradation in spiked soil.The two soils behaved differently with respect to the time-course of PAH dissipation. The less polluted and more highly organic soil showed low initial PAH dissipation rates, with small positive effects of plants after 13 weeks. At the final harvest (26 weeks), the amounts of PAHs extracted from nonplanted pots were higher than the initial concentrations. In parallel planted pots, PAH concentrations decreased as a function of proximity to roots.The most polluted soil showed higher initial PAH dissipation (25% during 13 weeks), but at the final harvest PAH concentrations had increased to values between the initial concentration and those at 13 weeks. An effect of root proximity was observed for the last harvest only. The presence of mycorrhiza generally enhanced plant growth and favored growth of clover at the expense of ryegrass. Mycorrhiza enhanced PAH dissipation when plant effects were observed.
Authors
S.C. Corgié Erik Jautris Joner C. LeyvalAbstract
Rhizodegradation of recalcitrant organic pollutants, such as polycyclic aromatic hydrocarbons (PAH), may benefit from the major role that root exudates have on rhizospheric microbial processes. We investigated the influence of the proximity to ryegrass (Lolium perenne L.) roots on microbial populations and their biodegradation of phenanthrene (PHE) using compartmented pots. PAH degrading bacteria, total heterotrophic bacteria and PHE biodegradation were quantified in three consecutive sections at different distance (03, 36, 69 mm) from a mat of actively exuding roots.A bacterial gradient was observed with higher numbers of heterotrophs and PAH degrading bacteria closest to the roots. In parallel, a PHE biodegradation gradient was evident in the presence of roots. The biodegradation reached 86%, 48% and 36% of initially added PHE, respectively, in the layers 03 mm, 36 and 69 mm from the roots. The biodegradation rate was similar throughout the three layers of the non planted control. The present experimental system seems well suited for spatial and dynamic studies of PAH rhizoremediation.
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The objective of this study was to provide empirical insight into dairy farmers’ goals, relative risk attitude, sources of risk and risk management responses. The study also examines whether organic dairy farming, leads to important risk sources not experienced in conventional farming and, if so, how those extra risks is managed. The data originate from a questionnaire survey of conventional (n=370) and organic (n = 160) dairy farmers in Norway. The results show that organic farmers have somewhat different goals than conventional farmers, and that the average organic farmer is less risk averse. Institutional risk was perceived as the most important source of risk, independently of conventional or organic production system, while organic farmers indicated greater concern about forage yield risk. Keeping cash on hand was the most important strategy to manage risk for all dairy farmers. Diversification and different kinds of flexibility was regarded as a more important risk management strategies among organic than conventional farmers.
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The Norwegian Ministry of Agriculture (1999) has announced its goal of converting 10% of the total agricultural area to organic farming methods by the year 2009. Considerations of profitability and risk will be especially important, when the conversion of a farm is planned. Studies of risk and risk management in organic farming have been lacking in Norway. Only very few such studies have been carried out internationally, thus showing that there is a definite need for more risk and risk management research in organic farming. The project aims to increase knowledge about risks and risk management in organic farming systems. It is a co-operation between NILF, NORSK, and NVH. Both biological and economic aspects of risk will be taken into consideration. We wish to test and apply acknowledged statistical and risk analysis theories and methods on issues related to organic farming. The project will deal with the extent of risk in organic farming, strategies used by organic farmers to handle risk and whole-farm models to analyse optimal economic solutions under uncertainty in organic farming. The project will cover farms that are still in conversion and completely converted farms. Results from the project will directly benefit farmers and farm advisers. Politicians and public administrators will receive access to significant information for the design of future policies.
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No abstract has been registered